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General
Wildcat well 1/3-4 was drilled on the northern part of the Hidra High in the North Sea. The objective was to test the hydrocarbon potential of the Danian and late Cretaceous Chalk, on a domal structure induced by halokinesis.
Operations and results
Well 1/3-4 was spudded with the semi-submersible installation Dyvi Alpha on 15 February 1983 and drilled to TD at 3198 m in the Late Permian Zechstein Group. While drilling through Middle Miocene claystones, the average background gas increased rapidly from 5% to 80% between 1580 m and 1595 m and, at this depth, the mud weight had to be increased gradually from 1.37 to 1.50 - 1.53 to lower the gas content. Furthermore, to stop the gas leakage and to isolate the weak zone, it was decided to set the 13 3/8" casing. Logs were run (ISF/BHC and LDT/CNL) and the casing was set with shoe at 1557 m. While circulating after the logging a gain of 1 m3 with gas and more than 100 litres of oil occurred. To stabilize the well, 2 cement plugs and 4 barite plugs were set, in order to stop the gas leaking from the formation. In total, twenty days were spent on circulating, logging (ISF/BHC and LDT/CNL), setting the 13 3/8" casing, and plugging before drilling of the 12 1/4" section commenced. While drilling the 12 1/4" hole, the background gas varied between 32 and 84% down to 1695 m where the mud-weight was raised to 1.60. The background gas then decreased between 10 and 25% and drilling continued normally. Logs performed at the end of the 12 1/4" phase and covering the zone of interest are strongly affected by large cavings and by barite squeezed into the formation. Side wall core recovery was very poor from the caved zone. The well was drilled water based.
The first ev General The wildcat 2/2-3 was drilled on a domal
structure, south of the Ula-Gyda fault zone. Main objective was Late Jurassic
sandstone in the Vestland Group. Secondary target was Middle Jurassic and Late
Triassic sandstones. According to the license agreement the
well should be drilled into the Triassic, salt, or a maximum depth of 5000 m
whatever came first Operations and results The well was spudded with the
semi-submersible rig Treasure Saga on 4 February 1983 and drilled to TD at 4100
m, 170 m into the Triassic Smith Bank Formation. At 3286 m the string was lost
after a wiper trip. The well had to be plugged back to 3053 m and sidetracked
from this point. At 3420 m the string was again lost but was recovered. The
well was drilled using water-based mud. The well was drilled with seawater and
bentonite down to 655 m, with polymer/gypsum/"SST 202" mud from 655 m
to 1910 m, with lignite/Drispac/gypsum mud from 1910 m to 3523 m, and with
lignite/lignosulphonate mud from 3523 m to TD. The well penetrated 2998 m of Cenozoic
sediments represented by the Nordland, Hordaland and Rogaland Groups. The
sequence was mainly composed of argillaceous deposits. The Oligocene Sand Unit
(Vade Formation) recognized in well 2/2-1 and 2/2-2, was not established in
this well. The Cretaceous sequence consisted of two lithostratgraphic units,
the Chalk and Cromer Knoll Group. They were separated by an unconformity
ranging from Santonian to Middle Albian. The Early Cretaceous and upper part of
the Late Jurassic (Ryazanian-Middle Volgian) are highly condensed. The Late
Jurassic predominantly consists of claystones of the Mandal (4m) and Farsund
Formations. The Ula Formation is present from 3880 m in the bottom part of the
Late Jurassic as a sandstone sequence of Early Kimmeridgian - Late Oxfordian
age. The formation is resting unconformably on sediments of the Triassic Group. The Shetland Group chalk, 2965 m to 3494
m, has General The appraisal well 30/6-12 was drilled in
a down flank position on the Alpha block east of the 30/6-1 Oseberg Discovery
well, which tested gas in the Middle Jurassic Brent Group. The main objectives
of the well were to confirm the reserves of hydrocarbons, to prove oil in the
Etive Formation, to define and refine the geological model for the Alpha
structure, to obtain core from the Brent Group, and to do a water injection
test in the oil zone. The well was planned to be drilled 50 m into the Drake
Formation to a total depth of 2764+/- 50 m. Operations and results Well 30/6-12 was spudded with the semi-submersible
installation Treasure Seeker on 20 February 1983. Drilling operations went
without significant problems down to 615 m. The 20" casing was set with
shoe at 600 m. During the subsequent landing of the BOP on the well head, the
ball joint parted, and the BOP fell down on the wellhead. The wellhead was so
badly damaged that the well had to be abandoned: Final TD of the well thus
became 615 m in Pliocene sediments; prospective depth was not reached. Top Pliocene was encountered at 350 m. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 9 March 1983 as a junk well. Replacement well 30/6-13 was spudded two days later on a
location ca 40 m to the south-west of 30/6-12 Testing No drill stem test was performed. General Well 34/10-17 was the first well drilled
on the Beta structure in the SE segment of block 34/10, south-west of the
Alpha-structure, which contained the Gullfaks Sør Field. The primary objective
of the well was to evaluate possible hydrocarbon accumulations in the Middle
Jurassic Brent sandstones. The secondary objectives were the Early Jurassic
Dunlin and Statfjord sandstones. Operations and results Wildcat well 34/10-17 was spudded with
the semi-submersible installation Deepsea Bergen on 22 February 1983 and
drilled to TD at 3466 m in the Early Jurassic Statfjord Formation. The well was
drilled down to 2687 m without special drilling problems. At 2687 m a heavy
flow was observed after a drilling break. The well was shut in, and due to a
plugged cement hose and kill line failsafe valve, about 200 hours were used to
circulate out the influx, stabilize, clean up and condition the hole. Further technical
failure and tight hole caused extensive time logging the 6" section, and
the logging programme was reduced. The well was drilled with Seawater/gel spud
mud down to 668 m and with seawater/gel/Lignosulphonate mud from 668 m to TD. The Brent Group was encountered at 2685 m
with hydrocarbon bearing sandstones in the Tarbert and Ness Formations. FMT
pressures indicated a gas/oil contact at ca 2862 m, and an oil/water contact at
ca 2914 m in the lower part of the Ness Formation. The logs indicated a total oil
and gas net pay of 122.5 m with average porosity 22.5% and average water
saturation 27%. Also the underlying water bearing Etive and Rannoch Formations of
the Brent Group had good reservoir quality sandstones. The Dunlin and Statfjord
sandstones were water bearing. Shows were recorded on cores down to 2947.5 m in
the Ranno General Well 31/2-11 was drilled as an appraisal
well in the Troll West oil province in the Northern North Sea. The main
objectives were to appraise the reservoir quality and the extension of the 28-m
oil column in the southern part of the 31/2-7 accumulation in the Viking Group
reservoir sequence. The well would assist in the mapping of the permeability
distribution in the oil province, provide an additional data point for the
correlation and mapping of the depositional units, and obtain additional oil
production test data for input to the field development. Operations and results Well 31/2-11 was spudded with the semi-submersible
installation Borgny Dolphin on 17 March 1983 and drilled to TD at 1744 m in the
Middle Jurassic Fensfjord Formation. No major problems occurred during
drilling. The well was drilled with Seawater and gel down to 810 m, with
KCl/polymer mud from 810 m to 1535 m, and with CaCl2/CaCO3/polymer mud from
1535 m to TD. Top Jurassic, Sognefjord Formation, was
encountered at 1558 m. The reservoir sands were found to be hydrocarbon bearing
with GOC at 1566 m (1541 m sub-sea) and OWC (50% saturation) at 1593 m (1567 m sub-sea),
in-line with the regional contacts in this area of the Troll West Oil Province.
Below OWC residual oil was interpreted down to some 1640 m. A total of eight cores were cut. To
enable investigation of the shallow sediments, 2 cores were cut in the interval
380 m to 399 m and one from 475 to 476 m. Five cores were cut in the Late
Jurassic reservoir sands from 1555 to 1629 m using fibre glass sleeve
techniques to achieve better recovery in the poorly consolidated sands. Attempts
to obtain RFT fluid samples were unsuccessful due to plugging of the tool with
chalk particles from the mud. The well was permanently abandoned on 25 May 1983 as an oil and gas appraisal. Testing Two DST's were performed, one in the
water zone and one in the oil zone. DST 1 General Well 30/6-13 is a replacement for the
30/6-12 well, which was terminated in Pliocene sediments due to technical
problems. The appraisal well 30/6-13 was drilled in a down flank position on
the Alpha block east of the 30/6-1 Oseberg Discovery well, which tested gas in
the Middle Jurassic Brent Group. The main objectives of the well were to
confirm the reserves of hydrocarbons, to prove oil in the Etive Formation, to
define and refine the geological model for the Alpha structure, to obtain core
from the Brent Group, and to do a water injection test in the oil zone. The
well was planned to be drilled 50 m into the Drake Formation to a total depth
of 2764+/- 50 m. Operations and results Well 30/6-13 was spudded with the semi-submersible
installation Treasure Seeker on a location ca 40 m to the south-east of well
30/6-12, on 11 March 1983. It was drilled to TD at 2775 m in the Early Jurassic
Drake Formation. No major problems occurred during drilling. The well was
drilled with spud mud down to 613 m and with a KCl/polymer mud from 613 m to TD.
A pill of Imco-spot/Pipelax 140 bbl pill with 50 bbl diesel was spotted from
1410 m to 1525 m to free the 13 3/8" casing, which was stuck. The casing
got free and was cemented with shoe at 1705 m. The well encountered hydrocarbons from
2571 to 2671 m in the Middle Jurassic Brent Group sandstones. No other
hydrocarbon bearing reservoirs were encountered. Oil shows reported from
limestone stringers in the interval 2120 - 2325 m in the Paleocene and Late
Cretaceous were considered uninteresting. A total of nine cores were cut
continuously from the Ness Formation to the Dunlin Group shales. One successful
segregated RFT fluid sample was obtained at 2661.5 m (3 l oil and 0.57 Sm3 gas).
The well was permanently abandoned on 14 May 1983 as an oil/gas appraisal well. Testing Three DST's were performed in the Brent
Group. DST 1 was a co General Well 7120/12-3 is located in the Hammerfest Basin, south of the Snøhvit area. The primary objective was to test a sandstone
reservoir of Middle to Early Jurassic age on a structure (Alke North) separate
from the Alke Structure tested in well 7120/12-1 and 7120/12-2. A secondary
objective was to test Middle Triassic sandstones, providing the Jurassic
reservoir proved a gas column greater than 60 m. The well was planned to be
drilled to 2498 + 30 m or to 3312 +100 m if the Jurassic test was positive. Operations and results Wildcat well 7120/12-3 was spudded with
the semi-submersible installation on 16 March 1983 and drilled to TD at 2523 m
in the Late Triassic Fruholmen Formation. Swelling shales and some tight hole
problems occurred in the 17 1/2" section; otherwise no significant
problems were encountered during drilling. The well was drilled using seawater
/ bentonite / hi-vis pills down to 605 m and with a gypsum / polymer mud from
605 m to TD. The Middle to Early Jurassic sandstone
reservoir was found gas bearing from 2157.5 to 2182.5 m (upper part of Stø
Formation) where the gas/water contact was established. The reservoir consisted
of very fine to fine, relatively homogeneous and clean sandstones made up of
clear quartz with traces of mica, glauconite and carbonaceous material. From
wire line logs the net pay was calculated to be 24 m, with an average porosity
of 17 % and an average water saturation of 17 %. Traces of very weak shows were
described from cuttings and sidewall cores between 1945 m to 2148.5 m in
shales of the Late Jurassic Hekkingen and Fuglen Formation, reflecting the
high organic content of these shales. Direct shows were only seen in the lower
part of the gas-bearing reservoir from 2170 m to 2182.5 m. They appeared on
sandstones as traces of dull yellow fluorescence with weak slow streaming dull
yellow to white crush cut, no stain or residue were detected. Very weak shows
were detected in shale General The purpose of appraisal well 7120/8-3
was to test the extension of the Askeladden North structure in the northeast
direction. The primary target was sandstones of Early to Middle Jurassic age. Operations and results The well was spudded with the
semi-submersible rig West Vanguard on 7 April 1983 and drilled to TD at 2335 in
Early Jurassic rocks of the Nordmela Formation. Two cores were cut in the Middle to
Lower Jurassic sequence. No major problems occurred during drilling. The well was
drilled water based with spud mud down to 671 m and with gypsum/polymer mud
from 671 m to TD. Shows were recorded on cores and cuttings
over the interval 2192 m to 2286 m. The Jurassic reservoir interval was found
to be below the gas/water contact known from well 7120/8-1, and thus water
bearing. Two cores were cut in the interval 2198 m to 2234.8 m. No fluid
samples were taken. The well was permanently abandoned on 24
May 1983 as a dry well. Testing No drill stem test was performed General Well 30/3-3 was drilled on the Lomre
Terrace between the Veslefrikk and Brage oil fields. The primary objective was
sandstone of the Middle Jurassic Brent Group, the secondary objective was
sandstone of the Early Jurassic Dunlin Group. Operations and results Wildcat well 30/3-3 was spudded with the
semi-submersible installation Ross Isle on 2 April 1983 and drilled to TD at 3419
m in the Early Jurassic Statfjord Formation. No significant problem was
encountered in the operations. The well was drilled with spud mud down to 969
m, with gypsum/lignosulphonate/CMC from 969 m to 2861 m, and
gel/lignosulphonate/CMC from 2861 m to TD. The well was dry. Oil shows were described
on sandstone cuttings from 3035 - 3037 m in the uppermost Etive Formation and
from 3185 m to TD. Sandstone side wall cores from the same interval had no
shows, and geochemical extracts proved only immature hydrocarbons from in-situ
shales. One core was cut in the Ness Formation
from 2979 m to 2992.5 m. No wire line fluid samples were taken. The well was permanently abandoned on 30
May 1983 as a dry well. Testing No drill stem test was performed. General The wildcat 30/9-2
was planned as the first well on the Gamma structure in block 30/9. Well 30/6-9
had previously penetrated the structure but this well failed to encounter the
oil/water contact. The primary objectives of 30/9-2 were to verify the reserve
estimate for the main part of the gamma structure and penetrate the oil/water
contact in the lower part of the Brent Group. Additional objectives were to
obtain core material from the oil zone in the Etive Formation and perform a
water injection test in this, obtain information on the quality of the
reservoir in the water zone and stratigraphical information on the southern
part of the Gamma structure.& The well
was temporarily abandoned for about one year and then re-entered for an
extended test. Operations and results Wildcat well 30/9-2
was spudded with the semi-submersible installation "Nortrym" on 1
April 1983 and drilled to a total depth of 2830 m in the Early Jurassic Dunlin
Group. The well was drilled using water-based mud down to the 12 1/4" hole
at 1715 m. The 12 1/4" hole was drilled to TD using oil based mud
("ENVIROMUL" and "IL 2832 oil" as oil base). While running
the 13 3/8" casing, this got stuck at 1334 m. The casing was worked free
using diesel in the mud and the casing was set at 1680 m. After drilling the 12
1/4" hole to 2203 m the drill pipe got stuck with the bit at 2170 m.
Several unsuccessful attempts were made to free the pipe. The drill pipe was
then backed off and the well was cemented back and sidetracked from 1482.5 m. The Brent Group
sandstones (2578-2767 m) RKB were hydrocarbon bearing down to 2737m where an
oil/water contact was encountered within the Etive Formation sandstones
(2698-2767m).& No additional hydrocarbon
bearing reservoirs were encountered by this well. Poor hydrocarbon shows
reported from Upper Cretaceous limestones were considered uninteresting. The
Ness Formation (2578-2698 m) consisted of General Well 6610/7-1 is located in the Helgeland
Basin outside Mid Norway and was drilled on a tilted fault block in the
southeastern corner of the block. The purpose of this wildcat well was
primarily to gather information about the hydrocarbon potential and
stratigraphy of the Helgeland Basin. The main targets were sandstones of Middle
to Lower Jurassic age. The well is Reference Well for the Ror
Formation. Operations and results Wildcat well 6610/7-1 was spudded with
the semi-submersible installation Nordraug on 18 April 1983 and drilled to TD
at 3333 m in the Late Triassic sediments Red Beds. Operations were interrupted
by a 10.5 days seamen's strike. No serious technical problems occurred during
drilling. The well was drilled to 815 m using spud mud. From 815 m to 2115 m
the well was drilled with gypsum/lignosulphonate mud, and from 2115 m to TD
with gel/lignosulphonate/lignite mud. The well was water bearing but
hydrocarbon shows were observed on cores and cuttings in Early Jurassic
sandstone beds from 2656 m to 2715 m. The Spekk Formation from 2271 m to 2315 m
is a good to rich source rock with around 9 % TOC and potential for gas and
oil. It is more gas-prone in the lower part. It has reached early oil window
maturity in well position. The Åre Formation consists mainly of low-TOC sand
with abundant seams of coals, carbargillites and organic-rich shales. The
coals/carbargillites have TOC contents ranging 37 - 59 % and are quite
liptinitic, containing kerogen type II/III-III with good potential for oil and
gas generation locally and a rich overall potential for gas. Four cores were cut, one from the Early
Cretaceous sequence and three from the Early Jurassic sands. A segregated
sample was taken at 2748 m. It contained mud filtrate. The well was permanently abandoned on 19
June 1983 as a dry hole with oil shows in Early Jurassic sandstone. Testing No drill stem test General Exploration well 7117/9-2 is located on
the Senja Ridge west of the Tromsø Basin. The primary objective of wildcat
7117/9-2 was to test sandstone or limestone reservoirs of Early Cretaceous age
in a well-defined offset bounded structure within the Senja Ridge (the Lom
structure). An alternative model suggested that the primary objective was
sandstones of Middle Jurassic age and the secondary objectives were sandstone
reservoirs of Triassic age or older. The well was planned to be drilled to a
total depth of 5000 m and serve as the deep commitment well on the block. Operations and results 7117/9-2 was spudded with the
semi-submersible installation Treasure Scout on 7 May 1983 and drilled to a
total depth of 5000 m in Early Cretaceous (?Aptian) clay stone. Nineteen rig
days were lost due to strike, otherwise no major problems occurred during
drilling of this well. The well was drilled with seawater and hi-vis pills down
to 358 m. with seawater and bentonite from 358 m to 915 m, and with gypsum /
polymer from 915 m to 2500 m. From 2500 m the mud was dispersed to a
lignosulphonate mud, which was used for the remaining well down to TD. Pleistocene deposits were encountered
down to 400 m and underlain by a thick sequence of Pliocene clays down to 1092
m. Paleocene rocks continued down to 1345 m followed by a thin sequence of
Campanian (1380 m to1396 m) and Late Albian to Early Cenomanian (1400? - 1410)
deposits. The lowermost strata penetrated by the well consisted of a thick,
poorly defined sequence of claystones. The upper sequence from 1625 m to 3440 m
is of Albian to Aptian age. In the lower section, few identifiable fossils were
recorded and preservation was poor. The Lom structure was penetrated in a down
flank position at approximately 3375 m. The structure proved to consist of
Early Cretaceous silty claystones of probable Aptian age and bounded by
fractured dolomites. No rocks with reservoir properties were encountered in General Well 31/2-12 was drilled as an appraisal well in the Troll
West oil province in the Northern North Sea. The main
objectives were to evaluate various techniques for gas production wells in the
Troll field, to establish the reservoir quality in the central part of the
Troll field gas accumulation, and to provide additional data point for the
correlation and mapping of the depositional units. Operations and results Well 31/2-12 was
spudded with the semi-submersible installation Borgny Dolphin on 26 May 1983 and drilled to TD at 1615 m in the Middle Jurassic Fensfjord Formation. On 4
June, after running the BOP-stack, operations were interrupted by a labour
dispute. After the strike ended on 17 June problems with the BOP lead to a further
4 days delay before normal drilling operations were resumed. Some instability
problems and well kicks were encountered while drilling and testing in the
reservoir. The well was drilled with Seawater and gel down to 807 m, with
KCl/polymer mud from 807 m to 1338 m, and with CaCl2/CaCO3/polymer mud from
1338 m to TD. Top reservoir in well 31/2-12 was
encountered at 1365 m. The formations were interpreted to be gas bearing all
through the Sognefjord Formation, the Heather Formation (1487 - 1541 m), and down
to a clear GOC at 1570.5 m in the Fensfjord Formation. The upper part of the Sognefjord
Formation consisted of generally clean sandstones. Below 1455 m the sands were
micaceous and silty. Tight calcareous streaks occurred over the whole section.
Oil was interpreted from 1570.5 m down to 1581.0 m, where an abrupt drop in
resistivity was interpreted as the oil/water contact. The contact was somewhat
obscured however by a change in lithology from clean, but rather tight,
sandstone to micaceous sandstone. No movable oil was calculated below this
depth, but shows (fluorescence and cut) was observed on sidewall cores down to
1608 m. Ten cores were cut in the Late Jurassic Sognefjord
reservo General Wildcat well 6609/11-1 was drilled on the
Northwestern side of the Helgeland Basin outside Mid Norway. The primary
objective was to test sandstone reservoirs of Middle to Early Jurassic age in a
structurally high position on a narrow SW-NE trending horst block. The
secondary objective was to test sandstone reservoirs of Early Jurassic to Upper
Triassic age. The well was planned to be drilled to 3200 m, 200 m into the
Triassic. Operations and results Wildcat well 6609/11-1 was spudded with
the semi-submersible installation Treasure Seeker on 19 May 1983 and drilled to
TD at 3068 m in Late Triassic sediments of the Åre Formation. No major
technical problems occurred during drilling. Operations were interrupted for 11
and a half days due to a crew strike. The well was drilled with seawater and
hi-vis pills to 915 m and with gypsum/polymer mud from 915 m to TD. The well encountered good quality
sandstone reservoirs of Early Jurassic and Late Triassic age. These reservoirs
were water bearing with minor amounts of residual hydrocarbons indicated on the
logs. The uppermost part of the sandstone interval, 2546 - 2570 m had the
highest reservoir quality encountered in the well. Porosities ranged from
15-30% (20.6% average in net sand) with a net/gross sand ratio of 0.85 and an
average SW of 90%. The unit ranged from Sinemurian to Pliensbachian in age and
consisted of massive to thinly bedded, very fine to fine grained sandstones
with interbeds and stringers of shale, siltstone and limestone. Below 2570 m
the sandstone units tended generally coarser grained and exhibited fining
upward sequences with reduced porosity and net/gross ratio. The only recorded
oil show in the well was on core no 1 at 2559.7 m to 2560.9 m. No significant
mud gas levels were recorded. The Late Jurassic shales and the Early Jurassic
coals and carbonaceous shales are rich source rocks for oil and gas. However,
the Late Jurassic shales are immature in the well General Well 6407/2-2 is located east on the
Halten Terrace off shore Mid Norway. The well tested the southern (Gamma) fault
compartment of a horst with true vertical closure below the base Cretaceous
level. The gas/condensate discovery well 6507/11-1 was located on the northern
(Alpha) compartment of the same structure. The primary target of the well was
the middle Jurassic sandstone; secondary target was Early Jurassic sandstone. The well is Reference Well for the Melke
Formation. Operations and results Wildcat well 6407/2-2 was spudded with
the semi-submersible installation Treasure Saga on 17 May 1983 and drilled to
TD at 3351 m, 71 m into the Triassic Grey Beds. After drilling the 26"
hole the well was observed flowing and the mud weight was corrected. No other
major problems occurred during drilling. After having drilled out of 13
3/8" casing shoe a cement plug was set from 1960 m - 1995 m, and one from
340 m - 400 m, due to temporarily plugging and abandonment of the well caused
by strike The strike was efficient (no drilling progress was obtained) for 13
days, from June 6th to June 19th. The well was drilled with spud mud down to
865 m, with gypsum/polymer mud from 865 m to 1995 m, and with lignosulphonate
mud from 1995 m to TD. The well proved mainly claystones down to
the Middle Jurassic Sandstone. The Cainozoic with a total thickness of 1809 m
overlies the Late Cretaceous where the topmost Maastrichtian is missing. Two
hundred and forty meter of Late Cretaceous and 81.5 m of Early Cretaceous is
preserved, separated by an unconformity ranging in age from Middle Santonian to
Albian. High gas readings were experienced in the upper part of the Cretaceous
together with heavier hydrocarbons detected for the first time in the well. A
study of wire line logs, sidewalls cores and hole response indicate that the
gas was overpressured, and trapped in a non-reservoir lithology. Base
Cretaceous unconformity was en General The primary objective of wildcat
7119/12-3 was to test possible hydrocarbon accumulations in sandstones of
Middle to Lower Jurassic age. Gas and condensate were discovered in the
sandstone sequences. Planned TD was 3765 m. Operations and results Exploration well 7119/12-3 was spudded
with the semi-submersible installation Dyvi Delta on 20 may 1982 and drilled to
TD at 3314 m in the Early Jurassic Nordmela Formation. A total of 121 days was
spent on this well including testing and a 9.5 days seamen's strike. The time
estimate was 106 days. No major problems occurred due to drilling. The well was
drilled using spud mud down to 303 m, with gel/seawater from 303 m to 716 m,
with gypsum/polymer from 716 m to 1618 m, and with gel/lignosulphonate from
1618 m to TD. Hydrocarbon accumulations were discovered
in sandstone sequences between 3144 - 3285 m in the Stø Formation. From log
evaluation the interval contained 118 m net sand. The gas/water contact at 3285
m is based on the log evaluation. Due to very tight and hard formation only two
RFT pressure points were obtained out of 16 attempts (seal failures). Organic
geochemical analyses found only poor source rock potential in the well. Shales
in the Late Jurassic Hekkingen Formation from 3026 m to 3107 m had high TOC
levels in the range 3% to 9%. However, with Hydrogen Indexes only in the range
30 - 40 mg HC/g TOC in non-caved, high-TOC samples, these shales are gas prone,
and can not produce any significant quantities of liquid hydrocarbons. The well
is immature down to ca 2300 m and reaches oil window maturity at ca 3000 m.
Three cores were cut in the sandstones of the Middle to Early Jurassic Stø
Formation. The two first were cut in the interval 3145 m to 3154.85 m with 100
% recovery. The third was cut from 3250 m to 3267 m with 97 % recovery. One RFT
segregated sample was taken at 3187 m. The 2 3/4 -gallon chamber was bled off
on the rig. It had an opening pressure of 38.9 ba General Well 7120/7-2 is located in the Snøhvit
Field area. The primary of the well was to test possible hydrocarbon
accumulations in sandstones of Middle to Early Jurassic age. Operations and results Wildcat well 7120/7-2 was spudded with
the semi-submersible rig West Vanguard on 26 May 1983 and drilled to TD at 2523
m, 5 meters into Late Triassic rocks. Due to boulders at the spud location the
rig was moved 11 m north and respudded. A sand body with shallow gas was
encountered at 378 m to 382.5 m and it was decided to set the 20" casing
shoe above this sand. After setting this casing the rig was shut down due to
strike from 3 June at 2400 hrs to 18 June at 1125 hrs. The well was drilled
using gel mud down to 815 m, with gypsum/polymer mud from 815 m to 1515, and
dispersed to a lignosulphonate (Unical) mud from 1515 m to TD. Hydrocarbon accumulations were discovered
in the Middle Jurassic Stø Formation sandstone sequence from 2149.5 m down to a
gas/water contact at 2228 m. Shows were recorded below 1809 m in the Cretaceous
Kolje Formation. Organic geochemical analyses showed that TOC increases down
through the Cretaceous, but generally the Cretaceous mudstones were regarded as
immature, poor source rocks with a primary potential for gas. Entering into the
silty shales and mudstones of the Late Jurassic Hekkingen Formation at 2107 m
TOC increases abruptly above 3%. TOC continues to increase to 9 % at the base
of the Hekkingen Formation. These shales are potentially very good source rocks
for gas and condensate above ca 2120 metres and rich sources for light oil and
gas below this depth. Maturity evaluation was difficult due to reworked
material and cavings, but most likely the well is immature all through,
possibly marginally mature below ca 2000 m. Five cores were cut in the
sandstones from 2168 m to 2244 m. Four RFT samples were taken. Sample 1 was
taken at 2150 m (gas, mud filtrate and film of condensate), sample 2 at 2 General Wildcat well 6609/7-1 is located in the
Nordland I area outside mid Norway. The objective was to test anticipated Late
Paleozoic sandstones within the Nordland Ridge. Operations and results Wildcat well 6609/7-1 was spudded with
the semi-submersible installation Nordraug on 21 June 1983 and drilled to TD at
1969 m in Pre-Devonian Basement. Mud problems occurred several times during
drilling, well flowing and lost circulations occurred from 1500 m to TD. The
well was drilled using Seawater/gel down to 1025 m and with
Lignosulphonate/Drispac mud from 1025 m to TD. A thin Eocene sand section was penetrated
at 1460 m at Top Hordaland Group. A 2.7% mud gas peak (methane) was recorded in
this sand. At 1820 m Late Cretaceous sediments of the Lange Formation
(Cenomanian age) was encountered. Below this section, at 1876 m, an undefined
section consisting of dolomite and thin sandstone beds was encountered. At this
point a 19.8 % mud gas peak was recorded. Metamorphic basement was encountered
at 1912 m. Paleozoic sands were absent. No oil shows were recorded in the well.
Organic geochemical analyses of cuttings indicated traces of migrated
hydrocarbons in the Cretaceous section from 1800 m to 1870 m. Only very poor
gas prone source sections were identified in the well, which was found immature
for any petroleum generation all through. Two cores were cut in the metamorphic
basement. No fluid sample was taken. No sidewall cores were taken. The well was permanently abandoned on 3
August 1983 as a dry hole. Testing No drill stem test was performed. General The wildcat 31/3-1 was drilled ca 17 km
NNE of well 13/6-1 in the Troll East area. The two wells were drilled at the
same time and together they established the existence of a Troll East gas
field. The objective of 31/3-1 was to test possible gas and oil accumulations
in sandstones of Late to Middle Jurassic age. Secondary objective was to test
possible hydrocarbon accumulations in Middle to Early Jurassic and Late
Triassic. Operations and results Wildcat well 31/3-1 was spudded with the
semi-submersible installation Deepsea Bergen on 17 July 1983 and drilled to TD
at 2374 m in the Triassic Hegre Group. No significant problems occurred during
drilling except some technical problems when running the BOP for the 26"
section. The well was drilled with spud mud down to 865 m, with KCl/polymer
from 865 m to 1300 m, with gel/lignosulphonate from 1300 m to 1833 m, and with
lignite/lignosulphonate from 1833 m to TD. Top reservoir (Sognefjord Formation) was
encountered at 1351.5 m. The Sognefjord, Heather, and Fensfjord Formations were
found to hold a gas column of ca 220 m gas down to an approximate 4 m oil
column. The OWC was at ca 1576m.Geochemical analyses of the reservoir gas
show clear signs of biodegradation. Neither the Early Jurassic nor the Late
Triassic contained hydrocarbons. Twelve cores were cut continuously from
1351 m to 1610 m in the Late and Middle Jurassic reservoir sequences. FMT fluid
samples were taken at 1374.2 m, 1570 m, 1574.2 m, and 1579.2 m. The well was permanently abandoned on 13
October 1983 as a gas appraisal well. Testing Two DST's were performed, and gas was
produced from both. DST 1 was performed from the interval 1519 m to 1529 m and
produced 842400 Sm3 gas /day on a 22 mm choke. The gas had a gravity of 0.635
(air = 1). DST2 was performed from the interval 1373 m to 1383 m and produced
733500 Sm3 gas /day on a 19 mm choke. The gas had a gravit General Exploration well 7119/7-1 is located in
the Tromsø Basin, ca 30 km west of the Snøhvit Field area. The primary well
objective was to test a sandstone and/or limestone reservoir of Late Cretaceous
age. The secondary objective of the well was to test a westward thinning wedge
interpreted as a sandstone reservoir of Late Cretaceous age. A further
objective of the well was to penetrate the Cenomanian unconformity with
possible associated basal sandstones. Planned TD was 4100 m or 100 m below the
Cenomanian unconformity. Operations and results Well 7119/7-1 was spudded with the
semi-submersible installation Treasure Seeker on 12 July 1983 and was drilled
to a total depth of 3167 m in salt. No major problems occurred during drilling.
The well was drilled with seawater and bentonite down to 622 m, and with
KCl/polymer mud from 622 m to 2518 m. From 2518 m to TD the mud was converted
to a dispersed gel system allowing natural depletion of the KCL. No rocks with reservoir qualities were
penetrated by this well. The prognosed Campanian sandstones/limestones were
developed as claystones, sometimes silty with occasional limestone stringers.
Insignificant traces of sand were noted in that interval. Top Campanian was
found between 1375 m and 1377 m based on biostratigraphy. The base Late
Cretaceous wedge interpreted as sandstone was found poorly developed as
siltstones and silty claystones without reservoir characteristics. The base
Late Cretaceous was encountered between 2796.5 m and 2810.5 m based on
biostratigraphy. The Cenomanian unconformity was penetrated at 2529 m without
any associated sandstones. The well encountered evaporites of possible Permian
age at 3094.5 m. No shows were recorded in the well. No conventional cores were
cut and no fluid samples taken The well was permanently abandoned on 11
September 1983 as a dry hole. Testing No drill stem test was performed General The primary objectives of the wildcat
31/6-1 was to test Late and Middle Jurassic sandstones on the main culmination
of the Troll east structure in the western part of block 31/6. Secondary
objectives were Middle to Early Jurassic and Triassic sandstones and a possible
sandstone reservoir of pre-Triassic age within a set of tilted fault blocks
buried by Triassic strata. The Troll east structure is a large tilted fault
block containing Jurassic and older strata. The closure at Sognefjord Formation level is
delineated by a flatspot covering most of the 31/6 block. The flatspot was
expected to be a gas/fluid contact evident on the seismic and penetrated by
nine wells in the Troll West area to the NNW in block 31/2. Planned TD of the well
was 3800 m into rocks of pre-Triassic (? Devonian age). Operations and results Wildcat well 31/6-1 was spudded with the
semi-submersible installation Nortrym on 15 July 1983 and drilled to TD at 4070
m in pre-Devonian basement rock. Problems with getting logging tools past the
30" casing shoe occurred due to gumbo problems. Further drilling went
forth without major problems. The well was drilled with spud mud down to 425 m,
with seawater / prehydrated gel and hi-vis pills from 425 m to 749 m, and with
KCl/polymer/PHPA mud from 749 m to TD The total net sand in the Viking Group
(1352-1805 m) found to be 424.25 m giving a net/gross ratio of 0.94 m with an
average porosity of 27.5%. The Sognefjord Formation (1352-1488 m), the Heather
Formation Unit B, (1488-1517.5 m) and the upper part of the Fensfjord Formation
were found gas bearing from 1352 to 1571 m where the gas/oil contact was found.
Below this a thin (3 m) oil zone was present with an oil/water contact at
approximately 1574 m. The hydrocarbon-bearing reservoir consisted of very fine
to fine grained sandstones, occasionally medium to coarse. They were generally
friable to loose with a few tight calcite cemented stringers. The General Well 34/10-18 is located in the Tampen
Spur area, south of the Vigdis Field and west-north-west of the Gullfaks Field.
The primary objective was the Brent Group sandstones of Middle Jurassic age. Secondary
objectives were Early Jurassic Cook and Statfjord Formation sandstones. Operations and results Wildcat well 34/10-18 was spudded with
the semi-submersible installation Ross Isle on 17 July 1983. A 12 1/4"
pilot hole was drilled from the 30" casing shoe to 765 m to check for shallow
gas. No shallow gas was seen, but lost circulation occurred in shallow sand lenses
when the pilot was underreamed to 26". A 17 1/2" hole was drilled and
logged to 2024 m. Two joints of 13 3/8" casing were dropped in the hole.
The hole was cemented back to 1882 m and sidetracked from 1900 m and drilled
without significant problems to TD at 3025 m in the Early Jurassic Statfjord
Formation. The well was drilled with spud mud down to 765 m and with
gel/Lignosulphonate mud from 765 m to TD. No live oil was seen in the well, but a
3.5 m unproductive oil-zone was encountered in a, sandy/marly and cemented
limestone at the base of a very thin Cromer Knoll sequence (Mime Formation).
The average porosity was 24.3% and the average water saturation was 53.4%, but
due to tight formation the RFT was not able to obtain any pressure points in
this zone. The permeability range was 0.1 to 1 mD. Only residual hydrocarbons
were encountered in the Brent sandstones. Here, the logs indicated an average water saturation
of 95% and an average porosity of 24.2% in the net sand. The RFT plot suggested a water gradient of
1.00 g/ General Wildcat well 6609/10-1 is located on the
Trøndelag Platform outside Mid Norway. The objective was to test the entire
stratigraphic column between the seabed and into the Late Triassic. The primary
target of the well was Jurassic sandstones on the Nordland Ridge, secondary to
test possible sand development in the Paleocene. Operations and results Wildcat well 6609/10-1 was spudded with
the semi-submersible installation Treasure Saga on 2 August 1983 and drilled to
TD at 2167 m in the Late Triassic Red Beds. The well was drilled with spud mud
down to 413 m, adding some lignosulphonate (Unical) from 413 m to 1265 m, and
with a full lignosulphonate mud from 1265 m to TD. Apart from the glaciomarine sands and
silts of Pleistocene age at the top, the well proved mainly clay and clay stone
down to the Lower Jurassic Sandstone. In the Tertiary two unconformities were
seen; a Late Miocene unconformity at 1312 m and a major unconformity at 1367 m,
ranging in age from Early Eocene to Middle Miocene. The Tertiary unconformably
overlies the Late Cretaceous, which in the well is of Campanian-Early
Maastrichtian age. This section rests unconformably on Middle Jurassic (Late
Toarcian-Early Bajocian) claystones at 1605 m. Beneath a Middle/Early Jurassic
unconformity at 1642 m the well penetrated Tilje Formation Sandstone (143 m
thick), the Åre Formation 1733 - 1993 m) and the Triassic Grey and Red Beds.
Both the Tilje and Åre Formation sandstones had significant shale content. The
drilling proved the pressure to be hydrostatic throughout the entire well. The
formation pressure is approximately 170 bar at 1700 m. The sand intervals
apparently belong to the same pressure regime. All sands proved water bearing.
No shows were recorded in any section of the well. As the Late Jurassic was not present in
the well location the only potential source rock found in the well was the
Early Jurassic - Late Triassic "Coal Unit" (År General Wildcat well 2/5-7 is located ca 9 km
North of the Tor Field in the southern Norwegian North Sea. The primary
objective was to test Late Jurassic and Middle Jurassic/Triassic sandstones on
top of a gentle salt-induced dome structure. Secondary objectives were Late
Cretaceous chalk and Paleocene sandstones. Operations and results Well was spudded with the jack-up
installation Neddrill Trigon on 11 August 1983 and drilled to TD at 4531 m in
the Triassic Skagerrak Formation. During drilling of the 17 1/2" hole
several tight spots and problems with cavings were experienced. While tripping
out of the hole at 3956 m, the drill string parted and 193 m of the bottom hole
assembly was left in the hole. The fish was recovered after some problems due
to tight hole conditions. When pressure testing the 9 5/8" casing the
float collar sheared out causing the casing to jump. After re-landing, the
casing was found to have dropped a couple of inches. Repair of the casing took
35 days extra rig time. A drilling break occurred at 4161 m where a 1.5 m thick
marl was encountered. Maximum gas reading at bottoms-up was 30 %, and slight
oil shows were observed in the mud. A kick was taken at 4519 m with an influx
of 2.5 m3 water. The well was drilled with seawater and gel down to 862 m, with
KCl/polymer mud from 862 m to 2254 m, with lignosulphonate mud from 2254 m to
3529 m, and with gel/lignosulphonate mud from 3529 m to TD. Only traces of sandstone were encountered
in the Late Paleocene, and there were no indications of hydrocarbons. Porous
chalk was encountered in the Ekofisk Formation at 3204 m and in the Tor
Formation at 3289 m. Both formations tested oil, but the oil flow in the
Ekofisk test was interpreted to originate from the Tor Formation (see below).
The matrix permeability in these zones is low, but the results from the
production tests indicated that fracture permeability is significant. No
hydrocarbons were found in the L General Wildcat well 6610/7-2 is located on the
Trøndelag Platform outside Mid Norway. The primary objective of the well was to
test the hydrocarbon potential of Early Jurassic and Late Triassic sandstones.
Secondary objectives were to gather information about the stratigraphy and
hydrocarbon potential down to approximately 4200 m. Operations and results Wildcat well 6610/7-2 was spudded with
the semi-submersible installation West Vanguard on 28 August 1983 and drilled
to TD at 4215 m in the Triassic Grey Beds. Drilling operations were problematic
and took 119 days more than programmed. Excessive reaming of tight spots had to
be done during drilling of the 22" hole section. In all the four first
hole sections a pilot hole was drilled before underreaming. Nineteen kg junk
was recovered from the hole after drilling out of the 13 3/8" casing shoe.
Several problems with stuck pipe occurred below 3000 m. At 3526 m the pipe was
stuck and was backed off at 3315 m. A cement plug was set from 3292 to 3148 m
and the hole was sidetracked from 3212 m. Severe problems with tight hole, was
experienced down to 3361 m. The well was drilled with seawater and spud mud
down to 701 m, with gypsum/lignosulphonate mud from 701 m to 2160 m. Due to
expected salt beds below 2500 m the well was drilled with oil based mud from
2160 m to TD. The oil base used was a Norol product, "hvitolje", a
low-aromatic mineral oil C13 - C20 distillate. The well encountered several sandstone
bodies, the first interpreted as the Egga Informal Unit in Paleocene. Earliest
Cretaceous - Late Jurassic were not present in the well. At 1487 m the Early
Jurassic Båt Group was encountered with massive and porous sandstone sequence.
The Triassic interval 3473 - 4218 m also had some clean sandstone, especially
in the upper part. Electrical logs and RFT pressure tests, however, proved all
potential reservoirs to be water bearing. Organic geochemical analyses showed General Well 31/5-1 was drilled as an appraisal well
at the southern part of the Troll West Field. The purpose of the well was to
test the reservoir qualities, the oil/gas columns, and the hydrocarbon/water
contact in the area. Operations and results Appraisal well 31/5-1 was spudded with
the semi-submersible installation Treasure Saga on 5 September 1983. The well
was drilled with seawater and hi-vis pills all through. After drilling to 860 m
and setting the 20" casing, the BOP was run on riser. When the BOP was 12
m above the well head the drill pipe elevator broke, and the BOP dropped down
and damaged the well head. The BOP and some riser joints were recovered before
the rig was towed to Bergen where the BOP was changed. No cores were cut and no wire line fluid
samples were taken. The well was abandoned on 30 September
1983 as a junk well. After repairs Treasure Saga returned to the location on 5
October 1983 to spud replacement well 31/5-2. Testing No drill stem test was performed. General Well 7/8-3 is located in the North Sea, north of the Mime field on the margin of the Cod Terrace. The primary objective
of 7/8-3 was to explore the hydrocarbon potential of the Late Jurassic
sandstones. Secondary objectives were to explore the Cretaceous Chalk and the
Triassic sandstones. Planned TD was at 4275 m in Permian salt. Operations and results Wildcat well 7/8-3 was spudded with the
semi-submersible installation Borgny Dolphin on 12 September 1983 and drilled
to TD at 4320 m in the Late Permian Zechstein Group. While running 13 3/8"
casing this got stuck and had to be pulled out of the hole. The hole was
cleaned and new casing was set without further complications. Otherwise no
significant problems were encountered during drilling. The well was drilled
with spud mud down to 199 m and with KCl polymer mud from 199 m to TD. The Cretaceous Chalk was encountered at a
depth of 3024 m, the Late Jurassic Ula Formation at 3724 m, and the Triassic at
3767 m. The Ula Formation sandstones were hydrocarbon bearing within a 43.5 m
gross sand interval. No oil/water contact was encountered. Oil shows were
recorded in shales and porous sections from 3699 m to 3751 m. Four cores were cut in the interval 3731
m to 3773 m, three in the Upper Jurassic Ula Formation and one into Upper
Triassic sandstones. A RFT fluid sample from the Triassic section at 4049.5 m
recovered only mud filtrate. The well was permanently abandoned on 12
December 1983 as an oil discovery. Testing Two DST's were performed in the Ula
Formation sandstones: DST 1 from interval 3762 m to 3767 m, and DST 2 from
interval 3734.5 m to 3740.5 m. The first produced oil at a slightly declining
rate during the final 5-hours flow period, the average rate being 207 Sm3/day
through a 2" choke. The GOR was 32 Sm3/Sm3, API oil gravity was 29 deg,
and gas gravity was 0.88 (air = 1). The second DST produced 70 Sm3 oil/day
th General Wildcat well 6407/1-3 was drilled in the
Haltenbanken area off shore Mid Norway. It is situated on a separate but
related structure to 6407/1-2, which found gas-condensate in the Middle
Jurassic Garn Formation. The primary target of well 6407/1-3 was Middle
Jurassic sandstones. Secondary target was Early Jurassic sandstones. Other
zones of interest were the Late and Early Cretaceous and the coal unit in the
Early Jurassic. The well is Type Well for the Brygge
Formation and Reference Well for the Hordaland Group, it is Type Well for the
Garn Formation, and it is Reference Well for the Ile and Not Formations. Operations and results Wildcat well 6407/1-3 was spudded with
the semi-submersible installation Dyvi Delta on 17 September 1983 and drilled
to TD at 4469 m in Late Triassic sediments of the Åre Formation. Hole problems
occurred when running back in the hole after a period of bad weather. The hole
had collapsed and had to be reamed back to bottom at 3136 M. A drilling break
occurred at 3746 to 3748 m. All in all, there was a total of 16 days downtime
caused by bad weather. Still, the well was drilled 22 days faster than
prognosed. This was mainly due to fast penetration in the 17 1/2" and
6" hole, an efficient coring operation and favourable weather conditions
compared to well 6407/1-2. The well was drilled with seawater/gel down to 948
m, with lignosulphonate/gypsum from 948 m to 3608 m, and with bentonite gel
from 3608 m to TD. Hydrocarbon bearing Middle Jurassic
sandstones (Garn Formation) were encountered at 3600 m. A gas cap extended to
3687.5 m followed by an oil zone down to 3709 m. At this point the sand grades
rapidly into the underlying silt and clay of the Not Formation at 3709.5 m.
This makes it difficult to conclude on an OWC for the discovery. The Nise
Formation from 2448 m to 2601 m had good gas shows whilst drilling and oil
contamination of drilling mud. Mud log data suggested a possibl General Wildcat well 7/11-8 is located on the Cod
Terrace of the North Sea, between the Mime Field to the South and the 7/8-3
Discovery to the North. The primary objective was to test Late Jurassic
sandstones of the Ula Formation. Secondary objective of the well was to test
continental sandstone reservoirs of Triassic age as seen in some nearby wells.
Rocks of early and middle Jurassic age were thought to be absent at this
location. The well was planned to be drilled to 4550 + 100 m, approximately 730
m into the Triassic to penetrate a strong intra Triassic reflector. Operations and results Well 7/11-8 was spudded with the
semi-submersible installation Treasure Scout on 22 September 1983 and drilled
to TD at 4750 m, almost one km into Triassic sediments. Gumbo problems and
problems with the seal assembly were experienced when running the 13 3/8"
casing. The well was drilled with seawater and pre-hydrated bentonite down to
620 m, with KCl polymer mud from 620 m to 3673 m, and with a bentonite/lignosulphonate/barite/lignite
mud system from 3673 m to TD. The well encountered water bearing
Triassic sandstones directly underlying lower Cretaceous shales. The Ula
Formation was thus missing. No shows or other hydrocarbon indications were seen
in the well. The intra Triassic marker was found at 4605 m in a shaly sequence. One core was cut in the Triassic
sandstones from 3725 to 3743.95 m. The entire core consisted of greyish red to
moderate brown sandstones, with occasional bands of greenish black to greenish
grey sandstones. The RFT tool was run to obtain pressure points in the Triassic
sands. The pressure data indicated a water gradient of 1.09 g/cm3 and no fluid
sample was taken The well was permanently abandoned on 12
December 1983 as a dry well. Testing No drill stem test was performed General Well 29/9-1 is located on the Hild
structure ca 1.5 km west of the UK border on the eastern margin of the East
Shetland Basin in the North Sea. The well was drilled to appraise the 30/7-2
discovery. The main objectives were to test the hydrocarbon prospectivity and
reservoir parameters of the Middle and Early Jurassic sequence. The well was
planned to be drilled 50 m into the Statfjord Formation at a total depth of
4640 +/- 200 m. Operations and results Appraisal well 29/9-1 was spudded with
the semi-submersible installation Treasure Seeker on 23 September 1983 and
drilled to TD at 4703 m in the Early Jurassic Statfjord Formation. During
drilling of the 17 1/2" hole, tight hole problems were experienced. The 9
5/8" casing had to be run twice due to problems with the casing hanger
seal. Due to high temperature and lack of circulation the mud in the 7"
liner gelled up and had to be replaced several times. This caused difficulties
operating the testing tool. The well was drilled with seawater and gel slugs
down to 1057 m and with KCl/polymer mud from 1057 m to TD. Mud retort test
showed 4-5% oil in the mud from top of the 12 1/4" section at 2752 m,
declining to traces at 3732 m. The well encountered oil in the Frigg
Formation in the interval 1782 to 1787 m (OWC), and gas in the middle Jurassic
Brent Group from 4386.5 m to 4421 m (gas down to top Dunlin Group; no
hydrocarbon contact was encountered). The Frigg Formation (1782-1981 m) consisted
of predominantly of fine to coarse grained porous sandstones. The uppermost 2.5
m was tight and calcareous cemented. Net pay was thus 2.5 m with 31% average
porosity and 40% average water saturation, based on logs. No General Well 31/5-2 is a replacement well for well
3/5-1 in the southern part of the Troll West Field. Well 31/5-1 was terminated
at 860 m and junked due to an incident where the BOP and riser was lost. Due to
this, the rig left the location and went to Bergen for repairs. It returned to
the location five days later for drilling 31/5-2. The purpose of the well was to
test the reservoir qualities, the oil/gas columns, and the hydrocarbon/water
contact in the area. Operations and results Appraisal well 31/5-2 was spudded with
the semi-submersible installation Treasure Saga on 5 October 1983 and was
drilled to TD at 2500 m in the Late Triassic Hegre Group. A total of 5 days
were lost on setting the 18 3/4" x 9 5/8" seal-assembly, otherwise no
significant technical problems occurred in the operations. The well was drilled
with seawater and hi-vis pills down to 860 m and with KCl/polymer mud from 860
m to TD. Well 31/5-2 penetrated top reservoir at
1521 m. The interval 1521 - 1569 m was gas bearing with 30% porosity and 15%
water saturation. The interval from 1569 - 1582 m was oil bearing with 27%
porosity and 30% water saturations. These intervals were the only hydrocarbon
bearing intervals in the well. Between 1569 and 1582 m there were good shows in
the cores. They showed brown oil stain, golden-yellow fluorescence and instant
cloudy, milky, white cut. There was strong hydrocarbon odour. A total of six cores were taken in the
interval 1505.0 -1599.9 m, covering the basal 16 m of the Draupne Formation and
the upper 78 m of the Sognefjord Formation. The core recovery was 81%. FMT
segregated fluid samples were taken at 1563 m (gas), 1575 m (oil at 135 bar),
and 1581 (oil at 90 bar). After surveying, logging and sidewall
coring, the well was plugged back to 1902 m and suspended on 11 November 1984.
The well was to be re-entered at a later stage for testing. Testing No drill stem General Well 34/10-19 was drilled to investigate
the southern section of the Gullfaks Phase II area. The primary objective was to
penetrate the Cook sandstone above the oil water contact at 2118 m seen in well
34/10-9, and to improve the understanding of the reserve distribution in this
part of the Gullfaks field. Secondary objective was the Statfjord sandstone. Operations and results Appraisal well 34/10-19 was spudded with
the semi-submersible installation Ross Isle on 5 October 1983 and drilled to TD
at 2218 m in the Triassic Hegre Formation. Shallow gas was encountered in a
sand at 332 to 338 m. A 16" liner was required to stop gas flow between
20" and 30" casings. Several drilling breaks occurred in the 12
1/4" hole and lost circulation occurred in the 8 1/2" hole. The well
was drilled with gel/seawater down to 8978 m, with gel/seawater/hi-vis pills
from 978 m to 1494 m, and with gel/lignosulphonate/lignite mud from 1494 m to
TD. The upper sandstone part of the Cook
formation (unit C3 and C2) was missing missing due to faulting and erosion. The
lower Cook C1 unit was penetrated at 1779 m. This unit consists of dominantly
claystones and it was water bearing. The sandstones of the Statfjord Formation
were water bearing. Trace shows were recorded in the Hordaland Group on
claystones from 960 m to 120 m and on claystone and on limestone from 1340 m to
1470 m. Trace to fair shows on siltstone, claystone and minor sandstones were
recorded intermittently below 1470 m and down to 1861 m. No trace of
hydrocarbons was seen below this depth. Three cores were cut; one in the interval
from 1763 in the Cromer Knoll Group to 1781.3 m in the Cook Formation, and two in General Appraisal well 31/6-2 was drilled on a
location on the south-east periphery on the Troll East gas province. The main
objective was to test the gas and oil accumulations in sandstones of Late to
Middle Jurassic age. The planned TD was about 200 m into rocks of Triassic age
to an estimated total depth of 2400 m RKB. The well is Reference well for the
Hardråde Formation and for the undifferentiated Shetland Group in the Troll
area. Operations and results Well 31/6-2 was spudded with the
semi-submersible installation Deepsea Bergen on 18 October 1983 and drilled to
TD at 2020 m in the Early Jurassic Drake Formation. Because of problems with a
leak in 20" casing and lost circulation problems in a major fault, both 13
3/8" and 9 5/8" casing had to be set high. The well was drilled with
sea water and hi-vis pills down to 412 m, with AQUAGEL/seawater spud mud from
412 m to 801 m, with KCl polymer mud from 801 m to TD. At 984 m Lost
Circulation Material -pills were added to cure lost circulation problems. No reservoir sections were developed
above the Jurassic. The well encountered 113 m of Draupne shale with top at
1322 m, overlying a 25 m thick Heather Formation sequence. The Sognefjord
Formation sandstone reservoir was encountered at 1460 m with a gas column of
approximately 110 m. No oil leg could be detected from electric logs or FMT's.
Oil shows were recorded on sidewall core sandstone in the interval from 1831 m
to 1988 m in the Middle to Early Jurassic. Nine cores were cut from 1435 m to
1619 m in the Heather and Sognefjord Formations. FMT sampling in the Sognefjord
Formation recovered small amounts of gas from 1475 m and 1572 m. A sample from
1577 m gave mud filtrate. The well was suspended on 11 December
1983 as a gas appraisal. Testing No drill stem test was performed. General The primary objective of the wildcat
31/6-3 was to assess possible hydrocarbon accumulations in the sands and
sandstones of the Late Jurassic Sognefjord Formation. The target was prospect
C, a structural trap in the southeastern corner of block 31/6 extending into
the adjacent blocks 31/9, 32/4 and 32/7. The well was located on the apex of
prospect C. The secondary objective of the well was to obtain Sedimentological
data for the Sognefjord Formation sandstones in the well location. The well was
planned to reach total depth at ca 2200 m, approximately 100 m into the
Triassic. Operations and results The well was spudded with the
semi-submersible installation Nortrym on 1 November 1983. Repositioning of the
rig had to be done due to anchoring problems. At 1950 m the drill string was
hung off. Problems when attempting to retrieve the drill string resulted in
pulling of BOP. When running in hole after 7 days, 10 m of fill was found. No
other major problems occurred during drilling and the well reached planned TD
at 2250 m in the Triassic Hegre Group. The well was drilled with seawater and
hi-vis pills down to 618 m and with KCl/Polymer mud from 618 m to TD. The well encountered water-bearing
sandstones in the Late/Middle Jurassic Sognefjord Formation as well as in the
lower lying sandstones. No oil shows were noted on cores, sidewall cores or
cuttings in any section of the well. Gas readings were low or nil throughout
except for a 2.6% methane reading in a shallow sand unit at 414 m. The Sognefjord
Formation sandstones (1511-1647 m) are very fine to fine, occasionally medium
grained, micaceous, occasionally carbonaceous and slightly argillaceous. In
places the sandstones grade into siltstones. They are well to moderately sorted
and have fair visible porosity. The underlying Sognefjord, Fensfjord, and
Krossfjord Formations (1647-1931.5m) are dominated by fine to medium, locally
very fine or coarse grained sandstones which are o General Well 15/9-18 is located between the
Sleipner Øst and Sleipner Vest Fields in the South Viking Graben in the North
Sea. It was designed primarily to test
hydrocarbon accumulations in the Middle Jurassic Hugin Formation. Secondary objectives
were Paleocene sandstones in the Heimdal and Sleipner Formations, and
sandstones of Triassic age. Operations and results Wildcat well 15/9-18 was spudded with the
semi-submersible installation Deepsea Bergen on 16 December 1983 and drilled to
TD at 3622 m in the Triassic Smith Bank Fm. No major problems occurred while
drilling this well, but some tight hole problems were experienced in the 12
1/4" hole section. The well was drilled with seawater gel down to 520 m
and with gypsum/lignosulphonate mud from 520 m to TD. Tertiary sands were penetrated at 866 m
(Utsira Formation), 1254 m, and at 2071 m ("Frigg Fm Equivalent"). The
Draupne Formation was encountered 105 m thick at 3108 m. The Hugin Formation
was encountered at 3237 m. It was found hydrocarbon bearing in a 7.5 m interval
from 3237.5 m and down to a coal layer at 3245.0 m but the hydrocarbons were
immovable. The well did not encounter other hydrocarbon bearing intervals. Shows
were however recorded further down in the Hugin Formation in the interval 3275
m to 3325 m. Four cores were cut, two in the Paleocene
and two in the Middle Jurassic sequence. Segregated FMT fluid samples were
taken in the hydrocarbon bearing interval in the Hugin Formation at 3238.3 m,
3239 m, and 3240 m. All samples were reported to recover mud filtrate only, but
the samples from 3240 m were analysed to contain 0.2 g petroleum hydrocarbons.< General Wildcat well 34/4-5 was drilled on the
Mort Horst in the Northeastern part of the block. The purpose of the well was
to test the Zeta structure for hydrocarbons and to test the stratigraphy below
the Base Cretaceous Unconformity. The well encountered hydrocarbons in the Cook
Formation and in the Statfjord Formation. Operations and results The well was spudded with the
semi-submersible installation Treasure Saga on November 13 1983 and drilled to
TD at 3917 m in Early - Middle Triassic sediments of the Lunde Formation. The
well was drilled with seawater and bentonite down to 533 m, with
bentonite/gypsum mud from 533 m to 1113 m, with gypsum/polymer mud from 1113 m
to 2025 m, with gypsum/lignosulfonate (Unical) mud from 2025 m to 3200 m, and
with lignosulfonate from 3200 m to TD. Due to severe boulder problems in the
26" hole section, the well had to be re-spudded three times before the
20" casing could be run and cemented. The 20" casing had to be worked
and washed down to the planned depth. This action most likely buckled or partly
collapsed the 20" casing. It took approximately 5 days to drill/mill out
the bottom section of the 20" casing. Circulation was lost at 2026 m when
drilling the 17 1/2" hole. Due to the lost circulation, the 13 3/8"
casing had to be set at 2011 m. The 12 1/4" section had to be plugged back
from 3106 m to 3005 m due to severe hole deviation problems. The maximum hole
angle was 8.75°. Re-drilling this hole section and deepening it down to 3200 m
the hole angle varied between 3° and 4°. The 9 5/8" casing was set at 3195
m. The 8 1/2" hole section was drilled down to 3424 m, where the first
core was cut. The core recovered shale, and it was decided to drill ahead. The
hole was drilled down to 3470 m, where a new drill break occurred. While
circulating bottoms up for samples a kick was taken. A total of 43 bbls were
gained before closing in the well General Well 15/6-6 was drilled to appraise the north
eastern flank of Alpha structure on the 15/6-3 Sleipner Vest Discovery in the North Sea. The primary target was a gas bearing Jurassic sandstone known as the Hugin Formation.
It was drilled to provide needed structural control and to establish a
gas/water contact. Operations and results Appraisal well 15/6-6 was spudded with
the semi-submersible installation Glomar Biscay II on 1 April 1982 and drilled
to TD at 3760 m in Late Triassic sediments of the Skagerrak Formation. The
36" hole had to be reamed several times due to ledging. This also occurred
in the top of the 26" section. Forty-six bbl's (7.3 m3) of fluid were lost
to the formation during cementing of the 13 3/8" casing. The mud weight in
this section was 1.68 which is lower than the previous Sleipner wells. This and
the fluid loss can possibly be related to an unconsolidated sand (Skade
Formation) interval from 1185 to 1199 m. Minor hole problems were encountered
in the 12 1/4" section. The drill string was temporarily stuck at 1627 m
after making a connection. The well was drilled with seawater and gel. The well proved sands in the Utsira, Grid,
Heimdal, and Sleipner Formations; all water bearing. The gas bearing Hugin
Formation was encountered at 3563 m and had a gross thickness of 58 m. The
gas/water contact was found at 3607 m, which gives a gross gas interval of 44
m. No oil shows were reported from the target reservoir or other sections in
the well. Three cores were taken in the Middle
Jurassic interval in the 8 1/2" section. Core 1 recovered 18.5 m sandstone
from 3591 m to 3609.5 m. Core 2 recovered 16.0 m sandstone from 3609.5 m to
3622 m. Core 3 recovered 18.9 m Sandstone, shale and coal from 3625.5 m to
3644.5 m. No wire line fluid sample was taken. The well was permanently abandoned on 9 June 1982 as a gas appraisal well. Testing The well w General Well 30/6-6 was drilled on the 30/6 Alpha
structure (Oseberg fault block) in the North Sea, as the fifth well drilled on
this structure. The well was drilled down-dip of 30/6-3 and 30/6-4. The primary
objective of this well was to define the oil-water contact for the structure. This
would be achieved by penetrating the OWC or by extrapolation of fluid gradients
from RFT and DST pressure measurements. Operations and results Appraisal well 30/6-6 was spudded with
the semi-submersible installation Deepsea Saga on 9 January 1982 and drilled to
TD at 3225 m in the Early Jurassic Cook Formation. Drilling operations proceeded
without specific problems down to ca 1300 m. At this depth problems related to excessive
torque and drag on short trips occurred. The mud weight was then reduced from
1.4 to 1.29 after which drilling again proceeded without problems. The well was
drilled with spud mud down to 200 m, with Gel/seawater/spud mud from 200 m to
1793 m, and with gel/lignosulphonate mud from 1793 m to TD. Top Viking Group was penetrated at 2587 m
and consisted of 113 m Draupne Formation shales on top of 120 m Heather
Formation. The Brent Group was encountered at 2820 m. It was water bearing.
Combined RFT-pressures from 30/6-6 and 30/6-4 gave an oil/water contact at 2720
+/- 20 m, which was later confirmed by the build-up pressures from the DST and
the calculated water density under reservoir conditions. No indications of H2S
were seen in this well. No shows are reported from the well. Three cores were taken in the Ness and
Etive formations from 2921 m - 2964 m. RFT water samples were attempted at 2879
m, 2955 m and 2956 m, but were only moderately successful due to poor recovery
and General The 16/7-2 well was drilled on the
western flank of the Utsira High in the North Sea. The primary objective was to
test the presence of a stratigraphic trap in Paleocene sandstones. Secondary
objectives were to test the Mesozoic structure for possible Triassic sands, and
also to test the Zechstein carbonate and Rotliegendes sandstone plays. The well
was the first to be drilled in connection with the 6th. License Round awards. Operations and results Well 16/7-2 was spudded with the
semi-submersible installation Glomar Biscay II on 11 January 1982 and drilled
to TD at 3146 m in Early Permian, Rotliegendes Group sediments. Drilling of the
36" and 26" holes went forth without any specific problems. While
cementing the 20" casing, the cement slurry was overdisplaced. A remedial
squeeze job was necessary. Problems also occurred when logging the 12 1/4"
section due to tight hole. In the 8 1/2" inch section problems with the
BOP choke valve/controls led to close to 9 days lost time, a major reason for
the 38% non-productive time in this well. The well was drilled with seawater
gel down to 171 m, and with lignite/lignosulphonate mud from 171 m to TD. Top Lista Formation was encountered at
2268 m and contained 9.5 m net of gas from 2292 m in thin sandstone intervals,
interbedded with shales. The average porosity is 22% and average water
saturation is 47% in the net sand. The Heimdal Formation sandstones were
massive, of very good reservoir quality, and contained 13.5 m of net gas sand
in a gross gas sand interval of 13.5 m down to the gas/water contact at 2352 m.
The average porosity is 26% and average water saturation is 34%. The well was
drilled on the crest of a structurally limited trap and the gas accumulation is
not connected to the 15/9 Paleocene Gamma discovery. In the Jurassic, 19 m of
water wet Hugin Formation sand was encountered. The Zechstein dolomites and
Rotliegendes sandstones were also wat General The primary objective of the exploration
well 34/4 4 was to drill the untested Triassic sequence in the fault blocks
west of well 34/4-1. The well location was chosen to be stratigraphically
higher relative to the Triassic sequence in well 34/4-1. The purpose of the
well location was also to penetrate and core the maximum oil column above the
tentative oil water contact interpreted in well 34/4-1 and to test possible
lateral fluid communication with 34/4-1. Operations and results Wildcat well 34/4-4 was spudded with the
semi-submersible installation Dyvi Alpha on 11 September 1982 and drilled to TD
at 3800 in Middle Triassic sediments, Teist Formation. As much as 15 % of total
rig time was WOW due to bad weather. While coring, after core number 12 was
taken, the mud was replaced with seawater by accident and caused a kick,
resulting in a 20 bbls influx. The well was drilled with spud mud down to 493
m, with gel mud from 493 m to 1212 m, with gypsum/polymer mud from 1212 m to
2116 m, with Lignosulphonate mud from 2116 m to 2475 m, and with
lignosulphonate/Chem-X mud from 2475 m to TD. First oil shows were recorded on cuttings
from thin sandstone stringers below 2075 m, accompanied by increased gas
readings. Sidewall cores from siltstone beds between 2100 and 2414 m also
occasionally had oil shows. The Early Cretaceous Åsgard Formation rested
unconformably on the Late Triassic Lunde Formation at 2425 m. The Lunde
Formation sandstones were oil bearing down to the oil water contact at 2586 m.
The OWC was set mostly on the intersection of the oil and water pressure
gradients from RFT data. The oil bearing sand was separated from the water zone
by a 22 m thick General Block 7/11 was awarded in 1965 to the
Phillips Group. The first commercial discovery (Cod) was found in this block in
1968. Both Norsk Hydro wells (7/11-5 and 7/11-6) were drilled in the
relinquished area awarded to them in Licence 070. The main objective of well
7/11-5 was the Late Jurassic sandstones. The secondary objective was the
Triassic sands. Operations and results Well 7/11-5 was spudded with the
semi-submersible installation Treasure Seeker on 9 February 1982 and drilled to
TD at 4478 m in the Triassic Smith Bank Formation. The drilling went forth
without incident except for gumbo problems in the top of the 17 1/2"
section and minor problems with tight hole in the 8 3/8" section. The well
was drilled with sea water and hi-vis pills down to 615 m and with KCl/Drispac
mud from 615 m to 2115 m. From 2115 m to TD the well was drilled with
KCl/Drispac mud, converted to a fully dispersed gel-lignosulphonate mud in the
limestone section. The well encountered hydrocarbon bearing
sandstones in the Late Jurassic Ula Formation with a gross sand interval of 86
m between 4155 and 4241 m. An oil water contact has been estimated to be at
4201 m (from logs). RFT pressure measurements and sampling were performed over
the sandstone interval. Below 4202 m, however, no formation pressures were
obtained due to seal problems caused by bad hole. Thus a contact based on
formation pressure data could not be obtained. The Ula Formation rests
unconformably on the Triassic at 4241 m. In the Triassic, thin stringers of
sandstones were encountered with a total net sand of 2.25 m and an average
porosity of 18%. These sandstones were 100% water saturated. Oil shows were
recorded from 3694 m in the Late Cretaceous and down to 4217 m in the Ula
Formation. Below 4217 m shows were weak and scattered, and no shows were
reported from the Triassic. Five cores were taken in the Ula
Formation from 4159 m to 4231 m. Cores 1 - 4 bled General Well 31/4-6 was drilled on the Bjørgvin
Arch in the Northern North Sea. The main objective was to appraise the 31/4-3
Discovery in the "Intra-Heather sand II" (Fensfjord Formation) and to
define the oil/water contact. Operations and results Appraisal well 31/4-6 was spudded with
the semi-submersible installation Nortrym on 28 February 1982 and drilled to TD
at 2447 m in the Early Jurassic Drake Formation. No significant problem was
encountered in the operations. The well was drilled with seawater and hi-vis
sweeps down to 927 m, with non-dispersed Shale Trol mud from 927 m to 1865 m,
and with a fully dispersed Lignosulphonate/Unical/Ligcon mud from 1865 m to TD. The Fensfjord Formation was encountered
at 2150 m. It is a predominantly fine grained to silty, micaceous to very
micaceous, subarcosic carbonaceous and occasionally glauconitic sandstone with
a clay matrix and some heavily calcite cemented stringers. It is 89 m thick and
oil bearing from 2156 m down to the OWC at 2172 m. Net pay in the oil bearing
interval was 12.5 m with an average porosity of 26.4% and an average water
saturation of 43.8%. As expected the overlying Sognefjord Formation seen in the
31/4-3 and 5 wells was not present at this location. Below the Heather Formation,
the well penetrated 62.5 m of the Brent Group, which contained 31 m of net sand
with an average porosity of 23.4% and was water saturated. No other reservoir
intervals were encountered. Occasional poor oil shows were recorded in the Ness
Formation and the Drake Formation. Five cores were cut through the Fensfjord
Formation from 2132 m to 2214.5 m. Correlation between the cores and the logs
indicates that core depths are two to thr General Well 1/9-6 S was drilled on the
north-west flank of the Tommeliten Gamma structure in the Feda Graben in the
southern North Sea. The main objective was to appraise the Tommeliten Field.
The well was drilled deviated due to the planned use of this well as a
production well. The main targets were the Ekofisk and Tor formations. Operations and results Appraisal well 1/9-6 was spudded with the
semi-submersible installation Sedco 703 on 21 March 1982. Drilling of the
36" and 26" holes went without incident. There was some difficulty in
getting logging tools in the 17 1/2" hole. Gumbo problems occurred while
drilling the 12 1/4" hole and both open hole and cased hole logging runs
were plagued with tool failures. Differential sticking also occurred while
drilling the bottom part of the 8 1/2" hole. TD was set 3880 m, 99 m into
the Late Cretaceous Hod Formation. After retrieving the RFT the well began
flowing and sloughing large amounts of shale below the 9 5/8" shoe. While
circulating and reaming to TD, the pipe became stuck many times due to shale
sloughing above the bit. A bit and bit sub were left in the hole during these
hole problems, and were never recovered. The well was drilled with
"native" mud/seawater down to 1471 m and with polymer/dispersed
solids/lignosulphonate/seawater from 1471 m to TD. Top Ekofisk Formation was penetrated at
3411 m (3110 m TVD) and top Tor Formation at 3516 m (3199 m TVD). Both
formations were gas/condensate bearing. No other permeable section in the well had
indications of hydrocarbons. A total of 14 cores were cut in the interval
3415.7 - 3619 m in the Ekofisk and Tor formations. Problems with jamming and General Well 15/9-13 was drilled on the Sleipner
East Field in the Viking Graben in the North Sea. The objective was to
delineate the hydrocarbon accumulation found in the Heimdal Formation of the
15/9 Gamma structure. Secondary objectives were to test possible hydrocarbons
in sandstones of Jurassic - Triassic age. The well is reference well for the
Utsira and Skade formations. Operations and results Appraisal well 15/9-13 was spudded with
the semi-submersible installation Ross Rig on 21 March 1982 and drilled to TD
at 3280 m in the Permian Zechstein Group. No
significant problem was encountered in the operations. The well was
drilled with seawater and hi-vis slugs down to 518 m, with gel/lignosulphonate
mud from 518 m to 1165 m, gypsum/lignosulphonate mud from 1165 m to 2642 m, and
gel/lignosulphonate mud from 2642 m to TD. The well proved gas
and condensate in the Heimdal Formation. Shows on cores indicate that all
sandstones in the Heimdal Formation are gas filled to a probable down-to contact
in top Shetland Group at 2440 m. Gas and condensate were also encountered in a
Jurassic sandstone from 2763 to a probable down-to contact at 2791 m. No
hydrocarbons were found in Triassic sandstones. No shows were recorded outside
of the hydrocarbon-bearing sections in the well. Seven cores were cut. Cores 1 - 3 were
cut from 2404 m in the Heimdal Formation to 2453.5 m in the Tor Formation with
84 to 100% recovery. Cores 4 - 7 were cut from 2763 m to 2801.6 m in the Hugin
Formation with 90 to 100% recovery. Segregated RFT fluid samples were taken at
2400 m, 2437 m, 2765.8 m, and 2766.5 m.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General Well 2/2-1 was a wildcat drilled on a
salt-induced dome structure in the SE corner of block 2/2. The main target was
Late Jurassic sandstone. Secondary targets were pre-Cretaceous sandstones, the
Late Cretaceous Chalk and a sandstone of Oligocene age. According to the
license agreement, the well should be drilled into the Triassic, salt or a
maximum depth of 5000m whatever came first. The well is Type Well for the Vade
Formation. Operations and results Exploration well 2/2-1 was spudded with
the semi-submersible installation Dyvi Alpha on 9 April 1982 and drilled to TD
at 4003 m in the Late Permian Zechstein Group. When drilling the 36"
section pipe stuck at 167 m due to a rotary table failure. The well had to be
re-spudded on 11 April. Forty barrels of mud was lost to the formation when
drilling the 17 1/2" pilot hole in the 26" section. The well was then
drilled to TD without serious problems apart from various tight spots. The
re-spudded well bore was drilled with sea water and gel down to 207 m, with
gel/gypsum mud from 207 m to 665 m, with polymer/gypsum mud from 665 m to 1448
m, added "Super Shale Trol" shale stabilizer at 1448 m, and drilled
with lignosulphonate mud from 3260 m to TD. The well penetrated porous layers in the
Oligocene, the Cretaceous and the Upper Jurassic. A full suit of logs was run
in these intervals. In the interval 2100 m to 2171 m of the Oligocene, a sand
(Vade Formation) with good reservoir rock quality was found. The net - gross
ratio reaches 0.95 and the porosity nearly 30%. The RFT measurements indicated
permeability in the order of 100 mD. The sand was generally clean, but became
shaly just towards the top. The uppermost part of the sand was gas bearing with
a net pay thickness of 8 m and a water saturation of 35%. The GWC was picked at
2111 m from the logs and confirmed by RFT measurements. The reservoir pressure
is approximately 230 bar (3336 psi) at Operations and result General Well 2/1-4 was drilled on the margin
between the southern Vestland Arch and the Central Trough in the North Sea. The
first well in the block, well 2/1-1 drilled in 1972, was abandoned after taking
a kick in the Late Jurassic. The second well, well 2/1-2 drilled in1978
encountered water wet Late Jurassic sandstones. The 2/1-3 well was drilled in
1980 on the downthrown side of a NW-SE trending fault complex and found oil in
a 60 m thick Late Jurassic sandstone. A second Jurassic sandstone in 2/1-3 (Ula
Formation) was water wet. The primary objective of the 2/1-4 well was to
appraise the oil in the Late Jurassic "2/1-3 sandstone" (Gyda member).
Secondary objectives were to test the Ula and Bryne Formations and the
Triassic. The well is reference well for the Vidar
Formation. Operations and results Appraisal well 2/1-4 was spudded with the
semi-submersible installation Aladdin on 5 April 1982 and drilled to TD at 4525
m in the Late Permian Zechstein Group. The first and second spuds were
unsuccessful and only the third spud, on 12 April and 60 + 50 ft in direction
315 deg away from the planned location, was successful. The 17 1/2"
section from 633 to 2006 m and the upper part of the 12 1/4" section were
drilled with severe swelling shale (gumbo) problems. The well was drilled with
seawater and hi-vis pills down to 633 m, with CMC/gypsum mud from 633 m to 2006
m, and with CMC/gypsum/lignoslulfonate mud from 2006 m to TD. Well 2/1-4 penetrated the top of the Late
Jurassic sandstone at 4040 m and the log and core analysis confirmed the
formation to be oil bearing. The log evaluation and core studies showed the Late
Jurassic sandstone to consist of two main zone General The wildcat 7117/9-1 was the first well
to be drilled in the western part of the Troms I area. It is located on the
western margin of the Tromsø Basin close to the Senja High. The primary
objectives of the well were to test two possible sandstone reservoirs of
assumed Late Cretaceous age. Flat spots indicating fluid contacts were noted in
each of these two target horizons. A secondary objective was to test sandstones
of assumed Middle to Early Jurassic age. Planned TD was 2500 m in sediments of
Triassic age. Operations and results The location survey showed the area to be
covered with iceberg scars with depths from l m to 10 m. The dominant direction
of these scars is ENE-WSW and most of them are filled with sand and silt. The
quaternary sediments were about 280 m thick and layered in three main zones.
There were no indications of shallow gas in the area. Exploration well 7117/9-1 was spudded
with the semi-submersible installation Treasure Scout on 20 April 1982. Due to
excessive hole deviation while drilling to 303 m the rig had to be moved to
respud the well on 24 April. In this attempt high torque in extremely hard top
layers caused the drill string to twist off at 299 m. The third hole was
spudded on 30 April. The drilling progressed without further problems. The last
section was drilled with 8 3/8" bit and the well reached TD at 3200 m in
Early Cretaceous (Middle Albian to ?Aptian) clay stone. The well was drilled
with seawater and hi-vis pills down to 348 m, with seawater/bentonite from 348
m to 817 m, and with gypsum / lignosulphonate from 817 m to 1220 m. From 1220 m
the mud was changed to a gel lignosulphonate system as the reactive clays
disappeared and the rest of the well was drilled with this mud system. The more shallow of the two Late
Cretaceous target reservoirs was found to be a low velocity clay stone interval
of Paleocene age, between 1277 m and 1328.5 m. The flat spot (at 1.4 sec TWT)
cou General The 7120/8-2 well was drilled on the
Alpha-South structure in the Western part of the Hammerfest Basin. The first well in the block, well 7120/8-1, was drilled on the Alpha North closure in
1981, north of the major east - west fault splitting the two
closures/structures. This well found gas-bearing sandstones in the Middle to
Early Jurassic. The primary objective of well 7120/8-2 was to test possible
hydrocarbon accumulations in sandstones of Middle to Early Jurassic age (Stø Formation)
in the Alpha-South structure. Operations and results Well 7120/8-2 was spudded with the
semi-submersible installation Neptuno Nordraug on 15 April 1982 and drilled to
TD at 2590 m in Late Triassic sediments (Fruholmen Formation). The drilling of
the 36" and 26" hole went forth without any problems. After this
several problems occurred and 78 days were used to reach TD, 29 days more than
programmed. The main hang-ups were: broken 20" csg, partly collapsed
13-3/8" csg, pulled BOP stack, roller system, and stucked stabilizer at
2156 m. The well was drilled with gel/spud mud down to 333 m, with gel/seawater
from 333 m to 752 m, and with gel/lignosulphonate/seawater from 752 m to TD. Hydrocarbon accumulations were discovered
in sandstone sequences between 2081-2161 m in the Stø Formaton. The reservoir
sandstones showed good to excellent reservoir properties. Gas composition from
the DST was almost identical to the gas composition of the DSTs performed in
the 7120/8-1 well. This was also indicated by gas gradients established from
the RFT pressure points taken in the two wells. RFT pressure points from the
two wells also indicated that the water zone most likely is in communication.
Organic geochemical analyses show TOC in the range 0.7 % to 2.8 % TOC in mudstones
from the Early Cretaceous. The kerogen in these samples are Type IV / III with
a poor potential, increasing to fair at the base, for gas. Olive black
claystones o General Wildcat well 6507/11-2 was drilled as the
fourth well offshore Mid-Norway in the Møre/Trøndelag II area. The well was
drilled on a symmetric, north-south trending horst called Y-1 in the
northeastern part of the block, where seismic line SG 8158-401 indicated a
possible minor rollover trending north-south at the Base Cretaceous level. The
objective of well 6507/11-2 was to test the stratigraphic sequence below the
Top Palaeocene reflector. The targets, represented by expected minor vertical
closures, were sandstone reservoirs of Early - Middle Jurassic age. The
entrapment of major petroleum accumulations was dependent upon a lateral
sealing mechanism in the northern part of the Y-l horst. Operations and results Well 6507/11-2 was spudded with the
semi-submersible installation West Venture on 18 April 1982 and drilled to TD
at 2905 m in the Late Triassic Grey Beds. No significant problems were
encountered during operations. The well was drilled with seawater and slugs of
spud mud down to 412 m, with gypsum mud from 412 m to 857 m, with
"Pro-mud" gypsum polymer mud from 857 m to 1775 m, and with
Lignosulphonate mud from 1775 m to TD. In the Jurassic and Triassic section
from 1898 to TD, sandstones with a total net porous sand thickness of 395 m was
found. They were all water bearing. The Net-Gross ratio of the Jurassic
interval, 1898-2622 m is 0.45. The Middle/Early Jurassic Ile Formation
(1948-2040 m) was fine to medium grained and well sorted sandstone. A net sand
thickness of 65 m was defined in Ile, with porosity of 31% and permeabilities
ranging from 100 mD to 28 D. The upper part was clean and showed extremely good
reservoir rock properties. The lower part of the sand contained significant
amounts of mica. Although this part was less permeable than the top, this too
was a very good reservoir rock. The Early Jurassic sand (2117 - 2289 m) was
less sorted than the Middle Jurassic sand. It was very fine grained and
contai General Well 15/3-5 was drilled on the Gudrun
Terrace, east of the 15/3-1 S Gudrun Discovery in the North Sea. Well 15/3-5
was drilled in a downdip position of a structure explored by the well 15/3-4,
where oil bearing reservoirs of Middle Jurassic age were tested. The main
objectives of 15/3-5 were to find the extension of these reservoirs and to
define a hydrocarbon/water contact. Operations and results Appraisal well 15/3-5 was spudded with
the semi-submersible installation Byford Dolphin on 28 December 1983 and
drilled to TD at 4130 m in the Middle Jurassic Sleipner Formation. Drilling was
suspended at 195 m due to bad weather. The well was re-spudded on 6 January 25
m west of the original location. Some technical problems with the BOP occurred
after setting of the 20" and 13 3/8" casings. A seat protector got
stuck in the riser during drilling of the 17 1/2" hole. Drilling breaks
occurred at 3943 m, 3954 m, 4018 m, 4032 m and at 4041 4043 m in the 8 1/2"
hole section. The well was drilled using water based mud. Top Draupne Formation was encountered at
3808 m, followed by the Heather Formation at 3881 m, and the target Middle
Jurassic Sleipner Formation at 3935 m. Several thin reservoir zones were
penetrated in the Sleipner Formation. The sands were interpreted as minor
fluvial channels (2 to 5m in thickness) deposited in two main sequences. Four
of the channels were oil-bearing with an oil gradient of 0.61 bar/10 m based on
pressure measurements. An OWC could be established at 4022.6 m. Pressure
measurements showed that the upper fluvial channel sequence is over-pressured,
and not in contact with the sands encountered in well 15/3-4. The lower fluvial
sequence could be connected between the two wells. Petro General Well 30/6-14 was drilled on the Zeta
structure on the Brage Horst, east of the main Oseberg Alpha structure and
south of the Oseberg Beta structure. The primary objectives for the well were
to find hydrocarbons in the Brent Group, and to find additional hydrocarbon
accumulations within possible Early and Late Jurassic sandstone deposits. Planned
TD of the well was ca 3100 m or 75 m into the Statfjord Formation. Operations and results Wildcat well 30/6-14 was spudded with the
semi-submersible installation Treasure Scout on 17 December 1983 and drilled to
TD at 2900 m in the Early Jurassic Statfjord Group. No significant problems
occurred in the operations. The well was drilled using water based mud. The
well was drilled with spud mud down to 618 m, with KCl/polymer mud from 618 m
to 1675 m, Top Brent Group was penetrated at 2650 m
and top Drake Formation at 2589 with an Intra Drake Sand at 2605 to 2621 m.
Both Brent and Drake were found water bearing. Hydrocarbons were encountered in
the top of the Early Jurassic Statfjord Group from 2783.5 m down to a depth of
2789 m. RFT pressures indicated the free water level to be at 2790 m. No
additional hydrocarbon bearing reservoirs were encountered. Apart from spots of
cut fluorescence on claystones in the Drake Formation no oil shows were
recorded outside of the Statfjord Group hydrocarbon bearing reservoir. Three cores were cut in the Jurassic
sequence, one from 2561 to 2567.6 m in the Etive Formation, one from 2608 to
2621.2 m in the Drake Formation, and one from 2785 to 2800 m in the upper part
of the Statfjord Group. No wire line fluid samples were taken. The well was permanen General Well 30/9-3 was drilled on the Gamma West
structure on the Oseberg Fault Block in the northern North Sea. The primary
objective was to find hydrocarbon accumulations in the Middle Jurassic Brent
Group. Secondary objective was to find additional hydrocarbon accumulations in
the Early Jurassic. Planned TD was ca 75 m below a possible intra Triassic
marker to a depth of 4188 +/- 100 m Operations and results Wildcat well 30/9-3 was spudded with the
semi-submersible installation Nortrym on 31 December 1983. The well was drilled
to a depth of 3113 m into Drake Formation shales where the pipe got stuck and
parted when pulling out of hole for logging. The fish was not recovered and no
wire line logs were recorded below 1713.5 m due to fish in hole. All lithostratigraphic
interpretation below this point is therefore based on cuttings description,
core description, chromatograph data and ROP information. A sidetrack was
decided to complete the well programme. The well was drilled with spud mud down
to 625 m and with Invermul/EZmul Oil Based Mud from 625 m to TD. The Brent Group (2712-3045 m) consisted
of a 259 m thick Ness Formation (2712 - 2971 m) made up of sandstones with stringers
of shale, siltstone and coal and 74 m of Etive Formation (2971 - 3045m)
sandstones. Based on chromatograph analysis on hydrocarbon samples extracted
from core samples a GOC was found at ca 2734 m and an OWC at ca 2815 m, both
located in the Ness Formation. From core and chromatograph data the Ness
Formation had a gross pay of 103 m. The net gas pay was estimated to 22 m and
the net oil pay to 36 m giving a total net pay of 58 m (cut off values porosity
< 12%, permeability < l mD). The average porosity was calculated from
cores to 22.5 % and average General Well 30/6-10 A is a sidetrack to
appraisal well 30/6-10 on the Alfa structure on the Oseberg Field in the North
Sea. The primary well found oil and gas all through the Brent Group with a
gas/oil contact at 2520 m, but no oil water contact. The main objective was to further
define the gas/oil contact and to perform drill stem tests over the reservoir. The
well was planned to penetrate the Brent reservoir approximately 300 m west of
the original hole. Operations and results Appraisal well 30/6-10 A was sidetracked
on 2 December 1982 through a milled window in the 13 3/8" casing at 1788
to 1803 m in the primary well bore. The sidetrack was drilled with the
semi-submersible installation Treasure Scout to 2665 m (2577 m TVD) in the Early
Jurassic Drake Formation. At 2657 m bad weather came up and caused some
problems and down time. The pipe got stuck at TD but was worked free after 32.5
hrs using pipe lax, Imco spot and diesel. Otherwise the sidetrack was drilled
with KCl/polymer mud from kick-off to TD. First oil shows were seen in cuttings
from limestone stringers in the Balder Formation at 2015 m. Oil shows on
limestone cuttings continued down through the Shetland Group to top Heather
Formation at 2448 m. The Brent Group interval from 2480 - 2608.5 m (2429 - 2531
m TVD) was found hydrocarbon bearing over the entire interval with the free
gas/oil contact based on RFT pressure gradients at 2594 m (2520 m TVD) in the
Ness Formation. No oil/water contact was found. The net pay in the Brent Group was
calculated to be 58 m with average porosity of 24.4% and average water
saturation of 27%. The net/gross ratio in 30/6-10 A is higher than in 30/6-10
due to a better sand development in the Ness Formation.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General The primary objective of the wildcat
7/11-7 S was Late Jurassic sandstone surrounding a small salt piercement below
the Paleocene Cod Field reservoir. Several discoveries had been made in the
vicinity of Cod, in the Upper Jurassic Ula Formation. The Triassic and Permian
constituted secondary targets. The well was drilled from the Cod platform with
planned bottom hole location ca 0.9 km to the east. Operations and results Wildcat well 7/11-7 S was spudded from
the fixed installation Cod on 29 December 1982 and drilled deviated to TD at
4927 m (4661 m TVD) m in the Late Permian Zechstein Group. The well was
scheduled as a 150-day project but a full drilling crew was still present on
day 349 and it took until day 364 to set a plug above the last set of
perforations. The length of this project was due to problems in drilling and
extended testing to adequately evaluate the three zones of interest. There were
delays in setting plugs, running casing, fishing, and installing necessary 10,000
psi surface equipment. The testing delays included problems with setting
DHSV's, parted tubing, aborted stimulations, bad weather, and bailing
operations. The well was drilled with seawater/lignite and Desco, an organic
thinner. The well reached all three targets. Late
Jurassic Ula Formation sandstone was encountered at 4527 m. The Ula Formation
rested unconformable on Triassic Skagerrak Formation sandstone at 4566 m. The
Permian Zechstein dolomites were encountered at 4856 m. Good shows were
recorded in the Ula Formation, with weaker shows extending down to 4609 m in
the Triassic Skagerrak Formation. A second Triassic zone with weak shows was
observed at 4785 m to 4810 m. Source rock formations were found in the Tertiary
interval from 1820 m to 2500 m, and in the Late Jurassic shales of the Mandal
and Farsund Formations at 4405 m to 4527. The Tertiary interval had TOC in the
range 2 - 4 %, Hydrogen Index from 100 to 120 mg HC/g rock, and was General Well 30/6-11 was drilled on the Delta
structure on the Flatfisk Slope, close to the northwestern end of the Oseberg
Fault Block in the North Sea. The primary objective was to find hydrocarbon
accumulations in the Brent Group. Secondary objective was to find additional hydrocarbon
accumulations within the Early Jurassic Cook Formation and Statfjord Group. The
well was placed in an area where a complete Jurassic succession could be
expected. Planned TD was 75 m into the Statfjord Group. Operations and results Wildcat well 30/6-11 was spudded with the
semi-submersible installation Nortrym on 20 December 1982 and drilled to TD at 4001
m in the Early Jurassic Statfjord Group. When running casing in the 17
1/2" section at 2165 m the rig had to wait on weather. Cavings accumulated
as fill on the bottom and the casing was differentially stuck. Various
additives were used to free the casing, including diesel. The well was drilled
with seawater and hi-vis pills down to 235 m, with pre-hydrated bentonite and
seawater from 235 m to 965 m, and with KCl/polymer mud from 965 m to 2165 m.
From 2165 m to 3654 m, the KCl/polymer mud was slowly converted to a dispersed
lignosulphonate/lignite mud and in the bottom 8 3/8" section, from 3654 m
to TD a dispersed lignosulphonate/lignite mud system was used. From 2165 and
downwards the diesel content in the mud was 5%, diminishing to traces below
3265 m. The Brent Group (3351 - 3561m) had a
gross thickness of 210 m with 118 m of net sand, giving a net to gross ratio of
0.56. The average porosity of the sandstones were calculated from wireline logs
to 16% with an average water saturation of 80%. The Cook Formation (3752.5 -
3768.5m) had a net sand thickness of 3 m, giving a net to gross ratio General Well 34/10-16 was drilled on the Gullfaks
Sør structure, 8 km south of the Gullfaks Field. The purpose of this well was
to investigate a fault block, en echelon to the first fault block tested by
well 34/10-2, for possible extension of hydrocarbon accumulation. The principal
drilling objective was sandstones of the Brent Group. Secondary objectives were
the Cook and Statfjord sands, of which the Statfjord sand proved the presence
of oil in well 34/10-2. Operations and results Appraisal well 34/10-16 was spudded with
the semi-submersible installation Nordraug on 14 December 1982 and drilled to
TD at 4042 m (4027 m TVD) in the Late Triassic Lunde Formation. Excessive time
were lost due to waiting on weather, hole problems, logging problems and other
technical problems. These problems consumed a total of 1080 hours or 45 days
downtime. The well was drilled with spud mud down to 225 m, with gel/seawater
from 225 m to 617 m, and with lignosulphonate CMC/gel mud from 617 m to TD. The Brent Group came in at 3171 m and contained
both oil and gas with the gas/oil contact at ca 3350 m and the oil/water
contact at ca 3422 m, according to the logs. The gas net pay was estimated to
84 m with average porosity 18.2% and average water saturation 22.5%. The oil
net pay was estimated to 29.5 m with average porosity 16.5% and average water
saturation 38.9%. No hydrocarbons were encountered in the Cook and Statfjord
Formations. No oil shows were recorded outside of the Brent Group. A total of 23 cores were cut, 22 of these
covering nearly all of the Brent Group and the last one covering a sandstone in
the upper Statfjord Formation. The RFT tool was run for fluid samples.
Segregated RFT sample General Well 15/9-17 was drilled on the Sleipner
Terrace in the Viking Graben of the North Sea. The primary objectives were to
test possible hydrocarbon accumulations in the Paleocene Heimdal Formation and
in Jurassic/Triassic sandstones. Operations and results Wildcat well 15/9-17 was spudded with the
semi-submersible installation West Vanguard and drilled to 3120 m in the
Triassic Smith Bank Formation. A 12 1/4" pilot hole was drilled down to
519 m, but no indications of shallow gas was found. Bad weather caused some
delay. Bad weather and repeated BOP problems caused some down time. The well
was drilled with spud mud down to 500 m, with gypsum/polymer mud from 519 m to
2616 m, with Lignosulphonate/Drispac mud from 2616 m to 2950 m, and with
Drispac from 2950 m to TD. Both the Heimdal Formation and the
Mesozoic sandstones contained gas and were tested. The log evaluation indicated top of the
hydrocarbon column in the Heimdal Formation at 2377.5 m. The logs indicated the
gas/water contact at 2418.5 m, while pressure data gave a gas/water contact a
bit shallower, at 2413 m. Weak and spotted shows were recorded on cored
sandstones in the Heimdal Formation below the contact down to 2425 m, and from
2442 to 2450 m. The top of the hydrocarbon column in the
Mesozoic sandstones was at 2715 m (top Vestland Group). The column extended
down into the Triassic. No definite gas/water contact was found but could be as
deep as 2848 m. Shows were recorded on cored sandstones throughout this
reservoir, getting weaker with depth. No shows were seen outside of the
hydrocarbon bearing sectio General The wildcat 6407/1-2 was drilled 43 m NW
of well 6407/1-1, which was drilled to 900 m before it was junked due to
problems with setting the 20" casing. The objective for both wells was to
test for hydrocarbons in Jurassic sandstones. The primary target was Middle
Jurassic sand horizons, Early Jurassic sands was secondary target. The well was
the first well north of 62 degrees to encounter liquid petroleum. The well is Type Well for the Kai
Formation and Reference Well for the Nordland Group. It is Reference Well for
the Lyr Formation, the Fangst Group, and the BÅt Group Operations and results Wildcat well 6407/1-2 was spudded with
the semi-submersible installation Dyvi Delta on 13 November 1982 and drilled to
TD at 4560 m in the Late Triassic Grey Beds. The well was drilled with
seawater/gel down to 901 m, with gypsum/lignosulphonate from 901 m to 3568 m,
and with Spersene/XP-20/resin from 3568 m to TD. At 1817 m loss of mud to the
formation was discovered. A survey showed that this was caused by a collapse of
20" casing from approximately 667 m. It was therefore decided to run the
13 3/8" casing at this point. A total of 164 days were spent on the
drilling phase, which was 56 days more than prognosed. 22 days were lost due to
bad weather, 17 days due to BOP problems, 4 days working with the collapsed
20" casing, 7 days were spent on fishing when the drill string parted. A
further 12 days were spent on excessive reaming in the 12 1/4" hole in the
Paleocene and top of the Cretaceous formation, and in the 8 1/2" hole in
the Heather formation. The reaming was necessary when running back in hole
after several days WOW with the BOP closed and the riser disconnected. The well
was drilled 60 meters deeper than prognosed. The testing phase lasted for 21
days, which includes a 7" casing tie back operation of 6 days, which was
necessary because of a leak in the 9 5/8" at approximately 1850 m. The General Well 30/11-3 was drilled in the Fensal
sub-basin in an area east of the Frigg and Odin Fields in the North Sea. The
primary objective was to test Middle Jurassic sandstones of the Brent Group and
Early Jurassic sandstones of the Statfjord Group in a westward tilted horst block. The well is type well for the Hardråde
Formation and reference well for the Svarte, Tryggvason and Kyrre formations. Operations and results Wildcat well 30/11-3 was spudded with the
semi-submersible installation Borgny Dolphin on 17 November 1982 and drilled to
TD at 4662 m in the Early Jurassic Statfjord Group. When entering sandstones in
the Statfjord Group at 4637 m the well kicked, probably due to overpressured
gas. After efforts to stabilise the well the decision was made to abandon the
well before a full evaluation of the Statfjord Group had been made. The well
was drilled with spud mud down to 640 m, with KCl/polymer mud from 640 m to
3053 m, and with Drispac/lignosulphonate - gel/Resinex mud from 3053 m to TD. Well 30/11-3 encountered reservoir
quality sands in the Tertiary (Frigg Formation and Heimdal Formation) and in
the Jurassic (Brent Group and Statfjord Group). Oil saturations were seen in
several thin sands in the Brent Group between 3434 m and 4025 m. Core and log
evaluation indicated that these were probably due to residual oil only
(saturations below a cut-off value of 50%). True oil shows were recorded
intermittently only between 3434 m and 3600 m. Possible pay zones with
reasonable porosity and permeability would be thin, with a net of only 13 m
based on petrophysical evaluation. Log evaluation also indicated high gas
saturations (up to more than 80%) in the Statfjord Group. However General Well 2/1-5 was drilled on the Cod Terrace
of the Central Graben in the southern North Sea. The primary objective was test
a Late Jurassic sandstone prospect on the south side of a large, central salt
culmination in block 2/1. The prospect was developed by analogy with the 2/1-3
oil discovery (Gyda) on the north-western slope of the same salt high. There,
the reservoir is a 60 to 90 m thick sand within the Farsund formation, with closure
formed primarily by pinch out/truncation beneath the Mandal Formation on
lapping on the central salt high. Secondary objectives were possible deeper
reservoirs such as the Ula and Bryne Formations and the Triassic down to top
salt. Operations and results Wildcat well 2/1-5 was spudded with the
semi-submersible installation Sedco 707 on 13 November 1982 and drilled to TD
at 4454 m. In the Cretaceous sequence the string got stuck and the well had to
be sidetracked from 2882 m. After a drilling break at 4186 m an oil kick occurred
with 21.5 m influx and oil appearing in the mud. RFT measurements in sandstone
units below the oil kick showed pore pressures on a gradient equivalent to a
mud weight of 2.10 g/cm. This gave little margin for safe onward drilling to
Top Salt and the well was terminated in dark, carbonaceous mudstone of
uncertain, possibly Early Jurassic age. The well was drilled with seawater/gel
down to 635 m, with gypsum/lignosulfonate mud from 635 m to 3830 m, and with
Lignosulphonate/lignite mud from 3830 m to TD. Well 2/1-5 reached the Base Cretaceous Unconformity
and the "Hot shale" at 3882 m as predicted. Coring was initiated when
traces of sand were observed near the predicted "top reservoir", but
only dark, carbonaceous mudstone/siltstone was recovered. In General Well 2/6-3 is located on the north western
flank of the Mandal High between the Søgne Basin and the Central Graben in the
North Sea.It was drilled to
test possible hydrocarbon accumulations in Late and Middle Jurassic sandstones.
A third objective was to reconnoitre below base Permian. Operations and results Wildcat well 2/6-3 was spudded with the
semi-submersible installation Byford Dolphin on 9 November 1982 and drilled to
TD at 4060 m, 270 meter into pre-Late Devonian basement rock. Technical
problems occurred in the 12 1/4" section due to twist-off of Kelly saver,
loss of 2700 m logging cable in hole, and 9 5/8" casing hanger collapse,
causing a total of 203 hrs lost time. In the 8 1/2" section an anchor
chain parted during a storm and four days were lost waiting on weather and
re-anchoring. The well was drilled with water based mud. In the Late Jurassic only marine shales
were encountered. At 3545 m, 200 m higher than prognosed a Middle Jurassic,
fluvial sandstone of Bajocian age (Bryne Formation) was found water bearing. A
sequence of anhydrite, dolomite and pure anhydrite was found below the Triassic
red-shales, but no salt or Rotliegendes reservoir rocks were encountered. The
Permian anhydrite was followed by a series of slated shales and phyllitic
rocks, getting progressively more and more deformed, and with an introduction
of metamorphism towards TD. Rb-Sr dating on 1-micron fraction material from
3875 m gave an age of 376 Ma in the Late Devonian. No oil shows were reported
from the well. Background gas was recorded down to top Permian. No gas was
recorded below top Permian. Three cores were cut. K1was cut at 3551 -
3560 m in Bryne Formation sandstone with 85% recovery. K2 was cut at 3886 -
3895 m in basement rock with 11% recovery (one meter, presumed to be from the
top of the interval), and K3 was cut in basement at TD with 58% recovery. RFT
pressure points were obtained but no wire l General Well 30/9-1 was drilled on the southeast
part of the Oseberg fault block (Alpha structure) in the North Sea. The Alpha structure
is an eastward tilted fault block that contains proven reserves of oil and gas
in the Middle Jurassic Brent Group sandstone reservoir. The primary objective
of the well was to establish the oil/water contact in this part of the
structure. The well was planned to be drilled to a total depth of 2850 m,
approximately 100 m into the Dunlin Group. Operations and results Appraisal well 30/9-1 was spudded with
the semi-submersible installation Treasure Seeker on 24 October 1982 and
drilled to TD at 2895 m in the Early Jurassic Drake Formation. No significant
problem was encountered in the operations. The well was drilled with
seawater/hi-vis pills and pre-hydrated bentonite down to 969 m, with
KCl/Drispac mud from 969 m to 2515 m, and with KCl/polysal mud from 2515 m to
TD. The Brent Group was found hydrocarbon
bearing from 2685 m down to 2738 m where the free water level was established.
This interval comprises the whole of the Ness Formation and the uppermost 3 m
of the Etive Formation. Net pay in the interval was 10.5 m. Poor oil shows were
recorded on limestone cuttings in the interval 2281 to 2232 m in the uppermost
Shetland Group. Good oil shows were recorded through the oil column of the
reservoir. Below the contact at 2738 m, shows became weaker and patchy down to
2778 m. Below this depth only some weak shows on claystone from three sidewall
cores in the interval 2872 m to 2895 m were reported. Seven conventional cores were cut from 2682
m at the top of the Ness formation to 2784.9 m, into the Dunlin Group shales. RFT
fluid samples were ta General Exploration well 6407/1-1 is located on
the Halten Terrace off shore Mid Norway. The purpose of the well was to test
possible hydrocarbon accumulations in sandstones of Middle and Early Jurassic
age. Operations and results Well 6407/1-1 was spudded with the
semi-submersible installation Dyvi Delta on 19 October 1982 and drilled to TD
at 900 m in Pliocene sediments (Nordland Group). The well was drilled with
seawater/gel all through. Due to problems with setting of the 20" casing, the
hole was plugged and abandoned on 13 November 1982. Spudding and drilling of
replacement well 6407/1-2 started the same day. Testing No drill stem test was performed General Well 34/10 15 was drilled as a wildcat on
a horst block in the south-eastern part of the Gullfaks Field. The primary
purpose of the well was to test hydrocarbon accumulations in the Jurassic and
Brent sands. Secondary objectives were the Early Jurassic Statfjord sands and
to test shallow gas accumulations in Pliocene sands. Operations and results Appraisal well 34/10-15 was spudded with
the semi-submersible installation Neptuno Nordraug on 16 October 1982 and
drilled to TD at 2400 m in Late Triassic sediments in the Statfjord Group. A 12
1/4” pilot hole was drilled from 250 m to 950 m to check for shallow gas. The
well was situated ca 90 m south of the location for the well 34/10-10, which
was abandoned due to gas flow from a gas filled sand at 428 m. The same
sandlense was penetrated in the well 34/10-15 from 444-447 m. The well was
drilled with spud mud down to 250 m and with gel/seawater/lignosulphonate mud
from 250 m to TD. Weak shows on cuttings, mostly on
limestone, were recorded intermittently from 1220 m in the Hordaland Group to
1630 m in the Lista Formation. The Brent Group sands were not encountered. Late
Triassic Statfjord Group sands were found water wet without shows. The Cook Formation
sands contained residual oil. Ten cores were cut. Cores 1 to 5 were cut
from 1870 m to 1945 m in the Cook Formation with recoveries varying from 34% to
75%. Cores 6, 7, and 8 were cut from 2170 m to 2213 m in the Amundsen Formation
with recoveries varying from 87% to 93%. Cores 9 and 10 were cut from 2301 m to
2323 m in the Statfjord Group with 90% and 85% recoveries, respectively. An RFT
fluid sample was taken at 1875.5 m in the Cook Formation residual oil zone. The
sample co General Wildcat well 6507/11-1 is located in the
Haltenbanken area and was the third well to be drilled off shore Mid Norway.
The purpose of drilling the well was to test the whole stratigraphic sequence
between seabed and 500 metres below the Near-Base Jurassic reflector or into
the Triassic, whichever came first. The specific targets, represented by
vertical closures, were Middle Jurassic sandstone, below the Base Cretaceous
Unconformity, and Early Jurassic sandstone below the Middle Jurassic
Unconformity. A possible flatspot was identified at this level. In addition,
any horizon below these reflectors will, according to Saga's interpretation, be
closed, and represent a possible reservoir. The well is Type Well for the Tilje
Formation. Operations and results Well 6507/11-1 was spudded with the
semi-submersible installation West Venture on 13 September 1981 and drilled to
TD at 3139 m in the Late Triassic Grey Beds. Two gas kicks occurred in the 12
1/4" section at 2125 m and 2128 m with up to 600 000 ppm gas readings
observed at surface. The blow out was killed by circulating increasing mud
weight in steps from 11.0 ppg to 13.2 ppg. The well was drilled with spud mud
down to 460 m, with gypsum mud from 460 m to 815 m, with gypsum/polymer mud
from 815 m to 1615 m, and with a lignosulphonate/causticized-lignite mud
through the 12 1/4" section from 1615 m to 2300 m. In this section a
number of mud additives were used in the kill well operations. The section from
2300 m to TD was drilled with a lignosulphonate mud. The well proved the existence of a
lithological sequence ranging in age from Late Triassic (Early Rhaetian) to
Quaternary. The Cenozoic succession was 1794 m thick. The dominant lithology of
the Nordland and Hordaland Group was clay stone, but the former was less
consolidated and contained more poorly sorted sand and rock fragments. An
argillaceous sandstone of Oligocene/Miocene age was encounte General Wildcat well is located between the
Sleipner Vest and Sleipner Øst Fields. The well was designed to test possible
hydrocarbon accumulations in the Upper Middle Jurassic sands and secondary test
Heimdal Formation Sand of Paleocene age. Operations and results Wildcat well 15/9-10 was spudded with the
semi-submersible installation Neptuno Nordraug on 15 September 1981 and drilled
to TD at 3289 m in the Triassic Smith Bank Formation. Drilling the 26"
hole section complete loss of returns occurred at 186 m and a cement plug was
set. Drilling out of the cement returns were again lost, at 178 m, requiring a
further cement plug. Total losses due to this loss zone were well in excess of
10 000 bbls. After this operations went without significant problems. The well
was drilled with seawater and hi-vis pills down to 172 m. The next section, the
26" section, was drilled down to 472 m with seawater/bentonite and
quantities of Mica Fine, Nutplug, Kwikseal, and other additives. From 472 m to
TD m the well was drilled with polymer/Drispac. The well encountered Tertiary sands in
the Utsira Formation at 884 - 1102 m, Grid Formation at 2049 - 2079 m, Heimdal
and Ty Formations at 2547 m to 2667 m. An RFT run in the Heimdal sand indicated
a water gradient, 1.02 g/cm3. The primary target Jurassic sandstones was
encountered at 3070 m in the Hugin and Sleipner Formations. Some shows were
recorded in the Hugin Formation, but from the logs the formations were all
water-wet. Possible source rocks were encountered in a comparatively thick and
marly Blodøks Formation from 2871 m to 2924 m, and in the Late Jurassic Draupne
and Heather Formations from 3004 m to 3070 m. Four conventional cores were cut.
Core 1 was cut from 3061 m to 3062.4 m in the Heather Formation, core 2 was cut
from 3082 m to 3100 m in the Hugin Formation, and cores 3 and 4 were cut from
3137 m to 3171 m in the Sleipner Formation. No fluid sample was taken. The w General Well 31/2-7 was drilled in the
Troll West oil province in the Northern North Sea. The primary
objective was to appraise the oil accumulation in the area west of well 31/2-4
in the Troll Field. Operations and results Well 31/2-7 was spudded with the semi-submersible
installation Borgny Dolphin on 22 April 1982 and drilled to TD at 1660 m in the
Late Jurassic Heather Formation. No significant problems were encountered
during operations. Tight spots were encountered in the 17 1/2" section. The
well was drilled with seawater and hi-vis pills down to 455, with
seawater/gel/CMC/Drispac from 455 m to 825 m, with KCl/polymer mud from 825 m
to 1517 m, and with KCl/polymer/gel/lingo mud from 1517 m to TD. The well penetrated 11 m f Late Jurassic
Draupne shale at 1535 m before entering the Sognefjord Formation reservoir
sands at 1546 m. The Heather Formation was encountered at 1601 m. The
Sognefjord Formation was hydrocarbon bearing with a 20.5 m gas column from
1545.5 - 1566 m and a 27.5 m oil column from 1566 to 1593.5 m. The gas
reservoir consisted of alternating micaceous, bioturbated fine to medium
grained sandstones and cross laminated, massive fine to coarse grained
sandstones. The upper part of the oil reservoir (down to 1586 m) was of the
same quality as the gas reservoir. Below 1586 m the sandstones were very fine
to medium grained with high mica content. Weak shows (fluorescence and cut)
were recorded on cores down to 1635 m. Six fibreglass sleeve cores were taken from
1547.0 m to 1635.0 m in the 8 1/2" section. Thus 88 m of core were cut of
which 72.25 m (82%) was recovered. In order to verify the higher than expected
GOC several unsuccessful (due to probe plugging) attempts were made to obtain RFT
fluid samples at around 1570 m. Eventually one of the RFT chambers was filled
at 1568 m. After a few more attempts the other chamber was filled at 1566.5 m.
At surface the contents of both chambers were check General Well 15/9-14 is located ca 7 km south of
the Sleipner Vest Field in the south Viking Graben of the North Sea. The main
objectives of the well were sandstones of Late to middle Jurassic age. The
secondary objective was the Triassic. Operations and results Wildcat well 15/9-14 was spudded with the
semi-submersible installation Deepsea Saga on 1 May 1982 and drilled to TD at 3563
m in Triassic Smith Bank Formation. Operations were conducted without incident
except some problems with tight hole and stuck pipe in the 12 1/4"
section. The well was drilled with spud mud down to 561 m, with seawater/gel/ lignosulphonate
from 561 m to 1371 m, with seawater/gypsum/ lignosulphonate from 1371 m to 3016
m, and with lignite/lignosulphonate from 3016 m to TD. All objectives proved water bearing
according to logs and RFT measurements. The RFT data also showed that the
predicted pore pressures had been on the low side. The well was shut in two
times due to flow, but there was no pressure build-up. Grains of siltstone and
sandstone in cuttings the interval 1220 to 1260 had weak shows (fluorescence,
no cut). Fluorescence and cut were observed on sandstones from 3220 to 3290 m
in the Vestland Group. Two cores were cut in the Vestland Group.
Core no 1 was cut from 3228 to 3243 m (recovered interval 3228.4 - 3636.6 m
corrected to loggers depth) and core no 2 was cut from 3267 to 3285.9 (recovered
interval 3267 m to 3285.9 m) corrected to loggers depth). One RFT run was
performed in the Middle Jurassic - Triassic Formations. Eleven pre-test samples
were obtained out of 19 sampling points. No wire line fluid samples were taken. The well was General Well 30/2-1 is located roughly mid-way
between the Oseberg Field complex and the Kvitebjørn Field in the Northern
North Sea. The primary objective of the well was sandstones of Middle Jurassic
age. Secondary objectives were sandstones of Paleocene and Late/Early Triassic
age. Operations and results Wildcat well 30/2-1 was spudded with the
semi-submersible installation Dyvi Delta on 17 May 1982 and drilled to TD at 4243 m, 133 m into the Early Jurassic Statfjord Formation. A total of 125 days
were spent on the drilling phase, which was 5 days more than prognosed. Twelve
days were lost due to problems with lost circulation, gas influx, stuck pipe
and a leaking liner overlap in the 8 1/2" hole section. Three and a half
days were lost to free the 13 3/8" casing when this got stuck at 1998 m. Most
of those days were caught up because total depth was reached 357 m shallower
than prognosed, and because of successfully turbodrilling with diamond bits in
the 12 1/4" and 6" hole section. The well was drilled with spud mud
down to 1035 m, with Gypsum mud from 1035 m to 1860 m, and with
Gypsum/Lignosulphonate mud from 1860 m to 2155 m. An oilfaze/pipelax and an
Imco spot/pipelax pill was spotted at 1998 m to free the pipe. From 2155 to TD
the well was drilled with Spersene XP 20 (Lignosulphonate). Hydrocarbons were encountered in the
Brent group. The secondary prospects were found to be water wet, although oil shows
were recorded in dolomite between 1852 m and 1911 m in the Eocene and in a 30
cm thick sandstone bed at 1952 m in the Late Paleocene Balder Formation. Weak
shows were also recorded on sandstones from 4119 m to 4202 m in the Statfjord
Formation. Eleven cores were cut with a total
recovery of 108.8 metres. Two cores were cut from 1952 m to 1969.5 m in the Late
Paleocene Balder Formation, while 9 cores were cut from 3696 m to 3794 m in the
Ness, Etive, and Rannoch Formations of the Brent Group. Fi General Well 30/6-7 is an appraisal well on the
Oseberg Field, discovered by well 30/6-1 in 1979.The primary objective was to
test for hydrocarbon accumulations in the Late Jurassic sandstones of the Brent
formation and the Late and Early Jurassic sandstones of the Dunlin and
Statfjord formations in the Alpha north structure. Secondary objectives were to
establish the type of communication between the Alpha and Alpha North
structures and to define the oil/water contact on Alpha North. The well was
planned to reach total depth at 3225 +- 50 m, 75 m into the Statfjord
Formation. The well is Type well for the Oseberg
Formation and Reference well for the Amundsen, Cook, Drake, Etive, Ness, and
Tarbert Formations. Operations and results Well 30/6-7 was spudded with the
semi-submersible installation Nortrym on 20 May 1982 and drilled to TD at 3236
m in Early Jurassic rocks of the Statfjord Formation. The 26" section was
initiated by a 17 1/2" pilot hole. One small pocket of shallow gas was
detected at 358 m (5.6% C1). The well was drilled with seawater and hi-vis
pills down to 952 m and with KCl/polymer mud from 952 m to 2285 m. At 2285 m
the 13 3/8" casing got stuck and a pill of EZY spot and diesel was pumped
in the hole, without effect. The drilling fluid used in the 12 1/4"
section from 2285 m to 2915 m the well was drilled with a Dextrid/KCl mud. From
2915 m to TD the mud was converted to a dispersed system by adding
lignosulfonate. The Brent Group was encountered at 2631.5
m. The Brent Group was hydrocarbon bearing with a total gross thickness of
154.5 m and a net sand interval of 106.9 m. The net pay was 50.7 m. Sandstone
intervals were also encountered in General Well 15/9-15 was drilled south of the
Sleipner Øst Field in the Viking Graben of the North Sea. The objectives were
to test possible hydrocarbon accumulations in Paleocene and Mesozoic sandstones
in the 15/9 My structure. Operations and results Wildcat well 15/9-15 was spudded with the
semi-submersible installation Ross Rig on 28 May 1982 and drilled to TD at 3200
m in the Triassic Skagerrak Formation. During drilling the 12 1/4" section,
a significant volume of mud was lost at 2200 m. The thief zone was most
probably in the Frigg sand. 3 days were spent locating the zone and pumping LCM
pills. Otherwise no significant problem was encountered in the operations,
which proceeded with little downtime. The well was drilled with spud mud down
to 515 m and with gypsum/lignosulphonate mud from 515 m to TD. The Paleocene sandstones were missing in
this well. The Mesozoic sandstones were encountered at 2806. The upper part
consisted of tight Melke Formation sandstones without shows. From 2821 m (top
Skagerrak Formation) they were gas bearing down to a true gas/water contact at
2923 m. No oil shows were recorded outside of the hydrocarbon-bearing reservoir
in this well. Four cores were cut across the reservoir
from 2805 m in the Heather Formation to 2878.2 m in the Skagerrak Formation.
The core-to-log depth shift was 2.8 m for all four cores. RFT fluid samples
were taken at 282.5 m (gas, condensate and mud filtrate), 2838.5 m (gas,
condensate and mud filtrate), and at 2907 m (gas, condensate and mud filtrate)
fluid samples were taken. The well was permanently abandoned on 1
August 1982 as a gas and condensate discovery.
wlbHistoryDateUpdated: 2019-04-25T00:00:00 General Exploration well 16/7-3 is located on the
Utsira High, about ten km east of the Sleipner East field. The objective of the
well was to test potential Jurassic sands on the large structure in the centre
of the block. The well would also test the Zechstein
carbonate and Rotliegendes sandstone plays in a small fault block structure. Operations and results The well was spudded with the
semi-submersible installation Glomar Biscay II and drilled without incident to
TD at 3141 m in the Rotliegendes Group. The well was drilled with seawater gel,
adding lignite from 2150 m. The Cretaceous sequence consisted of the
Late Cretaceous Tor and Hod chalk formations resting unconformably on a very
thin Late Jurassic Draupne shale. Thirty-seven net m of good quality sand was
encountered in the Jurassic Hugin Formation. The Triassic consisted of red beds
with no major sand development. The Zechstein contained tight anhydritic
dolomite, some vuggy dolomite, and shales, while the Rotliegendes Group had poor
reservoir quality dolomite cemented sandstones, siltstones and shales. A shows
on a core was recorded in the interval 2345 m to 2350.7 m in the upper part of
the Jurassic Hugin Formation. Otherwise no hydrocarbons were encountered in the
well. Two cores were taken in the 8 1/2" section, in the interval 2342 m
to 2365.5 m in the Jurassic Hugin Formation. Forty sidewall cores were taken in
the interval 2296 m to 3130 m. No fluid samples were taken. The well was
permanently abandoned as dry on 28 August 1982. Testing No drill stem test was performed General Wildcat well 6407/2-1 was drilled in the
MØre-TrØndelag II area offshore Mid-Norway, approximately 215 km NW of
Trondheim. The overall goal with this early well was to establish the total
stratigraphic column down to Late Triassic. The primary targets were Middle and
the Early Jurassic Sandstone units. Secondary targets were the sequence below
the Top Palaeocene reflector, the Early Cretaceous sequence, which could show
development of sand, and the Triassic sandstones/si1tstones immediately below
the Åre Formation. The well is Type Well for the Spekk and
Ror Formations. Operations and results Well 6407/2-1 was spudded with the
semi-submersible installation West Venture on 3 June 1982 and drilled to TD at
3870 m, 40 into the Late Triassic Red Beds. Operations went without significant
problems. The well was drilled with spud mud down to 409 m. The 26"
section was first drilled as a 14 3/3" pilot hole from 409 m to 1013 m
using gel/gypsum mud. At this point 30 bbl of diesel was added to reduce mud
weight. The hole section was then opened up with a 26" underreamer using
gel/gypsum mud with further diesel addition. The 17 1/2 section was drilled
with polymer/gypsum/lignosulphonate from 1013 m to 2215 m, and the remaining
well was drilled with a lignite/lignosulphonate mud down to TD. The well proved mainly claystones down to
Middle and Early Jurassic Sandstones. The Tertiary with a total thickness of
1848.5 m, rested unconformably on the Late Cretaceous where the topmost
Maastrichtian was missing. Otherwise the Cretaceous section was nearly
complete, and relatively thick (ca 700 m) compared to other wells in the area.
High gas readings were experienced in the upper part of the Cretaceous
(Santonian - Campanian) with weak oil shows on cuttings and two SWCs. A study
of wire line logs, sidewall cores and hole response indicated that the gas was
overpressured, and trapped in a non-reservoir lithology. The bas General Well 30/6-8 was drilled on the Epsilon
structure between the Oseberg and Brage discoveries. At the well location
seismic mapping indicated structural closure at Brent Group level and below. The
primary objectives were to find hydrocarbon accumulations within the Brent
Group and the overlying clastic wedge of Bathonian-Callovian age. Other
Jurassic sandstones were also considered as prospective targets. The well was
planned to reach ca 3500 m total depth, 75m into the Statfjord Group. Operations and results Wildcat well 30/6-8 was spudded with the
semi-submersible installation Treasure Seeker on 15 June 1982 and drilled to TD
at 3600 m in the Early Jurassic Statfjord Formation. A 17 1/2" pilot hole
was drilled from 232 m to 950 m. No shallow gas was reported. No serious
problems occurred while drilling. The well was drilled with seawater and hi-vis
pills down to 232 m, with seawater/hi-vis pills and Drispac from 232 m to 955
m, and with KCl/polymer mud from 955 m to TD. No hydrocarbon bearing sandstone
intervals were encountered in this well. The only hydrocarbon indications were fluorescence
and cut fluorescence in sandstone cuttings at 3560 to 3563 m in the Statfjord
Group and trace fluorescence, no cut, in sidewall cores at 3147 and 3154 m in
the Etive Formation. The well penetrated an Intra Heather Formation Sandstone
interval (2445.5 - 2523.5 m) with 10.6 m net with average porosity of 15.7 %. A
Callovian wedge (2712.5 - 3024 m) was encountered by the well, but no clastic
sediments with reservoir properties were found within the wedge. A total of 147
m of Brent Group (3024 - 3171 m) sediments were encountered. Net sand was 45.9 m
with an average porosity of 16.1 %. Net sand within the Cook Formation (3349.5 -
3404. General Well 31/2-8 was drilled in the northern
part of block 31/2, some 3 km NW of the Troll Field boundary, to test a
downthrown Jurassic fault-block outside the Troll Field. The primary objective
was the Late Jurassic, shallow marine sands of the Viking Group, especially the
Sognefjord Formation. The Early Jurassic was secondary objective and would be
evaluated by drilling into Triassic sediments. Operations and results Wildcat well 31/2-8 was spudded with the
semi-submersible installation Borgny Dolphin on 16 June 1982 and drilled to TD
at 3375 m in the Triassic Hegre Group. A gas zone (confirmed by logs) between
510 - 530 m did not cause any problems during drilling of the 14 3/4"
pilot hole. Maximum gas reading through this zone was 10 %. The hole was
drilled to 840 m and under-reamed to 26" without incident. The 17
1/2" section was drilled first by an 8 1/2" pilot hole down to 1063 m
to provide better control when drilling through a potential gas charged fault
plane. No indications of gas were seen. 3 cores were taken in the 12 1/4"
section. Two washouts occurred when drilling the 8 1/2" hole below 3317 m.
The well was drilled with seawater gel down to 840 m, with KCl/polymer from 840
m to 1745 m, with seawater and Drispac from 1745 m to 2743 m and wit
Drispac/lignosulphonate from 2743 m to TD. Only 13 m of Shetland Group chalk was found on top of the Kimmerian unconformity at 1821 m. The Viking
Group contained a 15.5 m thick Draupne shale on top of a 680 m thick sequence
of sandstone units interbedded in the Heather Formation. The Middle to Early
Jurassic was also well developed. Shows occurred sporadically in limestones,
siltstone, and claystones through the Early Tertiary and Late Cretaceous. When
entering into the Late Jurassic reservoir sands at 1836.5 m (Sognefjord
Formation) ditch gas readings went up to more than 4% from a background lower
than 1%, but without oil indications in the upp General Well 15/9-16 was drilled on the Sleipner
Øst discovery in the southern Viking Graben of the North Sea. The primary
objective was to delineate the hydrocarbon accumulations in the Heimdal
Formation on the gamma structure. Sandstones of Jurassic/Triassic age were
secondary objectives. It was the fourth well drilled on this structure. Operations and results Appraisal well 15/9-16 was spudded with
the semi-submersible installation Deepsea Saga on 28 June 1982 and drilled to
TD at 3120 m, 52 m into the Permian Rotliegendes Group. The 9 5/8" casing
had a leak at 522 m. It was squeezed twice with cement before it held a reduced
pressure. Otherwise, no significant problem was encountered in the operations.
The well was drilled with gel/seawater spud mud down to 515 m, with
gypsum/lignosulphonate mud from 515 m to 2652 m, and with a
seawater/lignite/lignosulphonate mud from 2652 m to TD. Top Heimdal was encountered at 2378 m. It
contained gas and condensate, but was thinner than expected. Pressure data
indicated a gas/water contact at 2434 m. The logs showed a sharp increase in
water saturation at 2428 m. Weak oil shows were recorded on cores between 2418
m and 2427.5 m. The prognosed sandstones of Jurassic/Triassic age were not
present at this location. Fair shows were recorded on cuttings in evaporites at
3014 m, at top Zechstein Group level. No shows were recorded on sidewall cores
from the same level. A total of 113.5 m of core (98% recovery)
was cut in seven cores in the interval 2382 to 2498 m. cores were cut and no
wire line logs were run in the well. An RFT fluid sample was taken at 2380 m
(good recovery), while attempts to sample at 2411m, 2413 m, and 2426 m gave
poor General Well 2/2-2 was located near the crest of
an elongated salt-induced domal structure in the NW corner of the block. The
main target was the Late Jurassic Ula Formation shallow marine sandstone.
Sandstones of Middle Jurassic and Late Triassic age were possible secondary
targets, having the same structural definition as the Ula sand. Secondary
objectives were further represented by the Late Cretaceous chalk and a
sandstone of Oligocene age. According to the license agreement, the
well should be drilled into the Triassic, salt or a maximum depth of 5000 m
whatever came first. The well reached a TD of 3124 m in Permian anhydrites thus
fulfilling the work commitment. Operations and results Well 2/2-2 was spudded with the
semi-submersible installation Dyvi Alpha on 4 April 1992 and drilled to TD at
3124 m in the Late Permian Zechstein Group. When drilling the 36" hole,
the pipe stuck. After the pipe was worked free, the drilling continued. The
well took a kick at 2425 m. The well was drilled with seawater and bentonite
down to 715 m, with polymer/gypsum/"SST 202" mud from 715 m to 1965
m, and with lignite mud from 1965 m to TD. The well penetrated porous layers in the
Oligocene, the Cretaceous and the Jurassic. A full suit of logs was run in
these sections. In the interval 1978-2057 m of the Oligocene, a bioturbated and
cross-laminated very fine sandstone, interbedded with siltstone and shale was
found (the Vade Formation). The upper part of the sand was found gas bearing
from 1978 m down to a GWC at 2002 m. Net pay thickness was 14 metres. A
segregated RFT gas sample was taken at 1996.4 m. The sand has a porosity of 24%
with a shale content of 25%. A water saturation of 40% was estimated. The core
analysis gave an average porosity of 27 %, but this is probably too high
because the core-plugs were drilled mainly in clean silt/sandstone intervals.
Below the gas water contact, a net sand thickness of 13 m w General Exploration well 6507/10-1 was the sixth
well drilled on the Mid Norway continental shelf area. It is located in between
later discoveries such as SmØrbukk, Heidrun, and Midgard. The main targets of
the well were sandstones of middle to Late Jurassic age. Secondary targets were
sandstones of Early Tertiary, Early Jurassic and Triassic age. The well is Reference Well for the Ror
Formation. Operations and results Wildcat well 6507/10-1 was spudded with
the semi-submersible installation Sedco 707 on 10 July 1982 and drilled to TD
at 3693 m in the Åre Formation. Tight hole was experienced at the bottom of the
13 3/8" section. While drilling the 12 1/4" section the drill string
stuck. After several attempts to free the string, the well was sidetracked. The
sidetrack was drilled to 2007 m where the string again got stuck. The well was
then sidetracked again to 2220 m at which point the string got stuck again.
This time the string was jarred free and the 12 1/4" hole was finally drilled
to 2780 m. Problems with the BOP and wellhead delayed operations in the 8
1/2" section. The well was drilled with spud mud down to 440 m, with a sea
water/clay built native mud from 440 m to 913 m, and with CMC/gypsum mud from
1971 m to 2149 m. From 2149 m to 2780 m the mud was gradually broken over to a
lignosulphonate (Spersene) mud, and from 2780 m to TD a Spersene/XP 20 mud was
used. Sandstones were found in the Middle and
Early Jurassic. The Early Tertiary sandstones were not present. The Triassic
sandstone horizon was not penetrated. An 11% methane gas peak was recorded from
a Miocene sandstone at 590 m but no fluorescence was noted. Sandstone in the
interval 1790-1805 m produced a slow crush cut fluorescence as did the Late
Jurassic mudstone between 2779 m and 2828 m in the Spekk Formation. These were
the only hydrocarbon indications recorded in the well. Logs and RFT pressure
gradients proved all potential rese General Well 7120/9-1 was drilled in the Hammerfest Basin. The primary objective of the well was to test sandstone reservoirs of
Early to Middle Jurassic age at a location very close to the highest position
of the prospective structure. The well was to be drilled into sediments
of Triassic age to a prognosed depth of 2180 m +100/-130. Operations and results Exploration well 7120/9-1 was spudded
with the semi-submersible installation Treasure Scout on 25July 1982 and
drilled to TD at 2300 m in the Triassic Snadd Formation. The 36" section
was drilled with a 17 1/2" bit followed by a 36" hole opener. Low
penetration rates were encountered due to the over-compacted nature of the clay
formation together with the presence of numerous erratic glacial boulders. The
hole had to be reamed 3 times before the 30" casing was set. After that
drilling proceeded without major problems. The 36" section was drilled
with mud left from the previous well (7117/9-1). The 26" section down to
760 m was drilled with seawater and prehydrated bentonite. From 760 m to 1651 m
the well was drilled with gypsum/"Milpolymer 302" mud, and from 1651
m to TD the well was drilled with "Milpolymer 302". The main reservoir was found hydrocarbon
bearing from 1840.5 m (Top Stø Formation) down to the gas/water contact at 1904
m, eight meter into the Nordmela Formation. This interval consists of fine to
medium, occasionally coarse sandstones with a few thin claystone stringers. RFT
pressure recordings and sampling were performed over the interval. This gave a
clear gas gradient of 0.084 psi/ft down to 1904 m with an underlying water
gradient of 0.48 psi/ft. Weak to good shows were reported in sandstones in the
interval from 1904 m in the lower part of the Early Jurassic and into the Triassic
at TD. The water saturation in this interval ranged from 50-100% and based on
log interpretation the hydrocarbons were assume General Well 30/6-9 was drilled on the Gamma
structure on the Oseberg Field in the northern North Sea. The Gamma structure
lies on the west side of the Alpha structure and is separated from it by a
large northwest-southeast fault. The primary objectives of well 30/6-9 were to
test hydrocarbon accumulations in the Brent Group and find additional
hydrocarbon accumulations within the Early Jurassic. This was the first well
located on the Gamma structure. Planned depth for the well was ca 3360 m or 75
m into the Triassic Lunde Formation. Operations and results Wildcat well 30/6-9 was spudded with the
semi-submersible installation Nortrym on 28 August 1982 and drilled to TD at 3476
m in the Late Triassic Lunde Formation. No significant problems occurred while
drilling the well. The well was drilled with seawater, bentonite and hi-vis
pills down to 975 m, with KCl/polymer mud from 975 m to 2750 m, and with
lignite/lignosulphonate/freshwater mud from 2750 m to TD Weak to strong shows were reported mainly
in soft limestone stringers in the lowermost part of the Lista Formation in the
Late Paleocene, in the Danian, and through the Maastrichtian. Further shows above
the Brent Group were reported in cuttings in limestones from 2410 to 2422.5 m,
just above the Late Jurassic unconformity. The main target, Brent Group was penetrated
from 2458 to 2620 m. It was hydrocarbon bearing over the entire interval with
the gas/oil contact calculated from FMT pressure recordings at ca 2520 m. This
is the same, as the GOC on the Alpha structure. No oil/water contact was
encountered. The net pay in the Brent Group is calculated to be 98 m giving a
net/gross ratio of 0.60. The average porosity is 22.7% with General Well 16/1-3 is located on the Gudrun
Terrace west of the Utsira High. The main objective of the well was to evaluate
the hydrocarbon potential of Jurassic sand reservoirs. Eocene and Paleocene
sands were secondary objectives. 16/1-3 was drilled on the flank of a
seismically defined structure. The prime crestal location could not be tested
due to the presence of a telephone cable on the sea floor. Operations and results Well 16/1-3 was spudded with the
semi-submersible installation Glomar Biscay II on 29 July 1982 and drilled to
TD at 3498 m in granite basement. After losing returns while drilling at 210 m,
the 30" casing was re-cemented. Shallow gas was encountered between 400
and 444 meters. Tight hole, swabbing on trips and reaming were recurrent
problems in the 12 1/4" hole due mainly to swelling of claystone and
siltstone. Mud was lost when drilling through a flint layer at 2638 m. The well
was drilled with seawater and bentonite down to 702 m, with a
lignosulphonate/CMC mud from 702 m to 2282 m, and with lignosulphonate/lignite
mud from 2282 m to TD. Mechanical log analysis over the Jurassic
interval indicated the presence of about 60 meters of gross sand. Two thin
zones of approximately 4 meters each in thickness were interpreted to be
hydrocarbon bearing. The remaining sands were judged to be water bearing or
non-reservoir. No reservoir was believed to be present in the Triassic sand,
siltstones and shales. Minor shows, consisting of stain, fluorescence and/or
mud gas manifestations were recorded in the Pliocene-Eocene, Miocene and
Paleocene sections. In addition, oily mud was recovered in one of the MFT
samples from the Jurassic Sleipner Formation. The Zechstein formation contained
generally tight anhydritic dolomites at the top. A porous but interpreted water
bearing limestone section was found in the middle portion of the Zechstein
Group. Below the limestone a 36 m thick sandstone sequence was encounte General Well 7120/7-1 is located on the
Ringvassøy-Loppa Fault Complex, in the Snøhvit Field area. It was drilled to
test possible hydrocarbon accumulations in sandstones of Middle to Early
Jurassic age in the Alpha structure. Operations and results Well 7120/7-1 was spudded with the
semi-submersible installation Neptuno Nordraug on 31 July 1982 and drilled to
TD at 2839 m in Late Triassic sediments of the Tubåen Formation. The 26"
section was first pilot-drilled with a 12 1/4" bit to 752 m. Logging of
the pilot hole confirmed a gas bearing sandstone from 375 to 392 m and it was
decided to set the 20" casing above the sand and then set the 13-3/8"
casing around the planned 20" casing shoe depth. Some gas problems delayed
plug-back operations, but otherwise operations went smoothly, and the well was
abandoned 4 days ahead of schedule. The well was drilled with seawater/gel down
to 865 m, with gypsum/polymer mud from 865 m to 1917 m, and with
gel/lignosulphonate mud from 1917 m to TD. Hydrocarbon accumulations were discovered
in the target sandstone sequence (Stø Formation) from 2408 m to 2473 m. The
sandstones showed good to excellent reservoir properties. Weak shows were
recorded in claystones in the interval from 1941 m to 2172 m and sporadically
in the lower part of the Hekkingen Formation. Shows were recorded in sandstones
throughout the reservoir and down to 2620 m. Sporadic shows were recorded from
this depth down to TD. Organic geochemical analyses show an excellent source
rock with high TOC (3 % to almost 9 % ) with type II/ III kerogen in the lower
part of the Hekkingen Formation, from 2274 m to its base. Source potential for
gas and condensate was seen in the Cretaceous Kolje Formation from 1995 m to
2205 m and in the Early Jurassic Tubåen Formation from 2651 m to 2799 m. The
well is immature down to ca 2000 m (%Ro ca 0.5) and at peak oil window maturity
at TD (%Ro ca 0.8). In contrast to the w General Well 7/11-6 is located approximately half
way between the Mime and the Ula Fields in the North Sea. The primary objective
of well 7/11-6 was to test Late Jurassic sandstones. The secondary objective of
the well was to test sandstones of Triassic age. The well was planned to reach
total depth at 4400 +/- 200 m, approximately 100 m in to the Triassic. Operations and results Wildcat well 7/11-6 was spudded with the
semi-submersible installation Treasure Seeker on 9 August 1982 and drilled to
TD at 4500 m in the Triassic Smith Bank Formation. The well was drilled without
incident except some problems with gumbo in the 17 1/2" section. The well
was drilled with seawater and high viscosity pills of pre-hydrated
bentonite/lime mud down to 670 m, with KCl/Drispac mud from 670 m to 2060 m,
with KCl/Drispac mud converting to gel/lignosulphonate mud in the 2060 m to
3970 m section, and with a lignosulphonate mud from 3970 m to TD. The well encountered a Late Jurassic Ula
Formation gross sand interval of 47 m between 4098 and 4145 m. Based on wire
line log evaluation net sand was 21.25 m with an average porosity of 15.8%. The
Ula Formation rests unconformable on the Triassic Smith Bank Formation, which
consists of interbedded sandstones and shales with local siltstones and rare
stringers of limestone. Both the Jurassic and Triassic sandstones proved water
bearing, but with residual hydrocarbons in the Ula Formation, based on logs.
Shows were reported in the interval 4007.5 m to 4038 m in the Late Jurassic hot
shale unit, in the Ula Formation, and some meters into the Triassic. Four cores were taken in the 8 3/8"
section. Cores 1 to 3 were cut mainly in the Ula Formation. The lower part of
core 3 and all of core 4 were cut in the Triassic Smith Bank Formation.
Thirteen RFT pressure tests were attempted in the well over the interval of
4106 to 4204.5 m. From the pressure tests a water gradient of 0.44 psi/ft
(1.014 gm/c General Well 1/3-3 is located on the Cod Terrace
in the North Sea. It was drilled to evaluate the hydrocarbon potential of both
the Late Jurassic and the Triassic sandstone formations. Main target was the Late
Jurassic Ula Formation found oil bearing in the Ula field, 17 km to the NW, and
in the well 2/1-3. Secondary target was the Triassic sandstone found oil
bearing in the well 7/12-6 in the Ula field. Operations and results Wildcat well 1/3-3 was spudded with the
semi-submersible installation Borgsten Dolphin on 22 August 1982 and drilled to
TD at 4876 m logger's depth (4867 m driller's depth). The well was drilled
using water based mud. Two drilling breaks occurred, one at 4127 m and one at
4180 m. Thin layers of sandstone were found in
the Palaeocene. The Chalk Group was 686 m thick. Less than 10 m of sandstones
scattered in several thin layers were encountered and partially cored in the
Farsund Formation, they were found tight. The Late Jurassic Ula Sandstones,
which were the main objective, were found at 4178 m and they were oil bearing
down to an OWC at 4221 m, but with only ca 5 m pay zone. The upper half with
the best reservoir qualities was cored (cores 2 to 6). The coaly Bryne
Formation is assigned at 4527 m, top Triassic Smith Bank Formation at 4620 m,
and the Zechstein evaporitic rocks, anhydrite (26 m) and halite was penetrated
from 4820 m to TD. Residual hydrocarbon saturation based on
electric logs were seen in the Paleocene at 3068 to 3093 m and in top Triassic
at 4622 to 4637 m. Shows were reported as follows: Direct yellow fluorescence
on cuttings at 2955 m; Weak direct fluorescence and poor streaming yellow cut fluorescence
on cuttings at 3075 - 3145 m; Yello General Well 31/2-9 was drilled northeast
of the well 31/2-7 in the Troll West oil province in the Northern North Sea. The
main objectives were to establish the extent of a previously proven thick oil
column province in the Troll Field and to complete the well near the OWC in
order to follow the development of water coning. Operations and results Well 31/2-9 was spudded with the semi-submersible
installation Borgny Dolphin on 29 August 1982 and drilled to TD at 1770 m in the Late Jurassic Fensfjord Formation. Some problems
were encountered with the well head after running the 20" casing (2.5 days
lost), and with the BOP after running the 13 3/8" casing (3.5 days lost). The
well was drilled with spud mud down to 460 m, with seawater and gel from 460 m
to 816 m, with KCl/polymer mud from 816 m to 1509 m, and with seawater/Drispac
mud from 1509 m to TD. Well 31/2-9 encountered a hydrocarbon bearing column of
34.5 m in the Late Jurassic Sognefjord Formation. The reservoir was gas bearing
from 1549 -1570 m (21 m gas column) and oil bearing down to 1583.5 m (13.5 m
oil column). This was a thinner oil column than expected. The gas reservoir
consisted of very fine to medium grained bioturbated sandstones with a high
mica content. The sandstones were very silty and well sorted. Around 1570 m a
change in lithology to medium/ coarse grained sandstones with low mica content
and less bioturbation was seen. In the lower part of the oil reservoir the mica
content was slightly more than in the upper part and the sandstones were siltier.
Below the OWC shows (moderate to very weak direct fluorescence) were observed
on cores throughout the cored section down to 1628 m. Five fiberglass sleeved cores were taken in the 12
1/4" section from 1554 to 1628 m. Four RFT runs were made and 5 samples
were obtained: at 1573 m (29 deg API oil), 1571 m (oil), 1565 m (gas), and two
samples at 1575 m (oil) The well was permanently ab General Well 8/3-2 is located in the Egersund
Basin in the North Sea. The primary objective of 8/3-2 was to test possible
hydrocarbon accumulations in sandstones of Middle Jurassic and Triassic
sandstones. Operations and results Wildcat well 8/3-2 was spudded with the
Semi-submersible installation West Vanguard on 4 October 1982 and drilled to TD
at 2657 m in the Triassic Skagerrak Formation. This was the first well drilled
by West Vanguard. Drilling of the 36" and 26" sections were without
incident, however the BOP stack required extensive repair and eight days were
spent waiting on parts and repairs. Gumbo caused some delay in the 17 1/2"
section. The well was drilled with spud mud down to 501 m, with polymer/gypsum
mud from 501 m to 1150 m, and with gel/lignosulphonate mud from 1150 m to TD.
The well encountered Middle Jurassic (Bryne Formation) sandstones with good
reservoir properties from 2375 m to 2417 m. This was thinner than expected. A thin
sandstone sequence was encountered from 2465 m to 2474 m in the underlying
Skagerrak Formation. Some shows were recorded in shales from the interval 2088
m to 2355. The lower part of the Tau Formation is a "hot shale"
characterized by very high gamma ray readings. No shows were seen in the porous
sections and electrical logs and RFT pressure gradients confirmed water wet
reservoirs. Organic geochemical analyses proved excellent source rock potential
in the Late Jurassic shales, with TOC in the range 2 % to 7 % and hydrogen
index in the range 250 to 600 mg HC/g TOC. Best potential is seen in the Tau
Formation. The well is immature for oil and gas generation with %Ro = 0.45 -
0.5 towards TD. The analyses indicate shows of wet gas in the Bryne Formation
sandstones, but otherwise confirm the shows recorded during drilling. Two
conventional cores were taken in the interval 2384 m to2397.3 m in the Bryne
Formation. No fluid samples were taken. The well w General Well 31/2-10 was drilled as an appraisal
well in the Troll West oil province in the Northern North Sea. The main
objectives were to define the top and intra reservoir markers in this area of
the Troll West, establish the extent of the 27.5 m oil column in the area in
which the GOC is at 1541 m sub-sea (1567 m RKB), and to determine the reserves
potential in the structurally low area east-north of well 31/2-5 and south east
of 31/2-7. Operations and results The site survey revealed, typical for the
area, numerous pockmarks. These had a fairly random distribution of 15 to 20
per km2. Although the size of individual pockmarks varied, average sizes were
between 30 and 40 m wide at the rim, and 3 to 4 m deep at the centre. At the
location itself no pockmark was seen. Well 31/2-10 was spudded with the semi-submersible
installation Borgny Dolphin on 2 October 1982 and drilled to TD at 1833 m, 40 m
into in the Early Jurassic Fensfjord Formation. After drilling the 36"
section, a 14 3/4" pilot hole was drilled to 810 m. The hole was then
logged without indication of shallow gas before opening up to 26". One and
a half days were lost during coring due to bad weather. The well was drilled
with spud mud down to 472 m, with gel/seawater from 472 m to 810 m, with KCl/polymer
mud from 810 m to 1530 m, and with seawater/Drispac from 130 m to TD. Top Jurassic was encountered with a 35 m
thick Draupne shale. The Sognefjord Formation sands were encountered at 1600 m,
below the prognosed OWC. The Heather Formation came in at 1733 m, and the
Fensfjord Formation at 1793 m. From top Sognefjord Formation to 1647 m bleeding
oil and oil stained grains were noted on the cores. However the petrophysical
interpretation concluded the sands to be water bearing. Ten cores were taken in the interval 1575
m to 1741.5 m and 127.98 m (77%) was recovered. All cores were taken in
fibreglass sleeves to achieve better recovery General Well 16/7-4 is located ca 10 km southeast
of the Sleipner Øst Field and 6 km east of the 15/9-15 gas discovery in the North Sea. The objective of the well was to test the presence of a structural trap in
Jurassic/Triassic sandstones on the A-North Prospect in the southwest corner of
Block 16/7. Operations and results Well 16/7-4 was spudded with the
semi-submersible installation Glomar Biscay II on 15 October 1982 and drilled
to TD at 2781 m in the Triassic Group. The well was drilled with seawater
and gel all through. Only 1.5 m Jurassic sediments (Draupne
Formation) were present in well position. The Triassic Group sandstone was
encountered at 2521.5 m and held a 117.8 m gas/condensate column from top and
down to 2639.3 m (-2314.3 m subsea). The gas-bearing sandstones were found
interbedded with a few thin shales. The reservoir quality was best near the top
of the sand, becoming gradually poorer downwards. The net gas sand was 85.4 m
with 23% porosity and 36% average water saturation. No shows were reported from
above or below the hydrocarbon-bearing interval in the well. Six conventional cores were cut from 2568
to 2681.5 m to in the Jurassic - Triassic interval. One Multi Formation Tester
(MFT) fluid sample was taken at 2638.5 m. It recovered 1.2 litres of 57 deg API
condensate, 1.3 Sm3 gas and 2 litres of water. The well was permanently abandoned on 6
December 1982 as a gas/condensate discovery. Testing Two drill stem tests were performed in
the Triassic Group. DST 1 at 2590.5 - 2597 m flowed 199 Sm3
condensate and 385110 Sm3 gas /day through a 42/64" choke. The
gas/condensate ratio was 1938 Sm3/Sm3, the oil gravity was 58 deg API, and the
gas gravity was 0.791 (air = 1). DST 2 at 2525 - 2535 m flowed 253 Sm3
condensate and 472890 Sm3 gas /day through a 42/64" choke. The
gas/condensate ratio was 1871 Sm3/Sm3, the oil gravity was 59 deg API, and General Well 30/6-10 was drilled to appraise the
hydrocarbon potential in the Alfa structure on the Oseberg Field in the North
Sea. The main objective was to define the gas/oil contact and to obtain cores
from this zone. Operations and results Appraisal well 30/6-10 was spudded with
the semi-submersible installation Treasure Scout on 4 October 1982 and drilled
to TD at 2656 m in the Early Jurassic Drake Formation. Some problems were
encountered while running both 20" and 13 3/8" casing. The drill
string got stuck at 1992 m and leakages in the BOP stack after installing the
13 3/8" casing also occurred. The well was drilled with seawater and
hi-vis pills down to 970 m and with KCl/polymer mud from 970 m to TD. At 1992 m
15 m3 diesel and 15.9 m3 Imco spot was pumped to free the pipe. First oil show in the well was recorded
at 1980 m in limestone stringers at top Balder Formation level. Poor oil shows
were recorded in the intervals 2030 to 2100 m and 2215 m to 2253 m. Good oil
shows were recorded on cuttings from marls and limestones in the Shetland Group
from 2253 m to 2380 m, then again poor shows were recorded down to top of the
Brent Group at 2457 m. The well encountered oil and gas in Middle Jurassic
Brent sandstones. The Brent Group was found hydrocarbon bearing over the entire
118 m interval. Net pay was 37.3 m with 23.3 % average porosity and 23.9%
average water saturation. The gas/oil contact was found from RFT pressure gradients
to be at 2520 m in the Ness Formation, but no oil/water contact was
encountered. A total of eleven conventional cores were
cut from the top of the Ness Formation and down into the Dunlin Group shales. Driller
depths through the cored General Well 31/2-13 S was drilled as an appraisal in the Troll
West oil province in the Northern North Sea. The main
objectives of were to investigate the reservoir properties and accumulation
conditions between the wells 31/2-5 and 31/2-11. Water and/or gas -coning tests
were to be conducted. Operations and results Appraisal well 31/2-13 S was spudded with
the semi-submersible installation Borgny Dolphin on 2 January 1984 and drilled
to TD at 2010 m in the Middle Jurassic Fensfjord Formation. Due to bad weather
the string parted and was observed lying across the temporary guide base when
the well was spudded. The fish was recovered. Straight hole was drilled down to
500 m where the hole was kicked off with an angle of 1 1/2 degree. Some
problems due to tight hole occurred in the 17 1/2" hole. Mud losses to the
formation occurred at 1531 and 1700 m, 100 bbls at each depth. A drill break
occurred at 1744 m in the 12 1/4" hole section. The well was drilled with
seawater and viscous pills down to 473 m, with Gelled mud from 473 m from 473 m
to 750 m, with seawater from 750 m to 825 m, and with oil based mud from 825 m
to TD. The Oil based mud used was termed "Fazekleen, low toxicity invert
oil emulsion mud, based on Shell Sol D70 oil" Top reservoir (top Sognefjord Formation) was
penetrated at 1732 m (1526.5 m TVD), top Heather Formation at 1855 m (1613 m
TVD), and top Fensford Formation sandstone at 1934 m (1671 m TVD). Oil and gas were
encountered in the Sognefjord Formation. The GOC was at 1790 m (1567 m TVD) and
the FWL was estimated at 1828.5 m (1594 m TVD). Strong to moderate fluorescence
was observed on the cores down to 1844 m (1606 m TVD), but heavy contamination
from the oil-based mud made shows detection somewhat uncertain. The upper half
of the oil bearing formation consisted of generally clean sandstones. Below
1555 m TVD the sands were micaceous. Tight calcareous streaks occurred over the
whole sectio General Well 15/12-1 was drilled in order to
evaluate the Paleocene and Jurassic formations on a closed structure 5 km
northeast of the Maureen Field which is located just across the UK-Norwegian
median line in UK territory. The principle objectives of the 15/12-1 test were
the Paleocene and Dogger (Hugin Formation) sandstones where oil accumulations
had been proven in the Maureen field 5 km to the southwest on British sector. The well is Reference Well for the
Sleipner Formation. Operations and results Wildcat well 15/12-1 was spudded with the
semi-submersible installation Ross Rig on 7 July 1975 and drilled to a total
depth of 3269 m in Triassic fine-grained sandstone with green and red-brown
shale of the Skagerrak Formation. The well was drilled with a lignosulphonate
type of mud. The Paleocene sandstone at 2633 m to 2643
m in 15/12-1 was encountered 6 m lower than in the Maureen no. 2 well. The
sandstone is medium to coarse grained with good porosity (26%), but water wet.
The Hugin sandstone was encountered some 50 m higher than in the Maureen no. 2
well. Oil shows were encountered on the cores from the Hugin Formation, but log
analysis and FIT proved the sandstone to be water bearing. The logs also
indicated shows of hydrocarbon in the Late Cretaceous limestone at 2925 - 2955
m, but log porosity was calculated from 0 to 6%, too tight to obtain a sample.
The Late Triassic has good sand development that could be adequate for
accumulation of hydrocarbons. During the drilling of the Triassic section, the
background gas in mud and cuttings was near zero. Eight cores were cut in the well.
Paleocene sands (Lista and Maureen Formations) were cored from 2612.1 m to
2651.1 m. One core was cut in the Heather Formation from 3067 m to 3073.3 m;
one core was cut from the Hugin Formation into the Sleipner Formation from
3125.7 m to 3143.7 m. The Sleipner Formation was further cored in three cores
down to 3183 m. On the bas General Well 34/10-14 was drilled on a horst
block in the north-eastern part of the Gullfaks field. The objectives of the
well were to prove the structural position of the middle- and early Jurassic
sandstones and to establish the oil-water contact in the Brent Group in this
part of the field. Operations and results Appraisal well 34/10-14 was spudded with
the semi-submersible installation Ross Rig on 24 December 1981 and drilled to
TD at 2647 m in the Triassic Hegre Group. Significant downtime (17% of total
rig time) was caused by the combined effect of bad weather and the need to pull
the BOP three times to detect leaks. The well was drilled with
gel/lignosulphonate/seawater mud all through. Weak shows on limestone and claystone
cuttings were recorded intermittently from 1506 m in the Hordaland down to top
Shetland Group at 1729 m. Sandstones of the Ness Formation were oil-bearing
from 1908 m to the oil-water contact, indicated by pressure measurements and
logs to be at 1972 m. This corresponds to the OWC found in the wells 34/10-3, 5
and 8. Shows on cores continued down to 2002 m. Ten cores were recovered, nine in the
interval from 1889 to 2047m KB and one core from 2210 to 2228 KB. RFT fluid sampling
was performed at 1917.5 m and 1961.5 m but the fluids recovered were not
representative for the reservoir fluid. The well was permanently abandoned on 19
March 1982 as an oil appraisal well. Testing One drill stem test was performed in the
interval 1933.5 m to 1937.5 m in the Ness Formation. The tes General Well 2/11-4 was drilled on the Lindesnes
Ridge in the Southern North Sea. The objective was to delineate the Valhall
discovery made by well 2/8-6 in 1975. The target was the Late Cretaceous chalks
in the Tor and Hod formations. Operations and results Appraisal well 2/11-4 was spudded with
the jack-up installation Dyvi Beta on 20 March 1978 and drilled to TD at 2858 m
in the Late Cretaceous Rødby Formation. No significant problems were
encountered in the operations. The well was drilled with sea water and hi-vis
pills down to 390 m, with sea water/gypsum mud from 390 m to 2559 m, and with Magcobar
oil based "Oilfaze" mud from 2559 m to TD. The well penetrated a normal Quaternary
and Tertiary sequence. Good oil shows with free oil present in the mud was
observed in siltstone and claystone from 1400 to 1800 m in the upper part of
the Hordaland Group. Occasional spotty oil shows in claystones and limestones
(direct and cut fluorescence) were recorded from 1800 to 2250 m. The Cretaceous
Chalk was penetrated at a depth of 2587 meters some 23 meters higher than
prognosed. The objective Tor Formation reservoir proved to be hydrocarbon
bearing with a gross pay section of 18 meters and oil saturations up to 62%. Hydrocarbon
saturation in the Hod Formation was insignificant due to low elevation on the
structure. Fair to excellent oil shows were seen in the reservoir section down
to 2607 m. Below 2607 m scattered poor shows were seen down to 2619 m. Coring commenced at 2582.5 meters, 4.5
meters above top Chalk, to ensure recovery from the uppermost part of the pay
section. A total of 5 conventional cores were attempted over the interval
2582.5 m to 2619 m. Cores no 1 and 2 ha General Well 2/4-3 (named 2/4-2X by operator
Phillips) was drilled to appraise the 2/4-2 Ekofisk discovery in the southern
Norwegian North Sea. The target was to test the Tertiary and the top of the
Late Cretaceous. Operations and results Well 2/4-3 was spudded with the
semi-submersible installation Ocean Viking on 27 January 1970 and drilled to TD
at 3431 m in the Late Cretaceous Tor Formation. The well was planned vertical,
but the deviation was significant. Maximum deviation was 1 deg at 618 m, 3
deg at 1077 m, 11.5 deg at 1316 m, 16.4 deg at 1605 m, 10 deg at 2167 m, 4
deg at 3002 m, and 1.7 deg at 3292 m. This indicates that TVD RKB is ca 30 m
shallower than MD RKB at TD, but exact records are not available. The well was
drilled with seawater and hi-vis mud down to 619 m, with CaCl2 / Dextrid
(modified potato starch) from 619 m to 1695 m, and with lignosulphonate /
seawater from 1695 m to TD. One - four percent diesel was added to the mud
below 619 m. The Danian chalk (Ekofisk Formation) was
encountered at 3090 m, and the Late Cretaceous chalk (Tor Formation) at 3253 m.
The formations were tested hydrocarbon bearing from 3124 m to 3319 m. Eighteen conventional cores were cut in
the well. Core 1was cut in the interval 1705 - 1717 m with only 0.6 m core
recovered. Cores 2 - 13 were cut in the Danian chalk (Ekofisk Formation), while
cores 14 - 18 were cut in the Maastrichtian chalk (Tor Formation). No fluid
samples were taken on wire line. The well was permanently abandoned on 31
May 1970 as an oil appraisal. Testing Ten drill stem tests were carried out
through perforations in the 7" liner. DST 1 and 2 tested the intervals
3352 - 3362 m and 3331 - 3341 in the in the Tor Formation. They produced only
water. DST 3 to 9 tested different zones in the interval from 3124 to 3319 m in
the Ekofisk and Tor Formations. They produced gas and oil. The oils were in the
range 33.2 to General Well 30/11-4 was drilled north-east of
the Frigg area in the Fensal Sub-basin in the North Sea. Previous well 30/11-3
was abandoned at top Statfjord Group for technical reasons, due to high
pressures, without being production-tested. Well 30/11-4 was then proposed as a
virtual re-drill, only some 400 m NE of 30/11-3. The objective of the well was
to test the hydrocarbon potential of the Middle Jurassic Vestland Group
sandstones and the Early Jurassic Statfjord Group sandstones in a westward
tilted horst block Operations and results Wildcat well 30/11-4 was spudded with the
semi-submersible installation Dyvi Delta on 25 January 1984 and drilled to TD
at 5255 m in Late Triassic sediments belonging to the Statfjord Group . At 2179
m the drill string parted, leaving a 24 m fish in the hole. After unsuccessful
fishing the well was sidetracked from 1918 m. The well was drilled with
bentonite and brack water down to 813 m, with KCl/polymer mud from 813 m to
4205 m, with gel/lignosulphonate/lignite mud from 4205 m to 5059 m, and with
gel/polymer lignite mud from 5059 m to TD. Well 30/11-4 penetrated water bearing
reservoir sands in the Tertiary Frigg and Heimdal formations. The Vestland
Group was penetrated at 3434 m. This section had oil shows at 3434 m to 3470 m,
where some oil emulsion was retrieved by RFT, at 3514 m to 3550 m, and at 3635
m to 3650 m. An anomaly in the reservoir pressure occurred at about 3580 m where
a siltstone/claystone interval possibly acts as a seal/pressure barrier. A total
of 615 m of sands and shales assigned to the Statfjord Group, between 4640 m
and TD in the well. Log interpretation pointed towards the presence of at least
75 metres of sands with porosities up to 20% and water saturations as low as
General Wildcat well 7120/12-4 is located on the
northern margin of the Finmark Platform ca 9 km south of the 7120/12-2 gas
discovery. The primary objective of the well was to test a sandstone reservoir
of Late Permian age on the platform area. The reservoir prospect was seen as
merging of two shale/limestone units separated by the reservoir sandstone.
These shale units were seen on the seismic as the "platform" event
and the "sub crop" event at 1160 ms and 1260 ms respectively. The sub
crop event was interpreted as a carbonate shelf edge and the reservoir as being
composed of shallow marine sandstones. The cap rock was the massive overlying
Triassic shale and the trap was sourced by migration from mature Late Triassic
and Permian shales in the Hammerfest basin. Basement was prognosed at 2430 m. Operations and results Well 7120/12-4 was spudded with the
semi-submersible installation Treasure Scout on 18 February 1984 and drilled to
TD at 2199 m in the Late Carboniferous Ugle Formation. No significant problems
occurred during operations. The well was drilled with seawater and hi-vis pills
down to 666 m and with KCl/polymer/gypsum mud from 666 m to TD. The well penetrated an interval of
Quaternary to Tertiary age sediments, which directly overlay rocks of Middle to
Late Triassic age (Snadd Formation) at 435 m. A Late Permian succession was
penetrated from 1366 m to 2118 m and consisted of alternating beds of
claystone/siltstone/sandstone (Ørret Formation) and cherty limestone (Røye
Formation). The "platform" event was penetrated at 1469 m and
correlate with a 33 m thick Røye sequence. The prognosed reservoir was
encountered at 1502 m and was composed of fine to occasionally very
coarse-grained sandstone belonging to the Ørret Formation. The reservoir was
water bearing with a gross interval of 56 m and net sand was 55 m. Average
calculated porosity was 18 %. The sub crop event was a second Røye sequen General Well 31/3-2 was drilled immediately to
the southeast of a fault that was interpreted as a boundary fault between Troll
West and Troll East. The main objectives of the appraisal well 31/3-2 were to
determine if hydrocarbons were present on the downthrown south side of the
fault, to determine the contacts, and to determine the degree of communication
across the fault plane. A test would be performed in the case of moveable
hydrocarbons, in order to observe boundary effects where the pay zone is narrow
and thin. The well was planned to reach total depth in the Early Jurassic Drake
Formation at 2050 m if drilling through the "boundary fault". In the
case of drilling entirely within the hanging-wall block the total depth was
estimated to 2130 m. Operations and results Well 31/3-2 was spudded with the
semi-submersible installation Treasure Seeker on 5 March 1984 and drilled to TD
at 2090 m in claystones of the Early Jurassic Drake Formation. No significant
technical problems occurred during drilling and testing. The well was drilled
with pre-hydrated gel/seawater with sweeps of high viscous mud down to 629 m
and with KCl/polymer mud from 629 m to TD. The Sognefjord Formation (1567 - 1706 m)
was found oil bearing down to 1578.5 m where the oil/water contact was
established. The oil-bearing reservoir consisted of very fine to very
coarse-grained sandstones. They are friable to loose with only traces of
siliceous or calcareous cement. The total net sand in the Sognefjord Formation
was calculated to 132 m out of 139 m gross thickness, giving a net/gross ratio
of 0.95 and an average porosity of 26.6%. A thin (0.5 m) gas cap could be
present on top of the oil column. This was identified from LDT/CNL logs and was
also consistent with the GOR development during the test, but was not confirmed
by RFT data. There were no oil shows above the Sognefjord Formation, and no oil
shows below1595 m, and the Middle to Early Jurassic sa General Well 31/5-3 was drilled in the southern
part of the Troll West Field. The main objectives were to appraise and test the
reservoir qualities and the lithology of the Late Jurassic Sognefjord
Formation. Operations and results Well 31/5-3 was spudded with the
semi-submersible installation Treasure Saga on 10 April 1984 and drilled to TD
at 2250 m in the Late Jurassic Drake Formation. At 1426 m circulation was lost,
and 450 bbls mud was lost to formation before the well was stabilized. The well
was drilled with spud mud down to 950 m, with KCl/polymer mud from 950 m to
1497 m, and with a Pro-wate/NaCl-brine/pro-salt mud from 1497 m to TD. The well proved the existence of a
stratigraphy ranging from Lower Jurassic to Quarternary. The Tertiary and
Quaternary sections were mainly composed of claystones, with a minor sand
developed in Pleistocene at the base of the Nordland Group. The Jurassic was
composed of sandstone and siltstones in the Viking and Brent Groups, and mainly
claystone with an interbedded sandstone layer in the Dunlin Group. One major
unconformity was found between Early Portlandian and Maastrichtian. Four other
unconformities were also observed in the well, from Aalenian to Bathonian, from
Early Kimmeridgian to Early Portlandian, from Late Oligocene to Pliocene, and
one intra-Oligocene. The Sognefjord Formation was hydrocarbon
bearing with a 39.5 m hydrocarbon column, of which 17.5 m was gas and 22 m was
oil. Top reservoir was found at 1555 m, the GOC was at 1572.5 m, and the OWC at
1594.5 m. Oil shows persisted further down, but decreased from 1595 m and
disappeared below 1622 m. No other interval in the well was hydrocarbon
bearing. Three cores were cut from 1550 m to
1622.5 m in the Late Jurassic Sognefjord Formation. FMT gas samples were taken
at 1557 m and 1567. Three more FMT fluid samples were taken in the oil zone at
1577 m, 1591 m, and at 1592 m. The well was permanently General Well 30/9-3 A is a sidetrack to well 30/9-3
on the Gamma West structure on the Oseberg Fault Block in the northern North
Sea. The primary objective of 30/9-3 was to find hydrocarbon accumulations in
the Middle Jurassic Brent Group. Secondary objective was to find additional
hydrocarbon accumulations in the Early Jurassic. Planned TD was ca 75 m below a
possible intra Triassic marker to a depth of 4188 +/- 100 m. Well 30/9-3
discovered oil in the Brent Group, but reached only 3113 m in the Drake
Formation due to fish in the hole. For the same reason no wire line logs were
run below 1713.5 m. Sidetrack well 30/9-3 A was drilled to
complete the well programme. Operations and results Well 30/9-3 A was kicked off on 26
February 1984, from a window from 1539 to 1562 m in the 13 3/8" casing.
The well was drilled to TD at 4300 m (4008 m TVD) in the Late Triassic Lunde
Formation using the semi-submersible installation Nortrym. No significant
problem was encountered in the operations. The well was drilled with
Invermul/EZmul Oil Based Mud from kick-off to TD. The Ness Formation (2853.5 - 3059 m, 2717.3
- 2890 m TVD) was encountered at a horizontal distance of 538 m to the west of
the 30/9-3 well. The top of the formation had been subjected to erosion and
lacked the sandstone units which were found in the upper part of the 30/9-3
well. The lithology was alternating sandstones, siltstones and shales with beds
of coal. The sandstones were generally very fine to fine grained, locally
medium grained, and occurred often as normally graded beds. The Ness Formation was found oil bearing
down to 3000 m (2840m TVD). No oil/water contact c General The objective of the well, located on the
Makrell horst on the northern margin of the East Shetland Basin, was to test
two possible sandstone reservoirs of Triassic and Permo-Triassic age
respectively. The first of these reservoirs was prognosed to be an Early
Triassic massive sandstone reservoir. Correlation with the U.K. well 211/13-1
indicated that this sandstone could be divided into two main sequences both
with increasing silt and clay content in the lower parts. These sands were
thought to be deposited in a braided alluvial system. The second was prognosed
to be Permo-Triassic fluvial sandstone similar to the higher reservoir but
separated from it by lacustrine or lagoonal shales, marls and limestones. The
well was planned to reach total depth below a seismic marker at approximately
3825 m. Well 33/5-1 is reference well for the
Triassic Teist and Lomvi Formations. Operations and results Wildcat well 33/5-1 was spudded with the
semi-submersible installation Treasure Seeker on 19 July 1979 and drilled to TD
at 3829 m in the Early Triassic Teist Formation, interpreted to be close to the
seismic "A" marker. A gas leakage from a shallow gas zone at 480 m to
490 m between the 20" and 30" casing was observed sporadically
throughout drilling of the well. The leakage was stopped when the gas zone were
squeezed off with cement during abandonment of the well. An 18 1/2" hole
was first drilled to 1516 m. When pulling out of the hole the string got stuck
at 1226 m and the well was sidetracked from 1019 m to 1071 m. Logs are from the
sidetrack. Further drilling went without significant problems. The well was
drilled with seawater/bentonite/CMC down to 1540 m. Diesel and lubricants were
added to the mud when attempting to free the stuck pipe. A
lignosulfonite/lignite mud was used from 1540 m to TD. A sequence of interbedded limestones of
Early Tertiary to Late Cretaceous age (Late/Middle Paleoc General Wildcat well 7120/7-3 is located on the
Ringvassøy-Loppa Fault Complex west of the Hammerfest Basin and the Snøhvit
Field. The primary objective of the well was to test possible hydrocarbon
accumulations in sandstones of Middle to Lower Jurassic age. Operations and results The well was spudded with the
semi-submersible rig West Vanguard on 18 March 1984 and drilled to TD at 3062 m
in the Early Jurassic Nordmela Formation. The well was drilled with seawater
and bentonite down to 331 m, with lignosulfonate/gypsum/polymer mud from 331 m
to 715 m, with gypsum/polymer mud from 715 m to 1720 m, with polymer mud from
1720 m to 2625 m, and with lignite/polymer mud from 2625 m to TD. The 36"
hole had to be reamed before setting of the 30" casing. During cementing
of 20" casing returns were lost. Technical problems occurred when testing
the BOP stack before drilling out of the 20" casing shoe, and after the 13
3/8" casing job. Mud problems occurred when drilling out of the 20"
casing shoe due to cement contamination. Because of tilted wellhead two
attempts to run in the casing was needed. When running in an 8 1/2" bit to
perform leak off test below the 9 5/8" casing shoe, problems occurred
getting the bit through wearbushing in wellhead. After this 4 kg junk was
recovered from the hole. The well penetrated Tertiary, Cretaceous,
and Jurassic sediments. Lithology down to 2759 m (Base Cretaceous) was
dominantly claystone with stringers of sandstone/siltstone/Limestone/Dolomite.
The Late Jurassic Hekkingen Formation from 2759 m to 2889 m consisted of shale
with stringers of siltstone and limestone and traces of sand. Pyrite was seen
in trace amounts in the upper part and was abundant in the lower part of the
sequence. From 2889 m to TD, in the Middle to Early Jurassic, the lithology was
sandstone with shale interbeds. Trace to faint shows were recorded in claystone
cuttings below 1200 m. Good show General Well 31/6-5 was drilled in the southern
part of the Troll East gas province, 30 m from well 31/6-4, which was junked
for technical reasons. The main purpose was to appraise and test possible oil
and gas accumulations in sandstones of Late to Middle Jurassic age, and to give
further information about lateral facies changes within the reservoir
sandstones. Operations and results Appraisal well 31/6-5 was spudded with
the semi-submersible installation Deepsea Bergen on 5 March 1984 and drilled to
TD at 2082 m in the Early Jurassic Drake Formation. In the 26" hole lost
circulation occurred at 653 m, two cement plugs were set. Several wiper trips
were taken due to tight hole. After setting of the 20" casing, the BOP had
to be repaired due to leaking during pressure testing. A drilling break
occurred at 1476 m in the 12 1/4" hole. The well was drilled with the spud
mud from the previous hole (31/6-4) treated with CMC-EHV down to 389 m, with
seawater/gel mud from 389 m to 663 m, with KCl/polymer mud from 663 m to 1720
m, and with seawater/gel/CMC mud from 1720 m to TD. Sandstone of Late to Middle Jurassic age
(Sognefjord Formation) was encountered at 1518 m with a 52 m gas column and a 4
m oil column. The gas/oil contact was at 1570 m and the oil/water contact at
1574 m. Oil shows were recorded on sidewall cores on top Fensfjord Formation
sandstone from 1722 m to 1726 m and on a sandstone SWC from 2010 m in the Ness
Formation. Ten cores were cut from 1470 m to 1721 m in the Late to Middle Jurassic
sequence (Heather Formation to Fensfjord Formation). One FMT fluid sample was
taken in the oil zone 1571.5 m. Geochemical analyses showed the oil to be
biodegraded. The well was permanently abandoned on 16
March 1984 as a gas and oil appraisal. Testing The Sognefjord Formation was tested
through gravel pack from the interval 1558 m to 1568 m. The first test gave a
non-representative General Appraisal well 31/2-14 was drilled on the
north-western margin of the Troll field. The main objectives of the well were
to demonstrate the production potential for oil in the northern part of the
Troll oil province, to evaluate the proposed template development scheme and to
confirm the predicted extension of high energy progradation sands in the
northern region. Operations and results Well 31/2-14 was spudded with the
semi-submersible installation Borgny Dolphin on 23 April 1984 and drilled to TD
at 1725 m in the Middle Jurassic Fensfjord Formation. The site survey before
spud showed, as usual for the area, a seabed with numerous pockmarks (12
pockmarks/km3 on average). After setting the 13 3/8" casing shoe at 1498 m
a leak in the kill-line was discovered, leading to repairs of the BOP and
replacement of the marine riser. After 10 days lost time normal operations
could resume. The well was drilled with seawater and hi-vis pills down to 814
m, with KCl/polymer mud from 814 m to 1513 m, and with chalk mud from 1513 m to
TD. No sands were encountered above the
Jurassic.The well encountered hydrocarbons in the Late Jurassic Sognefjord
Formation. Top reservoir was penetrated at 1533 m (1508 m SS). The GOC was at
1566 m (1541 m SS) and the FWL was at 1592 m (1567 m SS). The oil-bearing
interval consists of medium to low quality sands with a very clean layer (7m)
some 3 m above the OWC. Below 1595 m (top Heather Formation) the sands are
micaceous. The core measured permeability values range from 10 mD to 10 Darcy.
In the gas bearing part of the cored interval no to weak fluorescence was
recorded. In the oil zone (1561 - 1592 m) the fluorescence varied from weak to
strong. Below 1594 m no fluorescence was recorded. Seven cores were cut from
1535 m to 1599 m in the Late Jurassic sequence. No samples were taken on wire
line. The well was permanently abandoned on 21
June as a gas and oil appraisal. General Wildcat well 7120/9-2 is located in The
Hammerfest Basin, west of the Albatross discovery, later included in the
Snøhvit Discovery. The structure comprised a dome like feature transected by a
few major N-S, and E-W oriented faults. The 7120/9-2 well was drilled in a
crestal position on this structure and planned total depth was 5500 m in rocks
of Permian/Carboniferous age. The objective of well 7120/9-2 was to test
Permian reservoirs confined by Permian Marker III (4810 m ±150 m), Permian
Marker II (4745 m ±50 m), and Permian Marker I (4620 m ±150 m) for
hydrocarbons. Operations and results Well 7120/9-2 was spudded with the
semi-submersible rig Treasure Scout on18 April 1984 and drilled to a total
depth of 5072 m in limestones, siltstones and cherts the Permian Røye
Formation. The well was drilled with Bentonite and seawater to 381 m, with
KCl/Polymer mud from 381 m to 1165 m, with Lignosulfonate /Polymer mud from
3900 m to 4270 m, and with Gel/Lignosulfonate mud from 4270 m to TD. A 17
1/2" pilot hole was drilled to 1165 m, before underreaming to 26"
hole. The underreamer was lost in the hole and the well was sidetracked at 1070
m. While running the 20" casing, it parted but was recovered. Before
drilling the 12 1/4" hole section two cement squeeze jobs were performed
due to a low leak off test. Due to lost circulation the 9 5/8" casing was
set at 4270 m. Before drilling the 8 3/8" hole section a cement squeeze
job was performed due to a low leak off test. Due to lost circulation the
7" liner was set at 4791 m. Two cement squeeze jobs were performed. At
5072 m lost circulation problems occurred, the well was logged and plugged back
and terminated earlier than prognosed. Some of the Jurassic sandstone intervals
encountered between 1970 m and 2290 m were gas bearing, with structural closure
at the point where the well bore penetrated the formation. The intervals were
subdivided into thr General Well 6406/3-1 is located in the southern
end of the block, west of the Tyrihans S ør Field on the Mid Norway continental
shelf. The primary objective was to test the reservoir potential of the Middle
Jurassic sandstones. Secondary objectives were the Early Jurassic sandstones,
penetration of the Triassic Grey Beds and Red Beds, and sampling of potential
source rocks. Operations and results Well 6406/3-1 was spudded with the
semi-submersible installation Ross Isle on 27 April 1984 and drilled to TD at
4902 in the Late Triassic Red Beds. The well was drilled with seawater and gel
(bentonite/soda) down to 962 m, with gypsum/lignosulphonate mud from 962 m to
3775 m, and with gel/lignosulphonate/lignite mud from 3775 m to TD. At 4498 m a
pill of IMCO SPOT/ Pipe Lax was added to free the pipe, which was stuck. A hydrocarbon bearing Middle Jurassic
sandstone was encountered at 3782 m, but a drill stem test proved only low
concentration of gas in a water phase. The pore pressures in the well were
higher than expected and the Middle Jurassic sandstone, which was believed to
have a pore pressure equivalent to 1.14 s.g., proved to have a pore pressure
equivalent to 1.82 s.g. Post-well geochemical analyses detected migrated
hydrocarbons frequently below 1650 metres. These shows were seen chiefly as wet
gas/condensate between 2405 - 2585 m and as wet to extremely wet gas at 3665 -
3785 m. Good shows of wet or marginally wet gas were associated with the coals
within the Early Jurassic and Trias (Åre Formation). These were suggested in
the geochemical report to be in-situ generated and not migrated. Four cores were cut in the well: three
from 3783 m to 3847 m in Middle Jurassic Sandstones (Garn Formation) and one
from 4539 m to 4549 m in the "Coal Unit" (Åre Formation). An RFT
fluid sample was taken at 3784.5 m in the Garn Formation. The well was permanently abandoned on 14
August 1984 as a well with strong ga General Well 2/1-6 is located on the northern
side of the Gyda structure on the Cod Terrace in the North Sea. The main target was the Late Jurassic
Sandstone, informally called the Gyda sandstone member. The well was located
such that it should prove the oil water contact of the 2/1-3 oil discovery, and
by this establish whether 2/1-3, 2/1-4 and 1/3-3 all have encountered the same
oil accumulation on the two sides of the saddle point. It should also test
further the extent and the quality of this Upper Jurassic reservoir. Operations and results Appraisal well 2/1-6 was spudded with the
semi-submersible installation Dyvi Alpha on 30 April 1984 and drilled to TD at 4583
m (4588 m loggers depth), one metre into Late Triassic sediments of the Skagerrak
Formation. The well was drilled with seawater and pre-hydrated bentonite spud
mud down to 635 m, with KCl/polymer mud from 635 m to 3424 m, with
lignosulfonate mud from 3424 m to 4124 m, and with high temperature polymer mud
from 4124 m to TD. The Gyda sandstone member was penetrated
at 4173 m logger's depth. The reservoir is 205 metres thick, generally very
fine to fine grained sandstone, but with a 28 metre thick siltstone
incorporated in the uppermost part. Reservoir properties were very variable.
Reasonable reservoir properties were found near the top of the reservoir. They were
poor in an upper siltstone zone, in an intermediate 77 metre thick quartz
overgrowth zone and at the base of the 2/1-3 sand where it shaled out into the
Farsund Formation. Shows were recorded from 4174 to 4178 m in a sandstone that
had very low permeability, and could not be tested. Minor patchily developed
shows were observed from 4178 down to 4203 m, all within General Well 30/6-15 was drilled on the Gamma
North structure west of the Oseberg Alpha structure. Gamma North is a NNW-SSE
trending fault block down-faulted to the adjacent Alpha structure. The primary
objective was to find hydrocarbon accumulations in the Statfjord Group. The
secondary objective was to test the hydrocarbon potential in the Cook
Formation. The total depth of the well was planned ca 270 m into the Triassic
at a depth of ca 3950 m, corresponding to ca 3200 m TVD. Operations and results Wildcat well 30/6-15was spudded with the
semi-submersible installation Treasure Seeker on 2 May 1984 and drilled
deviated to TD at 3972 m (3200 m TVD) at a position ca 2180 meters west of the
surface position. Operations suffered from comparatively much down time due to
hole problems and equipment repairs. The 8 3/8" and 6" sections in
particular suffered hole problems and difficult logging. The well was drilled
with spud mud down to 195 m, with gel/sea water from 195 m to 617 m, with
SafeMul oil based mud from 617 m to 3005 m, and with NaCl/polymer mud from 3005
m to TD. The Etive Formation (2884 - 2902 m, 2358
- 2372 m TVD) truncated by Cretaceous strata was found water bearing. No Cook Formation reservoir was
encountered. The Statfjord Formation (3241 - 3548 m, 2641.5 -2878.5 m TVD)
sandstones were found gas bearing down to 3313 m (2697 m TVD), and oil bearing
down to 3348 m (2723.5 m TVD). An oil/water transition zone is seen down to
3359 m MD (2732 m TVD). The lithology of the hydrocarbon bearing interval was
predominantly sandstones with some interbeds of claystones/shales. Net pay in
the gas zone was calculated on logs to 67.4 m giving a net to gross ratio of
0.94. Ne General The wildcat 34/7-1 was drilled on the
E-structure northeast in block 34/7, on a location ca 9 km south-south west of
the 34/4-1 Snorre Discovery well in the northern North Sea. The continuation of
this structure was explored by well 34/4-4. The main objective of 34/7-1 was Late
Triassic sandstones, which proved hydrocarbon bearing in 34/4-1 and 34/4-4. Operations and results Well 34/7-1 was spudded with the
semi-submersible installation Vildkat on 9 May 1984 and drilled to TD at 2905 m
in the Late Triassic Lunde Formation. The 26" hole was drilled and logged
first as a 17 1/2" pilot hole to 1106 m as a precaution against shallow gas
then opened up to 26" by using underreamer. Tight spots occurred in the
26" hole section. In the 17 1/2" hole the string got stuck at 1274 m.
The string had to be backed off and was fished out of the hole. Some tight
spots occurred in this section too. When running the 9 5/8" casing, lost
returns were experienced three times and the casing was pulled out of the hole.
A velocity log was run, and the well was plugged back to 2640 m by setting two
cement plugs and the 9 5/8" casing was landed at 2632 m. The well was
drilled with seawater and bentonite down to 1106 m and with polymer/KCl mud
from 1106 m to TD. The Tertiary and Cretaceous sections were
mainly composed of claystones, with sand development in lower the Pliocene and
in the Late Miocene. The Triassic consisted of sandstones alternating with
siltstones, claystones and minor marl. A major unconformity is observed at 2392
m between the Late Triassic and the Lower Cretaceous. Apart from this, four
other unconformities are observed in the well, one in Cretac Well 16/11-1 S is located in the Danish
Norwegian Basin. The objective of the well was to test the hydrocarbon
potential of the Tertiary, Mesozoic and Permian sediments. Specifically,
Tertiary sandstones, Cretaceous sandstones and limestones, Jurassic and
Triassic sandstones, Permian carbonates and Permian Rotligendes sandstone were
considered to be prospective. Operations and results Wildcat well 16/11-1 S was spudded with
the semi-submersible installation Ocean Viking on 17 July 1967 and drilled to
TD at 3050 m (ca 3020 m TVD RKB) in the Late Permian Zechstein Group. The well
is classified as deviated, but was not meant to be. During reaming operation at
about 1463 m the hole was accidentally sidetracked. This was not discovered until
13 3/8" casing was set and the cement plug drilled through. Hole deviation
was then determined to be 16 deg at the casing shoe. In order to prevent a
dogleg the deviation was gradually decreased to 12.5 deg at about 2322 m and
stabilized at an average of 12 deg to TD. The dip meter log indicates that the
hole drifted in a N 45 deg E direction. While drilling at 2952 m the drill
string stuck and a fish was left in the hole. A cement plug was set and the
fish was bypassed by sidetracking with jet action from the bit. Upon reaching
2952 m, the pipe stuck a second time, which resulted in leaving a new fish. A
second cement plug was set and the hole sidetracked using a Neyrpic turbine
drill. The pipe stuck a third time at 2954 m and another fish was left. The
hole was again sidetracked and mud weight increased to about 16 ppg. Drilling
then continued to TD, before 9 5/8" casing was set. Circulation was lost
immediately after drilling through the 9 5/8" casing shoe at 2957 m. Five
Diaseal "M" squeezes and five DOC squeezes were performed in an
attempt to regain circulation with a 16.0 ppg mud, but all attempts were
unsuccessful. A Drispac/Flosal/Desco mud system was used to a depth of 2326 m.
At this de General Well 15/12-5 was drilled on the Beta
Central structure ca 3.3 km north-east of the 15/12-4 Varg discovery well in
the North Sea. Primary objective was the Jurassic sandstones. Secondary
objective was the Frigg Formation sand and fractured limestone of Cretaceous
age. Seismic anomalies indicated shallow gas. Prognosed TD was 3100 m RKB in
sandstone of Triassic age. Operations and results Well 15/12-5 was spudded with the
semi-submersible installation Ross Isle on 12 March 1986 and drilled to TD at
3150 m in the Late Triassic Skagerrak Formation. No shallow gas was
encountered. Drilling proceeded without significant problems. The well was
drilled with Spud mud down to 217 m, with gel/seawater/XC-polymer from 217 m to
619 m, with gypsum/polymer mud from 619 m to 2889 m, and with
gel/lignosulphonate/lignite from 2889 m to TD. Top Cretaceous came in at 2457 m, and top
Jurassic at 2841 m. Top of the reservoir, an Oxfordian sandstone, was
encountered at 2918 m with good shows. The OWC was found at 2942 m, 28 m below
that of well 15/12-4. This is probably due to a flow barrier caused by the
fault system with a maximum throw of ca 100 m that separates the Beta West and
Beta Central structures. Due to FMT pressure measurements and fluid samples,
Statoil decided to go for "sole risk" testing, since Esso denied
participating in the testing program. Three cores were cut in the interval 2892
m to 2967 m with 100% recovery. The core-log depth shifts were small, in the
range 0.0 to -0.5 m for all three cores. FMT fluid samples were taken at 2919.3
m (oil), 2923.5 m, 2937.0 m (oil), and at 2941.5 m (water mud filtrate and a
little oil).
wlbHistoryDateUpdated: 2020-02-21T00:00:00 General Well 7119/12-2 is located in the Troms I area in the southwestern part of the Hammmerfest Basin. It was designed to test
possible hydrocarbon accumulations in a seismic closure (Zeta-structure) in the
southeastern part of the block. The primary objective of the well was
sandstones of Middle Jurassic age. Secondary objectives were clastics of lower
Jurassic and Upper Triassic age. Operations and results Wildcat well 7119/12-2 was spudded with
the semi-submersible installation Ross Rig on 16 April 1981 and drilled to TD
at 1902 m in the Late Triassic Fruholmen Formation. Boulder clays in the top
36" hole caused low rate of penetration and considerable difficulties in
setting the 30" casing. Gas sands were encountered in the interval from
404-410 m. The 20" casing was set above this sands instead of the planned
setting depth at 600 m. Due to high gas readings and increasing pore pressure,
the drilling below 20" casing could not continue to planned 13 3/8"
casing depth. Hence a 16" liner was set at 590 m. While underreaming below
the liner, the underreamer failed to close and consequently could not be pulled
to surface. The underreamer was left in the hole and the well sidetracked at
1215 m. The well was plugged back and the BOP-stack pulled when gas bubbles
were observed coming out of the wellhead. To cure this problem the BOP-stack
was installed again and previously set cement plugs drilled out to 275 m. A
packer was set inside the 20" casing at 273 m and no more gas was seen coming
from the well head. The well was then plugged back and abandoned. The well was
drilled with spud mud down to 394 m and with gel/lignosulphonate/seawater from
394 m to TD. Middle Jurassic to Late Triassic
sandstones with good reservoir properties were encountered from 1372 m to TD.
Drill cuttings and extensive coring had oil shows throughout, but RFT pressure
gradients as well as logs and DST proved 100% water General Well 33/12-5 was drilled on the Tampen
Spur in the northern North Sea. It was drilled on the southeast, downfaulted
flank of the Statfjord structure, but on the upthrown block of the major,
east-bounding Statfjord fault. The well was programmed to test in a higher
structural position, a Triassic sand, found water bearing in the 33/12-2 well,
and to evaluate older, untested section beneath the sand. The Triassic sand in
33/12-2, defined seismically by the "R2" horizon, had been tentatively
identified as Early Triassic. Secondary objectives were possible Jurassic
reservoirs preserved within this downfaulted area east of the Statfjord Field.
The 33/12-4 well was a similar test on the east flank of the Statfjord feature.
This well found a thin Jurassic/Upper Triassic? sand with good porosity, which
tested saltwater with minor amounts of oil. The well is type well for the Lomvi and
Teist formations. Operations and results Appraisal well 33/12-5 was spudded with
the semi-submersible installation Norskald on 9 October 1975 and drilled to TD
at 4574 m in the Triassic Lomvi Formation. The well was drilled water based
with a lignosulphonate mud from 485 m to TD. The Tertiary and Late Cretaceous sections
were similar to other wells in the area, consisting predominantly of claystones
and siltstones with minor sands. Along the southeast flank of the Statfjord
feature, erosion appears to have removed Jurassic sediments and a portion of
the Upper Triassic prior to draping of an indeterminate Jurassic sand,
interpreted as reworked Statfjord Formation sand, on the eroded Triassic
surface. Only minor shows were encountered in the reworked Jurassic sand, which
tested saltwater on DS General Well 2/7-14 was drilled to delineate the
southern limits of the Ekofisk Field in the southern Norwegian North Sea. The
primary target was the Danian limestone. It was anticipated that the proposed
location would have a similar structural position as development well 2/4-A-3
and a comparable amount of Danian net pay. The secondary target was the Late
Cretaceous limestone, which was untested on the southern nose of the Ekofisk
Field. Operations and results Appraisal well 2/7-14 was spudded with
the semi-submersible installation Haakon Magnus on 9 August 1979 and drilled to
TD at 3390 m in Late Cretaceous limestone. The well was drilled with
Bentonite/Flosal spud mud to 20" casing point at 609 m, with
Seawater/Native solids mud from 609 m to 13 3/8" casing point at 1526 m,
with Drispac/ Lignosulphonate dispersed, inhibitive mud from 1526 m to 9
5/8" casing point at 3068 m, and with Bentonite/ Lignite/Drispac low fluid
loss mud from 3068 m to TD. Top Paleocene was encountered at 3045 m.
Top of the Danian Limestone was penetrated at 3146 m, 15 m low to prognosis,
with 52 m of Danian net pay, compared to 86 m Danian net pay in well 2/4-A-3.
The Danian reservoir pressures were found to be less than virgin Ekofisk
pressures, evidence that the interval had been drained by the nearby well
2/4-A-3. The Late Cretaceous was encountered at 3257 m, 13 m low to prognosis.
The section flowed oil with a large volume of associated water in DST 2. A total of 119 m core was recovered in 13
cores from the Paleocene and Late Cretaceous in the interval 3123 - 3306 m. No
fluid sample was taken on wire line. The well was suspended on 20 January 1980
as an oil appraisal. Testing Five drill stem tests were made through
perforations in the 7" liner. DST 1 at 3346.7 - 3349.8 m in the Late
Cretaceous Limestone recovered 12 m3 water cushion plus 21 m3 formation fluid
(85% water, General Well 2/8-3 is located in the Feda Graben,
ca 2 km north-east of the Valhall Field in the southern North Sea. The primary
objective was to test the Jurassic hydrocarbon potential. The secondary
objective was the chalk of the Shetland Group. The well is reference well for the Haugesund
and Farsund Formations. Operations and results Wildcat well 2/8-3 was spudded with the jack-up
installation Zapata Explorer on 16 June 1972 and drilled to TD at 4115 m in
Late Jurassic shales of the Haugesund Formation. The well took 48 days to
complete and was drilled with unical/lignosulphonate/caustic based mud. Reservoir quality rock was absent
throughout the well. The first signs of oil were seen in Palaeocene tight siltstones
with poor porosities. These were described as bright gold yellow fluorescence
with a bright white streaming cut. Gas levels in the Shetland Group were low
and no shows were seen in this group. A DST was run over part of this section
but yielded only drilling mud. From 3267.3 m, within the Early Cretaceous, gas
levels rose significantly and were associated with fair to poor shows in the
Marls. The fluorescence was described as gold in colour with a slow pale yellow
cut. From 3444 m, gas and shows increased and were contained in slightly
argillaceous, hard limestone. Oil staining was seen and the fluorescence
described as dark yellow gold with a pale yellow to very light brown cut. Mandal
Formation shale was the first Jurassic age rocks seen. Gas levels were very
high through these shales and the shows were described as bituminous with no
direct fluorescence and a pale yellow cut. Between 3578 - 3600 m a gross
sandstone unit was indicated by the gamma ray log. In rough General Well 30/6-5 was drilled on the Brage
Horst east of the Gullfaks fault block in the North Sea. The main purpose was
to test the hydrocarbon potential in Middle Jurassic sandstone. Operations and results Wildcat well 30/6-5 was spudded with the
semi-submersible installation Deepsea Saga on 11 June 1981 and drilled to TD at
3550 m in the Triassic Lunde Formation. No significant problem was encountered
in the operations. The well was drilled with spud mud down to 951 m, with
gypsum/polymer mud from 951 m to 1801 m, and with gel/lignosulphonate mud from
1801 m to TD. The Brent Group, Tarbert Formation was
encountered at 2824 m. From wire line logs and petrophysical analysis oil was
found from 2841 m down to 2899 m. Pressure measurements indicated oil/water
contact at 2907 m. Shows on cores continued down to 2933 m. The Etive Formation
represented the main part of the net pay. Eight cores were cut in the well. Cores 1
and 2 were cut in the interval 2843.5 - 2854.7 m. Cores 3 to 8 were cut in the
interval 2871.5 - 2949.8 m. RFT oil samples were taken at 2847.5 m, 2867.1 m
(film of oil), 2871.2 m (traces of oil), 2874.5 m, 2881 m, 2889 m, 2923 m (film
of oil). The samples proved H2S contents in the range 30 - 50 ppm. The well was permanently abandoned on 15
August 1981 as an oil discovery. Testing The rig lacked qualified equipment and
personnel trained for drill stem testing with the levels of H2S proven by RFT
sampling. Testing was therefore abandoned. General Well 33/12-6 was drilled on Tampen Spur in
the North Sea between the Gullfaks Sør Field area and the UK border. The
objective was to test a large structural feature in the southeastern part of
Block 33/12, located across a major regional fault bounding the eastern flank
of the Brent and Statfjord Fields. The targets were sands in the Early and
Middle Jurassic sandstones of the Statfjord and Brent Groups. Operations and results Wildcat well 33/12-6 was spudded with the
semi-submersible installation Norskald on 2 March 1976 and drilled to TD at
4612 m in the Triassic Hegre Group. The Middle Jurassic Brent Group was
encountered at 2973. Gross thickness was 312 meters. Only rare fluorescence
with minor gas readings were noted in the sands. Higher gas readings
encountered were associated with coal beds. Using cutoffs of 40 percent clay
volume and 12.5 percent porosity, Schlumberger’s coriband analysis indicates
103 meters of net sand with an average porosity of 20 percent. The coriband analysis
showed the sands to be water wet with only 6 m of net pay with water
saturations less than 65 percent, scattered throughout the unit. The Early Jurassic
Statfjord Group sands were topped at 3721 meters. Gross thickness was 309.5
meters. Using the same cutoff parameters as for the Brent formation, log
analysis indicated 149 meters of net sand with an average porosity of 16
percent and showed the sands to be water wet. Only 3 m of scattered thin zones
had water saturations less than 65 percent. No shows were seen in the samples.
However, the core in the Statfjord sands had residual oil saturation over the
6.51 meters recovered indicating earlier oil migration through the section. The core w General Wildcat well 7120/8-1 is located in the
Snøhvit Field area. It was designed to test possible hydrocarbon accumulations
in a seismic closure (Alpha prime structure) located to the east of a major N-S
running fault in the western part of the block. The primary target was
sandstone of Middle Jurassic age. Operations and results Well 7120/8-1 was spudded with the
semi-submersible installation Ross Rig on 28 June 1981 and drilled to TD in
Late Triassic rocks ((Fruholmen Formation). The 17 1/2" hole was drilled
to 1128 m when the lower marine riser accidentally unlatched and two days of
rig time were lost curing this problem before drilling could continue. When
plugging back the well, gas bubbles were observed in the riser. Four days of
rig time were lost before this problem was cured. Apart from this no
significant difficulties were encountered and the well was drilled according to
schedule. The well was drilled with spud mud down to 358 m, with gel mud from
358 m to 750 m, and with gel/lignosulphonate mud from 750 m to TD. Relatively dry gas was encountered at
2092 m in sandstone of the Middle to Early Jurassic Stø Formation. Log
analysis, confirmed by RFT data, found a gas column down to a water contact at
2180 m. The reservoir sandstone showed good to excellent reservoir properties.
Organic geochemical analyses showed TOC levels in the Early Cretaceous
mudstones in the range ca 1.3 % to ca 5 %, generally increasing downwards to
the base of the Cretaceous. Within the Late Jurassic Hekkingen Formation shales
TOC increases from ca 3 % to at the top (1990 m) to more than 9 % at the base.
In the Early Jurassic to Triassic below 2190 m occasional shales and thin coal
beds have good potential for gas and oil, but are restricted in volume. The sediments
are immature for petroleum generation down to ca 2000 m and marginally mature
from this depth to TD. Kerogen is generally of Type II, with some addition of
Type III in the lower General Well 7119/12-1 was the first exploration
well to be drilled in the Barents Sea. It was placed on a horst block forming
the upper part of the seismic closure 7119/12-1 Alpha structure. The well was
designed to gather information about the hydrocarbon potential of the Troms I area, specifically to test hydrocarbon potential and reservoir rock quality of
7119/12-Alpha. The primary target was sandstone of middle Jurassic age.
Secondary targets were Early Jurassic and Late Triassic sandstones. Planned TD
was into rocks of probable Triassic age at an estimated depth of 3500 m. Operations and results Wildcat well 7119/12-1 was spudded with
the semi-submersible installation Ross Rig on 14 June 1980 and drilled to TD at
3088 m in Early Jurassic Stø Formation. Two major problems were encountered in
the drilling phase of the well. The first one concerned boulders while drilling
36" hole, causing low ROP and the hole caving in. The second problem was
the combination of junk in hole and a very hard, well-cemented sandstone at
2654 m causing heavy bit wear. On 13 July drilling was interrupted by a 38 days
strike. Due to a late start-up and the strike, and as drilling season ended on
1 October, no test could be performed. The well was drilled with spud mud down
to 615 m and with bentonite / lignosulphonate mud from 615 m to TD. Top reservoir, Stø Formation, came in at
2658 m. Logs, RFT samples, and shows on cores and cuttings proved oil in the
reservoir. The reservoir properties were however poor, with only 18,5 m net
sand out of 430 m, and a moderate 13.6% average porosity in the net sand. Six
RFT runs were conducted from 2658 m to TD. Out of a total of 73 pressure tests
attempted only 15 pressure points were obtained due to tight formation. The pressure
gradients obtained corresponded to 0.92 to 0.95 g/cc. Both logs and RFT showed
that the OWC had not been reached. Repeat Formation Test (RFT) segregated fluid
samples were collecte General The primary objectives of well 7120/12-2
were to test sandstone reservoirs of Middle to Early Jurassic age in the
central compartment of the Alke structure, and a deep seismic marker
interpreted to represent top of a possible carbonate reservoir of Permian age.
A secondary objective was to test sandstones of Early Triassic age. The well
was planned to be drilled to 5000 m or into basement rocks to serve as the deep
commitment well on the licence. Operations and results Well 7120/12-2 was spudded with the
semi-submersible installation Treasure Seeker on 15 April 1981 and drilled to
TD at 4680 m in basement rocks. After setting the 20" casing the kill line
outlet flange was accidentally damaged and 5 days were spent repairing the BOP.
The well was drilled with bentonite/seawater mud down to 515 m and with
lignosulphonate (Spersene / XP-20) mud from 515 m to TD. Severe problems were
encountered with gumbo type clays during the interval from about 800 m to 1400
m. A major fault was penetrated at 2410 m in
the well, faulting out approximately 400 m of the Triassic section. This is
evident from comparing the Triassic sequences penetrated in the well 7120/12-1
and 7120/12-2. Rocks of Permian age were encountered from 3657 m while
metamorphic basement was encountered at 4664 m. Hydrocarbon bearing sandstones
were encountered in the Middle to Late Jurassic and in the Middle to Late
Triassic. The "Alke Formation" from 1892
m to 2314 m (Stø, Nordmela, Tubåen , and most of the Fruholmen Formation) was
found hydrocarbon bearing from 1888 m to the gas/water contact at 1981.5 m.
This interval consisted of relatively clean, fine to occasionally coarse
grained, homog Well 7120/12-1 was, together with
Statoil's well 7119/12-1, the first well to be drilled offshore northern Norway
in the Norwegian Sea, Troms I area. Based on seismic interpretation and
regional geological data the location of the well was planned to test possible
sandstone reservoirs of Middle Jurassic, Early Jurassic, and Late Triassic age.
Post-Jurassic sediments were not considered prospective due to lack of closure
and/or reservoir rocks. The well was planned to be drilled through a seismic
marker at 1965 + 90 m and down to 2500 m (+ 300 m). Operations and results Exploration well 7120/12-1 was spudded
with the semi-submersible installation Treasure Seeker on 1 June 1980 and
drilled to TD at 3573 m in Middle Triassic sandstones and shales (Kobbe
Formation). When testing the BOP after setting the 20" casing a leakage
was detected in the kill line. Three days was spent repairing this before
operations could continue. At 1900 m drilling was interrupted by a 35-days
labour strike, from 10 July to 14 August. The hole deviation was significant in
the 8 3/4" section, building angle from 4 deg at 1875 m to 23 deg at TD. This
resulted in a 57 m difference between drilled depth and true vertical depth at
final TD. The well was drilled with seawater and hi-vis pills through the
36" and 26" sections down to 710 m and with lignosulphonate/lignite
(Spersene/XP-20) mud from 710 m to TD. The well encountered traces of
hydrocarbons in thin sandstone reservoirs of Early Cretaceous and Late Triassic
age. The target seismic marker was reached at
2019 m (the Fuglen Formation). A 450 m thick sequence of sandstones with minor
interbeds of shales of Middle to Lower Jurassic and Late Triassic age was
penetrated below this marker, from 2047 m to 2497 m (Stø, Nordmela, Tubåen, and
Fruholmen Formations). The sandstones in this sequence were water bearing. From
log evaluation total net sand in the sequence was 271.5 m with an average
porosi General Well 2/8-1 was the eighth, and at the
time the most southerly exploration well to be drilled in Norwegian waters. The
geological objective of the well, in this early stage of exploration, was to
test all horizons down to the Permian Rotliegendes Group. The well also had as
a technical objective to test the use of a large, single hull vessel for
drilling in the North Sea. Operations and results Well 2/8-1 was spudded with the vessel
"Drillship" on 28 November 1967. This was the first drilling
operation in Norwegian waters in which a vessel was used. Many problems arose
during the drilling of 2/8-1. Repeated failures of the anchor mooring chains at
tensions loads of only 10?50 % of their rated breaking occurred. To this, the
weather conditions in the North Sea turned out to be more severe than had been
predicted. Several storms in the 25 to 30 year category were encountered, and
in January a storm that would be expected once every 75?100 years occurred with
maximum waves of 15 - 17 m. After this storm the Drillship was in shipyard for
repairs and modifications from 19 January to 8 March 1968. Even so, these
failures of anchor chains eventually resulted in failure of the BOP stack and
13 3/8" well head after having drilled to 2595 m, and made clear that
drilling could not continue safely. Besides the mooring problems, other
difficulties occurred. While testing in the 12 1/4" hole, the Drill Stem
Test (DST) - tool dropped into the hole. The hole was reamed and the fish
retrieved. The drill pipe stuck twice when making trips, first at 2118 m. The
pipe was not recovered and a fish was left from 2007 - 2118 m. A cement plug
was set and the hole side tracked. The pipe stuck again at 2237 m and a new
fish was left from 2052 to 2237 m. Two cement plugs were set, one in the 13
3/8" casing shoe and one in the casing from 140 m to sea floor. This
occurred in connection with the BOP and wellhead break, and th General Well 33/9-3 was drilled on the Statfjord
structure on Tampen Spur in the northern North Sea, as a replacement well for
the junk well 33/9-2. The primary objective was to provide seismic velocity
control for detailed field mapping and to provide additional reservoir data for
the Statfjord Field development. Operations and results Wildcat well 33/9-3 was spudded with the semi-submersible
installation Norskald on 15 September 1974 and drilled to TD at 2992 m in Late
Triassic sediments of the Statfjord Group. The target reservoir Brent Group was
encountered at 2411 m. It contained oil all through down to top Dunlin Group at
2599 m. The base of the reservoir was encountered above the oil water contact.
The reservoir quality was excellent with average measured core porosity of 29%
and measured permeabilities up to 7.7 Darcy. A total of 152 m core was recovered in 13
cores from the interval 2422.9 m to 2622.2 m in the reservoir section. Total
core recovery was 76.1%. Six FIT fluid samples were taken at 2419 m (35.4 °API
oil and mud filtrate), 2455 m (38.4 °API oil and mud filtrate), 2422 m (36.4
°API oil, gas and mud), 2423 m (36.6 °API oil and gas), 2534 m (35.6 °API oil
and mud filtrate), and 2595 m (water, mud filtrate and trace oil). The well was permanently abandoned on 14
November as an oil appraisal well. Testing A DST over the interval 2479 to 2481 m did
not produce fluids due to tool failure. General Well 33/12-3 was drilled on the Statfjord
structure in the Tampen Spur area. It was designed to test the erosional
escarpment on the east flank of the structure for possible trapping of
hydrocarbons in an area downfaulted to the Statfjord Field pay section to the
west. Primary objectives of the well were the Early Jurassic Statfjord Group
sands and possible Middle Jurassic Brent Formation sands. Well 33/12-3 was
junked due to technical problems. The rig was moved 30 m and re-spudded as
replacement well 33/12-4. Operations and results Appraisal well 33/12-4 was spudded with
the semi-submersible installation Nordskald on 17 May and drilled to 2896 m in Late
Triassic sediments in the Statfjord Group. The well was drilled with seawater
down to 495 m and with water based lignosulphonate mud from 495 m to TD. The Middle Jurassic Brent Group was
encountered at 2675 m, ca 55 m high to prognosis but, as anticipated, well
below the Brent oil/water contact of 2609 m (2584 m MSL) in the upthrown block
of the field. Scattered poor to fair hydrocarbon indications were noted in the
cores but gas readings were low. Average core porosity in the sands is 23 %,
ranging from two to 29 %. Measured horizontal permeabilities average 604 mD and
range between 0.01 and 2028 mD. The CPI log indicated some 40 feet of
prospective net pay with 23 percent average porosity and 53 percent average
water saturation. The top of the Statfjord Group was
penetrated at 2757 m, only 2 m low to prognosis. Core 4 at the top of Statfjord
recovered sand, siltstones and claystones with no shows. However, poor shows
were recorded above and below the cored section. Using a 65% water saturation
cut-off Schlumberger's pre General Well 31/6-6 was drilled in the Troll East
gas province. It was designed to test possible gas accumulations in the Late to
Middle Jurassic sandstones and to test the quality of a reservoir siltstone in
the Heather Formation. Operations and results Well 31/6-6 was spudded with the
semi-submersible installation Deepsea Bergen on 22 May 1984 and drilled to TD
2293 m in the Late Triassic Hegre Group. No significant problem was encountered
in the operations. The well was drilled with spud mud down to 716 m, with
KCl/polymer mud from 716 m to 1771.5 m, and with pre-hydrated bentonite/CMC mud
from 1771.5 m to TD. The well encountered gas from top Heather
reservoir at 1516 m to a GWC at 1568.5 m, 7.5 m into the Sognefjord Formation.
No oil shows were reported from the well. Nine conventional cores were cut in
the interval 1525 m to 1771.5 m in the Middle to Late Jurassic. FMT samples
were taken at 1571.8 m and 1576.5 m in the Sognefjord Formation. Both contained
formation water and mud filtrate. The well was completed on 29 July 1984 as
a gas appraisal. Testing Two drill stem tests were performed in
the well. DST 1A tested 1562 m to 1567.5 m in the Sognefjord Formation
sandstone. It produced maximum 779 x 10 Sm3 gas /day on a 64/64" choke. DST
2 from 1523 m to 1536 m in the Heather Formation siltstone showed a very low
production rate, 10.7 x 10 Sm3/day. The reservoir temperature was 62.5 deg. C
in DST 1A and 58 deg. C in DST 2. General Wildcat well 35/11-1 was drilled on the
"A" structure close to the border between Block 35/11 and Block
35/12, and ca 25 km north of the Troll Field. Its primary objective was to
assess the hydrocarbon potential in Middle to Upper Jurassic strata on the
"A" structure that straddles the border between Block 35/11 and the
unlicensed Block 35/12. Sands of Lower Jurassic age were regarded as secondary
objectives. Planned TD was into the Triassic. Operations and results A total of 317 pockmarks were identified
in the area from the site survey. The average density was estimated to 20 per
square kilometre. The average depth of these was 1-2 m, though some were of
greater depth. None of the pockmarks were seen to be active. Wildcat well 35/11-1 was spudded with the
semi-submersible installation on 23 May 1984 and drilled to TD at 3361 m,
approximately 100 meters into in the Triassic Hegre Group. The 36" hole
section was drilled through boulder beds causing the bit to build angle. Because
of high deviation the well was re-spudded. After drilling the 26" hole,
the well flowed several times. Although the well would not stay static, it was
decided to run the 20" casing in an attempt to seal off the water flow.
This resulted in the 20" casing parting at the wellhead, but was
successfully recovered. After reaming some tight spots the 20" casing was
set and cement was squeezed to seabed to stop the water flow in annulus. Some
tight spots were experienced in the 17 1/2" and 12 1/4" hole
sections. Lost circulation occurred at 2439 m, due to this the 9 5/8"
casing was run. The well was drilled with gelled seawater spotted with hi-vis
pills down to 1015 m and with KCl/polymer mud fr General Well 2/3-4 was drilled by Gulf Oil
Corporation - Norway Branch as a non-obligatory well on behalf of the
participants in Production Licence 022. All obligatory work had been previously
been done. The well is situated 275 km SSW of Stavanger. Geologically, the
location was chosen on the "Ula Trend" on the NE flank of the Central
Graben in the southern Norwegian North Sea. The principal objective of the well
was to test structural closure of Upper Jurassic Ula Formation sandstone. This
formation was believed to exist within 100 m below the nearest representative
mappable seismic reflection, the Base Cretaceous Unconformity. The well was
also planned to penetrate an Oligocene sand down-dip from a very small gas
accumulation defined by a seismic flat spot anomaly, and which was therefore
believed to be water wet at the location. The chalk reservoir was not predicted
to be hydrocarbon bearing, nor was the well located within its mapped closure. Operations and results Exploration well 2/3-4 was spudded with
the jack-up installation Glomar Moray Firth I on 28 may 1984 and drilled to a
total depth of 3386.3 m in Permian (Zechstein) evaporites. The well was drilled
with seawater and gel down to 651 m and with Safemul oil based mud from 651 m to
TD. Some swelling of the Miocene clay occurred during drilling of the 17
1/2" hole, otherwise no major problems occurred. Well 2/3-4 was the first
exploration well for which NPD approved that conventional wire line logs was
replaced with a suite of MWD logs. The primary objective, Ula Formation
sands, was penetrated at 3006 m and was 207 m thick. The porosity of
particularly the uppermost 170 m was excellent, generally between 25% and 30%.
Electric logs, and a formation fluid sample (from FMT), indicated that the
reservoir was water bearing throughout. Shows detection was made difficult due
to the mud used. However, spectrofluorometric analyses on cuttings samples
while drilli General Well 7121/7-1 was drilled in order to
test the Lower/Middle Jurassic sandstone on the eastern part of the Albatross
structure on Tromsøflaket. The primary target was defined as sandstone
intervals in Early-Middle Jurassic and Late Triassic. Operations and results Wildcat well 7121/7-1 was spudded with
the semi-submersible installation West Vanguard on 11 June 1984 and drilled to
TD at 2160 m in the Late Triassic Fruholmen Formation. No significant problems
were encountered during drilling. The well was drilled with spud mud down to
764 m and with a gypsum/polymer mud from 764 m to TD. Logs, RFT pressure gradients, and cores
indicated gas in the Lower/Middle Jurassic sandstone (Stø Formation)
encountered at a depth of 1849 m. Gas/water contact was evaluated to 1902.5 m
RKB, the same as found in well 7120/9-1, also drilled on the Albatross
structure. From the GWC down to TD in the well shows were observed in
sandstones on cores and cuttings. Four cores were cut in the interval 1851 m to
1935 m in the Stø Formation. Two segregated samples were taken, at 1900.2 m and
at 1851.0 m. The 2-3/4 gallon chamber from 1900.2 m was bled off offshore and
gave an opening pressure at 2220 psig. The sample contained 58.25 cuft of gas
and 1 litre of liquid consisting of 800 cc water/mud filtrate and 200 cc
condensate. The 2 3/4 gallon chamber from 1850.5 m contained 2200 psig with
4500 cc water based liquid, a small volume condensate, and 41 cuft of gas. The well was permanently abandoned on 5
August 1984 as a gas appraisal well. Testing Two DST were performed, one water test
over the interval 1947.2 m to 1960.18 m and one gas test over the interval 1867
m to 1872 m. The recorded temperatures were in agreement with those observed in
well 7120/9-1. The reservoir fluids had the same composition in well 7121/7-1
as in well 7120/9-1. The sandstone in the tested water zone had good reservoir
properties. The General The appraisal well 25/2-8 was drilled on
the East Frigg Field. The main objectives of the well were to obtain a better
estimation of the gas reserves on East Frigg and good pressure data in both the
Frigg sand and the Paleocene sand. To achieve better knowledge about the
petrophysical characteristics of the different reservoirs, it was decided to
core the Frigg sand, the shaly member, the tuff zone and the Paleocene sand. Operations and results The well was spudded with the drill ship
Le Pelerin on 18 June 1984 and drilled to TD at 2380 m in the Lower Paleocene
Lista Formation. Problems due to tight hole occurred in the 12 1/4" hole
section. The pipe got stuck at 1397 m, but was worked free. Problems pressure
testing the BOP occurred with hole depth at 1745 m. A cement plug was set from
1000 m to 890 m due to the BOP problems. The core barrel was lost in the hole
when pulling out of the hole with core no 9. The fish was recovered. The well
was drilled using a water-based mud. The Frigg sand was reached as prognosed
at 1917.5 m. This formation is 283 m thick with a 48.5 m hydrocarbon bearing
column: gas from 1917.5 m to 1957 m and oil from 1957 to 1966 m. Below this
level was 18 m of residual oil. Shows were detected on cores and cuttings down
to 2040 m. Balder formation (Paleocene) was reached at 2201 m with several
Intra Balder Formation Sandstones. RFT pressure measurements in the Frigg sand
and Intra Balder Formation Sandstone indicated that there is no direct fluid
communication between the two formations. RFT segregated fluid samples were
recovered from 2259 m in Intra Balder Formation Sandstone and at 1956.7 m and
1993 m in the Frigg Formation. The Intra Balder Formation Sandstone sample and
the deeper Frigg sample recovered only water and mud filtrate and no gas, while
the upper Frigg Sample recovered mud filtrate with traces of oil and about one
litre of gas. Nine cores were cut, seven in the Eocene and two in General Exploration well 7119/9-1 is located on
the Ringvassøy ? Loppa Fault Complex west of the Snøhvit Field area. The well
was designed to test a narrow horst, elongated in a NE-SW direction. The horst
brings the main prospect, the Middle to Lower Jurassic Sandstones up to a depth
of about 2700 m, in a position surrounded with Cretaceous Shale. The well is
located close to the top of the horst. This target was found gas bearing in the
two nearest wells: 7119/12-3 to the south, located in the same structural
trend, and 7120/7-1, located higher up toward the Hammerfest Basin to the
south-east. Operations and results The well was spudded with the
semi-submersible installation Byford Dolphin on 28 June 1984 and drilled to TD
at 3248 m in Late Triassic rocks. The well took a kick at 2744 m where a pit
gain of 2 m3 was observed. Some technical problems occurred on the rig during a
wiper trip before final logging of the 8 1/2" hole. During logging of the
same sequence the RFT tool got stuck twice but was recovered in both cases. The
well was drilled using water-based mud. The well drilled through mainly claystone
and shale formations down to top Jurassic at 2702 m. The lower Cretaceous
Kolmule Formation was found silty and sandy between 2400 m and 2450 m. Top
Jurassic Hekkingen Formation was penetrated at 2702 m and contained two good
reservoir sections, a Middle ? Early reservoir and a deeper Pliensbachian
reservoir. Above the upper reservoir zone 46 m of Late Jurassic shale was
drilled. This sequence consisted of an upper Volgian ? Kimmeridgian sequence
and a lower Oxfordian-Callovian shale sequence separated by an Oxfordian
unconformity near 2719 m (more accurate depth cannot be proven due to logging
problems in this section of the well). The upper Jurassic sandstone reservoir (Stø
Formation) was penetrated at 2748 meters. The reservoir was well developed with
a 120 meter gross thickness. The two cores cut near the top of t General Wildcat well 6407/9-1 was drilled in the Froan Basin offshore Mid Norway. The primary objective of the well was evaluation of
possible reservoirs of Early to Middle Jurassic age. Secondary objectives were
evaluation of deeper reservoirs of Early Jurassic to Upper Triassic age. The well is Type Well for the Rogn
Formation. It is Reference well for the Viking Group and Spekk Formation Operations and results Wildcat well 6407/9-1 was spudded with
the semi-submersible installation Borgny Dolphin on 26 June 1984 and drilled to
TD at 2500 m in the Late Triassic Red Beds. Due to high deviation in the
36" hole section, the well was re-spudded. Junk was fished out of the hole
before and after performing a leak off test below the 20" casing shoe. Gas
bubbles were observed around the BOP stack, the 20" casing was perforated
and several cement squeeze jobs were performed. The 13 3/8" casing was run
just below the 20" casing. Some technical problems occurred while drilling
the 12 1/4" hole. Some tight spots occurred in the two lowermost hole
sections. The bottom hole assembly got stuck at 2027 m, but was successfully
freed. The well was drilled with seawater and bentonite down to 809 m and with
KCl/Polymer mud from 809 m to TD. The well encountered a Late Jurassic
intra-Spekk Formation sandstone unit which was previously unknown in the
Haltenbanken area. It has later formally been named the Rogn Formation. It was
oil filled from the top at 1621 m down to an OWC at 1660 m. Tests showed light
oil with a low content of gas and condensate. The underlying reservoir
sandstones of Middle/Early Jurassic to Late Triassic age were all water
bearing, nor were oil shows reported in any other porous section in the well.
Five cores were cut from the Late Jurassic into the Middle Jurassic. The three
first were cut in the Rogn Formation while the two last recovered an underlying
Spekk sequence and upper part of th Well 16/7-5 is located ca 10 km east of
the Sleipner Øst field in the North Sea. The primary objective was to test
potential gas bearing Jurassic/Triassic sandstones. Operations and results Wildcat well 16/7-5 was spudded with the
semi-submersible installation Zapata Ugland on 2 July 1984 and drilled to TD at
2900 m in the Triassic Smith Bank Formation. Due to turning of the permanent
guide base the 30" casing had to be re-landed. No other major problems
occurred during drilling. The well was drilled with gel/sea water down to 170
m, and with seawater/lignosulphonate gel from 470 m to TD. The ?Jurassic/Triassic (Skagerrak
Formation) was encountered at 2594, underlying an interpreted one-meter layer
of Draupne shale. A 306 m gross / 120.5 m net (22% average porosity) sequence
of sands was penetrated. No significant hydrocarbon shows were encountered
while drilling the well. Electric log analysis also confirmed that the
Jurassic/Triassic Sandstone (primary objective) was water bearing. RFT pressure
measurements and samples suggested the possible presence of minor amount of gas
in the upper part (2594 m to 2642.6 m) where the pressure gradient was lower
than the water gradient (below 2662.5 m). However, the pressure readings were
scattered in this interval and very much subject to interpretation. One core was cut from 2590 to 2603 m (2596
- 2612.5 m logger's depth) in the top of the target sands in the Skagerrak
Formation. Three successful RFT fluid samples were taken. The first sample, at
2691 m, recovered "2800 cc. of light brown fluid, mainly mud filtrate and
mud, no gas, no fluorescence". The second, at 2806.5 m, recovered "8600
cc. of clear medium brown fluid, mainly mud filtrate with a few cc's of gas.
The fluid had no odour or taste but it had a very pale bluish white
fluorescence". The third, at 2603 m, recovered "8700 cc. of none
clear (turbid) fluid + few cc's of gas. The fluid had no odour or tast General Exploration well 7121/4-1 was drilled in
the Hammerfest Basin in the Troms I area. The primary objective was to test
possible hydrocarbon accumulations in sandstones of Middle to Early Jurassic
age. Operations and results Well 7121/4-1 was spudded with the
semi-submersible rig West Vanguard on 6 August 1984 and drilled to TD at 2609 m
in Late Triassic sediments (Fruholmen Formation). Loss of circulation occurred
at TD in 12 1/4" section at 2285 m, and several times during drilling of 8
1/2" hole but otherwise operations went without significant problems. The
well was drilled with spud mud down to 817 m, with gypsum/Celpol from 817 m to
2285 m, and with gel/chromium-lignosulphonate from 2285 m to TD. Hydrocarbon accumulations were discovered
in two separated sandstone sequences. The uppermost sequence between 2318 m and
2442 m in the Stø and Nordmela formations contained gas over oil,
while the lower sequence was gas bearing between 2468.5 m and 2473 m in the
uppermost few meters of the Tubåen Formation. The gas/oil contact in the
upper reservoir was seen from RFT to be at 2425. The oil zone, 2425 m to 2442 m
in the Nordmela Formation, consists of an interbedded sandstone/shale sequence
with fair/poor reservoir properties. There is a sealing shale between 2444 and
2468.5 m that screens off the upper gas-oil system from the lower Tubåen gas
reservoir. The lower gas zone has good reservoir properties. The sandstone
continues to TD at 2587 m, interrupted by some minor shale beds and one major
shale bed at 2532 m to 2560 m. Four cores were cut in the reservoir interval
from 2321 m to 2416.35 m in the Middle Jurassic down into the Early Jurassic.
Three segregated RFT samples were taken. For all three samples the 2 3/4 gallon
chambers were bled off at well site. Sample 1 from 2365 m recovered gas, black
condensate, and mud filtrate. Sample 2 from 2470 m recovered gas, brown
condensate, and mud filtrate. Sample 3 from General Whereas Saga Petroleum operated license
041, BP operated wildcat well 35/3-2 under license 041 by special agreement.
The well was the second well drilled on this block, 35/3-1 was abandoned in the
Middle Jurassic due to high calculated pore pressures. Well 35/3-2 was drilled
on a westerly dipping fault block. The primary target of the well was Early
Jurassic sandstone, secondary targets were any other Jurassic sandstones
encountered. Operations and results Wildcat well 35/3-2 was spudded with the
semi-submersible installation Sedco 707 on 19 May 1980 and drilled to TD at
4400 m in ?Caledonian age basement rocks. The well was drilled with seawater
and gel down to 902 m, with gypsum/CMC mud from 902 m to 2305 m, with Poly
RX/Drispac from 2305 m to 3833m, and with Poly RX/Lignosulfonate mud from 3833
m to TD. The well started to flow while drilling the 24" hole. Heavy mud
was pumped down the hole, but there was very little difference between the
fracture gradient and the bottom hole pressure and returns were lost several
times. A loss/gain situation was maintained until the casing setting depth was
reached. When running the 18 5/8" casing the string parted and 22 joints
were left in the hole. The string was recovered successfully, and a new string
was run and cemented without problems. The well penetrated strata from Tertiary
through Jurassic and Triassic before reaching basement. Hydrocarbon shows were
encountered in Lower Cretaceous and Lower Jurassic sands. The primary target
Jurassic sandstones were found to be very tight, and no DST was carried out in
these. In stead two zones in the Lower Cretaceous Sandstone were tested,
producing water and gas/condensate respectively. The lower Cretaceous sands are
interpreted as submarine fan deposits. The Lower Jurassic coarsening upward
sequences may represent offshore open marine bars cut by tidal channel deposits
and capped by a transgressive marine sheet sand. Log General Wildcat well 2/1-7 was drilled on a
structure in the centre of the block. The primary target was Rothliegendes
sandstone in a large fault bounded structure mapped at base Zechstein Group
level. A secondary objective was Late Jurassic Ula Formation sandstone in an
extension of the 2/1-3 Gyda discovery. In the 2/1-3 well two sequences of Ula
Formation sandstone had been encountered, and the upper of the two had been
oil-bearing Operations and results Wildcat well 2/1-7 was spudded with the
3-leg jack installation Glomar Moray Firth 1 on 6 September 1984 and drilled
to TD at 5464 m in the Permian Rotliegendes Group. Pumping lost circulation
material, without changing the mud weight, stopped loss of mud at 1710 m. Top
chalk came in at 3190 m. This whole sequence was drilled with turbine. At 3746
m the drill string got stuck, and the tight interval was located between
2600-2900 m. The string was freed by circulating acidic mud. Full circulation
was maintained during this whole operation. While pulling out to change bit at
5077 m the drill string was lost in the hole. At the same time 170 bbls of mud
was lost. One reason for this mud loss could be the "piston effect"
caused by the drill string falling down the hole. The pipe was fished out piece
by piece, and the stabilisers above the bit were milled out. At 5081 m the
drill string was screwed off 300 m above the bit. Fishing was successful and
drilling continued. Drilling was stopped at 5113 a to perform pressure test.
During this operation, before reliable results were obtained, the RFT-tool got
stuck in the hole. After extensive fishing the operator decided to plug back
and sidetrack the hole. The technical sidetrack was kicked off at 5092 m, and
drilled to 5119 m. Problems at this depth made another sidetrack necessary, and
the hole was plugged back to 4747 m. The new sidetrack was kicked off from 5080
m and dri1led to a TD of 5464 m, which made this hole 4 m short of being th General License 095 was awarded to the
Conoco/Statoil/Arco/Tenneco group in 1984 with Conoco as operator. The area,
known as Haltenbanken, is a promising oil and gas province. It straddles two
major Mesozoic structural features, the Trøndelag Platform and the Vøring Basin
and lies along the western flank of the series of NNE-SSW faults, which
separate them. The well was drilled on the A-prospect and was designed to test
a major fault block. It was hoped to test oil bearing Middle Jurassic
Sandstone at approximately 3898 m with a secondary objective at the Early
Jurassic level. The well is Type Well for the Lysing
Formation. Operations and results Wildcat well 6507/7-1 was spudded with
the semi-submersible drilling rig Nortrym on 10 August 1984 and drilled to TD
at a depth of 4825 in the Early Jurassic Tilje Formation. The well was drilled
with seawater and hi-vis pills down to 906 m, with gypsum/polymer mud from 906
m to 3803 m, and with gypsum/lignite mud from 3803 m to TD. Few problems were
experienced whilst drilling the well. Some time was lost due to
gumbo-associated problems. Mud was lost to formation while cementing the 13
3/8" casing, resulting in the top of cement being lower than planned.
However this did not affect the strength at the shoe, as it was possible to
make a good leak off test after drilling out. Tight hole problems were
experienced on a bit trip from 3716 meters, with over pull recorded on the
majority of subsequent trips. In addition a gain of 45 bbls of mud at 4360
meters indicated apparent under balanced conditions. Mud weight was
progressively raised from 11.2 ppg at 4081 meters to 12.6 ppg by 4360 meters in
response to this problem. A further increase to 13.1 ppg was made at TD due to
logging difficulties associated with tight hole. The overall operation took 115
days from spud. Total depth was reached in 87 days, while an additional 28 days
were used to log, test and abandon the well. General Well 34/10-9 was drilled on the central
part of the Gullfaks Field. The primary objective was to test sandstones of the
Early Jurassic Cook Formation. Originally the well was planned to be drilled to
a total depth of 2000 m. Results from the well required further drilling into
sandstones of the Statfjord Formation. Operations and results Appraisal well 34/10-9 was spudded with
the semi-submersible installation Ross Rig on 24 March 1980 and drilled to TD
at 2200 m in the Early Jurassic Burton Formation. As in other wells drilled in
the area the pore pressure was close to the formation integrity in the pressure
transition zone. Lost circulation combined with high gas readings, was
experienced on several occasions in this zone between ca 1730 and 1760 m. Apart
from that, the drilling was carried out without any specific problems. The well
was drilled with seawater and high viscosity slugs down to 845 m, and with a
gel/lignosulphonate mud system from 845 m to TD. From the well site sample
description diesel was added to the mud in the interval 1260 to 1350 m. The Brent Group, Ness formation was
encountered at 1833 m, directly underlying the Late Cretaceous Kyrre Formation.
The Brent Group was hydrocarbon bearing down to base Rannoch Formation at 1945
m with ca 97 m net hydrocarbon bearing sands. The Cook Formation was
hydrocarbon bearing with an oil/water contact at 2118 m. First trace of oil
shows, fluorescence, was seen at 1220 m. Weak shows on claystone and limestone
were recorded from this depth to 1500 m. Stronger oil shows with "oil
streaks over shaker" and oil-smell were recorded from 1690 m to 1720 m in
the Lista Formation. Four cores were cut in the well. Cor General Appraisal well 31/6-7 was drilled in the
south-west corner of the Troll East gas province. The main objectives of the
well was to determine the lateral extent of the reservoir, to determine the
fluid contacts in the Sognefjord Formation and to obtain the best possible
seismic correlation within the reservoir from well 31/6-1. If hydrocarbons were
encountered the well would be tested to obtain a number of reservoir
engineering parameters: permeabilities and skin, fluid samples, pressure/temperature
drops in tubing at various flow rates, reservoir inflow at high flow rates, and
behaviour of gravel pack at high rates. Operations and results Well 31/6-7 was spudded with the
semi-submersible installation Treasure Seeker on 1 April 1985 and drilled to TD
at 698 m in Oligocene sediments. After drilling the 26" hole to 694 m, and
setting the 20" casing it was discovered that the angle of the 18
3/8" wellhead was 2.5 degrees and it was decided to junk the well. The
well was permanently plugged and abandoned on 13 April 1985, and the rig was
moved 50 m due north to spud replacement well 31/6-8. Testing No drill stem test was performed General Wildcat well 8/3-1 was the first
exploration well to be drilled in Norwegian waters. The chosen location was
northwestern part of the Danish Norwegian. The well was proposed to investigate
the largely unknown stratigraphic sequence and lithologies in a virgin area on
an attractive, representative seismic structure. Although the seismic feature
was based on low-density reconnaissance control, the structure qualified for
testing in terms of vertical and areal closure and inferred thickness of
sediments. The well site location was thought to lie on the east flank of the
Tertiary "Viking" basin, but on the west flank of a Mesozoic sub
basin. The position and delineation of older basins was uncertain, although
Permian? salts of sufficient thickness to flow were recognized as probably
present at depth. Interpretation of data from a seismic grid with about 7 Km
line spacing indicated a regionally high, west-dipping, normally faulted block
to be present. The well location was sited near the crest of the highest step
faulted block. A diapiric Zechstein? salt plug was interpreted to be present,
to the east on the down side of the principal fault block. The salt could have
partially intruded along the fault plane, up through the Kimmerian horizon." Operations and results Well 8/3-1 was spudded with the
semi-submersible installation Ocean Traveller on 19 July 1966 and drilled to TD
at 3015 m in Caledonian schists. While pulling out of the hole to pick up a
core barrel at a depth of 296I m the pipe stuck at 1660 m, and was pumped free
with seawater. The hole began caving immediately. Extensive caving over the
interval 1320 m to 2030 m lead to bridging, stuck pipe, and logging problems.
Eighteen rig-days were spent to cure the problems by reaming and raising the
mud weight and to log the section in various logging attempts. The hole was
eventually cased to 2963 m. No further problems developed. From sea bed to 277
m the initial dri General Well 25/11-1 is located on the Utsira
High in the Northern North Sea. The objective of the well was to test the
hydrocarbon potential of the sedimentary section; to investigate the lithology
and sequence in this portion of the North Sea basin; and to partially fulfil
Esso's drilling obligation to the Norwegian Government incurred on behalf of
the Licenses. Operations and results Wildcat well 25/11-1 was spudded with the
semi-submersible installation Ocean Traveler on and drilled to TD at 2459 m in Basement
rock. Actual drilling problems with the 25/11-1 were few. However, other major
problems occurred. The number 2 column of Ocean Traveler was bumped by a supply
boat on 6 November and began taking water. On 18 November, 1966 the rig was towed to Stavanger for repairs. By 14 April, 1967 the rig was able to continue drilling at the 25/11-1 location. Bad weather caused a new break in the
drilling operations from 17 April to 10 May. From the sea floor to 370 m (1213'), the
hole was drilled with sea water and gel. Returns in this interval were to the
sea floor. Below 370 m to total depth a sea water slurry with Bentonite,
Zeogel, Spersene, XP-20, Caustic Soda and 0 -12% diesel oil was used. First show in the well was reported in
thin siltstone and sandstone bands at ca1690 m. Gas and live oil were found in
Paleocene clastic sediments (Balder Formation; top has been set at 1698). The
recovered cores from this interval (1726.7 to 1745.9 m) showed a predominantly
shale section containing interbedded tuffaceous siltstone and sandstone. The
shale bled gas throughout and developed a film of oil along fractured surfaces.
The siltstone, though tight, bled oil at the base of most beds. The sandstone,
whether 1/2 inch or three feet thick, was saturated with live oil which gave a
yellow fluorescence and a streaming yellow-white or blue-white cut. Two FIT
tests at 1755 and 1777 m yielded oil and gas, while a FIT at 1801.4 m recovere General Well 16/2-1 is located on the very
western part of the Utsira High in the central part of the Vestland Arch. The
Utsira High is a large, flat, fault bounded basement feature. The objective of
this early well in the North Sea was: "To test the hydrocarbon potential
of the sedimentary section; investigate the lithology and sequence in this
portion of the North Sea basin; and to partially fulfil Esso's drilling
obligation to the Norwegian Government incurred on behalf of the Licences."
Operations and results Wildcat well 16/2-1 was spudded with the
semi-submersible installation Ocean Traveler on 11 July 1967 and drilled to TD
at 1906 m, 33 m into basement rock. There were no noteworthy drilling problems
encountered while drilling. Initial drilling from the sea floor to 381 m was
with seawater and gel without casing. Returns were to the sea floor. Below 381
m to total depth of 1906 m, a seawater slurry with gel, CMC, Spersene, XP-20,
Caustic Soda, Barite, and 0-10% diesel oil was used. Oil shows were seen on cores in tight
Cretaceous carbonate rocks in the Tor Formation. The shows were strong and
continuous from top Tor Formation down to 1776 m, and then became patchy. These
rocks were too impermeable to justify further tests in this well. Weak shows
were seen also in a thin Oligocene sand from 1256 m to 1263 m and in Eocene
mudstones from 1631 m to 1637 m, Balder Formation. Dead oil/tar was observed in
fractures in the basement rock. Five cores were cut from 1739.5 m to
1821.8 m in the Tor Formation chalk and two more cores were cut from 1879.1 m
to 1883.7 m in the basement. Four Formation Interval Tests (FIT) were performed
at 1748.9 m, 1733.4 m, 1642.6 m, and at 1738.2 m. The tests, one in Early
Tertiary shales and three in Late Cretaceous carbonates, did not show any
hydrocarbons. The well was permanently abandoned on 9
August 1967 as a well with shows. Testing No dr General The 9/8-1 well is located in the central
western part of the Norwegian-Danish Basin in the North Sea. The objective was
to test the hydrocarbon potential of the sedimentary section present on the
crest of a closed seismic structure interpreted to be a salt pillow.
Prospective reservoir sands were anticipated towards the base of the Tertiary,
in the Early Cretaceous and in the Early Triassic. Operations and results Wildcat well 9/8-1 was spudded with the
jack-up installation Endeavour on 23 May 1968 and drilled to TD at 2176 m in
the Late Permian Zechstein Group. It was the first well drilled in Norwegian
waters with a jack-up platform. After the 36" conductor was set at 137 m,
the hole was drilled with a 17 1/2" bit to 411 m. While reaming the hole
to 26", cavings and fill of shell fragments and gravel caused problems
from about 300 m, necessitating the 20" casing to be set high at 360 m.
The only additional drilling problem of note was a twist off while drilling at
1546 m. The fish was recovered in a few hours without difficulty. From here,
operations were successfully carried out to TD. Initial drilling from the sea
floor to 1350 feet was with seawater and gel without casing. Returns were to
the sea floor. Below 1350 to TD at 7138 feet, a Spersene, XP-20, Salinex mud
with up to 10 % diesel oil was used. The interpreted salt pillow structure was
found to be a piercement which breached the Triassic with the result that the Triassic Bunter sand section was not
present in this well. Top Permian Zechstein evaporites at 2109 m were
immediately overlain by the Middle Jurassic Dogger formation. The Dogger
contained some porous sandstones (Sandnes Formation) but these had only weak
shows in the uppermost few feet and the logs indicated high water saturation.
Both the Lower Cretaceous and the entire Tertiary section consisted mainly of
clays. No sands were developed at the base of either the Lower Cre General Wildcat well 16/7-1 is located in the Ling Depression between the Utsira High and the Danish Norwegian Basin. The main objectives were to test the hydrocarbon potential of the sedimentary section and to investigate the lithology and sequence in this portion of the North Sea basin. Operations and results Well 16/7-1 was spudded with the semi-submersible installation Ocean Traveller on 11 August 1967 and drilled to TD at 2781 m in salt of the Late Permian Zechstein Group. Initial drilling from the sea floor to 381 m was with seawater and gel without casing. Returns were to the sea floor. Below 381 m to a depth of 2150 m, a Spersene XP-20 Lignosulphonate mud with 3% to 8% diesel oil was used. From 2150 m to TD, the mud system contained salt saturated Spersene XP-20 Lignosulphonate mud with 5% to 9% diesel oil. After cementing the 30-inch casing at 131 m, the well was drilled to 213 m. On pulling out of the hole, it was found that the guide structure had sunk 5 m into the seabed or 2.5 m below the mud line. The ocean floor str General Well 16/1-1 is located roughly midway
between the Gudrun Discovery and the Balder Field in the North Sea. This early wildcat
well had the general objective to: " -test the hydrocarbon potential and
investigate the lithology in this portion of the North Sea basin". The well is Type Well for the Utsira
Formation. Operations and results Wildcat well 16/1-1 was spudded with the
semi-submersible installation Ocean Traveler on 26 September 1967 and drilled
to TD at 3203 m in the Late Cretaceous Hod Formation. No significant problems
were reported from the operations. Initial drilling from the sea floor to 392 m
was with seawater and gel without casing. Returns were to the sea floor. Below
392 m to total depth, a seawater slurry with Bentonite, Zeogel, Spersene,
XP-20, Caustic Soda, and 0-12% diesel oil was used. Porous sandstone was observed in the
Miocene, Oligocene, and Eocene. There were also Paleocene sands in the well.
Traces of possible residual oil stain were encountered in cuttings and cores
from the Oligocene and Eocene. In addition, questionable shows (non-fluorescent
dead oil) were reported on cores from the Paleocene. However, neither the hot
wire gas indicator nor chromatograph suggested the presence of hydrocarbons. A total of 18 cores were cut from the
different formations within the Hordaland, Rogaland, and Shetland Groups,
recovering a total of 171 m core. The depth for core 2 is probably incorrect,
possibly be five meter shallow due to malfunction of the bumper subs. FIT wire
line fluid samples were taken in potential hydrocarbon-yielding beds at 1878.5
m, 2532.9 m, and at 2592.3 m. Only water and mud were recovered. The well was permanently abandoned on 10
December 1967 as a dry well. Testing No drill stem test was performed. General The 16/6-1 ("ODIN 1") is
located on the Utsira High in the North Sea. The well was positioned crestally
on the southern tip of a big, seismically defined, horst feature. This horst,
trending N-S and sharply limited by faults on west, east and south sides, has
induced a vast anticline in his Mesozoic and Tertiary overburden. The well was
programmed to investigate the sedimentary section down to pre-Permian
formations. Operations and results Wildcat well 16/6-1 was spudded with semi-submersible
installation Ocean Viking on 7 November 1967 and drilled to TD at 2061 m in
basement rock. The well was drilled with seawater down to 360 m, and with a
seawater / Q'Broxin / CMC type mud from 360 m to TD. Gas shows (C1) were observed with a GAL
21 type chromatograph while drilling the Tertiary series, mainly in the upper
part with a maximum of 12 % at 630 m, decreasing to 2-3 % below 790 m. In the
Cretaceous, no gas was seen and only a very small show (0.02 %å was recorded at
the top of Jurassic shale. In the Utsira Formation 28 m net sand was
encountered. The sands had high porosities, but were water wet. From 2019 m
to2050.5 m a very rich Draupne source rock shale with 6 % to 7 % TOC was
penetrated. The sequence is immature in the well position. At 2050.5 m 4.5 m of
lithic sand was found directly overlying basement. The sand is probably a
basement "wash" which reflects the transition from an erosive stage
to a depositional one. The lower 4 m of this sand had very good porosities (>32%)
but were also water saturated. Permian and Triassic objectives were not present
in the well. One core was cut in basement from 2057 to 2060.5 m (TD) with 100 %
recovery. Two series of log-operations were run at 1362 m and 2060.5 m. Trouble
occurred with gumbo type clay bridging the hole during the first operations and
three cleaning trips were necessary. No fluid samples were attempted. The well
was permanently abandoned as a d General Well 7/11-1 was drilled on eastern side
of the Breiflabb Basin in the southern North Sea, ca 3km from the UK Border. The
main objective was to test the hydrocarbon potential of the Tertiary and the
Mesozoic sediments. Specific objectives were Paleocene sandstone, the Late
Cretaceous carbonate section, and the Jurassic. Sandstones in the Early
Cretaceous and Triassic were seen as possible secondary targets. Operations and results Wildcat well 7/11-1 was spudded with the
semi-submersible installation Ocean Viking on 26 February 1986 and drilled to
TD at 3974 m in Late Permian Zechstein Salt. The only significant drilling problem
encountered was sloughing of shale between ca 1675 m and 2315 m. Deviation was
negligible above 3500 m, from where it increased from 4.5 deg to 11.5 deg at
approximately 3960 m. The true vertical depth therefore probably is 4-5 m short
of measured depth at TD. A Drispac-Flosal-Desco mud system was used to a depth
of 3290 m. At this depth the system was converted to a sodium chloride saturated
Drispac-Flosal-Desco system. The salt saturated system was used to total depth. The well proved gas and condensate in three
tests in a 5 m thick intra-Balder Formation sand (DST 5) and the Forties
Formation from top at 2904 m down to 2989 m (DST 3 and 4). Below this depth DST
1 and 2 produced only minor amounts of hydrocarbons due to tight formation. Top
salt came in under the Late Cretaceous Hidra Formation at 3740 m. Three cores were taken in the Paleocene
sandstone in the intervals 2922.7 - 2932.8 m, 2932.8 - 2949.9 m, and 2952.9 - 2966.9
m. A fourth core at TD had no recovery. No wire line fluid samples were taken.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General Well 9/4-1 is situated northeast in the
Åsta Graben in the Danish-Norwegian Basin. The chosen well location allowed
multiple Tertiary to Mesozoic prospects to be tested. The primary objectives of
9/4-1 were Middle Jurassic and Early Triassic (Bunter) sandstones, while basal
Tertiary and Early Cretaceous sandstones and Late Cretaceous limestones were
secondary objectives. The well is Type Well for the Egersund
Formation. Operations and results Wildcat well 9/4-1 was spudded with the
jack-up installation Endeavour on 31 Marc 1968 and drilled to TD at 2963 m in
Late Permian Zechstein salt. Three casing strings were set in the hole.
Seawater was used as drilling fluid down to 1106 m, from where an XP-20
lignosulphonate type mud was used. When the drilling commenced after the
30" conductor pipe was set, several drilling problems arose. The
circulation was lost, and the hole fell in repeatedly, so the conductor pipe
had to be re-driven and cemented several times until the hole conditions allowed
the 20" casing to be set. At 2963 m the drill pipe stuck in salt, and
after five days of unsuccessful fishing operations, it was decided to abandon
the hole. The lower part of the hole could not be logged due to the unrecovered
fish. Twenty-five net meter of Jurassic
sandstone was penetrated in a sand body (Sandnes Formation) at 2288 m. The
section was water wet, but fair shows were logged in the upper 5 m of the sand.
The remainder had very scattered poor shows. Porosity averaged 25 percent and examination
of sidewall cores indicated a clean permeable sandstone reservoir. The second
primary objective, the Bunter Sandstone, was represented by an estimated 60 m
of thin interbedded sands and sandstones scattered throughout a thick Triassic
section composed predominantly of silty red brown to pastel claystones. Due to
lack of logs the interpretation of the Triassic section is somewhat tentative.
Late Cretaceous Chalk General Well 16/9-1 is located in the Ling
Depression between the Utsira High and the Danish Norwegian Basin. A relatively
thick Jurassic/Triassic section was anticipated and was expected to contain
porous sandstones. The main objectives were to test the oil and gas potential
and investigate the lithology of the sedimentary section on an anticlinal
structure between salt dome features. Operations and results Wildcat well 16/9-1 was spudded with the
vessel Glomar Grand Isle on 8 May 1968 and drilled to TD at 3654 m in salt of
the Permian Zechstein Group. Drilling operations were normal to 3654 m (TD),
while drilling at this depth on 24 June 1968, a sudden storm struck the Glomar
Grand Isle causing the drill pipe to part and drop in the hole. The top of the
fish was at 859 m. A jet cutter was run, the drill pipe was cut at 3321 m and
recovered on 28 June. Attempts to recover the remaining fish failed and on 7-8
July final logs were run to the top of the fish at 3321 feet. Following final logs,
the well was prepared for abandonment. Initial drilling from the sea floor to
402 m was with seawater and gel. Returns were to the sea floor. Below 402 m to
3395 m, the mud system consisted of a sea water/Spersene/XP-20 Salinex mud with
5% to 8% diesel oil. From 3395 to TD a salt saturated mud system was used. The Danian and Cretaceous carbonates had
no shows. The remaining sections penetrated by the well were predominantly
clays, shales or evaporites. The well penetrated a 169 m Jurassic section and a
735 m thick Triassic sequence before entering the Late Permian Zechstein Group
at 3199 m. Some porous sandstones were present in the Jurassic and Triassic on
structure but these had no hydrocarbon shows and were indicated to be water
bearing on the electric logs. Two conventional cores were cut, one from 1227 m
to 1245 m in the Tertiary Hordaland Group and one from 2396 m to 2404.5 m in
the Middle Jurassic Vestland Group. No fluid samples were tak General Well 9/4-3 was drilled on a salt-induced,
anticlinal structure in the Egersund Basin in the North Sea, 17 km to the east
of the 9/4-1 location. The primary objective was the Middle Jurassic sandstone,
but also Triassic sands were considered prospective. Danian and Late Cretaceous
chalks were seen as secondary objectives. The well is Type Well for the Jurassic
Bryne, Sandnes, Tau, and Sauda Formations in the Norwegian-Danish Basin. Operations and results Wildcat well 9/4-3 was spudded with the
jack-up installation Ocean Tide on 14 July 1972 and drilled to TD at 2682 m in
Late Triassic sediments of the Skagerrak Formation. The hole was drilled
without significant drilling problems, although heaving shales in the lower
Tertiary caused some difficulties. After drilling out the 20" casing shoe
at 404 m the drilling fluid was changed from a gelled seawater gel to a
lignosulphonate seawater mud system, which was used to TD. The only sandy Formation encountered
above the Jurassic level was the Late Paleocene Fiskebank Formation at 1150 m,
with a 50 m thickness. A complete sequence of Early Cretaceous stages was
present between 1967 and 2250 m. The Kimmeridge section also appeared complete
and represented entirely by an argillaceous succession. No sandy facies of
Early Kimmeridgian/ Late Oxfordian was detected. The Bathonian-Bajocian
sandstone/shale sequence between 2490 m to 2613 m (the Vestland Group) is
comparable with adjacent wells in the area although clearly thicker in the
current section. No oil shows were recorded in any section of the well during
drilling and the logs confirmed that the Jurassic and Triassic sections were
water wet. From organic geochemical analyses source
rocks were found in shales of the Late Jurassic Tau and Egersund Formations,
and the coals of the Middle Jurassic. The 37 m thick Tau Formation at 2400 m
contained an average kerogen type II/III with TOC around 5% and has a r General Well 17/4-1 was drilled on a NNE-SSW
trending monocline in the Ling Depression between the Sele High and the Utsira
High /Patch Bank ridge. The objective was to investigate the sedimentary
section down to the pre-Permian, and particularly to test the hydrocarbon
potential of the Mesozoic sands and Zechstein dolomites. Furthermore, Early
Permian and/or pre-Permian reservoirs were to be evaluated if present. Operations and results Wildcat well 17/4-1 was spudded with the
semi-submersible installation Ocean Viking on 15 June 1968 and drilled to TD at
3997 m in conglomerate in the Early Permian Rotliegend Group. Initial drilling
to 444 m was with seawater, and the returns were to the sea floor. The 17
1/2" hole was drilled out using an LFC-LC/sea water type mud, and the 13
3/8" casing shoe was set at 1803 m. From this depth the mud system was
salt saturated. The 12 1/4" hole was drilled down to 3942 m from where the
hole diameter was reduced to 8 1/2". An inverted oil-base mud was used from
2900 m to TD. Sandstones were encountered in the
Jurassic and Triassic. They had medium to good porosities, but generally poor
permeabilities due to calcite cement. The pre-Zechstein conglomerate was very
tight with no porosity. On top of this there were nearly 1200 m of evaporites,
apparently undisturbed by halokinesis. The evaporites were overlain by around
300 m of continental Triassic deposits. The Jurassic consisted of fluvial
sandstones overlain by carbonaceous dark shales belonging to the Late Jurassic
"hot" shale (Draupne Formation). This shale was penetrated at 2122 m
and is 95 m thick in the well position. No samples of any kind was recovered
from this interval, but analysis of caved cuttings believed to originate from
Draupne indicated TOC in the range 2 % to 7 % with potential for oil and gas.
The Draupne formation is immature in the well. The Early Cretaceous marine, low
energy shales range in age General Well 1/3-1 was drilled on the crest of a
salt-induced anticline on the Hidra High in the North Sea. The purpose of the
well was to investigate Tertiary and Mesozoic sequences down to top salt. The well is Type Well for the Våle, Hidra,
Hod, and Tor Formations, and Reference Well for the Vidar, Ekofisk and Blodøks Formations. Operations and results Well 1/3-1 was spudded with the four leg
jack-up installation Orion on 6 July 1968 and drilled to TD at 4877 m in the
Permian Zechstein Group. From the deviation survey it is seen that the well
starts to deviate significantly at 4037 m (8 deg deviation), and at TD the
deviation is 18 deg. This will correspond to a TVD RKB that is ca 25 m less
than MD RKB.Several drilling
problems occurred during the drilling operations of well 1/3-1. While drilling
the 17 1/2" hole for the 20" casing, circulation losses started at
220 m (720') and became total at 238 m (781'). While drilling on with sea
water, without returns, the pipe stuck. The lost circulation zone eventually
had to be sealed off with a cement plug. In the Tertiary plastic clays the
problems included tight hole conditions, bit balling, and difficulties in
lowering the logging tools. The mud weight had to be raised from 10.8 ppg to 13.6
ppg to stabilize the hole. At 4131 m (13554') the bit twisted off, but was
retrieved on the second fishing run. A hydrocarbon bearing zone was encountered
at 4567 m (14984'). The mud became gas cut. At 4592 m (15064') the degasser was
overloaded and the circulation lost, probably higher in the hole. A cement plug
was needed to combat the lost circulation problems. It was then decided to set
a 7" casing. Circulation was lost while running the casing, which had General Exploration well 2/8-2 is located about 8
km south of the 2/5-3 Sørøst Tor Discovery. Danian and Maastrichtian limestones
were the main objectives. Another objective was to investigate if the Paleocene
hydrocarbon bearing sandstones, which had been encountered in the Cod Field,
extend across the 2/8-2 location. Operations and results Well 2/8-2 was spudded with the jack-up
installation Orion on 28 June 1970 and drilled to TD at 3245 m in the Late
Cretaceous Rødby Formation. While drilling at approximately 1774 m large chunks
of clay came over the shale shaker, followed by a gas kick at 1777 m. The mud
weight was reduced to 10.0 ppg and degasser was run for two hours. Then the
weight was increased to 14.1 ppg, the hole circulated and drilling continued.
Sloughing of shale occurred around 2490 m, and the mud weight was increased to
14.3 ppg to control this problem. TD was reached and the well successfully
logged. Seawater was used for drilling the 36" hole down to 129 m. A seawater/
gel mud was used to drill out the 36" casing and down to 427 m. From 427 m
to TD the well was drilled with an Emulsite/Drill aid system with 2 to 5 %
diesel oil added. Only traces of sandstone and siltstone
were encountered in the Paleocene section, and the rocks showed no indications
of hydrocarbons. Neither the Danian sequence, which was thinner than expected,
nor the Maastrichtian limestones contained hydrocarbons. The only significant
hydrocarbon shows encountered in 2/8-2 were from thin dolomite and limestone
stringers of Eocene age. These exhibited good oil stains but generally showed
poor porosities, and further evaluations were not made. Two cores were cut in
the well. Core l from 2962 m to 2971 m recovered 9 m of Danian chalk and core 2
from 3231 m to 3238 m recovered 6.4 m of Rødby Formation shale. No fluid sample
was collected from the well. The well was permanently abandoned on 30
July as a well with shows General Well 7/11-2 was drilled , ca 1.5 km from
the UK Border on the eastern side of the Breiflabb Basin in the southern North
Sea. The objective was to test the hydrocarbon potential in the Paleocene on
the west flank of the Cod structure, and to confirm the gas and condensate
discovery made by the 7/11-1 well. Well 7/11-1 tested up to 430 Sm3 condensate
and 1254000 Sm3 gas /day from the Late Paleocene Forties Formation. Operations and results Appraisal well 7/11-2 was spudded with
the semi-submersible installation Ocean Traveller on 21 July 1968 and drilled
to TD at 3427 m in the Late Cretaceous Tor Formation. Tight hole was
experienced when pulling out of the 17 12" hole. The hole was washed back
to TD and mud weight increased to 14 ppg. Logging and casing operations could
then be successfully carried out. The well was drilled with sea water down to
1219 m where the system was changed to a salt-saturated Drispac-Desco-Flosal
type. The well tested gas and condensate in
Paleocene sandstones (the Forties Formation). One core was taken in the Paleocene
sandstone in the interval 3030.6 m to 3045 m. No wire line fluid samples were
taken. The well was permanently abandoned on as
a dry well. Testing Three drill stem tests were performed. DST 1 tested the interval 3166.3 m to
3192.5 m. This test produced only 3.7 m3 salt water-cut mud and mud filtrate. DST2 tested the interval 3027.3 m to
3105.9 m. General Well 7/12-1 S was drilled on the Cod
Terrace in the North Sea. The primary objective was to test possible Late
Paleocene sandstones. Operations and results Wildcat well 7/12-1 S was spudded with
the jack-up installation Gulftide on 31 August 1968 and drilled to TD at 3311 m
in claystone believed at the time to be Jurassic sediments but which since has
been assigned to the Cromer Knoll Group. The pipe stuck at 2270 m. Fishing was
unsuccessful and the well was plugged back and technically sidetracked from
1443 m. The well was drilled with seawater/Flosal/Drispac down to 1009 m and
with seawater/Q-Broxin mud from 1009 m to TD. The well was dry. The target section from
2588 to 2627 m had only very thin laminations of sandstone without shows. No cores were cut and no fluid samples
were taken. The well was permanently abandoned on 18
October 1968 as a dry well. Testing No drill stem test was performed. Well 7/8-1 was drilled on an anticlinal
structure in the westernmost part of the Norwegian-Danish Basin and marginal to
the northern slope of the Central Through. The anticline was interpreted as a
salt-induced structure with closure at top Paleocene and top Cretaceous, and
these horizons were defined as the main objectives of the well. The well should
be drilled into Permian salt with prognosed top at 3261 m (10700 ft). Operations and results Wildcat well 7/8-1 was spudded with the
semi-submersible installation Ocean Viking on 31 August 1968 and drilled to TD at 3334 m in Triassic sediments of the Gassum Formation. The well did not
reach the planned TD in Permian salt. Drilling went without significant
problems down to 1981 m. From this depth on, several drilling problems arose.
After the casing had parted at two places the well had to be sidetracked from
1831 m. This hole was then drilled to 3334 m, which is recorded as TD for the
well. At this depth the well kicked and the mud density was increased from 12.3
ppg to 12.8 ppg. While circulating, the hole gave up mud and sloughing finally
caused the pipe to stick. After having backed off the drill pipe and displaced
the hole with 14.0 ppg mud, a high pressure was observed on the drill pipe and
the mud system density was increased to 14.3 ppg. Several mud conditioning
operations were necessary until the well seemed dead. After recovering 2650 m
of drill pipe out of the hole the well was plugged from 2657 m to 2469 m and
displaced with 14.7 ppg mud. A second sidetracked hole was then drilled from
2538 m to 3316 m where the final logs were run. The operations were also
delayed significantly by severe weather conditions in December and January. The
well was drilled with seawater and high viscosity pills down to 1166 m, and with
a saturated salt water mud from 1166 m to TD. Below 1920 m the mud contained
from 2 - 6 % oil. Both objective formations were encountered.
However, both were thinner tha General Well 7/11-3 was drilled ca 3.5 km
south-east of the 7/11-1 Cod discovery well on the eastern side of the
Breiflabb Basin in the southern North Sea. The objective was to test the extension
of the Paleocene sands that were found hydrocarbon bearing in wells 7/11-1 and
7/11-2. Operations and results Appraisal well 7/11-3 was spudded with
the semi-submersible installation Ocean Traveller on 17 October 1968 and
drilled to TD at 3350 m. The hole collapsed when drilling a shale section between
1950 m and 2300 m. Bridging took place until the mud weight was increased to
14.5 ppg. Otherwise the well was drilled without significant problems. The well
was drilled with a Drispac-Flosal-Desco system, which was salt saturated when
drilling the lower part of the hole. Minor amounts of oil and gas was tested
in a Forties Formation sandstone sequence correlated to the best sandstone
sequences that were tested in the two first Cod wells. Three cores were cut in the intervals
3074.2 to 3082 m, 3092.8 to 3105 m, and 3160.3 to 3177.2 m. No wire line fluid
samples were taken. The well was permanently abandoned on 7
January 1969 as an oil appraisal well. Testing Eight drill stem testes were carried out. DST 1 tested the interval 3239.7 to
3246.4 m. It produced a total of 15 m3 diesel cushion, mud and water. Bottom
hole temperature was 129 deg C. DST 2 tested the interval 3210.2 to
3231.8 m. It produced a total of General Well 2/6-1 is located on the north
eastern slope of the Mandal High between the Søgne Basin and the Central Graben
in the North Sea. It was drilled on a salt induced anticlinal structure. The
objective of the well was to investigate the sedimentary section down to the
Permian salt, and particularly to test the hydrocarbon potential of the
Tertiary and Mesozoic sands. Operations and results Wildcat well 2/6-1was spudded with the semi-submersible
installation Ocean Viking on 21 April 1969 and drilled to TD at 3336 m in salt
belonging to the Late Permian Zechstein Group. Down to 615 m the well was
drilled with sea water as drilling fluid, and the returns were to the sea
floor. From 615 m to TD a sea water/LFC type mud was used. The only significant
drilling problem occurred at a depth of 3220 m in the top of the Mesozoic sands
when the well kicked 6.35 m3 of water associated with a gas show. The flow rate
was 20 m3/hr and the pressure was estimated to 480 kg/cm2. The kick was killed
with a 1.65 g/cm3 mud. Forty meter of Middle and Late Jurassic
sands revealed good reservoir properties, but contained no hydrocarbons.
Average reservoir properties in these sands were 20% porosity and 140 mD permeability.
The Tertiary sediments contained very little sand. Shows were described as
follows: in the Paleocene siltstones and shales, a small chloroform cut was
obtained on sidewall samples and in the Mesozoic sands, traces of bitumen occur
and a chloroform cut was obtained. One conventional core of Jurassic sandstone
was cut at 3223 to 3235 m. No wire line fluid samples were taken. The well was permanently abandoned on 30
May 1969 as a dry well. Testing No drill stem test was performed. General Well 17/10-1 is situated in the
Norwegian- Danish Basin near the western margin of the Sele High, which is a
shallow basement feature. The structure on which the well was drilled is a very
gentle anticline in an area with prominent salt walls. The objective of the
17/10-1 well was to test the Mesozoic section. Operations and results Well 17/10-1 was spudded with the
semi-submersible installation Sedneth I and drilled to TD at 3590 m in the
Triassic Smith Bank Formation. The hole was drilled with a 18 1/2" bit to
160 m, but during enlarging with a 36" hole opener the temporary guide
base sank 2.5 m into the seabed and tilted, due to heavy washing out. This made
it impossible to enter the hole and the rig was moved 30 m NNE of its original
position where a new hole was spudded. An 18 1/2" hole was drilled to 430
m. Seawater was used as drilling fluid and the returns were to the sea floor.
Thereafter the mud system was converted to a Spersene/XP-20 seawater mud. At
3367 m the mud was converted to a salt saturated system since this was below
the prognosed depth for top Zechstein salt. The chief reservoir zone of interest was
the massive Jurassic/Triassic sandstone (Gassum and Skagerrak Formations) from
2682 m to 3405 m. This section had porosities mainly between 20 % and 25 % and
was entirely water bearing. There is a major unconformity on top of these sands
to the overlying Late Jurassic shales. The claystone section from about 2651 m
to 2682 m (Tau and Egersund Formations) had an exceptionally high gamma ray
with readings up to 300 API units. Resistivities varied between 2 and 7 ohm/m
compared with 1 - 1.5 ohm/m for the overlying shales. Cuttings from this
section were very carbonaceous and were bleeding gas when first examined. Chromatograph
readings were up to 700 ppm C1 with small quantities of C2, C3, and C4. Above
and below this section the C1 reading was about 300 ppm. Nearly 700 m of Lower
Cretaceous s General Well 2/3-1 is located approximately in
the centre of the block on the Sørvestlandet High. The aim of the well was to
test potential reservoirs in the Tertiary, Cretaceous, Jurassic, and Trias. Operations and results Wildcat well 2/3-1 was spudded with the
semi-submersible installation Ocean Traveler on 10 February 1969 and drilled to
TD at 2934 m in the Late Permian Zechstein Group. Bad weather with wind up to
31 m/s caused the rig to drift up to ca 40 feet off location on several
occasions, interrupting drilling operations. The well was drilled with seawater
and bentonite down to 463 m. A water based mud system was used in the remaining
borehole. The well encountered gas in two zones in
Oligocene. From log analyses most of the reservoir interval from 1623 m to 1636
m, except a shale break, had a porosity around 22% with Sw = 30%.á Best part of
the second zone had a porosity of 23% with an Sw of 23%, (1597 m to 1600 m). No
cores were cut in the well and no fluid samples were taken other than during
the tests. The well was permanently abandoned as a
gas discovery on 3 April 1969. Testing Seven inch casing was run to 1673 m and
two flowing drill stem tests were made successfully.á The first test was made
from perforations at 1624 m to 1636 m and flowed dry gas at rates of 207000 to
304000 Sm3/day on choke sizes varying from 24/64" to 30/64". The
second test flowed dry gas at rates of 40000 to 92000/day on choke sizes
varying from 12/64" to 3O/64" from perforations at 1588 m to 1600 m. General Well 9/12-1 is located in the North Sea,
in the Danish-Norwegian Basin west of the Krabbe Fault Zone and Lista Fault
Blocks. It was drilled near the crest of a salt induced anticlinal feature. The
well is very similar to the 9/8-1 well, but the various geological units are
somewhat thinner in 9/8-1. The objective of the well was to test the Tertiary
and Mesozoic sequences. Operations and results Wildcat well 9/12-1 was spudded with the
semi-submersible installation Sedneth I on 28 March 1969 and drilled to TD at
2698 m in the Triassic Smith Bank Formation. The 36" hole was drilled to
133 m and the 30" casing was run to 131 m. An 18 1/2" hole was
drilled to 403 m, and two joints of 20" casing were hung from the 30"
housing before the 13 3/8" casing was set at 395 m. Seawater was used as
drilling fluid in the 36" and 18" holes and the returns were to the
sea floor. After the setting of the 13 3/8" casing the mud system was
converted to a Spersene/ XP-20 seawater mud, which was used to TD. The well encountered porous Danian/Late
Cretaceous limestones as well as Triassic and Jurassic sandstones, but no
hydrocarbons. The Triassic was represented by about 600 m of continental red
beds. There was a major unconformity to the overlying 65 m thick Middle
Jurassic sandstones, which represent a marginal marine, deltaic environment.
The Late Jurassic consisted of 165 m of mainly dark shales. During the Early
Cretaceous in excess of 300 m of shales were deposited in the area while the
Late Cretaceous is represented by 375 m of carbonates. From the Tertiary on the
sedimentation turned to a clastic regime. Deposition of fine-grained sediments
prevailed although this was interrupted by the deposition of more sandy units.
The Tertiary is made up of about 1200 m of sediments in this well. Late
Jurassic source rocks were confirmed by the well, but were found immature. The
absence of hydrocarbons General Exploration well 7/3-1 was drilled on the
Sørvestlandet High close to the Western part of the Danish Norwegian Basin.
Objectives were to test all horizons down to Permian Rotliegendes. The well is Reference well for the Ran
Sandstone Units. Operations and results Well 7/3-1 was spudded with the jack-up
installation Orion on 7 April and drilled to TD at 4699 m in carbonates of an
assumed pre-Permian age. Seawater was used to drill the 36" hole and
returns were to the sea floor. A sea water/ Spersene/XP-20 mud was used to a
depth of 2735 m, approximately to the top of the rock salt. The mud system was
then converted to an invert emulsion oil based mud, which was used to TD. While
drilling at 4699 m (TD) a salt water flow occurred and contaminated the mud.
The flow was controlled, but the condition of the hole was bad and the lower
approximately 120 m of the well, therefore, has not been logged. The well penetrated relatively complete
Tertiary, Cretaceous, Late Jurassic, and the Permian sequences. The Triassic
and the Early Jurassic were missing. The Permian Zechstein salt was 1437 m
thick, resting on a thin Kupferschiefer sequence. None of the sedimentary
sequences penetrated contained significant amounts of hydrocarbons. Three conventional
cores were cut in the interval from 4380.6 m to 4575.4 m from the Zechstein
salt and into the Rotliegendes Group. No fluid samples were taken. The well was permanently abandoned 10
June 1969 as a dry well. Testing No drill stem test was performed General Well 1/3-2 was drilled on the crest of a
salt-induced anticline on the Hidra High in the North Sea.The main objective was possible L. Tertiary
sands, well developed and productive in Phillips 7/11-1. Secondary objective
was the Late Cretaceous chalky limestone, which had given shows in 1/3-1. Operations and results Wildcat well 1/3-2 was spudded with the
semi-submersible installation Sedneth I on 14 May 1969 and drilled to TD at
4297 m in the Early Cretaceous Sola Formation. When drilling out of the
20" casing shoe, circulation was lost immediately, and the lost
circulation zone had to be cemented off. The plastic clays caused continuous
troubles, such as bit balling and plugged shaker screens, and the hole had to
be reamed and washed several times. Below 3378 m diamond bits were used, and
the drilling was interrupted frequently because of leaking bumper subs. The
well was drilled water based with a 1 - 4 % addition of diesel through most of
the well bore. Tertiary sands were not developed, and
whilst thick Late Cretaceous chalky limestone was found as predicted, there
were no hydrocarbon bearing intervals in it, and reservoir qualities were poor.
No source rock intervals were encountered, and only very minor traces of higher
hydrocarbons were detected in the Late Paleocene-Early Eocene section, and in
the interval 3761 to 3901 m in the Hod Formation. A small core recovered by junk basket was
taken at 3589.02 - 3589.5 m. No wire line fluid samples were taken. The well was permanently abandoned on 27
July 1969 as a dry well. Testing< General Exploration well 8/10-1 was drilled on a
gentle salt dome structure about 12 km west of the Ula Field on the
Sørvestlandet High. The objectives were to test Tertiary and Mesozoic horizons.
More specifically, the well should test the Tertiary Miocene section equivalent
to the gas-bearing sand section in well 2/3-1 (35 miles southeast), Eocene
sands which had minor gas shows in well 7/8-1 (25 miles northwest) and with oil
shows in the Shell 1/3-1, Paleocene sands productive in the Cod Field (25 miles
east), fractured Upper Cretaceous limestone with condensate and gas shows in
well 1/3-1 (20 miles southwest), and Jurassic and Triassic sands that were very
porous and permeable in well 7/8-1. The latter also had small shows in wells 7/8-1
and 9/4-1 (50 miles northwest). Operations and results The well was spudded with the
semi-submersible installation Ocean Viking on 30 May 1969 and drilled to TD at
3099 m in the Late Permian Zechstein Group. The hole deviation increased
considerably from about 2225 m to TD, with a maximum of 13.5 degrees at 2774 m
and about 10 degrees at the last survey point at 3018 m. Assuming an average
deviation of 9 degrees from 2200 m to TD this results in 3089 m TVD RKB at TD.
The pipe stuck at 3042 m. It was worked free after spotting diesel and Mudban.
Otherwise no significant problems were encountered during drilling operations.
The well was drilled with seawater down to 655 m, with a sea water/gel mud
system from 655 m to 2134 m, and with a lignosulphonate type mud from 2134 m to
TD. Below 655 m the well was drilled with 1 % to 8 % of diesel oil in the mud,
with the higher concentrations towards TD. None of the sedimentary sequences
penetrated by the well contained hydrocarbons. A more or less continuous
Triassic section consisted of mainly shale /claystone with traces of sand. The
Late Jurassic was represented by the Sandnes Formation sandstone and the
Kimmeridge Clay (Flekkefjord Formation). An un General Well 7/11-4 is located ca 8 km north-east
of the Cod Field in the North Sea. The objective of the well was to test the Late
Paleocene "Cod Formation" sands, gas bearing in the Cod 7/11-1 and -2
wells; and the Early Paleocene, Danian, which had gas and oil shows in the
7/11-1 well. Other objectives with possible but less likely development of
porosity were sands of the Late - Middle Eocene and the top of the Late
Cretaceous chalk. Operations and results Wildcat well 7/11-4 was spudded with the
semi-submersible installation Ocean Viking on 2 July 1969 and drilled to TD at 3321 m in the Late Cretaceous Tor Formation. No significant problems were
encountered in the operations. None of the objectives, the Late - Middle
Eocene, the Paleocene Forties Formation, the Danian,
or the Late Cretaceous materialized as productive zones. Sand was lacking in
the Eocene, and was shaly and tight in the top of the Paleocene Rogaland Group.
Only 9 m net of porous sand was encountered in the interval 3082 - 3098 m in
the Middle and Lower Rogaland Group. This was below the postulated water table
and from logs the net sand interval was water wet. Sands in the Danian section were
tight and calcareous, and no porosity was present in the Late Cretaceous chalk.
Shows reported from SWC's from the well were described as "oil
specks" and "bituminous specks" in sandstones and shales in the
interval 3024 - 3093 m in the Rogaland Group. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 31 July 1969 as a dry well. The next well on the structure, well
7/11-5, was drilled in 1982 and found oil in Jurassic Ula sands. Testing No drill stem test was performed. General Exploration well 2/11-1 is located on the
southern periphery of the Valhall Field in the North Sea. The objective of this
early wildcat was to test all horizons down to the Rotliegendes, estimated at
14100 ft (4298 m). Top Permian was expected at 10300 ft (3139 m). Planned TD
was at 15000 ft (4572 m). The well is Reference Well for the
Åsgard, Sola, and Rødby Formations. Operations and results Well was spudded with the
semi-submersible installation on and drilled to TD at 4691 m in the Late
Jurassic Tyne Group. The well started to build angle from below ca 3500 m with
maximum 11 deg deviation at 4444 m. Otherwise no significant drilling problems
were reported from this deep well. The well was drilled water based down to
3432 m and with an invert oil mud (Vertoil) from 3432 m to TD. Top Paleocene, Balder Formation, was
encountered at 2590 m. Top chalks of the Shetland Group (Tor Formation) was
encountered at 2635 m. In addition to shows from the gas detector, free oil was
seen floating on the mud pits and samples showed good fluorescence and cut
through the interval 2585 m to 2633 m (Balder, Sele, and Lista Formations).
Post-well geochemical analyses reported significant oil staining down to 2776
m. By testing live oil was confirmed in the uppermost Tor Formation. The tests
were inconclusive with regard to an OWC, but the logs indicated that the
contact was at 2655 m. Base Cretaceous was at 3555 m. The well did not reach
Permian sediments; in stead the well drilled 1136 m in Late Jurassic shale
(Mandal, Farsund and Haugesund Formations) before final TD was set. One
conventional core was cut from 3864 to 3878 m in the Farsund formation.No wire
line fluid samples were taken. The well was permanently abandoned on 3
October 1969 as a minor discovery. After the 2/8-6 Valhall Discovery well was
drilled 6 years later well 2/11-1 was re-classified to oil appraisal well for
the Valhall Field. Test General Well 2/3-2 is located on the
Sørvestlandet High north of the Søgne Basin and south of the Åsta Graben. The
well was drilled to determine if Oligocene - Miocene reservoirs were developed
off the flanks of the 2/3-1 structure and if the hydrocarbon accumulations
tested in the 2/3-1 well extended beyond the spill point of the structure.
Total depth of the well was planned in Lower Oligocene. The well is Reference Well for the Vade
Formation. Operations and results Appraisal well 2/3-2 was spudded with the
semi-submersible installation Ocean Traveller on 26 July 1969 and drilled to TD
at 2297 m in Paleocene sediments. The water depth at the location is 58 m. The surface hole
was drilled to 299 m, to simulataneously run the 30 inch and 20 inch casings. Problems with stuck pipe occurred. High pump pressure and
difficulty in washing past 265 m required pulling out of the hole again. It was
found that two drill collars and the bit had backed off. A dive was made to
determine if the fish was on the ocean floor. It could not be found. The hole
was abandoned and repositioned 20 m due east of the original location, for
re-spudding. After this no significant problems occurred during drilling.
The 36" and 26" holes, down to 211 m were drilled with sea water and returns
were to the sea floor. The rest of the well was drilled with a Q-Broxin/Caustic type mud.
As in well 2/3-1 bridging caused problema during the logging operations. This was especially
evident in the 17 1/2 inch hole, which had to be reamed and circulated. Still it turned out
to be impossible to obtain an open hole GR/BHC-Sonic survey. At 1795 m a sandy sequence, the Vade
Formation, was encountered. It was described as two sandstone beds, greenish
gray, very fine grained, poorly consolidated, porous and permeable. The
sandstone beds were separated by about 15 m of dark brown shale with thin
streaks of dolomitic limestone. Below the Vade sand only thin sand beds coul General Wildcat well 11/10-1 was drilled in the eastern
part of the Danish Norwegian Basin close to the borderline between the
Norwegian and the Danish sectors. The well is situated close to the Kreps fault
zone on the western flank of the Horns Graben. The main objectives of the
11/10-1 well were to test the hydrocarbon potential of the Tertiary and the
Mesozoic formations. Well 11/10-1 is the first well in quadrant 11 and one of
the few wells drilled in the southeastern part of the Norwegian continental
shelf so long. Operations and results Wildcat well 11/10-1 was spudded with the
semi-submersible rig "Ocean Viking" on 2 August 1969 and completed 19 August
the same year. The well was drilled at 63 m water depth and bottomed at a total
depth of 2430 m in a Triassic sand section without having encountered
hydrocarbons in any of the targets. Three casing strings were set in the
well. Sea water was used for the initial drilling down to 253 m. From this
depth down to 1023 m a sea water gel mud was used and from 1023 down to TD a
sea water Q-Broxin mud system was the drilling fluid. No significant drilling
problems occurred during the drilling of this well. No samples are available from the sea
floor down to 305 m. From 305 to 430 m the sampled sequence consists of medium
to coarse grained, subangular to subrounded, glauconitic sand and sandstone
with scattered rock fragments. The sand is generally unconsolidated and mostly
clear quartz and is relatively well sorted. Carbonaceous material, plant
remains and shell fragments occur throughout. Dolomitic limestone are also
present, increasing towards the bottom of the unit where the dolomite forms the
cement of the sand. The underlying shales are dated Late Oligocene, the age of
the sandy section is questionable as the upper 300m of the well has not been
sampled. No sandstones are developed in the
Rogaland Group which is much reduced in this well. The Upper Cretaceous General Wildcat well 2/4-2 (originally termed
2/4-1AX by the License) was drilled by Phillips as a replacement for well
2/4-1, which was junked at 1662 m in Miocene sediments due to an oil kick and
severe circulation problems. The objective was to test the hydrocarbon
potential of the Tertiary and top Cretaceous. Operations and results Wildcat well 2/4-2 was spudded with the
semi-submersible installation Ocean Viking on 18 September 1969 and drilled to
TD at 3305 m in the Late Cretaceous Tor Formation. No significant problems
occurred in the operations. The well was drilled with seawater and hi-vis pills
down to 619 m, and with lignosulphonate mud from 619 m to TD. The well discovered oil in Danian and
Late Cretaceous chalk (Ekofisk and Tor Formations). The oil was found in two
reservoirs separated by a hard, grey and tight lime mudstone in the base of the
Ekofisk Formation. The upper, Ekofisk Formation reservoir was encountered at
3033 m and continued down to the tight lime mudstone at 3183 m. The lower, Tor
Formation reservoir extended from 3203 m to 3257 m. Comparison between DST oil
from the Ekofisk Formation in well 2/4-2 and the Miocene "kick-oil"
encountered in well 2/4-1 showed that the 2/4-1 Miocene oil is a heavier oil with
a higher asphaltene content and lower paraffin content than the 2/4-2 oil. Eight conventional cores were cut with a
total of 48.5 m recovered. Core 1 was cut in Early Miocene from 1664 to 1679.4
m, while cores 2 - 8 were cut in the Ekofisk and Tor Formations in the interval
3051 m to 3280 m. No wire line fluid samples were taken The well was suspended on 24 December
1969 as the Ekofisk Discovery well, the first economic petroleum discovery on
the Norwegian Continental Shelf. Testing One successful drill stem tests (DST 4)
was conducted in open hole in the interval 3159 to 3195.5 m at the base of the
Ekofisk Formation. It flowed 5.9 MMCFD (16706 General Well 25/8-1 was drilled on the Utsira
High in the North Sea. The main purpose was to test an Eocene structural
closure, up dip from oil-bearing Eocene sands in Well 25/11-1. Operations and results Wildcat well 25/8-1 was spudded with the vessel
Glomar Grand Isle on 28 April 1970. Drilling operations were normal down to
2606 m, which became TD in the well, 289 m into the Early Permian Undefined
Group. While drilling at this depth the drilling pipe parted. After recovering
the upper portion of the drill pipe the top of the portion left in the hole was
found to be at 2559. Attempts to recover the fish failed and after logging and
taking sidewall cores in the uncased hole the well was prepared for testing. Initial
drilling from the sea floor to 378 m was with sea water and gell. Below 378 m
to 1311 m, the mud system consisted of sea water, spersene XP-20 salinex. From 1311
m to TD fresh water, spersene XP-20 mud was used. The well penetrated several Tertiary sands
above the Paleocene (Utsira and Skade Formations). These sands were water wet,
but some methane was recorded in the upper part of the Utsira Formation.Two Paleoocene sands (Hermod Formation at 1754.4
- 1758.1 m and 1759.0 - 1763.0 m) were found. The sands were separated by a
thin 1 m shale section. Upon testing, the sands were found to be capable of
producing approximately 429 Sm3 of 21.7 deg API gravity, low sulphur (0.77 to 0.80%)
oil per day. All other sands or reservoirs penetrated by the well, including
the Heimdal Formation at 1777 to 1812 m, were water wet without shows. Seven cores were cut in the well. Core no
1 was cut from 1676.4 to 1684.9 m in the Balder Formation, cores no 2 t General Well 2/4-4 (named 2/4-3X by operator
Phillips) was drilled to appraise the southern segment of the 2/4-2 Ekofisk
discovery. The Ekofisk discovery is located in the Central Trough in the
southern Norwegian North Sea and its structure is an anticline, uplifted by
halokinetic movements of Permian salt. The objective of well 2/4-4 was to test
the Tertiary and the top of the Late Cretaceous. Planned total depth was 11000
ft (3352 m). Operations and results Well 2/4-4 was spudded with the
semi-submersible installation Ocean Viking on 2 June 1970 and drilled to TD at
3424 m in the Late Cretaceous Tor Formation. The well was drilled with seawater
and hi-vis mud down to 622 m, and with seawater/drill-aid mud from 622 m to TD.
Two - six percent oil was added to the mud below 622 m. The Shetland Group was encountered with
top Ekofisk Formation at 3116 m and top Tor Formation at 3259 m. Oil was tested
in the Ekofisk Formation in various zones in the interval 3127 - 3225 m. The
Tor Formation produced only water. Two short cores were cut in the Ekofisk
Formation and one 8-m core was cut in the Tor Formation. No fluid samples were
taken on wire line. The well was permanently abandoned on 1
August 1970 as an oil appraisal. Testing Eight drill stem tests through
perforations in the 7" liner were carried out, one in the Tor Formation,
the rest in the Ekofisk Formation. The Tor test produced only water, the
lowermost test in Ekofisk did not produce liquid to the surface, but 100 ft
(30.5 m) gas cut mud was reversed out of the test string. The next lowermost
Ekofisk test, DST 3 from 3233 - 3236 m, also produced water and no
hydrocarbons. The remaining tests, all in the Ekofisk Formation gave oil.
Maximum flow was obtained from the interval 3162 - 3200 m in DST 8 with 601 Sm3
oil /day on two 3/4" chokes. The oil gravity was in the range 34.2 - 35.6
deg API and the GOR was in the range 165 General The 10/8-1 well is situated close to the
Lista Nose in the eastern part of the Norwegian-Danish Basin. It was drilled on
a salt induced anticlinal structure related to a salt pillow. The structure is
well defined from the Permian salt up to the upper cretaceous chalk. It has a
vertical closure of 300 m for a closed area of 80 km2 at a seismic horizon
assumed to be the Jurassic sandstone. A fault cuts the unconformably underlying
horizons attributed to Triassic. The specific objective of the 10/8-1 well was
to test the hydrocarbon potential of the Jurassic sandstone section, estimated
to be 60 m thick, with additional reservoir being furnished by the Triassic
sandstones immediately below. The well is Type Well for the Skagerrak
Formation and Reference Well for the Smith Bank Formation Operations and results Wildcat well 10/8-1 was spudded with the
semi-submersible installation Pentagone 81 and drilled to TD at 2861 m in the
Late Permian Zechstein salt deposits. The well was completed in 37 days without
reported problems. The well was drilled with seawater with returns on the sea
floor down to 510 m, and with a LFC/sea water mud system from 510 m to TD. One thousand three hundred meter of
continental deposits of Triassic age is present. On top of this is the Gassum
Formation. The Early to Middle Jurassic was not encountered in the well. One
hundred and fifty meter Late Jurassic sand and shale is directly overlying the
Gassum Formation. Around 200 m of shale was deposited during the Early
Cretaceous while the Late Cretaceous is represented by 425 m of lime mudstones.
The lower 200 m of the Tertiary was developed in mostly sandy facies. All
Formations penetrated by the well were found water wet. The only show recorded
was traces of gas (C1 and C2) from 1010 m to 1050 m. Organic geochemical
screening analyses show TOC in range 0.1 - 1.5 % with the highest values in the
Late Jurassic and Cretaceous sequences. The Tr General Well 9/4-2 was drilled on a salt-induced,
anticlinal structure in the Egersund Basin in the North Sea, 11 km to the north
of the 9/4-1 location. The primary objective was the Middle Jurassic sandstone,
but also Triassic sands were considered prospective. Danian and Late Cretaceous
chalks were seen as secondary objectives. The well is Type Well for the Base
Cretaceous Flekkefjord Formation in the Norwegian-Danish Basin. Operations and results Wildcat well 9/4-2 was spudded with the
jack-up installation Gulf Tide on 19 July 1970 and drilled to TD at 3025 m in
the Middle Triassic Skagerrak Formation. Three casing strings were set in the
hole. The 20" casing was originally planned around 600 m but stopped short
at 282 m where it had to be set. Except for this, the hole was drilled without
significant technical problems. The hole was drilled with seawater as drilling
fluid down to 99 m from where a seawater gel with spersene was used. Diesel oil
was used as emulsifier. Danian and Late Cretaceous chalks were
penetrated from 1323 m to 1936 m and were found water wet. The target Middle
Jurassic sands (Sandnes Formation) was encountered at 2490 m. The sand was
white, medium to coarse grained, poorly consolidated, calcareous, with thin
interbeds of red to grey, micaceous shale. This sandstone appears to be an
excellent reservoir, of the total thickness of 50 m about 48 m appeared to be a
porous sandstone on the logs with porosity of about 24 percent. The Triassic
(Skagerrak Formation) was encountered at 2633 m. It consisted of red, soft,
occasionally calcareous and micaceous claystone with interbedded red to white,
fine to coarse grained, in part calcareous sandstone. No hydrocarbon shows were
encountered in the well. No conventional cores were cut and no fluid samples
taken. The well was permanently abandoned on 29
August as a dry hole. Testing No drill stem test was performed. General Well 2/4-5 (named 2/4-4X by operator
Phillips) was drilled to appraise the northern segment of the 2/4-2 Ekofisk
discovery. The Ekofisk discovery is located in the Central Trough in the
southern Norwegian North Sea and its structure is an anticline, uplifted by
halokinetic movements of Permian salt. The objective of well 2/4-4 was to test
the Tertiary and the top of the Late Cretaceous. Planned total depth was 11000
ft (3352 m). The well is Type Well for the Ekofisk
Formation. Operations and results Well 2/4-5 was spudded with the
semi-submersible installation Neptune 7 on 21 June 1970 and drilled to TD at
3320 m in the Late Cretaceous Tor Formation. The well was drilled with seawater
and hi-vis mud down to 585 m, with seawater/lignosulphonate mud from 585 to
3217 m, and with seawater/drill-aid mud from 3217 m to TD. Below 584 m 2 - 5 %
diesel was added to the mud. The Danian Chalk (Ekofisk Formation) was
encountered at 3037 m and the Maastrichtian chalk (Tor Formation) was encountered
at 3164 m. Both formations were hydrocarbon bearing. A total of 86.2 m core was
recovered in 12 cores in the interval 3094 to 3206 m in the Ekofisk and Tor
Formations. No fluid samples were taken on wire line. The well was permanently abandoned on 27
August 1970 as an oil appraisal. Testing Five zones in the Ekofisk and Tor
Formations were perforated for testing. DST 1 and DST 1A tested the intervals
3164 -3203 m and 3177 - 3186 m in the Tor Formation, respectively. DST 1
produced at maximum 165795 Sm3 gas and 701 Sm3 oil /day on a 24/64" choke.
The GOR was 236 Sm3/Sm3; the oil gravity was 37.3 deg API. The reservoir
temperature in the DST1 zone was reported to be 129.4 deg C. DST 1A was
conducted with smaller choke sizes and gave somewhat lower rates than in DST 1,
but fluid properties were similar. DST 2 tested the interval 3106 -3143 m in
the Ekofisk Formation, but was General Wildcat well 2/5-1 is located ca 10 km
northeast of the Ekofisk Field. It was drilled on an essentially northwest -
southeast striking anticlinal seismic structure extending into the adjacent
block 2/4. The well is Reference Well for the
Ekofisk Formation. Operations and results Well 2/5-1 was spudded with the jack-up
installation Orion on 1 August 1970 and drilled to TD at 3972 m in Late
Jurassic shales. At 2997 m cones of the bit was lost in the hole and five days
were spent fishing for them. The well was planned vertical, and was essentially
vertical with maximum deviation 1.5 deg down to 3238 m. From there deviation
increased to 7.1 deg at 3639 m, 12.5 deg at 3821 m, 19.2 deg at 3932 m, and
21.9 deg at 3967 m. The well was drilled with seawater and bentonite down to
381 m and with a Drill aid/XP-20 mud with 3- 6 % diesel from 381 m to TD. The Danian limestone (Ekofisk Formation)
was encountered at 3041. Then a Late Cretaceous succession was penetrated with
chalks of the Tor and Hod Formations at 3132 m and 3475 m, respectively,
followed by the Blodøks Formation shales at 3551 m and the Hidra Formation
chalk at 3594 m. Commercial quantities of hydrocarbons were encountered and
tested in the Ekofisk and Tor Formations. The well also penetrated 133 m of
Late Jurassic source rock quality shales. Organic geochemical analyses of these
shales showed TOC in the range 2 - 4 % and thermal maturity corresponding to
late oil window (%Ro around 0.8), in well position. Twenty-three conventional cores were cut
in the chalk. Ten were cut in the Ekofisk Formation (75.2 m recovered), and
thirteen in the Tor Formation (171.6 m recovered). No wire line fluid samples
were taken. The well was permanently abandoned on 22
November 1970 as an oil discovery. Testing One open-hole DST and eight DSTs through
liner perforation were performed. The op Well 2/7-1 was drilled on the Eldfisk
structure on the Lindesnes Ridge in the North Sea. The primary objective was to
test the Late Cretaceous to Paleocene chalk sequence that had proved oil in the
Ekofisk structure north of Eldfisk. A secondary objective was to test older
Mesozoic sediments Operations and results Wildcat well 2/7-1 was spudded with the semi-submersible
installation Ocean Viking on 3 August 1970 and drilled to TD at 4573 m in the Vestland
Group. The well was drilled with seawater and hi-vis sweeps down to 588 m, with
seawater/Drill Aid mud from 588 m to 3102 m, and with seawater/lignosulphonate
mud from3102 m to TD. Top of the Danian chalk sequence, Ekofisk
Formation, is at 2934 m, while top of the Cretaceous chalk, Tor Formation, is
at 3014 m. In this first well on the structure, only small amounts of live hydrocarbons
were found in the Ekofisk carbonates. Three cores were cut from 2956.6 to
2987.3 m in the Ekofisk Formation. A fourth core was cut from 3032.8 to 3041.9
m. No fluid sample was taken. The well was permanently abandoned on 11
December 1970 as an oil discovery Testing A drill stem test was performed in the
interval 2942 to 2954 m plus 2957 to 2975 m in the Danian chalk (Ekofisk
Formation). The flow rate after acidizing was too small to measure. The
recovered fluid was composed of 65% oil and 35% water. The oil density was 32.2
°API. General Well 25/10-2 was
drilled to test a structural closure on the down faulted west flank of the
basement high on which Esso wells 25/11-1 (Balder Discovery well), 25/8-1 and
25/10-1 had been drilled. The original
primary objective, as stated in the Operator's Final Well Report from 1972, was
Early Paleocene to Late Eocene sands, which had a thin oil leg in the three
wells drilled previously. It was
anticipated that appreciably thicker Early Eocene sands would be encountered in
the oil leg of 25/10-2. Additional prospects were in Middle - Late Eocene
sands, Danian carbonates, and sands of Early Cretaceous, Jurassic or Triassic
age. The results of the
well given below is reported with today's knowledge of the area (anno 2003) and
cannot be compared directly with the original objectives. Operations and results Wildcat well 25/10-2
was spudded with the drilling vessel "Glomar Grand Isle" on 5 August
1970 and drilled to TD at 2191 m (7187 feet) in the Paleocene Lista Formation.
Drilling operations went without mechanical problems and there was no lost time
waiting on weather. Well 25/10-2 was suspended 25 August 1970 as a well with
oil shows. The well was re-entered (25/10-2 R) using "Glomar Grand
Isle" on 2 May 1972 and drilled to a total depth of 3180.6 m (10435 feet)
in basement rock. After drilling out
the plug in the bottom of the casing in the re-entry some difficulty was
experienced in staying in the old hole.
The well was drilled to a depth of 2369 m where lost circulation was
encountered. Later the pipe became stuck, with the bottom of the fish at 2213
m, and it became necessary to sidetrack the hole. Six cones were lost in the hole while drilling at 2497 m in the
sidetrack hole; otherwise no problems were experienced. Initial drilling from
the sea floor to 396 m was with seawater and gel. From 396 m to 1036 m the hole
was drilled with seawater / Spersene / XP 20 / Salinex sys General Well 2/4-6 (named 2/4-5X by operator
Phillips) was drilled on a structure ca six km west off the Ekofisk discovery.
The objective of the well was to test the Danian and Late Cretaceous limestone,
which had proved oil productive in the other wells drilled within the block
2/4. Operations and results Wildcat well 2/4-6 was spudded with the
semi-submersible installation Neptune 7 on 28 August 1970 and drilled to TD at
3411 m in the Late Cretaceous Tor Formation. The well was drilled with sweater
and hi-vis mud down to 585 m, with seawater/drill aid mud from 585 m to 3107 m,
and with seawater lignosulphonate mud from 3107 m to TD. The well penetrated a thick, nearly
complete Tertiary succession consisting mostly of shales and claystones. A ca
50 m thick sandy sequence with gas shows was encountered at 2956 m in the
uppermost Paleocene. Danian Limestone (Ekofisk Formation) was penetrated at
3110 m and Late Cretaceous limestone (Tor Formation) was encountered at 3270 m.
A rich condensate and gas was tested from these formations Five conventional cores were cut between
3120.5 and 3223.4 m in the Ekofisk Formation. No wire line fluid samples were
taken. The well was permanently abandoned on 10
December 1970 as a gas and condensate discovery Testing Five drill stem tests through
perforations of the 7" liner were carried out. The following results are
maximum flow after acidization: DST 1 tested the zone 3370 - 3374 m in
the Tor Formation. It produced only water at a rate of 13 m3 /day. Bottom hole
temperature (BHT) in the test was reported to be 136.7 deg C. DST 2 tested the intervals 3271 - 3286 m
and 3295 - 3310 m in the Tor Formation. This test flowed 568 Sm3 oil /day on a
1" choke. Oil gravity was 42.8 deg API and the GOR was 452 Sm3/Sm3. The
BHT was reported to be 133.9 deg C. DST 3 tested the interval 3243 - 3246 m
in the lower Ekofisk Forma General Well 25/10-3 is located in the western part
of the Balder Field complex on the Utsira High in the North Sea. Lower Eocene
oil sands had been encountered in Esso wells 25/10-1, 25/11-1 and 25/8-1. The
objective of 25/10-3 was to test the Eocene sand in a lower structural position
to accurately establish the oil/water contact in the area; to determine their
lateral continuity and if they would thicken towards the northwest. Operations and results Well 25/10-3 was spudded with the vessel
Glomar Grand Isle on 27 August 1970 and drilled to TD at 1921 m in the Early
Paleocene Ekofisk Formation. Except for stuck pipe at 1247 m, which was worked
free with Diesel oil and pipe lax in 4 hours, drilling operations were routine
and trouble-free. The well was drilled with seawater/gel down to 402 m, with
seawater Spersene/XP-20/Salinex mud from 402 m to 951 m, and with fresh
water/Spersene/XP-20 mud from 951 m to TD. The Oligocene to Recent sediments
consisted of clays and sands with no indications of hydrocarbons. The 518 m thick
Eocene section was chiefly grey to grey green clay shales with 6.7 m of wet sand
in the interval 1401 m to 1413 m (Grid Formation), a 4 m oil-bearing sand from 1750
to 1754 m (Intra Balder Formation sandstone), and a 1 m wet sand at 1799 m. The
4 m oil sand had 32-36% porosity and tested 26 deg API gravity oil on a wire
line formation test. Oil shows were observed in cuttings from 1716 m and down
to the top of the oil bearing sand, and shows continued down to 1768 m, all through
the cored section. In addition to the Intra Balder Formation sandstone the
Paleocene section penetrated was composed primarily of 3 sands interbedded with
grey green shale. From top to bottom the Paleocene sands were respectively 29 m
th General Well 9/10-1 is located in the Åsta Graben
of the Danish Norwegian Basin in the North Sea. The location was selected to
explore the northeast regional limit of Oligocene sands at a non-structural
site and to reach the Danian very low on the South flank of the seismic
"L" structure. The main objectives were the first and second
Oligocene sands, which were gas bearing in the 2/3-1 well. The location, in
addition, tested for presence of the Danian section, which had proved to be oil
bearing in the Phillips Ekofisk area approximately 40 miles to the Southwest.
There was also a possibility of the development of gas bearing zones within the
Miocene section. Operations and results Wildcat well 9/10-1 was spudded with the
jack-up installation Gulftide on 30 August 1970 and drilled to TD at 2205 m in
the Late Cretaceous Tor Formation. A 38" hole was drilled to 143 m with
seawater. After spotting a gel slurry, 36" drive pipe was set at 123 m.
Drilling was continued with a 26" bit to 221 m using seawater where lost
circulation became excessive. Attempts with a 50-barrel LCM slurry and a
300-sack cement plug were unsuccessful in sealing off the thief zone. The
drilling was continued "blind" to 251 m where a 450-sack gel slurry
was spotted and 20" casing run to 248 m and cemented. After installing
20" BOP, 17 1/2" hole was drilled to 953 m using a 10.7 lb gel mud.
Three attempts were made to log this surface section but hole bridging
conditions occurring at 279 m and 457 m would not permit deeper penetration.
Went into the hole with the bit, tagged bottom, and then drilled 5 m with no
obstruction. The hole was conditioned and logged from 457 m to 88 m. Rigged up
BHA and went to bottom with the bit, cleaned out to 957 m, and drilled an
additional 6 m. The 13 3/8'' casing was then run and set with no problems to a
depth of 960 m. Drilling continued with a 12 1/4" bit from under the 13
3/8'' ca General Well 25/11-2 was drilled to appraise the
25/11-1 Balder discovery on the Utsira High in the North Sea. The objective was
to define the continuity and reservoir thickness of the Early Eocene oil
bearing sands in a northward direction from well 25/11-1 and a southward
direction from well 25/8-1. Operations and results Appraisal well 25/11-2 was spudded with
the vessel Glomar Grand Isle on 13 September 1970 and drilled to TD at 1823 m
in the Paleocene Sele Formation. No significant problems occurred during the
operations. The well was drilled with seawater/gel down to 175 m, with seawater/Spersene/
XP-20/Salinex from 175 m to 945 m, and with fresh water/ Spersene/XP-20 from
945 to TD. The well penetrated the Utsira Formation
and several Skade Formation sand units and then entered a ca 600 m thick section
of shales belonging to the lower Hordaland Group before top Balder formation was
encountered at 1699 m. The Balder Formation contained several thin Intra Balder
Formation sandstones, of which a seven meter thick sandstone at 1727 m was the
thickest. The sands were oil bearing down to 1747 m. Hermod sandstones were
penetrated from 1780 to 1817 m. They had better reservoir properties than the
Intra Balder Formation sands, but were water bearing without shows. No conventional cores were cut in the
well. Out of four attempts with the Formation Interval Tester (FIT) three tests
were seal failures while test no 4, at 1728.5 m, was successful and recovered
0.33 Sm3 gas, 6.9 l oil, and 3.25 l oil and gas cut mud. The well was permanently abandoned on 24
September as an oil appraisal.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General Well 25/11-3 was drilled ca 1.5 km south
of the 25/11-1 Balder discovery well on the Utsira High in the North Sea. The
objective was to test the reservoir continuity, sand correlation and possible
thickening of the 25/11-1 Early Eocene oil sands in a South-easterly direction. Operations and results Appraisal well 25/11-3 was spudded with
the vessel Glomar Grand Isle on 25 September 1970 and drilled to TD at 1858 m
in the Early Paleocene Ekofisk Formation. North Sea fall storms were the cause
of drilling problems experienced on this well. Cumulative lost time due to
waiting-on-weather alone amounted to 23.3% of the total rig days. While at the
depth of 1228 m, one of the severe storms necessitated pulling the bit into the
9-5/8 inch casing and hanging off the drill pipe. After the storm abated and
the hang off tool recovered, it was found that the 5 inch drill pipe extension
below the tool had parted, allowing the drill string to fall to bottom.
Fortunately the fish was recovered in one run with an overshot. The hole was
then drilled to TD with no further problems. Initial drilling from the seafloor
to 396 m was with sea water and gel. Below 396 to a depth of 960 m, the mud
system consisted of seawater, Spersene XP-20 Salinex. From 960 m to TD fresh
water Spersene XP-20 mud was used. The well penetrated the Utsira Formation
and several Skade Formation sand units and then entered a ca 600 m thick
section of shales belonging to the lower Hordaland Group before top Balder
formation was encountered at 1711 m. Only thin Paleocene sands were
encountered, and all were water wet without shows. No conventional cores were cut in the
well. Four FIT fluid samplings were attempted in the General Well 25/11-4 was drilled ca 2.6 km south-south
west of the 25/11-1 Balder discovery well on the Utsira High in the North Sea.
The objective was to define the continuity of oil bearing sands of Early Eocene
age that were present in 25/11-1 well. Operations and results Appraisal well 25/11-4 was spudded with
the vessel Glomar Grand Isle on 15 October 1970 and drilled to TD at 1896 m in
the Early Paleocene Ekofisk Formation. Drilling operations were normal down to 963
m and at that depth problems with the Hydril necessitated pulling the riser and
upper part of the B.O.P. stack. While drilling at 1753 m weather conditions
hampered drilling and it was necessary to again pull the riser and upper part
of the stack. After losing several days due to weather conditions the well was
completed, however, during the midst of the logging operations, storm warnings
made it necessary to shorten the program and the planned velocity survey was
not made. Initial drilling from the seafloor to 179 m was with sea water and
gel. Below 179 to a depth of 948 m, the mud system consisted of seawater,
Spersene XP-20 Salinex. From 948 m to TD fresh water Spersene XP-20 mud was
used. The well penetrated the Utsira Formation
and several Skade Formation sand units and then entered a ca 500 m thick
section of shales belonging to the lower Hordaland Group before top Balder
formation was encountered at 1695 m. The Balder Formation (Early Eocene) proved
almost void of reservoirs. It was all silty shale except a 4 foot sand section
between 1740 and 1742 m. This sand had a good oil stain, bright yellow
fluorescence and a bright yellow cut. The only massive reservoir present was
the Paleocene Hermod Formation sand from 1792 to 1816 m. This sand had no
hydrocarbon General Well 2/7-2 was drilled on the Grensen
Nose structural element in the Central Graben of the North Sea. The primary
targets for the well were Paleocene Sands and Danian Limestones; the secondary
targets were Late Cretaceous carbonates, Early Cretaceous sandstones, Jurassic
sandstones, and possibly Permo-Triassic sandstone reservoirs. Operations and results Well 2/7-2 was spudded with the
semi-submersible installation Ocean Viking on 13 December 1970 and drilled to
TD at 3964 m in the Early Permian Rotliegend Group. No significant technical
problem was encountered in the operations The well was drilled with sea water and
viscous slugs down to 594 m and with sea water, lignosulphonate, and 2 - 7 %
oil from 594 m to TD. The well encountered the Late Paleocene
Balder Formation at 2856 m, top Ekofisk Formation at 2966 m, and top Tor
Formation at 3005 m. The Jurassic was encountered at 3862 m and consisted of 13
m Mandal Formation. Total organic carbon content in the Mandal Formation was 7-9
%, estimated to be of middle oil window maturity (vitrinite reflectance ca
0.75). The Mandal Formation rested directly on sandstones of the Rotliegend
Group. Good oil shows decreasing to no shows were observed on cores 1 and 2 (3013.9
to 3027.9 m) in the Tor Formation. Otherwise no significant shows or other
hydrocarbon indications were reported from the well. Three cores wore cut with 100% recovery. Cores
1 and 2 were cut from 3013.9 to 3027.9 m, while core 3 was cut in basaltic rock
at TD from 3955.1 to 3963.6 m. No wire line pressures or fluid samples were
taken. General Well 2/5-2 was drilled as an appraisal
well on the 2/5-1 Tor Discovery in the southern Norwegian North Sea. The
objective was to evaluate the eastern part of the structure. Operations and results Appraisal well 2/5-2 was spudded with the
jack-up installation M ærsk Explorer on 15 January 1971 and drilled to TD at
3597 m in the Late Cretaceous Tor Formation. The well was drilled water based,
but with diesel addition below 1830 m. The well encountered top Paleocene
(Balder Formation at 2978 m, top Danian chalk (Ekofisk Formation) at 3118 m,
and top Late Cretaceous chalk (Tor Formation) at 3360 m. Commercial quantities
of hydrocarbons were encountered in the Ekofisk Formation where a total of
approximately 57 m net pay out of a gross section of 244 m was found. This was
a significant reduction from the 89 m net pay in the 2/5-1 discovery well.
Furthermore, the water saturation in Ekofisk was higher in 2/5-2 compared to
2/5-1 (41% and 22%, respectively). Five conventional cores were cut in the
intervals 3120 - 3188 m and 3235 - 3311 m in the Ekofisk Formation. No wire
line fluid samples were taken. The well was permanently abandoned on 20
April 1971 as a an oil appraisal. Testing Six drill stem tests were carried out:
DST 1 in Late Cretaceous chalk (Tor Formation), DST 2 in the Late Cretaceous/
Danian boundary, and DST 3 - 6 in Danian chalk (Ekofisk Formation). The
following results are after acidization: DST 1 in the interval 3511 to 3513 m
flowed minor quantities of slightly oil-cut mud. DST 2 at 3350 - 3361 m flowed 165 Sm3, 34
m3 water, and 39077 Sm3 gas /day on 64/64" + 32/64" choke. The oil
gravity was 39 deg API and the GOR was 237 Sm3/Sm3. DST 3 at 3299 - 3314 m flowed 629 Sm3 oil
and 159900 Sm3 gas /day on a 23/64" choke. The oil gravity was 40.5 deg
API and the GOR was 254 Sm3/Sm3. Maximum bottom hole temperature recorded in
General Well 16/5-1 is located on the Utsira High
in the North Sea. The main target of the 16/5-1 well ("Vali") was a
pinch-out of Paleocene sands on a seismic monoclinal. The interest in this trap
was emphasized by oil-shows in Paleocene sands in surrounding wells. Operations and results Wildcat well 16/5-1 was spudded with the
semi-submersible installation Pentagone 81 on 17 January 1971 and drilled to TD
at 1943 m in granitic basement rocks. The well was drilled using seawater-based
mud. The Paleocene sands, which were the main
objective of the Vali well, were not present. A thin Cretaceous series was
found directly overlaying Caledonian basement rocks. From 1923 m to TD the well
penetrated migmatitic granite, highly fractured and slightly weathered down to
1940 m. No shows were recorded, only background gas of C1 from1% to 3 % while
drilling the tertiary series. The only reservoirs encountered in Vali well were
164 m net sand in the sand-shale sequence in the Utsira Formation from 754 m to
1012 m. These sands, very fine to medium and shelly, have very high porosity,
more than 32 %. However, they are not sufficiently buried to form a trap and
they were water wet. Two cores were cut: the first from 1573 to 1584 m in the
Sele and Lista Formations, 15 m below the cinerites, and the second from 1929
to 1943 m in the basement rocks. No fluid samples were attempted. The well was
permanently abandoned as a dry well on 8 February 1971. Testing No drill stem test was performed General Well 25/1-1 was drilled in the middle of block
25/1 in the Viking Graben, close to the UK border. Seismic surveys had defined
structural closure at several levels in Mesozoic and into lower Tertiary
horizons. At Paleocene level an "amoeboid" feature extending as much
as 350 km2 with a vertical closure of 180 m was mapped. The primary objective
of the well was to test the hydrocarbon potential of the Early Tertiary,
interpreted to be a deltaic sand build-up. Secondary objective was Jurassic
sandstones. The well is Type Well for the Frigg, Svarte,
Blodøks, Tryggvason, Kyrre, and Jorsalfare Formations. Operations and results Wildcat well 25/1-1 was spudded with the
semi-submersible installation Pentagone 81 on 30 March 1971 and drilled to TD
at 4570 m in Middle Jurassic Hugin Formation. The well was drilled with a
seawater/LFC mud system down to TD. Apart from sandy sections in the Nordland
Group, the lithology down to top Frigg Formation at 1836 m was mainly
claystones. The Frigg Formation sandstones had porosities in the range 30 to
40% with permeabilities of several Darcy. It was hydrocarbon bearing with a
gas/oil contact at 1972 m, and an oil/water contact at 1992 m. Further shows
were seen in a thin sand at 2470 m in the Lista Formation. An FIT sample recovered
a small amount of oil from this sand. Oil shows were also recorded on limestone
on core K5 in the Jorsalfare Formation. The Jurassic sequence penetrated by the
well was mainly shales of the Viking Group and only 10 m of Hugin Formation
sand at TD. No shows were reported from the Hugin Formation. Six conventional cores were cut. Cores K1
to K3 were cut from 1868 to 1910 m in the Frigg Formation. K4 was cut from 2687
to 2696 m in the lower Lista Formation, while K5 and K6 were cut from 2826 to
2843 m and from 2993 m to 2997.5 m in the Jorsalfare Formation. Wire line fluid
sampling was attempted at nine different depths. Hydrocarbon flu General Well 7/9-1 is located on the Reke Fault
Zone between the Jæren High and the Sørvestlandet High. The objective of the
well was to test for hydrocarbons in Tertiary, Cretaceous, Jurassic, and
Triassic reservoirs over a Zechstein salt well which showed 1300 feet of
vertical closure over an area of about 65 square km at the base Tertiary level. The well is Reference Well for the Gassum
and Fjerritslev formations. Operations and results Wildcat well 7/9-1 was spudded with the
jack-up installation Mærsk Explorer on 22 April 1970 and drilled to TD at 2931
m in Zechstein salt. The well was spudded using a high viscosity gel-seawater
mud. After drilling out of the 20" casing, which stuck at 242 m, the mud
was converted to a lignosulphonate-seawater. The 213 m of 26" rat hole
left below the 20" casing gave considerable trouble by acting as a build
up area for large balls of gumbo, which collected there as 17 1/2" hole
was being made. An attempt to run electric logs at the 13 3/8" casing
point failed because of the fill at 442 m. Drilling detergent was used to
reduce torque and drag and was successful in the upper part of the hole. The
diesel oil content of the mud was maintained between 4% and 7%. A deviation
problem arose in the 8 1/2" hole, starting around 2255 m where the angle
was 4.5°. It increased steadily and at 2723 m the last survey point was 5.5°.
Light bit weight, high rotary speeds, and a bottom hole assembly usually
successful in dropping angle had no effect. The Tertiary Paleocene Sands were not
developed over the structure. The other objectives, the Tertiary Danian
calceranites, the late Cretaceous Maastrichtian chalk, and the Middle Jurassic
to Triassic sandstones, were confirmed, but were water bearing. During the
drilling of the Tertiary section to a depth of 1676 m shale gas from the
sometimes richly organic shales maintained a high background between 0.5% and
1% methane in General Well 7/1-1 was drilled on the J{ren High
in the southern part of the North Sea, ca 8 km east of the UK border line. Operations and results Wildcat well 7/1-1 was spudded with the
semi-submersible installation Sedco 135 F on 3 July 1971 and drilled to TD at
2808 m in the Triassic Skagerrak Formation. There were indications of shallow
gas at 472 m, otherwise no significant problems were reported from the drilling
operations. The well penetrated Quaternary and
Tertiary sediments with no significant sand development down to a depth of 2224
m where Cretaceous Chalk of the Tor Formation was encountered. The Cretaceous
section continued down to 2661 m where the sandy Triassic Skagerrak Formation
was encountered. The well was dry and no shows were reported from the well other
than those originating from diesel added to the mud. Two cores were cut, one from 2243.3 to
2261.6 m in the Tor Formation and the other from 2451.2 to 2468.9 m in the Hod
Formation. No wire line fluid samples were taken. The well was permanently abandoned on 5
August 1971 as a dry well. Testing No drill stem test was performed. General Well 8/12-1 is located in the Åsta
Graben. It was drilled on a salt dome with about 122 m of vertical closure over
an area of about 23 km2. The well was programmed to test all porous formations
from the Miocene to the Triassic. The main objectives were the Palaeocene
Danian, Middle Jurassic, and Triassic sections. Secondary possibilities were
seen in the Oligocene - Miocene, Late Cretaceous, and Early Cretaceous. The well is Reference Well for the Bryne
Formation. Operations and results Wildcat well 8/12-1 was spudded with the
jack-up installation Maersk Explorer on 31 May 1971 and drilled to TD at 2875m
in the Skagerrak Formation. Some difficulties were encountered with
over-pressured shales from 853 m to 1113 m before setting 13-3/8" casing,
cementing the 13-3/8" casing, and with lost returns immediately below the
9-5/8" casing set at 1903 m. The well was drilled with a
Seawater/gel/IMCO-RD-333 mud system with 3 % to 5 % oil. Methane gas in quantities up to 12% was
recorded on the mud-gas detector during drilling of the Miocene and Oligocene
clays. No significant reservoir sections were encountered in this section, and
the gas was most probably released directly from the richly organic clays. Two
very weak oil shows were obtained in the Middle Jurassic sandstones. In porous
sandstones from core No.3, where one of these shows was observed, up to 9.4%
residual oil was measured. However, evaluation of the logs showed that all
porous intervals penetrated were water bearing. The formation water in the
Middle Jurassic sandstones was calculated to have a salinity of 140,000 ppm
NaCl. Three conventional cores were cut in the
intervals 6181 feet - 6237 feet (1884.0 m - 1901.0 m), 8811 feet - 8817 feet
(2685.6 m - 2687.4 m), and 8919 feet - 8969 feet (2718.5 m to 2733.8 m). One
fluid sample was taken on wire line at 2666 m. The tool was opened for 10 min
and recovered 100 cc of salt water (55, General Well 9/11-1 is situated in the Åsta
Graben in the Danish-Norwegian Basin in the North Sea. The purpose of the well
was to test the hydrocarbon and reservoir potential of Triassic to basal
Tertiary sediments over a north-south elongated salt dome. The Jurassic -
Triassic sandstones were the primary objective, with the Late Cretaceous -
Danian carbonates and Palaeocene sandstones as secondary objectives. The well is Type Well for the Late
Paleocene Fiskebank Formation Operations and results Wildcat well 9/11-1 was spudded with the
semi-submersible installation Transworld 61 on 3 July 1971 and drilled to TD at
2196 m in the Late Triassic Skagerrak Formation. The 26" section was first
drilled with a 17 1/2" bit to 412 m using gel/seawater mud. The hole was
then under-reamed to 26" to 411 m. The 26" bit was run in hole but
could not get past 119 m. When reaming was attempted, circulation was lost at
127 m. The hole was then re-drilled to 412 m with a 17 1/2" bit and opened
to 26" with no problems. The 20" casing was run and cemented at 378
m. Eleven days were used on this interval and 700 bbl mud lost to seabed. The
remaining well was drilled without significant problems. The well was drilled
with seawater and hi-vis pills to 127 m, with seawater and gel from 127 m to
412 m, and with seawater / lignosulphonate (Spersene) and 1 -6 % diesel from
412 m to TD. The well drilled a thick
Tertiary-Quaternary section (approx. 1600 m), composed mainly of
Oligocene-Miocene brown-grey clays and Pliocene-Pleistocene grey sandy clays.
The Eocene (Lower part) is represented by green clays overlying varicoloured
Paleocene clays without sands. There was a thin chalk, all of Late Cretaceous
age (Tor Formation). No Danian was present. The Early Cretaceous was
represented by a condensed sequence ranging from Valanginian to Aptian/Albian.
From 1766 m to 1993 m there was a series of transitional Early Cret Well 25/1-2 was drilled to appraise the
25/1-1 Frigg Discovery in the North Sea. The primary objective was to test the Eocene
Frigg Formation sandstone. Operations and results Wildcat well 25/1-2 was spudded with the semi-submersible
installation Pentagone 81 on 22 July 1971 and drilled to 1159 m where the tool
stuck. The well was then sidetracked from 719 m and drilled to TD at 2772 m in
the Late Cretaceous Shetland Group. The well was drilled with a water-LFC mud
system. The Frigg Formation sandstone was
encountered at 1948 m. The Frigg sandstones were gas filled down to the gas/oil
contact at 1974 and oil filled to the oil/water contact at 1983 m. Thin
sandstones and sandstone stringers in the interval 2441 to 2513 m had good oil
shows. No cores were cut. FIT fluid samples were
taken at 1984 m (oil and gas), 1986.3 m (oil, filtrate and gas), 1993.5 m (oil,
filtrate and gas), 2503 m (filtrate and trace oil), and 2508.5 m (filtrate and
trace oil), The well was permanently abandoned on 25 August
as an oil and gas appraisal well. Testing No drill stem test was performed. General Well 2/4-7 was drilled on a structure ca
six km west off the Ekofisk discovery. The objective of the well was to test
the Danian limestone with estimated 200 m gross / 120 m net pay, and the Late
Cretaceous limestone with estimated 60 m gross / 15 m net pay. These Formations
had proved oil productive in the other wells on the Tor structure. Secondary
objective was possible Paleocene sand in the interval 3020 - 3140 m. Planned
depth was 3414 m (11200 ft). Operations and results Appraisal well 2/4-7 was spudded with the
jack-up installation M ærsk Explorer on and drilled to TD at 3493 m in the Late
Cretaceous Tor Formation. The drill pipe stuck at 3405 m, but was freed after
seven hours working. The well was drilled with seawater and gel down to 555 m
and with seawater/drill aid and 2 - 5% diesel from 555 m to TD. Top Paleocene (Balder Formation) was
encountered at 3048 m. The Paleocene contained only minor, thin sand beds. The
chalk group came in with the Ekofisk Formation at 3175 m and the Tor Formation
at 3304 m. Fair shows were recorded on cores in the top 2 m of the Ekofisk
Formation, otherwise Ekofisk only had scattered shows. Fair to good shows were
again recorded in the Tor Formation, from the top and down to 3332 m. Below this
depth shows were reported as spotty, on fracture plains. Oil was confirmed by
testing in the top 24 m of the Tor Formation. The test in top Ekofisk gave only
water with a trace of gas. Thirteen cores were cut in the well, recovering a
total of 164 m core. Core 1 to 9 were cut throughout the Ekofisk Formation, the
rest were cut in the upper part of the Tor Formation. Core depths were reported
to be 4 - 5 m shallower than log depth for all cores except core 5, which need
to be shifted only + 1 m. No wire line fluid samples were taken. The well was permanently abandoned on 18
October as an oil appraisal. Testing Seven drill stem tests were carried out
through per General Well 15/6-1 is located ca 5 km north of
the Sleipner Field. The primary objective of the well was Eocene sands. Operations and results Well 15/6-1 was spudded with the drill
vessel Glomar Grand Isle on 7 August 1971and drilled to TD at 1679 m in Eocene
sediments of the Hordaland Group. Initial drilling from the sea floor to 384 m was
with sea water and gel. Below 384 m to a depth of 1247 m the mud system
consisted of sea water and Spersene XP-20 Salinex with drilling detergent. From
1247 m to TD a fresh water Spersene XP-20 system was used. Due to problems with
the casing seal assembly the well was abandoned without reaching its target.
The vessel vas moved approximately 335 m east and a replacement hole (15/6-2) was
drilled. The only reservoir penetrated was a thick
Miocene sand section (the Utsira Formation) between 768 and 996 m. No hydrocarbon
shows were encountered. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 8 September 1971 as a junk well. Testing No drill stem test was performed. General Well 2/3-3 is located east of the
Steinbit Terrace on the Sørvestlandet High. The main targets for the well were
Danian limestones, Jurassic sands, and Oligocene sands. Operations and results Wildcat well 2/3-3 was spudded with the
Jack-up installation Ocean Tide on 8 October 1971 and drilled to TD at in Late
Permian Zechstein salt. Operations went without major problems except for some
delays due to bad weather (on 17 November with winds in excess of 40 m/s and
seas up to 17 m). The well was drilled with Bentonite and salt gel down to 269
m and with Spersene mud with 2% - 6.5% diesel from 269 m to TD. The well drilled a thick
Tertiary/Quaternary section, mainly represented by grey sandy clays of Pliocene
and Pleistocene age and by brown clays and mudstones of Oligocene to Miocene
age. The Paleocene and Early Eocene consisted of varicoloured clays. No
potential reservoirs (sands, sandstones and limestones) were found in the
Tertiary. A moderate thickness (235 m) of Chalk was
penetrated. The top 41 m was of Danian age (Ekofisk Formation, the remainder
was of Santonian-Maastrichtian age (Tor and Hod Formations). One hundred and
forty seven meters of Early Cretaceous rested on Kimmeridgian shales. From the
base of the Kimmeridgian downwards, the section was poorly fossiliferous and
only tentatively dated. The only shows observed were elevated methane readings
in sand stringers in the interval 400 m to 900 m and in shales below this
depth. No liquid hydrocarbons were observed in any part of the well. No cores
were cut and no fluid samples taken. The well was abandoned as dry on 20
November 1971. Testing No drill stem test was performed Well 15/12-3 is located in the South
Viking Graben in the North Sea, south of the Sleipner Øst Field. The primary objective
of the well was to test possible hydrocarbons in late Jurassic sand. This sand
was proven in 15/12-2. Secondary objectives were Danian and Rotliegendes sands.
Minor Danian sand beds were proved in 15/12-1, and further west on the UK side oil was produced from Palaeocene sands on the Maureen Field. The well should be
drilled through ca 1100 m of prognosed salt and 100 m into the Rotliegendes or
to a total depth of 4900 m. Operations and results Well 15/12-3 was spudded with the
semi-submersible installation Nordraug on 21 June 1980 and drilled to TD at
4450 m in Early Permian Rotliegendes sandstone. After setting the 13 3/8"
casing the rig crew went on strike from 20 July to 14 August. While drilling 12
1/4" hole with salt saturated mud the bottom hole assembly got stuck at
2715 m when pulling out of the hole. Eleven days were spent working on the fish
before the hole was eventually sidetracked from 2488 m. The well was drilled
with seawater/bentonite/lignosulphonate mud down to 2185 m, with salt saturated
polymer mud from 2185 m to 3361 m, and with oil based mud (Oilfaze) from 3361 m
to TD. The primary objective, Jurassic sandstone,
was only a few meter thick. The sand was found deeper and was thinner than
expected. The well proved no sand in Palaeocene. The other secondary objective,
Rotliegendes sandstone, was highly interbedded with shale. None of the sands had
shows of hydrocarbons. One core was cut from 3256 to 3263 m in
the Zechstein Group above the salt. A second core was cut near final TD in the
Rotliegendes Group from 4424 to 4433 m. No wire line fluid samples were taken. The well was permanently abandoned on 22
December 1980 as a dry well. Testing No drill stem test was performed. General Wildcat well 2/7-17 was drilled on a low
relief structure to the southwest of the Eldfisk Field in the southern
Norwegian North Sea. The primary objective was to test the Danian - Late
Cretaceous limestone and chalk. Secondary objectives were the Late Cretaceous
and Jurassic where irregular and lens-shaped structures on the seismic records
were interpreted as possible sandstones with stratigraphically trapped
hydrocarbons. Operations and results Well 2/7-17 was spudded with the semi-submersible
installation Borgsten Dolphin on 24 June 1980 and drilled to 1600 m in Miocene
sediments. After setting the 13 3/8" casing the casing collapsed, forcing
abandonment of the well. The objectives were not reached. The well was drilled
with seawater, native solids, gel, and bentonite. No reservoir sections or hydrocarbon
indications were reported in the penetrated sediment column. No cores were cut and no wire line fluid
samples taken. The well was permanently abandoned on 12
July 1980 as a junk well. Testing No drill stem test was performed General Well 25/4-5 was drilled ca 1 km SW of the
25/4-1 Heimdal Discovery well. The primary objective was to test the Vestland Group and
the Statfjord Formation on a down-thrown panel west of the high drilled by the
25/4-1 well, which found several hydrocarbon bearing Jurassic levels in
addition to the main Heimdal Discovery. The secondary objective was to appraise
the gas-bearing section in the Paleocene Heimdal Formation. Operations and results Wildcat well 25/4-5 was spudded with the
semi-submersible installation Dyvi Alpha on 26 June 1980 and drilled to TD at
4355 m in the Triassic Smith Bank Formation. Operations were interrupted by a
strike that led to 4.5 days down time. The Heimdal reservoir was found at 2150 m
with gas down to a GOC at 2172 m and a 7 m oil column down to the oil-water
contact at 2179 m. Drill with 8 1/2" bit from 3600 m to 4198.5 m When
running in hole in the 8 1/2" section the bit stuck at 4174. The hole was
then backed off to 3891 m and a technical sidetrack was made from 3769 m. A 128 m thick Vestland Group was
penetrated from 3692 m to 3820 m. The Hugin and Sleipner formations were found water bearing with
residual hydrocarbons with the exception of a thin oil bearing interval from
3777.5 m to 3781.5 m. RFT sampling over this zone indicated a water gradient,
but an RFT fluid sample recovered both oil (0.25 l) and gas (139 l). The Statfjord was encountered at 3949 m
and was 178 m thick. It contained sandstones in the upper 50 m and in the
interval from 4064 to 4098 m. The upper interval could be interpreted as
hydrocarbon bearing. Direct fluorescence (yellow) and cuts (yellow -pale blue)
were observed on the cores from this formation, and migrated hydrocarbons were
also found by post-well organic geochemical analyses. Tests (DST and RFT) recovered
only water. The triassic Group contained a 50 meters
sandstone reservoir, which was drilled with good shows. The tests General Wildcat well 6507/12-1 was the first well
to be drilled offshore Mid-Norway. It was drilled to test the stratigraphic
sequence between seabed and at least 500 m below "reflector E" as
defined in the licence agreement. The primary target was a mapped Intra
Jurassic seismic reflector at a depth of approximately 2575 m. This reflector
was interpreted to be associated with a Middle to Early Jurassic sandstone
sequence. The secondary target was represented by possible sandstone sequences
between the mapped Base Cretaceous reflector and the Intra Jurassic reflector.
Thirdly there was a small vertical closure in the basal part of the Tertiary
sequence that could have prospective interest. The well is Type Well for the Båt Group,
the Tare Formation and the Naust Formation. It is Reference Well for the Fangst
Group. Operations and results The well was spudded with the
semi-submersible installation Byford Dolphin on 1 July 1980 in a water depth of
225 m, and drilled to a total depth of 3713 m in Late Triassic Red Beds. The
well was drilled with spud mud down to 778 m, with Gypsum PAC mud from 778 m to
1448 m, and with Lignosulfonate/PAC mud from 1448 m to TD. The well penetrated a section of 1105 m
below reflector E and thus meets the requirement set in the work programme for
licence 059. The well encountered a Cenozoic sequence
of 1679 m and the Tertiary succession was, at the time the well was drilled,
subdivided into lithostratigraphic units according to Deegan & Scull's
nomenclature for the northern North Sea. The well proved a slightly thicker
Tertiary sequence than expected. The seismic leg interpreted to represent Base
Tertiary proved to be related to a tuff sequence (Tare Formation). The Top Cretaceous reflector was easily
determined from acoustic and density logs. The base of the Cretaceous was
encountered in the well at 2032 m. The prognosed depth was 1975 m. The
Cretaceous seque General Well 30/3-2 is located ca 7 km north of the Oseberg Field in the Northern
North Sea. The primary objective of the well was to
test sandstones belonging to the Brent and Dunlin group. Secondary objective
was sandstones in the Statfjord formation. Operations and results Wildcat well 30/3-2 was spudded with the
semi-submersible installation Deepsea Saga on 4 July 1980. Due to a strike beginning at July 13 drilling was temporary abandoned at 955 m in Miocene
sediments of the Hordaland Group. The well was drilled with pre-hydrated gel. No cores were cut and no wire line fluid
samples were taken. The well was suspended on 15 August 1980 and
the rig was taken to Bergen. The strike was terminated on 14 August and the rig
was back on location on August 29. The well was re-entered and operations
resumed, now formally as a new well, 30/3-2 R. Testing No drill stem test was performed. General Well 34/10-12 was drilled on Tampen Spur
in the North Sea close to the western side of the Gullfaks Fault Block. The
primary objective of the well was to test sandstones of Middle Jurassic age.
Secondary objectives were sandstones of Early Jurassic age. Operations and results Wildcat well 34/10-12 was spudded with
the semi-submersible installation Neptuno Nordraug on 16 July 1981 and drilled
to TD at 2800 m in the Early Jurassic Statfjord Group. The well was drilled
with seawater and prehydrated Gel pills down to 298 m and with
gel/lignosulphonate mud from 298 m to TD. The sandstones of both Middle and Early Jurassic
age were water saturated. Shows were recorded on cuttings from claystones,
limestone and occasional thin sandstones from 1260 m in the Hordaland Group to
1657 m in the Balder Formation. The Jurassic had only trace fluorescence in
sandstone cuttings at 2094 to 2110 m in the Ness Formation, otherwise no trace
of hydrocarbons were seen. One core was cut from 2037 m to 2042.7 m
in the Ness Formation. No wire line fluid samples were taken. The well was permanently abandoned on 12
September as a dry well. Testing No drill stem test was performed. General Well 35/8-1 is located on the Marflo
Spur, ca 30 km west of the Gjøa Field in the northern North Sea. The principal
objective of this well was to test the hydrocarbon potential of sandstones
within the Jurassic section beneath the Late Cimmerian Unconformity. Operations and results Wildcat well 35/8-1 was spudded with the
semi-submersible installation Sedco-704 on 27 July 1980 and drilled to TD at 4345
m in Late Triassic sediments of the Statfjord Formation. The well was drilled without
significant technical problems, but two well kicks occurred .After penetrating
the Jurassic sand reservoir at 3516m a sudden rapid gas increase was noted, but
due to mechanical problems could not be measured. This increase was associated with
a quantity of reservoir fluids entering the borehole. During controlling of the
kick, a large proportion of gas was vented and light low gravity yellowish oil
recovered from the mud. A second kick with formation fluids entering the well
bore was taken after coring core no 3 at 3549.6 to 3567.1 m. The well was
drilled with seawater and viscous slugs down to 890 m, with
gypsum/Lignosulphonate mud from 890 m to 2196 m, and with KCl/polymer mud from
2196 m to TD. The top sections down to Top Rogaland
Group, Balder Formation at 1683 m contained a number of sands and sandy
intervals. From top Rogaland and throughout the Cretaceous section down to top
Draupne Formation at 3186 m the lithology was mainly claystone and limestone.
The heather Formation came in at 3200 m with two thin Intra-Heather Formation
sandstones at 3219 and 3250 m. Heather Formation shale continued down to the
Brent Group at 3516 m. Frequent sandstones were penetrated in the Brent and
Dunlin Groups, and in the Statfjord Formation.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General Wildcat well 2/7-18 was drilled as
replacement well for 2/7-17, which was junked for technical reasons. The well
should evaluate a low relief structure to the southwest of the Eldfisk Field in
the southern Norwegian North Sea. The primary objective was to test the Danian
- Late Cretaceous limestone and chalk. Secondary objectives were the Late
Cretaceous and Jurassic where irregular and lens-shaped structures on the
seismic records were interpreted as possible sandstones with stratigraphically
trapped hydrocarbons. Operations and results Well 2/7-18 was spudded with the
semi-submersible installation Borgsten Dolphin on 20 August 1980 and drilled to
601 m in assumed Pliocene sediments. After setting the 20" casing,
mechanical problems forced abandonment of the well. The objectives were not
reached. The well was drilled with seawater. No logs were run, and no sample of any
kind was collected. The well was permanently abandoned on 31
August 1980 as a junk well. Testing No drill stem test was performed General Well 15/5-3 was drilled in the Vilje
Sub-basin between the Enoch and the Gudrun fields in the North Sea. The primary
objective was to test possible sandstone reservoirs of Triassic age. A
secondary objective was to test the Middle Jurassic Sleipner Formation. The
well was planned to penetrate approximately 400 m into the Triassic and had a
projected total depth of 4200 m. Operations and results After two unsuccessful spuds, wildcat
well 15/5-3 was spudded with the semi-submersible installation Nortrym on 21
August 1980 and drilled to TD at 5042 m in shale and sandstones of Late Permian
age. Hole reaming was necessary in intervals below 2250 m, otherwise the well
was drilled without significant problems or incidents. The hole was good and
vertical down to ca 3000 m. Below 3200 m the hole deviation increased to
between 3° and 8°. The well was drilled with seawater and hi-vis sweeps down to
615 m, with a seawater/Dextrid mud from 615 m to 2029 m, with
seawater/polymer/Q.Broxin mud from 2029 m to 3834 m, and with a salt-saturated
Dextrid mud from 3834 to TD. None of the objective sandstone
reservoirs were found in the well. The Draupne Formation was encountered at
3665 m. After penetrating 135 m of Draupne shales, the well encountered 1050 m
of Zechstein evaporites. At this point, it was decided to deepen the well
further in order to explore the pre-salt rocks. Below these, undefined shales
and thin sandstones of Late Permian age were found. Traces of oil in the mud was observed
during P&A - see below. Poor oil shows were recorded in thin limestone
stringers at 2850 m, 2920, and in the interval 3355 to 3365 m. No shows were
recorded in the pre-Zechstein shales and sand se General Well 31/2-4 is located some 10 km NNW of
the discovery well 31/2-1 in a separate fault compartment near the crest of the
Jurassic gas accumulation. This crestal area appeared also to coincide with the
culminations of all deeper horizons that could be mapped. The well had two main
objectives. The first was to appraise the Jurassic gas accumulation in the
31/2-1 Troll Discovery in a location with nearly maximum gross hydrocarbon
column. The well should test lateral variations in this reservoir. The second
major objective was to explore deeper Triassic/Palaeozoic Formations. The well
would test possible hydrocarbon accumulations under the Late Jurassic Troll
reservoir, explore possible pre-Jurassic source rocks, and provide geological
ages for deep horizons and thus improve the regional geological setting. TD of the well was proposed to be 5000 m
below sea level or in Palaeozoic formations whatever came first. Operations and results Well 31/2-4 was spudded with the
semi-submersible installation Borgny Dolphin on 1 September 1980 and drilled to
TD at 815 m in the Hordaland Group. The well was drilled with seawater and
hi-vis pills. After having set the 20" casing, the well was secured and
suspended on September 13 due to a farm out of the rig to Statoil. Statoil had
requested the Borgny Dolphin to be released to secure their well 34/10-10,
which was blowing gas from a shallow gas zone. The well was classified as a dry well. Testing No drill stem test was performed in the
well. General Wildcat well 31/2-5 is located in the
southern part of the oil province in the Troll West area, some 6 km west of the
discovery well 31/2-1, in a downthrown fault block. The objectives of the well
were to test presence and nature of hydrocarbons in a structure west of the
main gas reservoir; to test lateral variation in reservoir characteristics
westwards; to investigate possible causes for the difference in flat spot
appearance in this fault block; and to get a good geologic identification of
the various seismic reflectors for lateral extrapolation of well data. Operations and results Problems were experienced during
positioning and anchoring of semi-submersible installation West Venture for the
wildcat well 31/2-5. After 6 days efforts the installation had to be
repositioned 25 m from the intended location and the anchors were successfully
laid out and tensioned. The well was spudded on 26 October 1980 and drilled to
TD at 2532 m in the Triassic Hegre Group. The well was drilled with seawater
and viscous pills down to 443 m, with gelled seawater from 443 m to 810 m, with
KCl/polymer mud from 810 m to 1807 m, and with seawater/gel from 1807 m to TD. Well 31/2-5 confirmed that the Late
Jurassic Sognefjord Formation sandstone reservoir was well developed also in
the western part of the structure. A gas column was penetrated from 1536 m to
1579 m (43 m), followed by a 21 m thick oil column down to an OWC at 1600 m.
Good oil shows continued down to 1644.5 m. The GOC was found at the same depth
as seen in the other wells in the area. The most interesting observation in
this well was the presence of the thick oil column below the gas, some 9 m
thicker than seen in any of the other wells, and the oil was encountered in a
section of the reservoir with very good clean sand. It is yet too early to
explain the difference in oil thickness, and the importance of a thicker oil
column in a good sand will remain unknown until a full produc General Well 34/10-11 was drilled on the Gullfaks
Delta structure in the North Sea. The primary objective of the well was to test
sandstones of Middle Jurassic age. Secondary objectives were sandstones of
Lower Jurassic age. Operations and results Appraisal well 34/10-11 was spudded with
the semi-submersible installation Ross Rig on 23 October 1980 and drilled to TD
at 2155 m in Late Triassic sediments of the Lunde Formation. Bad weather caused
511 hrs lost time (15.7% of total rig time). Significant lost time (509 hrs) was
caused also by malfunction and repairs of the BOP. The well was drilled with
spud mud down to 463 m, with gel/lignosulphonate/seawater mud from 463 m to
1100 m, with Gypsum/lignosulphonate/sweater mud from 1100 m to 1720 m, and with
gel/lignosulphonate/seawater mud from 1720 m to TD. First oil shows were recorded from 1090 m
to 1200 m, intermittent weak shows were seen from 1420 to 1495, and more or
less continuous oil shows were recorded on limestone from 1660 m to top
reservoir at 1868 m. The well proved oil in sandstones from top of the Early
Jurassic Amundsen Formation at 1868 down to the OWC at 2038 m in Late Triassic
sediments of the Raude Formation. Below 2038 m shows were recorded down to TD. Six cores were cut in the interval 1870 m
to 1926.5 m in the Amundsen and Nansen formations. Two FIT fluid samplings were
attempted. FIT 1 at 2081 m recovered 3 litres 35 °API oil and 7 litres of mud
filtrate in the 2 3/4 gallon chamber. The FIT 2 at 2051 m did not recover any
fluids. The well was permanently abandoned on 5
march 1981 as a as an oil appraisal well on the Gullfaks field.
wlbHistoryDateUpdated: 2016-05-19T00:00:00 General Well 34/10-20 was the first well drilled
on the Gamma structure south of Gullfaks Sør in the northern North Sea. The
primary objective was the Middle Jurassic Brent Group. Secondary objectives
were Early Cretaceous sandstones, the Cook Formation and the Statfjord Group. Operations and results Wildcat well 34/10-20 was spudded with
the semi-submersible installation Ross Isle on 23 December 1983 and drilled to
TD at 3747 m in the Early Cretaceous Cromer Knoll Group. The well was plugged
back and abandoned without reaching the targets. Engineering difficulties associated
with high fluid pressure and low formation integrity was the reason why the
well had to be abandoned. It was drilled with gel/seawater down to 1053 m, with
KCl/polymer mud from 1053 m to 2990 m, and with lignosulphonate mud from 2990 m
to TD. The well was dry. Zones with weak shows,
mostly on claystone cuttings, were recorded from 1860 m to 2050 m in the
Rogaland Group. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 23
April 1984 as a junk well. Testing No drill stem test was performed. General Well 25/11-9 was drilled ca km west-south
west of the 25/11-1 Balder discovery well on the Utsira High in the North Sea.
The objective was to establish the presence of a thick accumulation of oil sand
in the southern part of the Balder Field, and to confirm the reservoir quality
of Lobe 8 penetrated in the 25/11-5 well. The top of the reservoir was
anticipated to be at 1688 m subsea. Operations and results Appraisal well 25/11-9 was spudded with
the semi-submersible installation Norskald on 4 November 1980 and drilled to TD
at 1910 m in the Late Cretaceous Tor Formation. The well was drilled with Seawater/Gel/Lignosulphonate. The well penetrated the Utsira Formation
and several Skade Formation sands and then penetrated a ca 560 m thick section
of shale/mudstone/siltstone belonging to the lower Hordaland Group before top
Balder Formation was encountered at 1670 m. Drilling revealed two oil sand
zones, one of Eocene age between 1708.5 m and 1742 m (Intra Balder Formation
sand), the second of Paleocene age (Hermod Formation) between 1781 m and 1785 m,
which is the Balder Field oil-water contact. A few thin sands in the upper
Balder Formation from 1671 m to1694 m also appeared to be oil bearing. A second
Hermod Formation from 1789 to 1818 m was water wet with some weak shows. Four conventional cores were attempted in
the interval 1718 to 1744 m in the Intra Balder Formation Sandstone, but only
3.5 m from the first and 1.5 m from the last core was retrieved. No wire line
fluid samples were taken. The well was permanently abandoned on 7
December 1980 as an oil appraisal well. General Wildcat well 31/4-4 is located on the
Lomre Terrace north of the Brage Field and east of the Oseberg Field. The
primary objective of the well was to test possible sandstone reservoirs of
Cretaceous age. The secondary objective was to test sandstone reservoirs of
Late Jurassic age, anticipated to be Intra Heather Formation sands. The well is Reference Well for the Etive,
Ness, and Tarbert Formations of the Brent Group. Operations and results Well 31/4-4 was spudded with the semi-submersible
installation Nortrym on 17 December 1980 and drilled to TD at 3150 m in Early
Jurassic sediments of the Statfjord Formation. The well was drilled with
seawater and viscous gel down to 900 m and with KCl / polymer mud from 900 m to
TD. No reservoir sands of Cretaceous age were
encountered in the well. Poor shows were reported from two limestone stringers
and a thin, tight sandstone stringer of Late Cretaceous (Maastrichtian and Late
Campanian) age. A Late Jurassic "Intra Heather Sand I" (Sognefjord
Formation) was encountered at 2363 m with a gross thickness of 39 m. The net
sand interval was 24 m and consisted of fine-grained to very fine-grained
argillaceous, micaceous sandstone. Average porosity was calculated to 16 %.
Eighty-nine percent water saturation was calculated for this sand indicating
that poor oil shows encountered while drilling the interval, were residual. A
second "Intra Heather Sand II" (Fensfjord Formation) was penetrated
at 2482 m with a gross thickness of 45 m. The sand was water bearing without
shows. The lithology was similar to the upper sand. The other reservoir
sequences encountered in the well, sandstones in the Middle Jurassic Brent
Formation, the Early Jurassic Cook Formation, and the Statfjord Formation, were
also water bearing. The gross sand thicknesses of these were 118 m, 21m and
67m, respectively. A single conventional core was cut
between 2490m and 250 8m, near the General Exploration well 34/2-2 is located a
northwestern part of the Tampen Spur area. It was intended to be the first well
to test the reflections below the Base Cretaceous (Kimmeridgian) Unconformity
on a seismically defined, northerly trending west-northwest dipping fault
block. The well was located near the apex of the structure at the Base
Cretaceous level, but down-dip with respect to deeper stratigraphy. Primary
targets were the Middle Jurassic Brent Formation and the Early Jurassic/Triassic
Statfjord Formation. Secondary targets were possible Early Tertiary and Late
Jurassic sandstones. Planned TD was 4300 m Sub Sea. Operations and results Well 34/2-2 was spudded with the
semi-submersible installation Sedco 703 on 27 November 1980. Drilling proceeded
to 513 m where bad weather caused a three days wait-on-weather interruption.
Resuming drilling the drill string parted and was lost in the hole. Fishing was
attempted but the fish could not be retrieved. The well bore was technically
suspended on 12 December 1980 as a dry well. Operations were resumed the same
day as the re-entry 34/2-2 R. Testing No drill stem test was performed. General Well 30/7-8 was drilled in the Norwegian
part of the Shetland Basin. The primary objective was to test the hydrocarbon
potential in the Middle Jurassic Brent group, which had previously proved gas
and condensate bearing in wells 30/4-2 and 30/7-6. The Early Jurassic Cook
Formation and Statfjord Group were secondary targets. The planned TD was 4600 m
in the Triassic Red Beds. Operations and results Appraisal well 30/7-8 was spudded with
the semi-submersible installation Treasure Seeker on 19 November 1980 and
drilled to 4287 m in the Middle Jurassic Brent Group . The drill pipe became
differentially stuck at 4069 m. After unsuccessful fishing, the well was
suspended with top of the fish at 4058 m, and 4287 m became official TD for the
well. The well was drilled with seawater and hi-vis pills down to 215 m, with
water based "lost circulation mud" from 215 m to 962 m, with
gypsum/lignosulphonate mud from 962 m to 2648 m, with a bentonite/lignosulfonate/lignite
mud type from 2648 m to TD. Frequent traces of oil shows were
described in many intervals from 1820 m and down to well TD. Most of the shows occurred
in limestone stringers and were rated poor. The primary target Middle Jurassic
(Bathonian-Bajocian) Brent Group reservoir was encountered at 4066 m. The shows
in the Brent Group sandstones were rated good. Five cores were cut in the well. One was
cut in the Draupne Formation from 3888.5 m, while the other four were cut in
the Brent Group reservoir section from 4082.3 m to 4129.3 m. No fluid sample
was taken. The well was suspended on 4 April 1980 as
a gas/condensate appraisal well.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General This well was drilled in two phases, a
primary well bore 25/10-4, and a re-entry well bore 25/10-4 R. The well was
drilled in the western part of the Balder Field in the North Sea. The primary
objective was to establish the presence of a thick accumulation of Paleocene
oil sand, and evaluate sand-shale distribution and reservoir quality. The top
of the reservoir was anticipated to be at 1698 m subsea. As a secondary
high-risk objective, the well was to be drilled to 2700 m to test for the
presence of hydrocarbons in the Permian. This test was necessary as any
hydrocarbons present could critically affect the design and location of a
possible production platform. Operations and results Appraisal well 25/10-4 was spudded with
the semi-submersible installation Glomar Biscay II on 8 December 1980 and
drilled to TD at 2348 m in the Late Permian Zechstein Group where the well was
suspended due at 18 January 1981 due to a pressing need for the rig to drill
other Balder Field delineation wells, combined with unexpected delays in the
25/10-4 well progress as a result of lost circulation. The re-entry commenced
on 29 May 1981 and deepened the well to 2550 m in a massive unconsolidated sand
of Permian/ Carboniferous age. The top hole down to 30" casing depth at
214 m was drilled with seawater. Below 214 m the well, including the re-entry
well, was drilled with seawater/gels/lignosulphonate. The main oil sand of Paleocene age was
encountered between 1759.5 m and 1784.0 m. The net oil sand was 22 m thick. The
Triassic section had several thin and oil-bearing sandstones not detected
before in the area. A wire line FIT in one of these sands proved live oil. In
total these sandstones made up 21 m net sand but the accumulation was
considered insignificant. Cuttings from 2130 m (Early Jurassic) through Permian
Zechstein and the upper part of the Permian/Carboniferous unconsolidated
sandstone contained traces/shows of hydrocarbons. General Well 15/9-7 was drilled as an appraisal
well on the south part of the Sleipner Vest Field in the North Sea. The primary
objective was to test for hydrocarbons in Callovian age sandstones in the
Epsilon structure. Operations and results Appraisal well 15/9-7 was spudded with
the semi-submersible installation Nordraug on 26 December 1980 and drilled to
TD at 3776 m in the Middle Jurassic Sleipner Formation. A total of 20 days was
spent on waiting on weather. The phase of running BOP after cemented 20"
casing took 15 days due to several broken guide wires combined with bad
weather. The well was drilled with spud mud down to 465 m, with gypsum/polymer
mud from 465 m to 2823 m, and with gel/lignosulphonate/Drispac mud from 2823 m
to TD. The primary target Hugin Formation was
penetrated at 3519 m and proved to hold gas and condensate down to a true gas/water
contact at 3673 m based on RFT gas gradients. The gross reservoir thickness was
185 m (3519 to 3704 m) with a net pay of 83 m with 18% porosity and 12 % water
saturation. There were no oil shows above top Hugin reservoir level. Oil shows
were described on the cores from the reservoir and on cuttings down to 3677 m. A total of 156 m core was recovered in 12
cores from the interval 3516 to 3671 m. The core-log depth shift was
significant for all cores: from +6.0 to +9.1 meter, the largest shifts are for
the deepest cores. Segregated RFT fluid samples were taken at 3560 m (gas, mud
filtrate and condensate), 3603 m (gas, mud filtrate and condensate), 3658.5 m
(gas, mud filtrate and condensate +dark oil emulsion), 3687 m (mud filtrate,
formation water and minor gas), and 3672.2 m (mud filtrate and water). General Wildcat wells 35/3-3 and 35/3-4 were
drilled in the Norwegian sector of the North Sea approximately 50 km west of
MålØy, Norway. The primary target was to test the possible extension of Lower
Cretaceous sandstones to the east of those encountered in wells 35/3-1 and
35/3-2. A stratigraphic trap was thought to exist in these sandstones. A
secondary target was possible sandstones of Early Jurassic age with a possible
pinch-out trap. Well 35/3-3 was spudded with the
semi-submersible installation Byford Dolphin on 30 October 1980. It was drilled
and logged to 900 m, then junked because of technical problems running the
20" casing. The rig was moved about 20 meters, and the well was respudded
as 35/3-4. Operations and results Well 35/3-4 was spudded with the
semi-submersible installation Byford Dolphin on 30 November 1980 and drilled to
TD at 4089 m in Basement rocks (Caledonian age). A sidetrack was drilled from
3768 m. The well was drilled with seawater and gel down to 457m, with seawater/gel/lignosulfonate
from 457 m to 879 m, with lignosulfonate/gypsum/gel mud from 879 m to 2388 m,
and with gel/lignosulfonate/PAC mud from 2388 m to TD. The well penetrated strata from Tertiary
through Jurassic before reaching basement rocks-of Caledonian age. Hydrocarbon shows were encountered in
Lower Cretaceous and Lower-Middle Jurassic sand. The Lower Cretaceous sediments
were interpreted as submarine fans. RFT measurements in Lower Cretaceous
indicate an upper zone with a gas gradient of 0.4 psi/m, and a deeper zone with
a water gradient of 1,54 psi/m. There seem to be no pressure communication
between these two zones. Log evaluation in General Well 3/7-2 was drilled on a structure
located across blocks 3/4 (Amoco Group) and 3/7 (Petronord Group. The primary
targets were: Tertiary sands found gas bearing in well 2/3-1; Danian/Late
Cretaceous limestone (chalk) hydrocarbon bearing in the Ekofisk area and in the
Danish well Lulu 1; Middle Jurassic sandstones which were hydrocarbon bearing
in well 2/6-2; and Rotliegendes sandstones. The TD was planned into the
Carboniferous in order to establish the source potential of this formation. Operations and results Wildcat well 3/7-2 was spudded with the
semi-submersible installation Dyvi Alpha on 30 March and drilled to TD at 4330
m in the Early Permian Rotliegendes Group. A drilling break occurred at 2534 m.
Flow check at 2553 m showed a weak flow, which was controlled by raising the
mud weight to 1.46 sg. Drilling resumed and was stopped at 2563 m for logging.
Three days were necessary to run the electric logs because of continuous slight
flow. Deviation problems were experienced in the salt. The deviation reached a
maximum of 9 1/2 deg at 3659 m then was reduced to 2 1/2 deg at 4004 m. The
well was drilled with a lignosulphonate mud from 2563 m to 3027 m. Below the 9
5/8" casing shoe at 3012 m the mud was displaced to a salt saturated mud. The Eocene/Oligocene sands were found
missing. Only 8 meters of sand were encountered in the Paleocene. The chalk was
tight and water bearing. The Jurassic sandstones were not as developed as
prognosed, and they were water bearing. No sandstones were encountered in the
Rotliegendes Group, which consisted of an upper shale and a lower volcanic
unit. Carboniferous sediments were not penetrated. All the targets above the
salt were found water bearing while no reservoir was encountered below 4166 m (base
salt, F horizon). Prognosed stratigraphy at base Cretaceous and below was in
error. Base Cretaceous was encountered 115 m higher than prognosed, top salt
was 209 m higher than prognosed, General Well 34/10-21 was the third well drilled
on the Gullfaks South structure in the Tampen Spur area in the northern North
Sea. The objective was to test for possible hydrocarbon accumulations and for a
possible extension of reserves in the Gullfaks South field. Targets included
the Brent, Cook and Statfjord Sandstones and possible sand accumulations in the
Early Cretaceous. Operations and results Appraisal well 34/10-21 was spudded with
the semi-submersible installation Dyvi Delta on 26 July 1984 and drilled to TD
at 4005 m in Late Triassic sediments of the Raude Formation. The well was
drilled with gel/seawater down to 615 m, with gypsum/CMC/lignosulphonate from
615 m 3196 m, and with gel/lignosulphonate from 3196 m to TD. No sandstones were encountered in the
Early Cretaceous. Hydrocarbon bearing Brent sandstone was encountered at 3287
m, with the hydrocarbon/water contact established at 3333 m+/-3 m. No
hydrocarbons were identified in the Cook sandstones. The logs indicated
hydrocarbons in the Statfjord Group, but drill stem test gave no flow from
these sandstones. No shows were described above the Tarbert reservoir. Below
the OWC, shows on sandstone were described down to 3359 m. Six cores were cut; four from 3289 m to
3383 in the Brent Group and two from 3970 m to 3985.5 in the Raude Formation.
Core recoveries were from 90 % to 100 %. RFT fluid samples were taken in the
Brent Group oil zone at 3298.5 m, 3317.3 m, and 3325.0 m. The well was permanently abandoned on 22
October 1984 as a gas appraisal well. Testing
wlbHistoryDateUpdated: 2020-02-21T00:00:00 General Well 34/10-7 was drilled on the eastern
segment of the Gullfaks Field. The primary objective was to test sandstones of
Middle Jurassic age. Secondary objective was sandstones of Early Jurassic age:
the Cook and the Statfjord Formations. Operations and results Appraisal well 34/10 7 was spudded with
the semi-submersible installation Ross Rig on 7 January 1980 and drilled to TD
at 2550 m in the Late Triassic Lunde Formation. Two major problems were
encountered during drilling. The first one concerned water sensitive clays
which caused difficulties when underreaming the hole for both the 16"
liner and the 13 3/8" casing. The second problem was the leak off test
below the 9 5/8" casing shoe. While circulating prior the second leak off test
the formation broke down. Four cement squeezes were required before a proper
formation test was obtained. The well was drilled with spud mud down to 845 m
and with gel/lignosulphonate mud from 845 m to TD. Weak to good oil shows were recorded from
1320 m in the lower Hordaland Group and downwards, mostly in limestone. Strong
shows with live oil in the mud were recorded between 1380 and 1415 m. Oil shows
of variable strength continued all the way down through the Hordaland, Rogaland
and Shetland Groups. The Shetland Group was found resting directly on the Early
Jurassic Cook Formation sandstone at 1810 m. Oil was found in sandstones of the
Cook and Statfjord Formations. No oil/water contact was observed in the Cook
Formation. In the Statfjord Formation an oil water contact was found at 2066 m.
A total 53.2 m core (67% recovery) was
recovered in 5 cores in the interval from 1813 m to 1892 m. A sixth core was
taken with 100% recove General Well 1/3-5 was drilled on a NW-SE
oriented fault block tilted towards the NW. The structure is located in the
northern Permian basin, on the east side of Central Graben, extending into
blocks 116, 211, and 2/4. The purpose of the well was to evaluate the
hydrocarbon potential of the Rotliegendes Group sandstones. Operations and results Wildcat well 1/3-5 was spudded with the
3-leg jack up installation Neddrill Trigon on 1 October 1984 and drilled to TD
at 4850 m in the Permian Rotliegendes Group. After setting the 30"
conductor a 14 3/4" pilot hole was drilled to 1195 m, before opening the
hole to 26". Drilling to 2470 m the mud weight was raised from 1.33 g/cm3
to 1.70 g/cm3 due to high formation pressure. This resulted in tight hole
during wiper trips, and high weight strain on the drill string, and also caused
the 13 3/8" casing to be set somewhat higher than prognosed. Through the
chalk sequence the hole seemed to be tight, and while tripping at 3523 m, the
drill string got stuck with the bit at 3515 m. It was assumed that the tight
interval was caused by one of the stabilizers between 3247 and 3267 m. The
string was freed by pumping acid. A high pressure sand sequence in the interval
4363-4395 m, with pore pressure close to the last leak-off Test, resulted in
the 7" liner being set 520 m higher than prognosed. The well was drilled
with spud mud down to 1195 m, with KCl/polymer mud from 1195 m to 3000 m, from
3000 m the mud was lightly treated with lignosulphonate. Fifty bbl of pipelax
with a mud/diesel ratio of 1:1 was added to the mud to free the stuck pipe at
3515 m. From 4122 m to TD the well was drilled with a polymer/sulphonated resin
mud. Traces of yellow direct fluorescence,
mainly on fractures, with a moderate milky-white cut fluorescence were observed
at the top of the Tor Formation and at several levels deeper down in the
formation. Also near the base of the Hod Formation, a very weak General Well 2/6-2 is located on the Piggvar
Terrace just east of the Mandal High in the southern Norwegian North Sea. The
main objective of the 2/6-2 well was to test a possible hydrocarbon
accumulation of a lens-shaped seismic anomaly in the Lower Cretaceous. The
anomaly showed both up dip truncation and structural closure, it was believed
to represent a deep sea fan type sand deposit. A secondary objective was to
explore the upper part of the Jurassic series below the Kimmeridgian unconformity. The well is Reference well for the Tuxen
Formation. Operations and results Wildcat well 2/6-2 was spudded with the
semi-submersible installation Dyvi Alpha on 3 January 1980 and drilled to TD at
4760 m in Permian Zechstein salt. The hole was side-tracked from 4175 m due to
loss of MFT tool in the hole at 4276 m. In the Early Cretaceous only tight,
mainly water bearing limestones were found. The Jurassic consisted of the
Mandal, Farsund, Haugesund, and the Bryne Formations, with the latter resting directly
on the salt at 4723 m. In the Late Jurassic a hydrocarbon bearing but tight limestone
body was unexpectedly found. The Middle Jurassic Bryne sandstones were found
gas bearing. Shows were reported as follows: Down to the top of the Jurassic at
4118 m only minor amounts of gas were recorded and the first occurrence of C2 was
seen at 4100 m. Fluorescence of a yellow golden colour and greenish white cut
was seen on Early Cretaceous limestones from 3870 to 3877 m, this led to the
cutting of Core 1 at 3877 to 3886 m. On the core no direct fluorescence was
seen, only a weak, cloudy yellow/greenish cut which terminated at 3881 m. Direct
fluorescence and cut was seen on Late Jurassic limestones between 4179 and 4230
m, further, on Cores 2 and 3 taken from 4220 to 4235.5 m there was seen good
yellow to bluish direct fluorescence. Some bubbling of gas was also seen and
seepage of oil from shaly joints. Some cut was seen on siltstone at General Well 2/7-15 was drilled on the Eldfisk
East structure in the Feda Graben of the southern North Sea. The well was an
appraisal of the productive Danian - Late Cretaceous chalks found in 2/7-8. The
well also had an explorative objective, namely to prove the existence of
productive Jurassic sandstones on the East Eldfisk structure. Projected total
depth was 14500 ft (4420 m). The well is Reference well for the Ran
Sandstone Units. Operations and results Well 2/7-15 was spudded with the
semi-submersible installation Haakon Magnus (now Borgsten Dolphin) on 29
January 1980 and drilled to TD at 4423 m in the Late Jurassic Haugesund
Formation. A 2.3 Sm3 influx was taken while drilling at 3667.7 m (3672.8 m logger's
depth) in the Farsund Formation. The well was shut in. After shut-in the
circulation was lost, probably because the formation broke down. The
circulation was resumed by appropriate mud adjustments, and the return mud then
contained 3% oil and was slightly gas-cut. The well was drilled with bentonite,
Flosal and lime down to 503 m, with Drispac mud from 503 m to 1387 m, and with
Drispac/lignosulphonate mud from 1387 m to TD. The Danian - Late Cretaceous section
tested small quantities of hydrocarbons. Shows were encountered, often in
fractures, on cored siltstone and claystone in the Early Cretaceous Ran
Sandstone Units and Åsgard Formation, but testing proved the section to be
generally tight. The logs indicated a 2 m HC-bearing sandstone stringer at 3672.8
m (where the influx was taken while drilling), but no shows were reported from
this depth. Isolated shows, in the form of dull yellow fluorescence, were
reported also on cored claystone in the Farsund Formation at 403 General Well 8/10-2 was drilled on the
Sørvestlandet High about 20 km east of the Ula Field. The primary objective of
the well was Jurassic sandstones expected to be 122 m thick. Secondary
objective was Paleocene sandstones. Operations and results Wildcat well 8/10-2 was spudded with the
semi-submersible installation Nortrym on 5 February 1980 and drilled to TD at
2997 m in the Late Permian Zechstein Group. The first samples to the surface were
from Miocene - Oligocene. They were badly contaminated with cement from the
casing shoe at 461 m. First clean formation samples were collected at 503 m and
they consisted of a soft grey brown clay with minor amounts of fine to medium
grained sand and occasional fossil frogs. This gave way at 570 m to a totally
argillaceous section, and soft grey-brown, slightly calcareous, claystone was
found. This became the dominant lithology down to the 13 3/8" casing point
at 1198 m. After casing point, cement contamination of samples occurred for
about 10 m. The claystone gave way to a grey-green-brown, soft, sticky clay,
which had occasional traces of carbonaceous material. Top Hordaland Group is
set at 1265 m. At 1471 m a thin hard white limestone occurred with an
associated drop in drilling rate from 61 m to 46 m per hour. Background gas
also decreased during this interval. After 1494 m the dominant lithology became
soft grey-brown clay, some sections of which were slightly calcareous.
Occasional fossil fragments and pyrite nodules were also found in this section.
There was a slow increase in the claystone content and by 1801 m a light grey
claystone had become the dominant lithology. This claystone was moderately
hard, slightly calcareous and micro micaceous; traces of dolomite and shelly
fragments were also found. By 1951 m the soft clays had disappeared completely
and were replaced by light grey and dark brown claystones, both soft to firm,
the light grey claystone being non-calcareous and the General Well 31/2-2 was drilled some 4 km east of
the discovery well 31/2-1 on seismic line 79-416 at SP 200. The concession
requirement for the wells were complete penetration of the prospective Jurassic
sequence and terminate in Triassic or older. The particular objectives of well
31/2-2 were: to evaluate lateral variation of reservoir parameters eastwards on
the flank of the structure: to test the zone of oil shows seen in 31/2-1 in
better reservoir conditions, to test the gas accumulation in a down-dip
location: to evaluate the nature of the seismic flatspot, and to provide
geological calibration of seismic reflectors above the reservoir for improved
regional evaluation. Operations and results Well was spudded with the
semi-submersible installation West Venture on 27 February 1980 and drilled to
TD at 1857 m in the Middle Jurassic Krossfjord Formation. The 36" hole was
drilled without incident to 433 m using seawater with viscous pills spotted on
connections. From 422 m to 433 m hard drilling was experienced. This was
interpreted as a boulder bed similar to that found at a comparable depth in the
previous 31/2-1 well. Problems were encountered with the stability of the
temporary guide base, and the well had to be abandoned. The rig was moved NE 25
m and re-spudded on 29 February. The well was drilled with seawater and hi-vis
pills down to 800 m, and with gypsum/lignosulphonate mud from 800 m to TD. Top reservoir (Sognefjord Formation) came
in at 1544 m and was gas bearing down to a gas/oil contact at 1579 m, and
oil-bearing from 1579 m down to an oil/water contact at 1591 m. Both contacts
were clearly defined on logs, the gas/oil contact was confirmed by RFT pressure
gradients, and moveable oil was confirmed by RFT sampling at 1587.5 m and 1590
m. Gas samples were obtained from 1548 m and 1571 m. Weak oil shows began at
1561 m in the gas zone, strong shows with stained and bleeding cores and a
paraffinic smell were obs General Well 34/4-2 is located in the northern North Sea, approximately 5 km west of the Snorre Field. The purpose of the well was to test
the stratigraphic sequence below the Base Cretaceous Unconformity. The primary
target was the Statfjord Formation, which was known from the license 037 area
to contain porous sandstones of appreciable thicknesses. The secondary target was possible Brent
Group / Late Jurassic sands immediately below the Base Cretaceous unconformity.
Thirdly, well 34/4-2 was a stratigraphic test of the Triassic deposits between
the Statfjord Formation and the Middle to Late Triassic sequence penetrated in
well 34/4-1. Operations and results Wildcat well 34/4-2 was spudded with the
semi-submersible installation Byford Dolphin on 6 March 1980 and drilled to TD at 3599 m in the Late Triassic Lunde Formation. No significant incidents
occurred during operations, but the well developed as much as 20 deg deviation
towards TD, giving a TVD RKB of 3571 m, 28 m less than measured depth. The well
was drilled with spud mud down to 816 m, with gypsum/lignosulphonate mud from
816 m to 1975 m, and with lignosulphonate mud from 1975 m to TD. The well penetrated Tertiary, Cretaceous,
Jurassic and Triassic strata as required in the work programme for License 057.
More than 900 m of Triassic deposits were penetrated in order to obtain
stratigraphic information. The Statfjord Formation was eroded and the reservoir
characteristics here were on large negative. The exception was the upper seven
meter thick Eiriksson Member with a net/gross-value of 1.00 and an average
porosity of 24.3%. The underlying Raude Member had a high clay content, which
reduced prospectiveness to a N/G value of 0.18 and porosities only rarely
exceeding 20%. The Jurassic sequence proved to be different from the expected
with Dunlin Group claystones directly underlying Barremian limestones. Hence,
no Brent/Late Jurassic sands were present. No s General Well 16/4-1 is located on the Utsira
High. The primary objective of the well was to test the Paleocene Heimdal
Formation. Secondary objectives were Jurassic and Triassic sandstones,
Zechstein carbonates and Rotliegendes conglomerates. The well was planned to
reach TD at 2850 m + 100 m after having identified a seismic reflector at this
depth, interpreted to represent Top Metamorphic Basement. Operations and results Wildcat well 16/4-1 was spudded with the
semi-submersible installation Treasure Seeker on 8 September 1984 and drilled
to TD at 2909 m in crystalline/metamorphic basement of Early Paleozoic age.
Under the 30" casing shoe a 17 1/2" pilot hole was drilled. At 494 m
in Pleistocene sand and shale, the well started to flow up the annulus from a
small gas pocket. The well died out by itself but there were problems with lost
circulation, so a cement plug was set from 494 - 415 m. The cement was drilled
out to 480 m and the hole was underreamed to 26" before landing of the
20" casing. No other major problems occurred during drilling of this well.
The well was drilled with seawater and bentonite down to 494 m, with
KCl/polymer mud from 494 m to 2052 m, and with NaCl/polymer mud from 2052 m to
TD. The well 16/4-1 encountered water-bearing
sandstones in the Paleocene Heimdal Formation as well as in the Triassic. The
latter is a 36 m thick sand in between the Smith Bank Formation and the
Zechstein Group. The Heimdal Formation Sandstones occur as interbedded
sand/claystone in the upper part (2100 m to 2142 m) and as a massive sandstone,
which is homogenous and very clean in the lower part (2142 m 2277 m). The
Triassic sandstones (2394 m to 2430 m) were very fine-to-fine grained with a
considerable amount of silt and mica. Log evaluations over these sands gave the
following results: The interval 2100 m to 2142 m gave a net/gross ratio of
0.095, with an average porosity of 23,06% and a shale volume of 43,58% General Well 34/10-8 was drilled on the southern
part of the Gullfaks Field. The primary objective was to test sandstones of
Middle Jurassic age. Secondary objectives were sandstones in the Early
Jurassic. Operations and results Appraisal well 34/10-8 was spudded with
the semi-submersible installation Deepsea Saga on 8 March and drilled to TD at 2214
m in the Early Jurassic Cook Formation. Some problems with lost circulation was
encountered when circulating prior to cementing the 13 3/8" casing. Also
the drill string became stuck during plug back operations at 2037 m and 9 days
were lost when fishing for it. The well was drilled with Gel/spud mud down to 875
m and with gel/lignosulphonate from 875 m to TD. The Middle Jurassic Brent Group sandstones
came in with Tarbert Formation on top at 1821 m and the Ness Formation at 1853
m. The Tarbert and Ness formations were hydrocarbon-bearing with a 151 m gross
pay zone from1821 to 1972 m. The Early Jurassic sandstones of the Cook
Formation were water saturated. Above the reservoir good oil shows were
recorded on limestone from 1712 to 1745 m and on limestone/mudstone/siltstone
from 1665 to 1705 m. Otherwise traces of oil shows were recorded above the
reservoir up to a depth of 1220 m. No shows were recorded below the oil bearing
reservoir. A total of 13 cores were taken from 1823 to
1976 m, with a total recovery of 140 m. The RFT tool was run in the Brent sand
and good data was obtained from 1826 to 2006 m. Fifteen out of seventeen tests
were successful. In the Ness zone a fluid sample was taken at 1950 m. The well was permanently abandoned on 25
May 1980 as an oil appraisal well.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 15/9-6 was drilled in the Sleipner
Vest area in the Viking Graben of the North Sea. The objective of the well was
to test possible hydrocarbons in Middle Jurassic sandstones on the northern
flank of the 15/9-Beta structure, and to get more information about the sand
distribution in this area. Operations and results Appraisal well 15/9-6 was spudded with
the semi-submersible installation Nordskald on 7 May 1980 and drilled to TD at
3946 m in the Triassic Skagerrak Formation. No significant problem was
encountered in the operations. The well was drilled with seawater and
pre-hydrated gel down to 465 m, with sweater/gel and SSP lubricant (a vegetable
oil) from 465 m to 1140 m, and with gel lignosulphonate/SSP lubricant from 140
m to TD. Top of the target reservoir sandstones (Callovian
age Hugin Formation) was found at 3762 m. This was deeper than expected and below
the field gas-water contact. The sandstones were also thinner than expected. Isolated
spots of shows on sandstones were described on cuttings and cores from the Hugin
and Sleipner formations and the Upper part of the Skagerrak Formation. One
cuttings sample from 3346 m in the Blodøks Formation was described with good
show on sandstone. Two cores were cut. Core 1 was cut from
3768.5 m to 3781.4 m in the Hugin Formation (75% recovery) and core 2 was cut
from 3810 m to 3814.5 m in the Sleipner Formation (37% recovery). An RFT fluid
sample was taken at 3774 m in the Hugin Formation. Laboratory analysis
indicated the content to be a mixture of formation water, mud, and fresh water
from the water cushion in the sampler. The well was permanently abandoned on 7
Sept General Wildcat well 2/7-16 was drilled on a
structure on a broad terrace to the south of Edda field and with a geological
environment similar to Edda. The primary objective was to test the potential
for hydrocarbon production from Danian and Late Cretaceous Limestones on a low
relief structural closure. Secondary objective was a possible stratigraphic
trap potential in Early Cretaceous sandstones. Operations and results Well 2/7-16 was spudded with the
semi-submersible installation Nortrym on 20 March 1980 and drilled to TD at
4818 m in the Early Cretaceous Ågard Formation. The well was drilled with
Seawater/Native Solids mud down to the 13 3/8" casing point at 1523 m,
with Seawater/Lignosulphonate from 1523 m to the 9 5/8" casing point at
3794 m, and with Calcium chloride/Sodium chloride XC polymer mud from 3794 m to
TD. Hydrocarbon shows were encountered in the
Danian and Upper Cretaceous limestone. The porosity was poorly developed and
testing verified the zones to be non-productive. Early Cretaceous had shows in
limestones, claystones, shales, and marls, but no sandstones were found. Thirteen conventional cores were cut
continuously from 3182 m to 3402 m in the Ekofisk and Tor Formations
Formations. Twenty-five RFT measurements were attempted in the gross interval
3823.8 - 4783.6 m. A fluid sample was obtained at 4587.9 m. It contained 50 ml
formation water and 39 cubic feet (1.1 Sm3) gas. The well was permanently abandoned on 12
July 1980 as a dry well with shows. Testing Two drill stem tests were conducted. DST
1 at 3279.7 to 3288.8 m in the Tor Formation produced 660 barrels (105 m3) of
water /day, with traces of oil and gas. DST 2 from the intervals 3193.1 -
3199.8 and 3201.4 - 3215.4 m in the Ekofisk Formation produced 28.8 barrels
(4.6 m3) water /day with no oil or gas before acid treatment. Well died
completely after acid, with only a very weak flow of acid gas. General Well 34/7-2 was drilled just north of the
Tordis Øst discovery in the northern North Sea. The main objectives were to
test for hydrocarbons in the Jurassic Statfjord Formation and in the Triassic
Lunde Formation. Operations and results Wildcat well 34/7-2 was spudded with the
semi-submersible installation Treasure Saga on 2 September 1984 and drilled to
TD at 2475 m in the Late Triassic Lunde Formation. A total of 83 hours rig time
was NPT due to repairs resulting from a failed RIH with the 26" bit after
underreaming to 816 m, and a leak in the acoustic system discovered after
setting the 9 5/8" casing at 2031 m. The well was drilled with seawater
and hi-vis pills down to 848 m, with KCl/polymer mud from 848 m to 2042 m, and
with lignosulfonate mud from 2042 m to TD. No shallow gas was encountered. Except for the sandy Utsira Formation and
two sandstone units in the Hordaland Group (in the order of 40 - 50 m each) the
well proved mainly claystones down to the Statfjord Formation at 2152 m. At BCU
(2085 m) there was a major hiatus from Pliensbachian to Campanian. The Lunde
Formation was encountered at 2271 m. The gross thickness of the Statfjord in
this well is 119 m with 43.5 m of net sand. The well drilled some 204 m into
the Lunde Formation, which in the upper part proved a siltstone sequence with
minor sandstone and claystone, while the lowermost 117 m proved a sequence of
sandstones alternating with claystones. Of this sequence some 41.3 m could be
considered as net. No live hydrocarbons were encountered by the well. Residual
oil was found in base Amundsen - top Statfjord Formations, however, cores showed
low porosity and essentially no net sand. Ex General Exploration well 16/8-2 is located in the
Ling Depression south of the Utsira High and North of the Danish Norwegian
Basin. The primary target was Late Jurassic sandstones; secondary target was
the Danian/Late Cretaceous limestones and Rotliegendes/Devonian sandstones. Operations and results Well 16/8-2 was spudded from the
semi-submersible installation Sedco H on 3 April 1980 and drilled to TD at 3585
m in Late Permian Zechstein evaporites. The well was drilled with bentonite and
seawater down to 542 m, with a Spersene lignosulphonate/gypsum/CMC mud from 542
m to 2275 m, and with a salt saturated Drispac polymer/XC polymer/Polysal
starch mud from 2275 m to TD. Down to the setting of the 13 3/8"
casing, the well progressed as programmed. However, the absence of the Triassic
and the appearance of the Zechstein evaporites much shallower than expected
caused the 9 5/8" casing to be set 474 metres higher than programmed. The
drilling of the 8 1/2" hole commenced with a 1.45 SG salt saturated mud as
programmed. Two runs with a turbine/Stratapac bit were made. However, on
pulling out of the hole from 3519 m, tight hole was encountered and while
attempting to work through this section, the drill string parted leaving 32.81
m of BHA at a depth of 3462 m. On running in with an overshot, the well was
observed to be flowing. It was shut in but pressure continued to increase even
after the appropriate mud weight increases had been effected. The mud weight
was eventually raised to 2.03 SG creating a fine balance between sufficient
fluid density and exceeding fracture pressure. The influx (thought to be from a
Carnallite zone at approximately 3513 m) had an adverse effect on the mud
properties causing the barite to settle out and reducing the pH to an acidic
level. The magnesium and calcium sensitive Drispac polymer was replaced with
the more tolerant 'XC Polymor1 to maintain the barite in suspension, and an
inhibitor was General Well 31/4-7 was drilled on the southernmost
part of the Brage Horst, close to the junction between the Brage/Oseberg fault
and the Troll Fault. The primary objective was to test the hydrocarbon
potential and the internal stratigraphy on the Brage Horst compartment on the
western flank of the Brage Field. Neighbouring well 31/4-2 to the north on the
Brage Horst found live oil in two thin sandstones in the Brent Group, while
wells 31/4-3, 4, and 5 on the main Brage structure on the Bjørgvin Arch had
proved oil in the "Intra-Heather Sandstone Unit II" (Fensfjord
Formation). The well was planned to be drilled 50 m into the Statfjord Group at
2765 +/- 50 m. Operations and results Wildcat well 31/4-7 was spudded with the
semi-submersible installation Vildkat Explorer on 26 July 1984 and drilled to
TD at 2505 m in Late Triassic sediments of the Statfjord Group. No significant
problem was encountered in the operations. The well was drilled with gel/spud
mud down to 1000 m, with KCl/polymer mud from 1000 m to 1816 m, and with a
NaCl/polymer mud from 1816 m to TD. The well encountered hydrocarbon bearing
sandstones and siltstones in the Fensfjord Formation and in the Statfjord Group
sandstones. The Fensfjord Formation was poorly developed with sandstones
grading to siltstones followed by siltstones. It was found gas bearing over the
interval 2026 - 2056 m with a calculated net pay of 8 m, an average porosity of
20.5% and an average water saturation of 45%. The Statfjord Group came in at 2384
m and was found oil bearing down to the OWC at 2406 m. It consisted of fine to
coarse sandstones. The net pay was calculated to be 12.5 m with a calculated
average porosity of 22.2% and an average water saturation of 42.3%. General Well 31/2-3 was drilled in the Troll West
area, approximately 8 km NNE of the Troll Discovery well 31/2-1. The well was
drilled to appraise the Troll Discovery. It should evaluate reservoir
parameters along the axis of maximum gross hydrocarbon column; prove maximum
hydrocarbon reserves in the major northern fault block; confirm the
significance of the seismic flatspot as a direct hydrocarbon indicator; further
assess the significance of the oil shows found in 31/2-1; and evaluate the
influence of earlier Kimmerian fault movements on reservoir characteristics. Operations and results Appraisal well 31/2-3 was spudded with
the semi-submersible installation Borgny Dolphin on 28 March and drilled to TD
at 2601 m in Late Triassic sediments in the Statfjord Formation. Drilling took
115 days. The reason for the long drilling period was safety inspection of the
rig as a result of the "Alexander Kielland" accident and a strike
amongst the Norwegian rig crew. The well was drilled with bentonite and
seawater down to 816 m and with a gypsum/lignosulphonate mud from 816 m to TD. No potential reservoir zones were
encountered above top Jurassic. The well confirmed that the Late Jurassic
sandstone reservoir encountered in wells 31/2-1 and 2 was well developed also
in this more northerly part of the structure. A gross gas column of 189 m was
penetrated with top at 1384 m. The uppermost 120 m was in a good clean sand
(Sognefjord Formation) while the lower part of the gas column was in a
micaceous and poor reservoir sand (Heather and Fensfjord Formations). Below the
gas a 12 m thick oil zone was encountered, the same thickness and at the same
level as in well 31/2-2. In this well however, the oil was in a very micaceous
and poorly developed reservoir. The reservoir was uncomformably overlain by
Palaeocene claystones, which thus act as an effective seal for the reservoir.
Below the OWC at 1585 no moveable hydrocarbons were seen in th General The Flyndre (1/5-1) well was drilled on a
structural high situated in the Feda Graben of the North Sea close to the UK
border. At the commencement of the well the principle objective horizons were
the Paleocene and Jurassic sand sections which had produced oil in the UK 30/13-2
well and the NO 2/7-3 wells respectively. It was estimated that at Paleocene
depth the structure was an irregular dome about 4 miles in diameter, with 12 square
miles of closure and 290 ft (88.4 m) of vertical relief while at Jurassic depth
the structure was a NW-SE trending anticline 4.5 miles by 3.5 miles with 12
square miles of closure at 190 ft (57.9 m) of vertical relief. Planned TD was
15000 ft (4572 m), Triassic sands, or the Zechstein Group, whichever came
first. Operations and results Wildcat well 1/5-1 was spudded with the
semi-submersible installation Ocean Viking on 12 October 1973. The well was
drilled to 491 m in the Nordland Formation. When running 20" casing the
casing got stuck. After an unsuccessful fishing operation the well was permanently
abandoned on 19 October 1973 as a junk well. No cores were cut and no wire line
fluid samples were taken. Replacement well 1/5-2 was spudded 15 m
away in a 320 deg true direction. Testing No drill stem test was performed. General The Flyndre well (1/5-2) was drilled on a
structural high situated in the Feda Graben of the North Sea close to the UK
border. The principle objective horizons were the Paleocene and Jurassic sand
sections which had produced oil in the UK 30/13-2 well and the NO 2/7-3 wells. It
was estimated that at Paleocene depth the structure was an irregular dome about
4 miles in diameter, with 12 square miles of closure and 290 ft (88.4 m) of
vertical relief while at Jurassic depth the structure was a NW-SE trending
anticline 4.5 miles by 3.5 miles with 12 square miles of closure at 190 ft (57.9
m) of vertical relief. Planned TD was 15000 ft (4572 m), Triassic sands, or the
Zechstein Group, whichever came first. Operations and results Well 1/5-2 was spudded on 19 October
1973, 15 m away from the original Flyndre well 1/5-1, which was junked at 491 m
for technical reasons. Well 1/5-2 was drilled with the semi-submersible
installation Ocean Viking. Total depth was set at 4287 m in Late Permian Zechstein
salt. The well was drilled with seawater and hi-vis pills down to 494 m. The
rest of the well was drilled with lignosulphonate mud. The well had shows throughout the
Paleocene and Late Cretaceous sections and four drill-stem tests were carried
out. The top sand in Paleocene at 2832 m (Forties
Formation sand) produced oil upon testing. Mud log shows were present in the
Danian, but testing proved the section to be tight and unproductive. A thick Late
Cretaceous section was encountered with oil shows at the top of the Maastrichtian
(Tor Formation) and in the Campanian (Lower Tor and Hod Formation) sections. Drill-stem
t General Wildcat well 1/6-1 is located ca 15 km
northwest of the Ekofisk Field in the southern Norwegian North Sea. It was
drilled in a crestal position on a large chalk structure shared between Norske
Shell's block l/6 and Phillips' block 2/4, the Ekofisk block. Phillips
participated in drilling this well on a 50/50 basis. The primary objective was
to investigate Danian and Maastrichtian chalk prospects. Secondary objective
was to evaluate possible sand developments in the Paleocene and the Lower
Cretaceous or older units. Planned total depth was 4572 m (1500 ft). Operations and results Well 1/6-1 was spudded with the jack-up
installation Zapata Nordic on 10 July 1972 and drilled to TD at 4822 m in the
Late Permian Zechstein Group. No major technical problems were encountered in
the operations and the drilling of this deep well was within the prognosed time
schedule. The drill string stuck at 228 m. After working the string and
spotting pipe-free/diesel the string came loose. Some highly porous limestone
intervals (1 - 8 m thick) resulted in lost circulation problems. The pipe stuck
at 3456 m, but was freed after spotting with pipe-free/diesel. The well was
drilled with seawater down to 448 m, with seawater/lignosulphonate and a shale
inhibitor (shalock) from 448 m to 1586 m, and with
seawater/lignosulphonate/ligcon (caustisized lignite) from 1586 m to TD. Reservoir development was encountered
only in the Chalk Formations, with hydrocarbon-bearing intervals being
developed in both the Danian and Late Cretaceous. Four hydrocarbon-bearing
intervals were encountered and tested within the Chalk, but only one zone in
the Maastrichtian (Tor Formation), yielded commercial flows of gas and
condensate. Reservoir developments in the Danian (Ekofisk Formation) and
earlier Maastrichtian (Hod Formation) were found to be considerably less
favourable in l/6-l than in the adjacent Ekofisk and West Ekofisk field. The
Early Cretaceous (Valanginian) w General Well 1/6-2 was drilled between the
Albuskjell and Flyndre Fields in the Feda Graben of the North Sea. The primary
objective was to evaluate the Danian and Maastrichtian Chalk prospects (Ekofisk
and Tor Formations) of a prominent diapiric domal structure. The well was
placed on the flank of the structure. Operations and results Wildcat well 1/6-2 was spudded with the jack-up
installation Zapata Nordic on 28 November 1972 and drilled to TD at 3383 m in
the Late Cretaceous Hod Formation. Some downtime recorded in the top hole was
due to a defect 20" casing shoe and bad weather, otherwise operations went
forth without significant problems. The maximum deviation down to 3226.6 m was
3.5 deg. The well was drilled with Sea water and viscous mud down to 460 m,
with Shaletrol mud from 460 m to 2445 m, and with Unical mud from 2445 m to TD. In the Tertiary shale sequence potential
reservoirs were limited to a few very thin (0.5 m or less) limestone or
dolomite streaks. Top of the Chalk was encountered at 3024 m. The reservoir
development in the Chalk was rather poor throughout, with the exception of a
zone of ca 12 m in the Danian Ekofisk Formation having a porosity of about 26%.
The Chalk formations were entirely water bearing as seen on the logs. However,
weak hydrocarbon indications were observed in the Chalk (namely weak
fluorescence and occasional slight oil staining), and relatively more abundant
indications of oil staining and dead oil traces were recorded in the overlying Tertiary
shales and interbedded carbonate layers. One core was cut from 3226.6 m to 3241.5
m in the Tor Formation. The core confirmed the generally dense nature of the
Chalk in this section. No wire line General Well 1/6-3 is located on the Albuskjell
Field in the southern Norwegian North Sea. The primary objective was appraisal
of reservoir development in the western part of the Albuskjell field. A Danian
- Maastrichtian gas condensate field had previously been confirmed by two wells
(A/S Norske Shell l/6-l and Phillips 2/4-9) drilled farther east along the WNW
- ESE trending structure. Secondary objectives were to investigate Danian Chalk
prospect and possible deeper prospects. Operations and results Appraisal well 1/6-3 was spudded with the
jack-up installation Zapata Nordic on 12 April 1974. Three sidetracks had
finally to be drilled, of which the second and deepest reached 3343 m in the
Late Cretaceous Tor Formation. The first sidetrack was kicked off at 314 m
after unsuccessful fishing (lost hole opener). The second sidetrack was kicked
off at 3022 m when it was realised that a core point had been missed so that a
Danian porous zone and 37 m of Maastrichtian had not been cored. Lost circulation
and stuck pipe led to the third side track, which was kicked off at 2995 m.
Further lost circulation problems and the discovery that there was a break in
the casing at 3140 m finally led to abandonment of the well without
investigating the deeper prospects. The well was drilled with seawater down to
417 m, with shale-trol/lignosulphonate from 417 m to 1221 m, with
shale-trol/lignosulphonate and lime from 1221 m to 2500 m, and with
lignosulphonate and lime from 2500 m to TD. A diesel/pipe lax pill was spotted
at 314 m. As prognosed, gas was encountered both in
the Danian and Late Maastrichtian Chalk. Hydrocarbons were present from Top
Ekofisk at 3110 m down to an OWC at 3289.7 m in the Tor Formation. The net
thicknesses were respectively 91 and 45 m. The great thickness of the Danian
reservoir was in contrast to the findings from wells l/6-l and 2/4-9, where
only a thin hydrocarbon-bearing zone was present in an otherwise tight Danian. General Well 1/6-4 was drilled in the southernmost
part of the Breiflabb Basin in the North Sea. The objective was to evaluate a
large low relief base Tertiary - Late Cretaceous structure with potential
reservoirs both in the Danian - Late Cretaceous Chalk and in the Paleocene
Sands. The primary target was the Chalk (Ekofisk and Tor formations). Operations and results Wildcat well 1/6-4 was spudded with the
semi-submersible installation Chris Chenery on 29 December 1975 and drilled to
TD at 3810 m in the Late Cretaceous Tor Formation. The drilling of 1/6-4 was
beset with rig mechanical problems, most notably failures in the mooring system
induced by adverse North Sea weather. All in all 34 days (ca 33%) of the total
rig time on the well was counted as down time. The well was drilled with bentonite/seawater
spud mud down to 437 m and with lime/Drispac/seawater mud from 437 m to TD. Top Rogaland Group, Balder Formation,
came in at 3110 m. A Paleocene sandstone, Andrew Formation was penetrated from
3197 to 3253 m. Top Shetland Group, Ekofisk Formation, came in at 3374 m. The Balder
Formation (Tuff marker) had some residual hydrocarbons up to 30%. This was
substantiated by gas readings and some shows of fluorescence in ditch cuttings.
The underlying Andrew Formation sandstones were found 100% water-bearing. Both the
Danian and Maastrichtian were fully water bearing based on petrophysical
analyses. This was in agreement with the lack of oil/gas shows while drilling
in this section. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 9
April 1978 as a dry well with shows. General Well 1/9-1 was drilled on a salt diapir
structure located in the Feda Graben in the southern North Sea. The primary objective
was to test hydrocarbon accumulations in the Danian and Late Cretaceous chalk. A
secondary objective was to test the Jurassic and Triassic sandstones. Operations and results Wildcat well 1/9-1 was spudded with the
semi-submersible installation Ross Rig on 14 October 1976 and drilled to TD at
3706 m in Cenomanian age limestone (Hidra Formation). The Jurassic was not
reached. The anchor chain broke on three occasions. The third breakdown occurred
during the last DST. The decision was then made to suspend the well for later
re-entry. The well was drilled with seawater and gel slugs down to 433 m, and
with seawater-lime-lignosulphonate from 433 m to TD. The Danian chalk (Ekofisk Formation) was
reached at 3043.5 m just below a marl section. It consisted of two hydrocarbon
bearing zones. Zone 1 from 3043.5 m to 3071.5 m and a tighter zone 2 from 3071.5
m to 3103.5 m. Maastrichtian (Tor Formation) starts at about 3103.5 m and is
also hydrocarbon bearing with water saturations below 50% down to 3141.5 m. A
transition zone with gradually increasing water content is seen from 3134.0 m
down to 3182.5 m. Apart from in the oil bearing reservoirs weak oil shows on minor
sandstones were recorded in the interval 2947 to 2958 m; weak to good oil shows
were seen on limestone in the interval 3300 m to 3500 m; and finally weak oil
shows were seen occasionally from 3645 m to 3675 m. The chalk section was cored in 11 cores from
3048 m to 3235.5 m (Ekofisk and Tor formations) and one core (core no 12) from
3327.2 General Well 1/9-2 was drilled on a salt diapir
structure located in the Feda Graben in the southern North Sea. It was drilled
to confirm and further evaluate the proven hydrocarbons found on this seismic
structure by the 1/9-1 well. Operations and results Appraisal well 1/9-2 was spudded with the
semi-submersible installation Ross Rig on 1 June 1977 and drilled to TD at 3459
m in the Late Cretaceous Hod Formation. No significant problems were
encountered in the operations. The well was drilled with spud mud down to 439 m
and water based with lime/Drispac/lignosulphonate mud systems from 438 m to TD. Good oil show was observed in a thin
sandstone stringer at 1632 m in the Hordaland Group. Oil in cuttings was
recorded also at 1710 m and 2858 m in claystones. The Ekofisk Formation was
encountered at 3120 m with shows and tested small amounts of oil. The Tor Formation
came in at 3195 m with shows and tested small amounts of oil. Below 3213.5 m
only rare and weak fluorescence was observed on limestone. The interval 3135-3215 in the Ekofisk and
Tor formations was cored with nearly 100% recovery. RFT pressure readings were attempted
in the Tor and Ekofisk formations, but all were unsuccessful due to tight
formation. No fluid samples were taken. The well was permanently abandoned on 12
August 1977. The poor results from DST are classified as shows. Testing Two drill stem tests were carried out. DST 1 tested the Maastrichtian Tor
Formation (3197 - 32 General Well 1/9-3 is located in the Feda Graben,
close to the UK border southwest in the Norwegian North Sea. The primary
objective of the well was to evaluate the Jurassic sandstones. The secondary
objective was to appraise and test the hydrocarbon bearing zones of Danian and
Maastrichtian age (Shetland Group) encountered in 1/9-1. The well was drilled
in two phases, of which Phase I is well bore 1/9-3 and Phase II is well bore
1/9-3 R. This procedure was a requirement from the Norwegian Petroleum
Directorate since Dyvi Gamma came directly from the yard and had therefore not
accumulated the experience needed to drill the high pressure Jurassic well to a
planned TD of 5000 m. Phase II was to be drilled with the rig Dyvi Beta. Operations and results Wildcat well was spudded with the
semi-submersible installation Dyvi Gamma on 13 August 1977 and drilled to TD at
27871 m in the Hordaland Group. The progress of the drilling was very much
delayed due to technical problems on Dyvi Gamma. As a result, also hole
problems were increased due to very long exposure in open hole condition. Due
to these problems the well bore was terminated after setting the 13 3/8"
casing instead of the plan, which was to drill down to the 9 5/8" casing
point. The well was drilled with seawater and gel all through. Several thin sand beds were penetrated in
the Hordaland Group between 1610 m and 1737 m. Oil shows were recorded in the
uppermost of these, from 1610 m to 1625 m. No cores were cut and no wire line fluid
samples taken in the well bore. The well was suspended as dry on 27
November 1977. Testing No drill stem test was performed General Well 1/9-3 is located in the Feda Graben,
close to the UK border southwest in the Norwegian North Sea. The primary
objective of the well was to evaluate the Jurassic sandstones. The secondary
objective was to appraise and test the hydrocarbon bearing zones of Danian and
Maastrichtian age (Shetland Group) encountered in 1/9-1. The well was drilled
in two phases, of which Phase I is named 1/9-3 and Phase II is named 1/9-3 R.
This procedure was a requirement from the Norwegian Petroleum Directorate since
Dyvi Gamma came directly from the yard and had therefore not accumulated the
experience needed to drill the high pressure Jurassic well to a planned TD of
5000 m. The re-entry 1/9-3 R was to be drilled with the rig Dyvi Beta. Operations and results Well 1/9-3 was re-entered (1/9-3 R) with
the semi-submersible installation Dyvi Beta on 27 May 1978 and drilled to TD at
4570 m in the Late Jurassic Haugesund Formation. When running the 9 5/8"
casing problems occurred with stuck pipe. This resulted in severe delays, but
the casing was landed at planned depth. In the 8 1/2" hole the progress
was delayed due to hole problems with high pressure and mud weight combined
with lost returns. Tight hole and stuck pipe occurred on several occasions. Max
mud weight was 2.04 g/cm. The well was drilled water based, but with several
additions of diesel from 9 5/8" casing depth and downwards, resulting in 1
- 12 % diesel in the mud at all times below 3835 m. Several problems arose during the logging
operations, which in the end resulted in a poor suit of logs over the
reservoir. In summary the problems were due to
uncontrolled stretch in the logging cable, generally poor log quality,
especially for FDC/CNL logs, and difficult hole conditions with high pressure/temperature
and excessive sticking. Logs that normally are run in combination had to be run
separately. This made petrophysical evaluation difficult, and several General Well 1/9-4 was drilled on a salt diapir
structure in the Central Graben in the neighbourhood of the Norwegian - UK
median line. The primary purpose was to test the Ekofisk and Tor formations of
Danian and Maastrichtian age. Lower possible porous zones in chalk and Jurassic
sands, if present, were secondary objectives. Operations and results Wildcat well 1/9-4 was spudded with the
semi-submersible installation Ross Rig on 13 August 1977 and drilled to TD at 3710
m in Late Permian Zechstein salt. There were no serious drilling problems down
to a depth of 3100 m. At 3100 m the bit-junksub assembly was lost in the hole. The
hole was cemented back and sidetracked after the fishing attempts proved
unsuccessful. After one unsuccessful sidetrack attempt the hole was sidetracked
again from 3041 m and drilled on to core point at 3122 m. When cutting core no 10
the bottom hole assembly got stuck and a long section of the BHA had to be left
in the hole. After some unsuccessful attempts on jarring, the hole was cemented
and sidetracked again, from 3059 m in the first sidetrack hole. This second sidetracked
hole was drilled to a measured depth of 3353 m. At this point 7" liner was
run. 6" hole was drilled to a total measured depth of 3710 m with only
minor problems and top of the salt was found at 3650 m. The 6" hole was
logged and plugged back. It was found necessary to perform a squeeze job around
the 7" liner shoe, but when attempting to pull out after this operation,
the BHA stuck just above the cementing stinger. Jarring did not free the pipe,
and a cement plug was set above the fish. The well was drilled with high
viscosity spud mud of pre-hydrated bentonite, lime, and caustic soda down to
437 m and with Drispac/lime mud from 437 m to 2580 m. From 2580 m the lime was
phased out and the remaining well to TD was drilled with a
lignite/lignosulphonate gel mud. During abandonment an anchor chain broke in
severe weather. Th General Well 1/9-5 was drilled in the Feda Graben
in the southern North Sea, in the saddle between the Tommeliten Gamma-structure
and the intrusive salt plug forming the Tommeliten Delta structure. The purpose
of the well was to appraise the Tommeliten Gamma discovery made by 1/9-4 and to
test the hydrocarbon potential and reservoir quality of the Ekofisk and Tor
formations. Operations and results Appraisal well 1/9-5 was spudded with the
jack-up installation Dyvi Beta on 3 October 1978 and drilled to TD at 3450 m in
the Late Cretaceous Hod Formation. The pipe got stuck at 3426 m during a
clean-up trip. When trying to come loose the hook broke and the drill string
dropped in the hole. This event caused material damage and rig shut-down for
three days, but nobody was injured. When fishing the drill string it came loose
above the jar but the rest of the BHA (approximately 260 m) was left in the
hole. The well was drilled with spud mud down to 435 m, with a lime/"Morex"
mud system from 435 m to 1377 m, with lime/"Morex"/Drispac mud from
1377 m to 2725 m, and with lignosulphonate/lignite mud from 2725 m to TD. A lot
of hole problems occurred in the 17 1/2" and 12 1/4" sections and
this was attributed to the lime/"Morex" mud system. The Ekofisk Formation came in at 3207 m
and the Tor Formation at 3282 m. No significant hydrocarbon shows were
encountered in any section of the well. One core was cut from 3215.5 to 3 233.5 m,
proving a dry carbonate section. No wire line fluid samples were taken. The well was permanently abandoned on 16
December 1978 as a dry well. General Well 2/1-1 was drilled on the Cod Terrace
on the eastern margin of the Central Graben of the North Sea. The objectives
were Danian - Late Cretaceous limestones and possible Jurassic sandstone. Operations and results Wildcat well 2/1-1 was spudded with the
jack-up installation Ocean Tide on 28 August 1972 and drilled to TD at 4178 m
in sediments believed to be of Late Jurassic age. The hole was drilled without
much problem down to TD in the 8 1/2" section at 3886 m where logs were run
and a 7" liner was set with shoe at 3885 m. A 5 7/8" hole was drilled
to 4178 (TD) where the well kicked and the pipe got stuck. During killing
operations returns were lost and circulation could not be re-established. The
kick was most likely caused by a salt water flow from a Late Jurassic sand
lense. When trying to back off the drill pipe twisted off, leaving a 340 m fish
in the hole. A cement retainer was set and the well was plugged back to 3789 m.
Hence, no logs were run below 3886 m. Oil shows (dull gold fluorescence with
slow straw-yellow cut) were observed in the shales at the base of the Middle
Palaeocene and at the top of the Danian limestone (3124 - 3178 m), especially
at 3161 m where there was a good straw-yellow streaming cut (faster than the
upper intervals) accompanied by a minor gas peak. In the lower part of the
Maastrichtian limestone gas peaks with 10% C2+ components appeared. Oil shows
were recorded in limestone horizons in the Campanian and in the Berriasian.
Weak fluorescence was observed also in thin sandstone lenses in the Late
Jurassic, above the kick-sand at TD. A core was cut from 3165.3 to 3179.1 m
(10385 to 10430 ft) in the Danian limestone (Ekofisk Fo General Well 2/1-2 is located on the Sørvestlandet
High, ca 6 km northwest of the Gyda Field in The North Sea. The objective was
to test possible Late Jurassic sands within a salt-induced structural high. The well is Reference Well for the Mandal
and Ula Formations. Operations and results Wildcat well 2/1-2 was spudded with the
semi-submersible installation Nordskald on 14 December 1977 and drilled to TD at 3555 m, 15 m into Late Permian Zechstein anhydrite. The well was drilled
with seawater and gel down to 174 m, with Lime Drispac from 174 m to 3135 m,
and with Lignosulphonate from 3551 m to TD. Fifty-two meter of Maureen Formation was
encountered at 2692 m, directly overlying the Tor Formation at 2743.5 m. The
Cromer Knoll Group came in at 3121.5 m, and top Jurassic shales (Mandal
Formation), at 3299 m. The Mandal Formation was seen as a potentially excellent
source rock for major oil, but was marginally mature on-structure. The well
penetrated water-bearing Late Jurassic sandstone (Ula Formation) at a depth of
3316 m. The sandstone was 30.5 m thick and had porosities of less than 10% and
permeabilities less than 1 md. The well then penetrated 37.5 m of argillaceous
Middle Jurassic sandstone and 156 m of interbedded Triassic sandstones and
siltstones with occasional mudstones. No shows were observed in the well while
drilling. One full hole core was cut within the Ula
Formation sandstone from 3318 to 3336 m. No wire line fluid samples were taken. The well was permanently abandoned on 26 February 1978 as a dry well. Testing No drill stem test was performed. General Well 2/1-3 was drilled on the Cod Terrace
on the margin between the southern Vestland Arch and the Central Trough in the
North Sea. The primary objective of the well was to test Late Jurassic
sandstone within a fault sealed dip closure, against the downthrown side of a
westerly heading fault complex at the base of the Cretaceous. Triassic
sandstone was a secondary objective. Operations and results Wildcat well 2/1-3 was spudded with the
semi-submersible installation SEDCO H on 3 November 1979 and drilled to TD at
4297 in the Late Permian Zechstein Group. The well was drilled with Seawater
down to 625 m and with Lignosulphonate mud from 625 m to TD. Top of the Tyne Group, Mandal Formation,
was encountered at 3791 m, with the Late Jurassic sandstone at 3819.5 m. The
Late Jurassic sandstone reservoir was oil-bearing all through. The reservoir is
a 59.5 m thick homogeneous fine to medium grained sandstone with a porosity
from 15% to 22%. The sandstone grades into a well cemented argillaceous
siltstone below. No oil/water contact was established. Oil shows were recorded
in Tor Formation limestone at 3000 - 3005 m, throughout the Late Jurassic
reservoir sandstone, and in Middle Jurassic Bryne Formation sandstone at 4020
to 4040 m. Four cores were cut from 3823.0 to 3893.5
m in the Ula Formation reservoir sandstones. The well was permanently abandoned on 29
March 1980 as an oil discovery. Testing Three drill stem tests were performed in the
Late Jurassic sandstones.
wlbHistoryDateUpdated: 2017-05-23T00:00:00 General Well 2/4-8 was drilled on the crest of
the Tor Discovery structure in the southern Norwegian North Sea. The principal
objective was to confirm the thick Danian-Cretaceous productive section present
in the Amoco 2/5-1 well and to provide a means of evaluating the maximum
anticipated productive section in the Tor Discovery. Jurassic sandstone was
also defined as principal objective, while secondary prospects could exist in
Paleocene sands. Prognosed top Jurassic was at 3691 m (12110 ft) with planned
TD at 4572 m (15000 ft). Operations and results Appraisal well 2/4-8 was spudded with the
jack-up installation Zapata Explorer on 25 November 1971. The original spud
location was 56 deg 38' 15.6'' N, 03 deg 18' 48'' E. This hole was drilled to
570 m at which point the well kicked and bridged off. The drill pipe became
stuck at 486 m and the hole was abandoned with the top of fish at 323 m. The
rig was moved 120 meters east where the well was re-spudded and drilled to
final TD at 4078 m in the Permian Zechstein Group. The well was drilled with
seawater and hi-vis mud down to 488 m, with drill aid / DAP (di-ammonium
phosphate) mud from 488 m to 1623 m, with drill aid / gypsum mud from 1623 m to
2211 m, with drill aid from 2211 m to 2984 m, with a lignosulphonate mud from
2984 m to 3810 m, and with Drispac / salt saturated mud from 3810 m to TD.
Below 488 m 2 -6 % diesel was added to the mud. At 2946 m the well penetrated a 3 m fine
grained Paleocene sand with a calcite matrix. This sandstone exhibited a dull
yellow fluorescence and a slow cut. Danian chalk was encountered at 2985 m and
Late Cretaceous chalk was encountered at 3086 m. Gas and oil was tested from
the Danian - Late Cretaceous chalk. Continuous zones of oil shows were observed
on all cores down to 3203 m, below this depth shows were scattered. Twenty cores with a total recovery of 176
m core were cut in the interval 2985 to 3242 m in Danian and Late Cretaceous
General Wildcat well 2/4-9 was drilled on the
southeast flank of the Albuskjell structure, 6 km southeast of the Shell 1/6-1
well, which was drilled on the saddle in the middle of the structure. The
Danian Limestone was the expected pay zone, and if porosity was present, the
Late Cretaceous Limestone was also expected to be hydrocarbon bearing. Planned
TD was 3810 m (12500 ft). Operations and results Well 2/4-9 was spudded with the jack-up
installation Zapata Explorer on 13 August 1973 and drilled to TD at 3752 m in
the Late Cretaceous Hod Formation. The well was drilled and tested in 58 days,
without significant technical problems. Deviation surveys were carried out down
to 2448 m and the maximum deviation to this depth was 1.25 deg. The Danian limestone was encountered at
3214 m and the Late Cretaceous limestone at 3306 m. The Late Cretaceous
limestone yielded commercial oil and gas on two drill stem tests while the
Danian limestone yielded no commercial hydrocarbons. No cores were cut and no wire line fluid
samples taken. The well was permanently abandoned on 9
October 1973 as a gas and condensate appraisal. Testing Four DST's were carried out in the chalk,
DST 1 and 2 in the Late Cretaceous and DST 3 and 4 in the Danian. The results here
are after acidizing: DST 1 from 3360 - 3368 m flowed 121 Sm3 oil and 97700 Sm3
gas /day through a 96/64" choke. The oil gravity was 43 deg API and the
GOR was 801 Sm3/Sm3. DST 2 from 3308 to 3359 m and 3360 to 3368 m flowed 461
Sm3 oil and 455900 Sm3 gas /day through chokes 20/64" + 24/64". The
oil gravity was 44 deg API and the GOR was 977 Sm3/Sm3. DST 3 from 3274 - 3283
m and DST 4 from 3222 - 3225 flowed only small amounts of water with traces of
oil. General Wildcat well 2/4-10 was drilled on an
anticlinal structure, 4.8 km long and 2.4 km wide, lying approximately 8 km
northwest of the centre of the Tor Field. The Danian limestone was the expected
pay zone, and if porosity was present, the Late Cretaceous Limestone could also
be hydrocarbon bearing. Prognosed top Danian was at 3139 m (10300 ft) with
planned TD at 3414 m (11200 ft). Operations and results Well 2/4-10 was spudded with the jack-up
rig Zapata Explorer on 13 October 1973 and drilled to TD at 3418 m in the Late
Cretaceous Tor Formation. The well was drilled and tested in 69 days, without
significant technical problems. Deviation surveys were carried out down to 2451
m and the maximum deviation to this depth was 2 deg. The well was drilled with
salt-water gel and Flosal down to 497 m, with Shale Trol from 497 to 2015 m,
with Unical (chromium-lignosulphonate) from 2015 m to 2819 m, and with Unical
and Ligcon (caustisized lignite) from 2819 m to TD. Top Danian limestone was encountered at
3162 m and top Late Cretaceous limestone at 3293 m. The Danian Limestone tested
only small amounts of water and no oil, after acidization, on two drill stem
tests. The Late Cretaceous Chalk produced oil, but with a very low GOR, and
with a high amount of water, which made its commerciality questionable. These
fluid characteristics were furthermore very different from the 2/4-7 fluids
(Tor discovery) and indicated 2/4-10 to be on a separate structure from the Tor
Field. No cores were cut and no wire line fluid
samples taken. The well was permanently abandoned on 20
December 1973 as an oil discovery Testing Six DST's were conducted: DST 1 and DST 2
in the Late Cretaceous and DST 3 to DST 6 in the Danian limestone. The results
given here are after acidization: DST 1 from 3304 - 3322 m flowed 583 Sm3 oil,
275 m3 water, and only 1150 Sm3 gas /day through a 24/64" choke. The oil
gravity was General Wildcat well 2/4-11 should evaluate the
southern part of a northwest-southeast trending seismic high about 3.2 km long
and 2.4 km wide. The well was drilled just south of the boundary between blocks
2/1 and 2/4 about two km southeast of the 2/1-1 well. The objective formations
were the Danian-Late Cretaceous limestone in addition to sandstones of the
Jurassic, which had gas and condensate shows in the 2/1-1 well. Top Paleocene
was anticipated at 2972 m (9750 ft), top Danian at 3078 m (10100 ft), top Late
Cretaceous at 3277 m (10750 ft), and top Jurassic at 3962 m (13000 ft). Planned
TD was at 4267 m (14000 ft). Operations and results Well 2/4-11 was spudded with the jack-up
installation Zapata Explorer on 25 December 1973 and drilled to TD at 4281 m in
the Late Permian Zechstein Group. Running 7" casing at 3838 m, the casing
could not get passed 3019 m. Pulling out of hole the casing stuck when 20
stands were left. Eleven days were spent working on the fish before it came loose.
The hole was reamed and casing was set. Maximum hole deviation down to a depth
of 2757 m was 4.75 deg, at 149 m. The well was drilled with spud mud (Seawater
gel and Flosal) down to 321 m, with Shale Trol mud from 321 m to 2265 m, and
with a Lignosulphonate mud (Unical and Ligcon) from 2265 m to TD. Below 792 m
one to four percent diesel was added to the mud. Top Paleocene was found at 2936 m, top
Danian limestone at 3146 m, top Late Cretaceous limestone at 3268 m, top Early
Cretaceous was found at 3782 m, top Late Jurassic (Kimmeridgian) at 3968 m, and
top of the Permian was encountered at 4211 m. Sub-commercial amounts of oil was
tested from the Danian and even smaller amounts from the Late Cretaceous. The
Jurassic section penetrated consisted of shale, claystone, and siltstone and
contained no reservoir rocks. Source rock analyses of sidewall cores
from the Jurassic showed TOC in the range 0.6 - 2% and vitrinite reflection
from 0.78 General Well 2/4-12 was drilled on a location ca
3 km west of the Ekofisk Field. The primary objective was to test the chalks in
the Late Cretaceous and Early Paleocene. Operations and results Wildcat well 2/4-12 was spudded with the
semi-submersible installation Ocean Viking on 28 July 1975 and drilled to TD at
3383 m in the Late Cretaceous Tor Formation. No significant problems were
encountered in the operations. The well was found dry. There were no
shows while drilling and electric logs showed low porosities and high water
saturations. Five cores were cut. Core 1 was cut in the basal part of the Våle
Formation and topmost Ekofisk Formation. Cores 2 and 3 were cut in the Ekofisk
Formation, and cores 4 and 5 in the Tor Formation. No wire line fluid samples
were taken. The well was permanently abandoned on 8
September 1975 as a dry well. Testing No drill stem test was performed General Well 2/4-19 B was drilled on the Ekofisk
Field in the Southern North Sea. Operations and results Well 2/4-19 B was drilled from the Jacket
12 legs installation Ekofisk B. It was spudded on 16 December 1975 and drilled
to TD at 4605 m in Jurassic age sediments. The hole was lost below 3926 m (the
7" casing shoe, in Early Cretaceous) after logging. The well penetrated top Jurassic at 4061
m. The whole of the Jurassic section penetrated was mainly claystone, shale and
limestone. Four cores were cut: core 1 from 2974 to 2992.5 m, core 2 from
3102.7 to 3113.8 m, and cores 3 and 4 from 3144.3 m to 3159.7 m. No wire line
fluid samples were taken. The well was plugged back to 3449 m and
re-classed to development well. It was permanently abandoned 15 March 1976. Testing The well was tested from perforations at
3006.5 m to 3009.6 m in the Danian Ekofisk Formation. Bottom hole samples were
taken, but no flow measurements were conducted. The DST temperature was 110 deg
C, measured at 2840.7 m General Well 2/5-3 was drilled ca 8 km southeast
of the Tor Field. The primary target was top Danian chalk. Secondary targets
were top Paleocene and base chalk at 3551 m (11650 ft). Planned total depth was
3597 m (11800 ft). Operations and results Well was spudded with the jack-up
installation Zapata Explorer on 2 April 1972 and drilled to TD at 3731 m in the
Late Permian Zechstein Group. Top Paleocene was encountered at 2929 m,
top Ekofisk Formation at 3037 m, top Tor Formation at 3121 m, and top Hod
Formation at 3481 m. First show was reported in a limestone stringer at 2259 m.
Occasional oils shows, in limestone stringers, were reported in the interval
2604 to 2877 m. The top 3 m of the Paleocene (Balder Formation) was silty and
had good oil shows. Oil was found by drill stem testing in the Ekofisk and Tor
Formations. Shows continued down to 3261 m in the Tor Formation. Fifteen conventional cores were cut in
the Ekofisk and Tor Formations, recovering a total length of 123.3 m core. The well was suspended on 15 June 1972 as
an oil discovery. Testing Three zones were drill stem tested. The
following results are after acidization: DST 1 tested the interval 3386 - 3395 m
in the lower part of the Tor Formation and flowed 21 m3 water /day. DST 2 tested the interval 3120 - 3191 m
in the upper part of the Tor Formation. Average flow parameters at maximum
choke, 40/64", was 682 Sm3 oil and 340400 Sm3 gas /day. The oil gravity
was 36 deg API and the GOR was 463 Sm3/Sm3. The GOR on smaller choke sizes was
significantly lower, down to 233 Sm3/Sm3 on a 16/64 "choke. DST 3 tested the interval 3053 - 3065 m
in the Ekofisk Formation and flowed on average 682 Sm3 oil and 141330 Sm3 gas
/day on a 32/64" choke. The water production during this flow decreased
from 57 to 17.5 m3 /day and the GOR decreased from 213 to 179 Sm3/Sm3. The oil
gravity was 38.2 deg A General Wildcat well 2/5-4 was drilled ca 21 km
southeast of the Tor Field in the southern Norwegian North Sea. The primary
targets were Paleocene prognosed at 2914 m (9560 ft), and Danian Carbonate
prognosed at 3011 (9880 ft). Operations and results Well 2/5-4 was spudded with the jack-up
installation Zapata Explorer on 3 November 1972 and drilled to TD at 3490 m in
the Late Cretaceous Hod Formation. No significant technical problems were
reported from the operations. The well was drilled with seawater and hi-vis mud
down to 395 m, with an XC polymer, Shale Trol mud from 395 m to 2743 m, and
with Chromium-lignosulphonate (Unical) / seawater mud from 2743 m to TD. From 1
to 6 % diesel addition was used all through. Top Paleocene (Balder Formation) was
encountered at 2928 m, top Danian chalk (Ekofisk Formation) at 3039 m, top
Maastrichtian chalk (Tor Formation) at 3131 m, and top Campanian chalk (Hod
Formation) at 3420 m. First show (appearance of C2+ on
chromatograph) was in shale at 2883 m. Thin sandstone stringers were penetrated
in the Paleocene section, but no shows were recorded in these. Oil shows were
recorded in the top of the Danian chalk at 3042 - 3063 m, in the top of the Tor
Formation at 3133 - 3167 m, and in the Hod Formation at 3435 - 3459 m. Oil was
confirmed by testing in the top of the Tor Formation. Five short cores were taken with the
Schlumberger core slicer. Core no 1 was taken at 3441.5 m in the Hod Formation;
cores no 2, 4, and 5 were cut at 3137.9 - 3159.6 m in the Tor Formation, and
core no 3 was taken at 3051.7 - 3052.6 m in the Ekofisk Formation. The cores
are no longer available from the NPD. No fluid sample was taken on wire line. The well was permanently abandoned on 31
October as an oil discovery. Testing Two drill stem tests were performed. The
following results are after acidizing: DST 1 tested the interval 3137 - 3170 in
the top of t General Well 2/5-5 was drilled ca 2 km southwest
of the 2/5-3 S ør øst Tor Discovery well in the southern Norwegian North Sea.
It was drilled to appraise the S ør øst Tor Discovery Operations and results Appraisal well 2/5-5 was spudded with the
jack-up installation Zapata Explorer on 9 December 1972 and drilled to TD at
3456 m in the Late Cretaceous Tor Formation. Top Paleocene was encountered at 3058 m,
top Danian chalk (Ekofisk Formation) at 3176 m, and top Maastrichtian chalk
(Tor Formation) at 3274 m. The only oil show reported above top Cretaceous was
in thin dolomite stringers at 2940 - 2950 m. Oil shows were recorded in the Tor
Formation from the top and down to 3383 m. Oil was confirmed by testing in the
Tor Formation. Two cores were cut in the interval 3284 -
3321 m in the Tor Formation. No wire line fluid sample was taken. The well was permanently abandoned on 9
February 1973 as an oil appraisal. Testing Three drill stem tests were conducted in
the Tor Formation. The following results are after acidizing: DST 1 tested the interval 3428 - 3437 m
in. At the end of the flow period only load water had come to surface and the
pressure had dropped to zero. DST 2 tested the interval 3355 - 3366 m.
After 31 hours flow only acid and water cushion was produced to surface. DST 3 tested the intervals 3297 to 3298 m
+ 3307 to 3308 + 3312.9 to 3313.5 m. This test produced 72 Sm3 oil, 12430 Sm3
gas, and 195 m3 water /day on a 64/64" choke. The GOR was 171 Sm3/Sm3 and
the oil gravity was 39.4 deg API. General Well 2/5-6 was drilled on the Siv
structure, only 800 m northeast of the 2/5-4 discovery well. The Siv structure
is a north-south trending anticline. The primary objective of well 2/5-6 was to
establish the possibility of Jurassic sands being present along the west side
of the Mandal High and to evaluate the hydrocarbon potential of these sands on
the Siv structure. Sands of this age had previously been encountered in the BP
block 7/12 further to the north. In addition, the well was planned to appraise
the Chalk reservoirs found to be oil-bearing by Amoco well 2/5-4. Operations and results Wildcat well 2/5-6 was spudded with the
semi-submersible installation Norskald on 14 May 1978 and drilled to TD at 4132
m in the Triassic Skagerrak Formation. A bentonite slurry used while drilling
the first two intervals, 30" casing was set at 166 m and 20" casing
at 540 m. The 17 1/2" hole was drilled using a seawater native solids mud.
Problems were encountered as casing point was approached, sloughing shale and
tight hole proved troublesome and the mud weight was increased to 10.6 lb/gal
before running 13 3/8" casing to 1852 m. The 12 1/4" hole was drilled
initially with a gypsum CMC mud. Tight hole was a significant problem until a
depth of approximately 2900 m. At 2950 m the mud was converted to a dispersed
lignosulphonate system to obtain more stable rheological properties. This mud
was used until a depth of 3967 m. Tight hole was experienced on trips at a
depth of 2000 m. The pipe was stuck at 3640 m and a fish was left in the hole.
The 9 5/8" casing was set above the fish at a depth of 3560 m and a
technical sidetrack was performed. The 8 1/2" hole was drilled using the
same mud to a depth of 3967 m. At this point, in a Middle Jurassic sand, a salt
water flow high in magnesium and calcium delayed operations considerably. The
mud was converted to a brine polymer type system and the mud weight was raised
to General Well 2/7-3, was drilled on the southern
compartment of the Eldfisk structure in the North Sea. The Eldfisk structure is
a NNW-SSE trending partly salt-related anticlinal structure located between the
Valhall and Embla fields to the south and the Ekofisk Field to the north. The
primary objectives were to test the Danian Limestone, and the possibility of
Jurassic sandstone development on the crest of the Eldfisk structure. Both
objectives were expected to be ca 120 m thick. The Late Cretaceous carbonate,
lower Cretaceous sandstones and Triassic sandstones were secondary objectives. Operations and results Wildcat well 2/7-3 was spudded with the jack-up
installation Orion on the 14 April 1972 and drilled to TD at 4359 m in the Permian
Zechstein Group. Note that the Daily Report records Decca final fix as 56° 23' 01.7"N,
03° 14' 44.6"E, 60 meters off desired location, while other parts of the Completion Report
seems to record the coordinates of the slightly different planned well location.
The well was drilled with seawater and hi-vis sweeps down to 482
m, with gypsum-CMC lignosulphonate mud from 482 m to 3195 m, and with salt
saturated gypsum-CMC lignosulphonate mud from 3195 m to TD. Between 482 m and
TD diesel was added to the mud. The Danian section was 90 m thick, highly
fractured, and yielded commercial quantities of oil. Logs and two drill stem
tests (DST 1 and DST 2) in the Late Cretaceous rocks indicated low porosity and
permeability. One hundred and fifty gross meter of Jurassic sandstones was
penetrated in the well. Log analysis indicated the sands are very shaly and
silty. Three of the sidewall cores from this interval were described as hard,
black shale and the fourth as a very calcareous sandstone. Although the logs
General Well 2/7-4 is located in the southern
part of the Norwegian North Sea and ca 10 km south east of the Ekofisk Field.
The primary objective was the Danian Chalk, expected to be 90 m thick and
possibly completely hydrocarbon bearing. Secondary objective was Late Cretaceous
carbonates, especially in the upper part, which could be oil bearing in
communication with the Danian. Planned TD was at 3353 m in the Late Cretaceous.
In the event that hydrocarbon shows were still evident at the proposed TD the
well would be deepened until potential productive zones were completely
penetrated. Operations and results Wildcat well 2/7-4 was spudded with the
semi-submersible installation Ocean Viking on 23 June 1972 and drilled to TD at
3356 m in the Late Cretaceous Tor Formation. The well was drilled without
significant problems. The "Danian Chalk" (Ekofisk
Formation) was encountered at 3096 m, and the Late Cretaceous Tor Formation at
3186 m. Both formations were oil bearing. DST's and logs indicate oil down to
3225 m, while the deepest test at 3291 - 3266 m produced water, some gas, and
trace oil. Oil shows were recorded on cores in the interval 3133 m to 3246 m. Twelve cores were cut from 3116 m to 3264
in the Ekofisk and Tor Formations. No wire line fluid samples taken. The well was permanently abandoned on 3
September 1972 on as an oil discovery. Testing Six DST's were conducted in the Ekofisk
and Tor Formations. Maximum production data after acid treatment follows: DST 1
tested the interval 3292 - 3266 m in the Tor Formation and produced 67 m3/day
water, 2800 Sm3/day gas, and trace oil. DST 2 tested the interval 3197 - 3234 m
in the Tor Formation and produced 1054 Sm3 oil and 273600 Sm3 gas /day on a
44/64" choke. The GOR was 260 Sm3/Sm3 and the oil gravity was 37.7 deg
API. DST 3 tested the interval 3149 - 3170 m in the Ekofisk Formation and
produced 200 Sm3 oil General Well 2/7-5 was drilled ca 4.5 km
north-northeast of the 2/7-4 well, which found oil in the Ekofisk and Tor
Formations, the Edda Discovery. The objective of the 2/7-5 well was to test the
Ekofisk and Tor Formations in order to appraise the extension of this
discovery. Operations and results Appraisal well 2/7-5 was spudded with the
semi-submersible installation Ocean Viking on 3 September 1972 and drilled to
TD at 3353 m in the Late Cretaceous Tor Formation. The well was drilled water
based with 3 - 6 % oil addition below 1217 m. The Ekofisk Formation was encountered at
3110 m, and the Tor Formation at 3205 m. Both formations appeared to be
hydrocarbon bearing, but the water saturation was high and the permeability was
generally low, which probably explained the low flow rates of the zones tested.
Eight conventional cores were cut in the
interval 3120 - 3158 m in the Ekofisk Formation, and another five cores were
cut in the interval 3219 - 3300 m in the Tor Formation. The cores were reported
to bleed gas and oil. Scattered shows (fluorescence) were observed from top of
the cored interval and down to 3285 m in the deepest core (core 13). No wire
line fluid samples were taken. The well was permanently abandoned on 1
January 1973 as a dry well with shows. Testing Several drill stem tests were conducted
in the limestone and chalk of the Ekofisk and Tor Formations. Many were
unsuccessful. Of the technically successful tests DST 1 from 3274 m to 3293 m
and DST 2 from 3225 - 3237 m flowed water. DST 3 from 3210 - 3219 m flowed
water with gas and trace of oil. DST 4 from 3160 - 3185 m and DST 5 from 3120 -
3130 m flowed minor amounts of gas and water. General Well 2/7-6, was drilled on the northern
part of the Eldfisk structure in the North Sea. The primary objective was to
test the Danian Limestone, and secondarily to test for possible further
hydrocarbons in the Late Cretaceous of the Eldfisk structure. Operations and results Wildcat well 2/7-6 was spudded with the semi-submersible
installation Ocean Viking on 31 March 1973 and drilled to TD at 3381 m in the Early
Cretaceous Cromer Knoll Group. The well was drilled with seawater and hi-vis sweeps
down to 488 m and with gypsum-lignosulphonate mud from 488 m to TD. Diesel was
added to the mud below 488 m. The Danian Ekofisk Formation and the
underlying Tor Formation were found oil bearing and tested to yield commercial
quantities of oil from top at 2911 m to 3078 m. No cores were cut and no fluid samples
were taken on wire line. The well was permanently abandoned on 8
June 1973 as an oil appraisal well. Testing Four drill stem tests were performed, two
in the Ekofisk Formation and two in the Tor Formation. DST1 tested the interval 2973 to 2987 m
and produced after acidization 46 Sm3 oil and 12400 Sm3 gas /day through a
96/64" choke. The GOR was 274 Sm3/Sm3, the gas gravity was 0.699 (air =
1), and the oil gravity was 36.6°API. DST2 tested the interval 3069 to 3078 m
and produced after acidization 158 Sm3 oil and 56900 Sm3 gas /day through a
96/64" choke. The GOR was 359 Sm3/Sm3 and th General Well 2/7-7, was drilled to appraise the southern
part of the Eldfisk structure in North Sea. The primary objective was to test
the Danian Limestone, expected to be about 120 m thick. Operations and results Appraisal well 2/7-7 was spudded with the
semi-submersible installation Ocean Viking on 2 January 1973 and drilled to TD
at 3084 m in the Early Cretaceous Rødby Formation. The well was drilled with seawater
and hi-vis sweeps down to 497 m and with gypsum/lignosulphonate mud from 497 m
to TD. 4-6% diesel additive was used below 497 m. The Danian Limestone was found to be
highly fractured, only3 0 m thick, and yielded commercial quantities of oil and
gas on one drill stem test. The Late Cretaceous, which was 195 m thick, was
also found to contain hydrocarbons, and yielded commercial amounts of oil and
gas on two out of three drill stem tests. The Danian Limestone and the upper
part of the Late Cretaceous were thinner than expected due to a fault throwing
Campanian on Turonian rocks. No cores were cut and no fluid samples
were taken. The well was permanently abandoned on 29
March 1973 as an oil appraisal. Testing Four intervals in the chalk section were
perforated and tested DST's 1 and 2 tested the interval 2911 to
2925. The interval gave a weak flow with headed oil + gas. The oil gravity was
measured to 36.2 °API. DST 3 tested the interval 2838 to 2905 m.
The interval produced after acidiz General Well 2/7-8 is located In the Feda Graben
of the southern North Sea, some 3 km west of the Eldfisk Field. It was drilled
on the East Eldfisk Structure, and the main objective was to test the Danian
Limestone. Secondary objective was to test the Late Cretaceous Chalk, which
could by hydrocarbon bearing if porosity is present. Operations and results Wildcat well 2/7-8 was spudded with the jack-up
installation Zapata Explorer on 8 June 1973 and drilled to TD at 3318 m in the
Late Cretaceous Hod Formation. The well was drilled with seawater and hi-vis
slugs down to 1220 m, and with a lignosulphonate mud (UNI-CAL / Caustic) from
1220 m to TD. According to the mud program the section below 1220 m was drilled
with 4% diesel in the mud. The Danian Limestone, which was expected
to be 100 m thick with 38 m of net pay, was found to be much thinner than the
other wells on Eldfisk, and was only 9 m thick. It was also less fractured than
other wells on Eldfisk, but still yielded commercial quantities of oil and gas,
after acidization, over the total interval on the third of three drill stem
tests. This test included the top 23 m of the Late Cretaceous (Maastrichtian). The
remaining tests below this interval, also in the Maastrichtian, did not produce
oil or gas in commercial amounts. The truncated Danian, the lack of fracturing
and secondarily porosity, and the fact that the produced oil was heavier than the
oils on the main Eldfisk structure to the west, suggested that East Eldfisk structure
is not in communication with the main Eldfisk structure. No cores were cut and no wire line fluid
samples were taken. General Well 2/7-9 is located in the Ål Basin south
of the Eldfisk structure in the southern North Sea. The main purpose of the
well was to test Danian -Cretaceous limestone and Jurassic sandstone on a
north-south trending anticline 6 - 8 km south of Eldfisk, where these intervals
had proven commercial oil in several wells. Operations and results Appraisal well 2/7-9 was spudded with the
jack-up installation Zapata Nordic on 25 December 1973 and drilled to TD 4448 m
in Devonian sediments. Appraisal well 2/7-9 was spudded with the jack-up installation Zapata Nordic on 25 December 1973 and drilled to TD 4448 m in Devonian sediments.
The Danian Limestone (Ekofisk Formation) came in at 3086 m. It was expected to be 90 m thick while 77 m was found.
The Late Cretaceous Chalk (Cromer Knoll Group) was anticipated to be 695 m thick, but a greater thickness of 800 m was found.
Good shows were seen in both intervals, but no hydrocarbons were produced when tested.
Sands initially dated Late Jurassic were encountered at 4313 m and proved to be hydrocarbon bearing with a 111 m pay section with average porosity of 13% and 55% oil saturation.
A clear OWC was found at 4424 m.These sands have later been interpreted as of Devonian age. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 10
April 1974. Testing Three drill stem tests were conducted in
the well. DST 1 tested the interval 4313 to 4356 m
in the Devonian sandstone General Well 2/7-10 was drilled on the Edda
structure in the southern North Sea. The principal zone of interest was the
Danian Limestone, which was found hydrocarbon-bearing ca 13 km to the northeast
on the Ekofisk field, and which held commercial quantities of oil and gas in
the 2/7-4 well on the Edda structure just over a mile to the southeast. The
Danian sequence was expected to be ca 90 m thick. The Late Cretaceous was a
secondary objective and could contain hydrocarbons if porosity was present. Operations and results Well 2/7-10 was spudded with the jack-up
installation Zapata Nordic on 6 October 1973 and drilled to TD at 3370 m in the
Late Cretaceous Tor Formation. Bad weather caused some technical problems and
delayed operations for some days. The well was drilled water based, but with
3-4 % addition of oil below 2691 m. The Danian limestone sequence (Ekofisk
Formation) was encountered at 3191 m. It was 90 m thick as prognosed but with
only 6 m of gross pay, which, after acidization, yielded nothing commercial.
The equivalent interval in the 2/7-4 well produced commercial oil and gas on
the deepest of three drill stem tests. The Late Cretaceous Tor Formation,
however, was found to have 31 m of potential pay, which correlates well with
the 2/7-4 interval. It flowed commercial amounts of oil and gas after acid, on
two drill stem tests. The upper one of these compared well with the equivalent
horizon in the 2/7-4, although less productive. Shows were recorded from top of
the Ekofisk and all through the limestone/chalk section down to ca 3338 m in
the Tor Formation. No cores were cut and no wire line fluid
samples taken in the 2/7-10 well The well was permanently abandoned on 5
December 1973 as an oil appraisal. Testing Five successful DST's were carried out in
the well. Maximum flow data after acidization follows: DST 1 from the interval
3313 - 3322 m (Tor Formation) produced 233 m3 water General Well 2/7-11 was drilled on the Lindesnes
Ridge in the North Sea, between the Eldfisk and Valhall fields. The primary objective
was to evaluate the Danian. Operations and results Wildcat well 2/7-11 was spudded with the semi-submersible
installation Ocean Viking on 24 February 1975 and drilled to TD at 3377 m in
the Early Cretaceous Rødby Formation. No significant problem was encountered in
the operations. The well encountered no porosity or
hydrocarbon accumulations of reservoir qualities. There were shows in
Eocene-Paleocene. No cores were cut and no fluid samples
were taken. The well was permanently abandoned on 30
March 1975 as a dry well. Testing No drill stem test was performed. General Wildcat well 2/7-12 was drilled on an
intrusive salt plug in the upper left corner of the block, some km west of the
Ekofisk and Edda fields in the Southern Norwegian North Sea. The salt plug is
located in the cross-junction between the four blocks 1/6, 1/9, 2/4, and 2/7.
The objective was to establish if Danian - Late Cretaceous carbonates were
present on the salt plug. If present the carbonates would be evaluated. Operations and results Well 2/7-12 was spudded with the semi-submersible
installation Dyvi Beta on 17 December 1978 and drilled to TD at 1832 m in the
Late Permian Zechstein Group. The well was drilled with salt-based mud,
possibly with some diesel addition according to geochemical analyses, in the
interval from 1402 m to TD. Several thin gas charged siltstone stringers were
penetrated between 433 m and 835 m. The salt (Permian Zechstein Group) was
encountered at 1686 m. The well did not encounter any Danian -Late Cretaceous
carbonates on top of the salt. Oil shows (fluorescence, cut, stain or
combinations) were recorded on SWC's and cuttings at 114.5 - 445 m (sandstone),
731 - 810 m (claystone with trace of fine sandstone), and scattered on
claystone, shale, and limestone from 1469 m to 1679 m. The resistivity log indicated
a probable hydrocarbon zone from 416 to 433 m in a shallow sand. It was not
possible to calculate reliable porosity from the sonic log, but a DST confirmed
minor amounts of oil. Ninety sidewall cores were attempted and
seventy-one were recovered from the overall interval 1417.3 to 173.7 m. No
conventional cores were cut and no wire line fluid samples taken in this well. The well was permanently abandoned on 30
January 1979 as a dry well with shows. Testing One drill stem test was performed through
perforations at 416.7 - 425.8 m. The tool was open 22 minutes; shut in one hour
and 58 minutes, open 3 hours and shut in 3 hours and 58 minutes. No General Exploration well 2/7-13 was drilled to
the East of an intrusive salt dome in the Ekofisk area of the Norwegian sector
of the North Sea. The structure had already been investigated by wells 1/9-4
and 1/9-5 to the west, and also above the salt dome in 2/7-12. The Danian/Late
Cretaceous was the primary objective. A secondary objective was the possibility
of a reservoir on the flank of the dome with the salt forming a seal. Operations and results Well 2/7-13 was spudded with the jack-up
installation Dyvi Beta on 1 February 1979 and drilled to TD at 3388 m in the
Early Cretaceous Sola Formation. No significant problems were reported from the
operations. The well was drilled with spud mud/Drispac/seawater down to 1309 m,
and with seawater/Drispac from 1309 m to TD. Higher hydrocarbon gasses were observed
from 975 m to 1113 m. Very poor fluorescence was noted in the clay and
occasional limestone in the same interval. Poor shows occurred in limestones at
2210 - 2225 m and 2265 - 2274 m, and also in dolomite limestone stringers from
2387 - 2591 m. The Danian and Cretaceous limestones also gave poor oil shows
with some staining in the Ekofisk Formation from 2719 to 2801 m. Five
conventional cores with a total of 22 m recovered were taken in this zone from
2725.5 m to 2790 m. No wire line fluid samples were taken. The well was permanently abandoned on 21
April 1979 as a dry well with shows. Testing Four intervals in the 8 1/2" section
were tested through 7" liner. DST 1 tested the Hidra Formation from 3188
to 3257 m and produced 504 Sm3 water with 1.5% oil/day, DST 2 tested the Hod
Formation from 3042 to 3085 m and produced 1441 Sm3 water with ca 3000 Sm3
gas/day, DST 3 tested the Ekofisk Formation from 2740 to 2774 m and 2793.5 to
2807 m, and DST 4 tested the Ekofisk Formation from 2697.5 to 2729 m. DST 3 and
DST 4 produced only small amounts of water (1 Sm3/day and 69 Sm3/day,
respect General Well 2/8-4 was drilled on the Valhall
structure in the Southern North Sea Operations and results Wildcat well 2/8-4 was spudded with the jack-up
installation Zapata Explorer on 28 April 1973 and drilled to TD at 2852 m. Top Shetland Group was encountered with
oil shows at 2577 m. The Shetland Group had only one meter of Tor Formation on
top of the Hod Formation. Three very short cores were cut: core 1
from 2607.3 to 2698.2 m, core 2 from 2597.8 to 2598.7 m, and core 3 from 2584.1
m to 2585 m. No wire line fluid samples were taken. The well was permanently abandoned on 7
June 1973, initially as a dry well with shows. After the 2/8-6 Valhall discovery
well two years later it was re-classified to oil appraisal well. Testing Two drill stem tests were performed. In
both tests the chalk was stimulated by acid. DST 1 tested the interval 2603 to 2622.5
m. The test produced 5.7 m3 load water during a 6.5 hrs flow DST 2 tested the interval 2578.6 to
2587.8 m. This test produced 2.5 m3 load water and 0.5 Sm3 26 deg API oil
during a 12 hrs flow. General Wildcat well 7120/10-1 is located in the Troms I area in the southwestern part of the Hammerfest Basin, close to the Troms-Finnmark
Fault Complex. The main objective of the well was to test the Middle to Early
Jurassic sands of the B-prospect located in the south-eastern part of the block
Operations and results The well was spudded with the
semi-submersible installation Zapata Ugland on 10 September 1984 and drilled to
TD at 2000 m in the Late Triassic. While drilling the 36" hole a boulder
zone was encountered at 210 m to 248 m, which made it difficult to set the
30" casing. When pressure testing the seal assembly before drilling out of
the 9 5/8" casing shoe, a leak was found in the well head connector. The
leakage was repaired before drilling of the 8 1/2" hole section. The well
was drilled using gel/seawater down to 534 m, with bentonite/CMC from 534 m to
1302 m, and with gel/lignosulphonate/seawater from 1302 m to TD. No hydrocarbons were encountered in the
well. No potential reservoir sands were present above the Middle Jurassic. In
the Middle Jurassic to Top Triassic interval a net 200 m of good quality
potential reservoir sandstone was penetrated. One core was cut in the Middle Jurassic
Stø Formation from 1570 m to 1584 m. Twenty-two RFT pressure readings were
obtained from 1570 m to 1589 m, showing a saltwater pressure gradient. A fluid
sample was taken at 1573.9 m. The sample contained mud filtrate without any gas
or any smell or sign of hydrocarbons. The well was permanently abandoned on 8
September 1984 as a dry hole. Testing No drill stem test was performed General Well 2/8-5 is located within closure of
the large NNW-SSE trending Valhall structure, close to well 2/8-2 and ca 8 km
south of the 2/5-3 Sørøst Tor Discovery. The primary target was
Danian/Maastrichtian chalk/limestones. Operations and results Exploration well 2/8-5 was spudded with
the jack-up installation Zapata Explorer on 11 April 1974 and drilled to TD at
3304 m in the Early Cretaceous Rødby Formation. Some problems with lost
circulation were experienced at 1618 m. At 1909 m in the Hordaland Group a gas
kick was taken. Otherwise drilling went without significant problems. No sand was encountered in Paleocene. The
well penetrated 88 m of Danian chalk (Ekofisk Formation) and 380 m Late
Cretaceous chalk (Tor Formation) before marls of the Rødby Formation were
encountered at 3264 m. Well logs indicated that all target formations were
water wet. Shows were reported as follows: Miocene (1600 m to1722 m): white bright
yellow amber fluorescence giving a fast yellow white slow cut. Associated with
a gas peak on the chromatograph analysis at the top. Patchy fluorescence was
recorded down section. Oligocene (1829 m): bleeding gas from limestone. (2353
m): pale yellow fluorescence, slow cut, with acid only. Eocene (2464 m to 2718
m): patchy shows, heavy brown oil stain, very dull amber to fast yellow
fluorescence, occasional fast bright yellow cut, dark brown cut colour. The
Shetland Group (2796 m to 3264 m): background gas only, maximum of 1.8% C1,
trace C2-C4 at 3254 m. Fair oil stain, fair to good fluorescence and cut. No conventional core was cut and no fluid
sample taken. The well was permanently abandoned on 23 May 1974 as a well with
oil shows. Testing No drill stem test was performed General Well 2/8-6 was drilled to test the chalk
approximately on the crest of the Valhall structure in the southern North Sea. The
Valhall structure was mapped as a large northwest-southeast trending anticline
at the Tertiary level covering approximately 65 km2 with a vertical relief of
ca 490 m. The crestal portion of the Valhall structure, ca 26 km2 in area, was
blanketed by a low velocity "bright spot" zone in the overlying
Tertiary (Miocene). Such "bright spot" had been observed also over the
Hod discovery, the Ekofisk and the Eldfisk. The 2/8-6 and 2/11-2 wells had confirmed
that these "bright spot" anomalies were caused by oil and gas present
in the younger Tertiary beds, creating extremely low velocities. Operations and results Wildcat well 2/8-6 was spudded with the
semi-submersible installation Waage Drill I on 7 April 1975 and drilled to TD
at 2669 m in the Early Cretaceous Sola Formation. The well was drilled in 38
days. Of these a total of 9 days were lost due to drilling problems; 2 days
cementing between the 20 and 13 3/8-inch casing to stop gas entry into the
annulus, 1.5 days to repair BOP stack connector, and 5.5 days to combat gas
kick and lost circulation while drilling at 2438 m. The well was drilled with
seawater and hi-vis mud down to 155 m, with shale-Trol gel mud from 155 m to 1890
m, and with lignosulphonate mud from 1890 m to TD. The chalk was encountered at 2463 m. Good
oil shows were encountered in the intervals 2465 - 2472 m and 2526 - 2551 m
with minor oil saturations occurring between the above intervals and down to
approximately 2560 m resulting in a gross oil column thickness of 110 m. Log
derived porosity in the oil column ranged between 27 and 43%, averaging 33 %. Cor General Well 2/8-7 is located on the western side
of the Piggvar Terrace towards the Feda Graben. The well was drilled to test
the Late Cretaceous Limestone in the Trud structure. Structurally, the Trud
anomaly is a high relief, salt induced, domal feature covering approximately 19
square kilometres. The structure was seen as highly faulted with a main fault
trending north south, with the down-thrown side to the east. The displacement
along this fault was estimated to approximately 150 m. No secondary objective
was defined. Operations and results Wildcat well 2/8-7 was spudded with the
jack-up installation Zapata Explorer on 23 July 1975 and drilled to a total
depth of 2868 m in the Late Permian salt. The well was drilled without major
problems. The well was drilled with seawater gel down to 375 m, and with a
Lime/Drispac/seawater mud system from 375 m to TD. The mud weight was cut and
LCM pills spotted at 2619 m to cure lost circulation problems. The Tertiary section consisted
predominantly of claystone and shale. The Paleocene ash markerá (Balder
Formation) was encountered at 2511 m and was found to be 12 m thick. The
Shetland Group chalk section (Ekofisk, Tor, and Hod Formations) was encountered
at 2596 m. The Chalk section had a vertical thickness of 223 m, which compares
to roughly 451 m in 2/5-4, 458 m in 2/9-1 and 280 m in 2/8-2. Oil shows were
recorded in limestone stringers below 1548 m. The target Late Crataceous
section had 12 m of oil shows from top of the Danian chalk (Ekofisk Formation),
the core from this section was boiling gas and bleeding oil from vugs and
fractures. Schlumberger logs were run before the 9 5/8-inch casing was set and
after total depth was reached. Coriband log analysis estimated a water
saturation around 60% in the top Ekofisk section. A core was cut from 8538 to
8554 feet (ca 2602 m to 2607 m) with 50% recovery. No fluid samples were taken.
The well was permanently abandoned on 24 August as a well General Well 2/8-8 was drilled to appraise the
Valhall discovery in the southern North Sea. The well is reference well for the
Hod Formation. Operations and results Appraisal well 2/8-8 was spudded with the
semi-submersible installation Deepsea Saga on 10 November 1975 and drilled to
TD at 2667 m in the Early Cretaceous Rødby Formation. While running the 13
3/8-inch casing, returns (125 barrels) were lost while pumping plug. While
cementing the 9 5/8-inch casing, the cement slurry was not properly displaced,
and the casing was cemented back on the inside to 1022 m. Three days were lost
due to this in drilling out the cement. Otherwise the well was drilled without
significant problems. The well was drilled with sea water and hi-vis mud down
to 169 m, with sea water/gel mud from 169 m to 402 m, and with lignosulphonate/gypsum
mud from 402 m to TD. Oil shows were recorded at several levels
above the chalk reservoir: 1320 - 1329 m had fair shows on siltstones; 1390 to
1426 m had poor shows in shales and limestone; 1512 to 1676 m had oil staining
with fluorescence and cut in shales; and 2050 to 2400 m had poor to fair shows
in thin stringers of limestone and dolomite. Top of the chalk reservoir, Tor
Formation, was encountered at 2447. It was oil bearing and had shows down to 2591
m. No shows were recorded below 2591 m. At total of 47.7 m core was recovered in
14 cores from 2450 to 2600.9 m. The overall recovery was 39 %. No wire line
fluid samples were taken. The well was permanently abandoned on 15
March 1978 as an oil appraisal well. Testing General Well 2/8-9 was drilled as an appraisal to
help establish the commerciality of the southern North Sea Valhall Field, which
had earlier been discovered by 2/8-6 and confirmed by 2/8-8. The primary
objective of 2/8-9 was an evaluation of the Chalk reservoirs of Maastrichtian (Tor
Formation) and pre-Maastrichtian (Hod Formation) age. The existence of
hydrocarbons in the Early-Middle Miocene section creates a low velocity
"bright spot" on the seismic, blanketing the crest of the Valhall
structure and causing "dimming" or total loss of the top chalk
section. The Valhall crest is therefore an area where the estimated thickness
of the Tor section and the fault patterns are questionable. Only one previous
well, 2/8-4, had been drilled in the vicinity some 2.5 km to the west. Well
2/8-4 was essentially a dry hole with only 1 m of Tor and tight but oil bearing
Hod Formation. Operations and results Appraisal well 2/8-9 was spudded with the
semi-submersible installation Sedco 135 G on 9 April 1976 and drilled to TD at 2703
m in the Early Cretaceous Rødby Formation. The well was drilled in a total of
30 days, without any major drilling problems. It was drilled with sea water and
viscous mud down to 183 m, with seawater and gel from 183 m to 392 m, and with
Drispac/lime/seawater mud from 392 m to TD. Well 2/8-9 penetrated a normal of
Quarternary -Tertiary section from surface to top of the Late Cretaceous. The
Danian was found to have been removed by erosion. The well found the Chalk
hydrocarbon bearing at 2524 m correlating 53.3 m high and 76.8 m low to wells
2/8-4 and 2/8-8, respectively. The Tor Formation was 5.5 m thick with high
reservoir quality; porosity of up to 48% and a water saturation close to zero. The
Ho General Well 2/8-10 was drilled as a field
delineation well intended to help establish the commerciality of the Valhall
Field, which was discovered by well 2/8-6 and confirmed by wells 2/8-8 and
2/8-9. The main purpose of 2/8-10 was to evaluate the Tor and Upper Hod
reservoirs on the south eastern flank of the Valhall structure. Operations and results Appraisal well 2/8-10 was spudded with
the semi-submersible installation Sedco 135 G on 30 June 1976 and drilled to TD
at 2682 m in the Early Cretaceous Rødby Formation. The well was drilled with
seawater and bentonite down to 375 m, and with seawater/lime/Drispac mud from
375 m to TD. The objective reservoirs, developed in
chalk of the Tor and Hod Formations, were encountered at depths of 2476.5 m and
2516 m respectively. A gross pay interval of 77 m was encountered. The Tor
Formation was approximately 38 m thick with an oil saturation of 95% and was
tested at rates of up to 1000 Sm3/day. The upper Hod reservoir, approximately
38 m thick, was found to be hydrocarbon bearing, although oil saturations were
low, averaging 25% and the reservoir was tested at up to 67 Sm3/day. As
anticipated, the lower Hod reservoir was wet. Only insignificant, although fairly
consistent, oil shows were encountered in the Hordaland and Rogaland Groups.
Excellent shows were recorded in the Tor Formation. The quality of the shows
decreased gradually through the upper part of the Hod Formation and only minor
oil shows were encountered below 2570 m. Four conventional cores were cut in the
interval 2477.1 m to 2508.5 m with an overall recovery of 70%. No wire line
fluid samples were taken. General Well 7/12-6 was drilled as an appraisal
well on the Ula Field in the southern North Sea. The objective was to determine
sand distribution in northern part of the Ula field, and production and
injection properties of reservoir and aquifer. Operations and results Appraisal well 7/12-6 was spudded with
the semi-submersible installation Sedco 707 on 10 April 1981 and drilled to TD
at 3700 m in the Triassic Skagerrak Formation. Some hole problems and excessive
cavings due to underbalanced drilling occurred in the 12 1/4" section
between 2633 and 3353 m, otherwise the well was drilled without significant
technical problems or delay. The well was drilled with gel/seawater and fluid
loss additives down to 480 m and with gypsum/lignosulphonate and fluid loss
additives from 480 m to TD. The Ula Formation sandstones were penetrated
at 3406 m. The sandstones were 115 m thick, very fine to fine grained with
porosities from 10 to 25% and permabilities from 1 to 2000 mD. The reservoir
was oil bearing throughout, no OWC was established. An unexpected Triassic
reservoir of good quality was found below the Ula Formation. The well drilled
179 m into it without reaching the OWC. The reservoir consisted of various
types of micaceous sandstones with porosities from 4 to 23% and permabilities
from 0.03 to 2600 mD. The first hydrocarbon indication was recorded as a weak
oil show at 2440 in siltstone. Further shows were recorded in the Late
Cretaceous between 3010 m and 3060 m, however the logs did not indicate any
significant mobile hydrocarbon. Hydrocarbon shows were recorded throughout the
Upper Jurassic Ula Formation between 3407 m and 3521 m. Patchy shows were
recorded in the Triassic interval between 3521 m and TD.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 Well 2/9-1 was the first exploratory well
to be drilled in Block 2/9 of the Norwegian concession area of the North Sea.
This block occupies a position in the central part of the North Sea, a little
to the southeast of the Eldfisk - Ekofisk - Tor Oilfields area. It is thus
located over the deepest part of the North Sea Tertiary Basin. The well was
planned to be drilled on the border between block 2/8 and block 2/9, the final
well position is actually in block 2/8. Operations and results Wildcat well 2/9-1 was spudded with the
jack-up installation Zapata Explorer on 3 November 1972 and drilled to TD at
3551 m in the Late Cretaceous Hod Formation. The well was drilled with a
seawater and bentonite down to 387 m and with a polymer mud system with 1 % û 4
% oil from 387 m to TD. The Rogaland Group was encountered at
2962.7 m and consisted of the Balder, Sele, Lista, and Maureen formations.
Interval 3065.7 m to Top Ekofisk Formation at 3092 m consisted of marl (Maureen
Formation). From this point to TD the well drilled Late Cretaceous chalk
(Ekofisk, Tor, and Hod formations). The best porosity in this sequence, based
on log analyses, was seen in the interval 3209.5 m to 3261 m in the Tor
Formation was. However, no shows were recorded in the well. No fluid samples
were taken and no conventional core was cut. A wire line core slice was
retrieved from 3499.4 m to 3500.3 m in the Hod Formation. The slice is
described in a report by Robertson Research. The well was permanently abandoned
as dry on 7 December 1972. Testing No drill stem test was performed General Well 2/9-2is located on the Piggvar
Terrace in the southern North Sea. The primary objective was to test a broad
structural closure where Jurassic Sands were postulated to be present along the
narrow intermediate zone between the Mandal High to the east and the Central
Graben to the west. Operations and results Wildcat well 2/9-2 was spudded with the
semi-submersible installation Dyvi Alpha on 7 July 1979 and drilled to TD at 4367
m in the Early Permian Rotliegend Group. The well was drilled without
significant problems. However, four days were spent on retrieving the wear
bushing prior to running the 13 3/8-inch casing. The well was drilled to 1513
meters using seawater, spotting high viscous gel pills occasionally while
drilling and upon completion of each hole interval. A weighted Gypsum-polymer
mud was used below this depth to TD. The Late Jurassic was encountered at 3653
m, 16 m low to prognosis, confirming the structural interpretation. The Late
Jurassic section (3653-4293 m) consisted of 640 meters of predominantly black
shale with no sands and was age-dated Middle Kimmeridgian-Portlandian. No
Jurassic rocks older than Middle Kimmeridgian were found. From 4290-4325 m, the
section was silty and sandy but impermeable. From 4325 m to TD lithology was
interpreted to be weathered volcanics of possibly Permian age, with caved
Kimmeridgian shales. Stratigraphic and petrophysical data pertinent to further
evaluation of the Jurassic zone was secured through the acquisition of one conventional
core and an almost complete set of open hole logs. Poor to very poor shows were
seen in the intervals 4135 - 4155 m and 4160 - 4182.5 m in the Late Jurassic.
They were describ General The 2/10-1 S "South East Eel"
well is located in the Grensen Nose, close to the southern tip of the Norwegian
sector. It was drilled in the Tertiary basin of the North Sea approximately 20
km south of the Embla discovery. The primary objective horizons were the Early
Cretaceous - Late Jurassic clastic sediments and the Danian - Late Cretaceous
limestones. Seismic data were interpreted as wedging out of the Early
Cretaceous - Late Jurassic sediments up-dip to the west of the well location.
These sediments produced oil in the Phillips 2/7-3 and 2/7-9 wells while Late
Jurassic turbidite sands were present in the Eldfisk 2/7-1 well. In addition a
small Danian/Late Cretaceous structure was defined on a seismic. The 2/7-2 well
a few miles to the north in a similar geological situation produced 345 BOPD
from the Danian. Secondary objectives were Tertiary and possible Rotliegendes
sandstones. Operations and results Exploration well 2/10-1 S was spudded
with the semi-submersible installation Ocean Viking on 16 September 1975 and
drilled deviated to TD at 4609 m (4267 m TVD RKB) in rocks of possibly
Carboniferous age. While drilling the 8 1/2" section at 4028 m the weather
deteriorated. The drill string was hung off before the rig started to drift,
and had to be towed to Stavanger. Winds were reported up to 30 m/s and waves up
to 22 m. Altogether 34 days were lost before the rig again was on location and
could continue drilling. The well was drilled with sea water and gel down to
442 m and with PAC/sea water with 4% oil from 442 m to TD. No oil shows were encountered during the
drilling, however, a gas kick was noted when drilling into the top of the
Rotliegendes sandstone section. No testing was carried out due to engineering
difficulties although three drill stem tests in the Permian were planned. The
well was drilled as per progress down to the base of the Cretaceous sediments.
No clastics were developed in the Te General Well 2/11-2 was drilled on the Hod
prospect on the Skrubbe Fault between the Lindesnes Ridge and the Ål Basin in
the southern North Sea. The "Hod" anticline is a satellite or
subsidiary feature immediately to the southwest of the large Valhall structure.
The primary objective was the Danian/Late Cretaceous chalk section, the
productive horizon in surrounding fields. Paleocene sand/siltstones would be
secondary objectives, if encountered. These had shows in well 2/11-1, located
6.4 km north. Operations and results Wildcat well 2/11-2 was spudded with the
semi-submersible installation Zapata Explorer on 6 November 1974 and drilled to
TD at 2806 m in the Early Cretaceous Rødby Formation. It was drilled in 37 days
without major problems, although 10 days were lost due to waiting on water,
combating lost circulation after an attempt to kill a gas kick, and waiting on
a new BOP stack after a leak was found on the old equipment. The well was drilled
with seawater and Milben saltgel mud down to 145 m, with seawater, pre-hydrated
Milben, Flosal mud from 145 m to 383 m, with Drispac/Flosal mud from 385 m to
1295 m, with Shale Trol until gumbo, converting to a Unical/seawater mud from
1295 m to 2660 m, and with a Unical/seawater mud from 2660 m to TD. High gas readings were recorded from
approximately 1415 m to 1675 m. Oil shows (dull yellow fluorescence and poor -
fair cut) and free oil in the mud was also noted during the drilling of the
above interval. Oil bearing Santonian - Coniacian chalk (Hod Formation) was
encountered at 2640.5. The section had 51.5 m net pay with estimated average
porosity of 27.7 percent and an average water saturation of 40.3 percent. A core was t General Well 2/11-3 is located 2.5 km due east
from 2/11-2 and 6.5 km south-southeast from the Valhall well 2/11-1. The
primary objective of well 2/11-3 was the Late Cretaceous chalk section on the
western flank of the East Lobe of the Hod structure. The West Lobe was found to
be oil bearing by 2/11-2 in 1974. Seismic indicated an expansion of the chalk
section compared to 2/11-2 and that the graben feature found on Valhall
extended south-eastward over the East Hod and therefore the possibility for the
high reservoir quality Maestrichtian rock to be present in this area. Operations and results Well 2/11-3 was spudded with the jacket 4
legs installation Dyvi Beta on 10 October 1977 and drilled to TD at 3052 m in
the Early Cretaceous Rødby Formation. The well was drilled in a total of 47
days without any major drilling problems. However, 3 days were spent waiting
for the correct Cameron BOP Adaptor Spool. Well 2/11-3 proved the Hod complex to
consist of two individual structures. A domal West Hod structure has a
seismically defined closure area of 7.5 square km. East Hod, where 2/11-3 was
located, is a northwest-southeast trending anticline covering approximately 6
square km. The well penetrated a normal sequence of
Quarternary-Tertiary section from the surface to the top of the Late Cretaceous
at 2774.5 m. This interval typically consists of predominantly clay and shale
with thin stringers of limestone and dolomite scattered throughout. The basal
Tertiary unit is marked by the occurrence of the Paleocene Ash marker that
displays the characteristic metallic blue grey-violet colour of the volcanic
tuff. This correlative unit was encountered at 2714.5 m and is 18 meters thick.
The cha General The Hod complex was proved to consist of
two individual structures by well 2/11-3, which was drilled about 2.5 km due
east of 2/11-2. Seismically, the Hod structural complex is difficult to map due
to shallow gas in the Tertiary, mainly over the western part of the structure,
which complicates the time to depth conversion. As it turned out, the chalk in 2/11-2
was drilled close to the limit of structural closure of the East Structure and
was therefore dry with shows only. Well 2/11-3 A was a sidetrack from well
2/11-3 to test Late Cretaceous chalk in a graben feature indicated by seismic
in the crestal regional of the East Hod structure. A graben, if present, would
have possibilities for preservation of younger Maastrichtian rock which in
general is of high reservoir quality with high porosity and often very high oil
saturation. Operations and results Well 2/11-3A was sidetracked from just
below the 13 3/8-inch casing shoe on 3 December 197 7 and drilled to TD at a
total measured depth of 3400 m (2857 m TVD) in the Late Cretaceous Hod
Formation. The pipe stuck at TD prior to logging and deviation survey. After
working on the stuck pipe the string was disconnected at 3189 m and the well
was kicked-off on the low side in order to complete logging and testing of the
pay-zone discovered before the pipe got stuck. This technical sidetrack was
drilled to 3333 m (2812 m TVD). Top Chalk was encountered in the
sidetrack at 3189.5 meters (2713 meters TVD). The uppermost 5 m belonged to the
Ekofisk Formation. Then followed 58.5 m of Tor Formation, 13 m of tight Middle
Hod Formation, and 70 m of Lower Hod. The Chalk was found oil bearing from top
Chalk to TD in the sidetrack, with exception of 8 m in Middle Hod. Shows on
cuttings wer General Well 2/11-5 was drilled on the western
lobe of the Hod Field to test the Late Cretaceous Chalk section. The well was
located 1.8 km SSE of 2/11-2 which tested oil from a very thin Chalk section of
the Lower Hod Formation. Structural interpretations were made showing a NW-SE
trending graben traversing the West Hod lobe. Based on a model from East Hod,
it was expected that the porous Tor Formation should be preserved below the
unconformity within this structure. Operations and results Well 2/11-5 was spudded with the
semi-submersible installation Dyvi Alpha on 18 May 1979 and drilled to TD at 2945
m in the Early Cretaceous Rødby Formation. No significant problem was
encountered in the operations, however six days were spent repairing the BOP
stack before it could be run and two days were spent while mixing oil-based
mud. The well was drilled with seawater, bentonite and CMC EHV down to 1285 m,
with gyp/CMC mud from 1285 m to 2320 m, with lignosulphonate mud from 2320 m to
2765 m, and with oil based "Oilfaze" mud from 2765 m to TD. The Paleocene Ash Marker (Balder
Formation) was encountered at 2715 m; 105 m low to prognosis. The top of the
Chalk Group, Ekofisk Formation was encountered at 2822 m; 117 m low to
prognosis. In total, the Chalk section was found to be 98 m thick, whereas 300
m was predicted. These discrepancies reflect the effects of the shallow gas in
the area on the seismic data. The velocity corrections which were applied to
the seismic were too large. As a consequence, the Chalk Group within the Graben
was found below the oil-water contact of the area and no moveable hydrocarbons
were encountered. Frequent oil shows were reported however, starting in the
upper part of the Hordaland Group: General Well 2/11-6 S was drilled on the
Lindesnes Ridge in the southern North Sea. The objective was to appraise the
Hod discovery made by well 2/11-2 in 1974 (Hod West) and appraisal well 2/11-3
in 1977 (Hod East). The Hod structure is oil-bearing in Late Cretaceous chalks,
the Hod and Tor formations. Well 2/11-6 S targeted the Hod East structure. Operations and results Appraisal well 2/11-6 S was the first
well to be drilled on a subsea template which was laid by the semi-submersible
installation Sedco 703. It was then drilled with Sedco 703 through slot number
W7 of the twelve slot templates, to TD at 3970 m (2905 m TVD) where the pipe got
stuck. The pipe was shot off with top of the fish at 3669 m and a technical
sidetrack 2/11-6 ST1 was kicked off from 3626 m. The sidetrack was drilled to
the final TD at 4076 m (2980 m TVD). The initial well bore was drilled with
seawater and hi-vis sweeps down to 1460 m, with Vertoil oil based mud from 1460
m to 3601 m, and with Oilfaze oil based mud from 3601 m to 3970 m. The 2/11-6
ST1 sidetrack was drilled with Vertoil oil based mud from kick-off to TD. Well 2/11-6 drilled a nearly complete
Tertiary section and penetrated top chalk at 3690 m (2732 m TVD). The sidetrack
penetrated top of the chalk group at 3685 m (2729 m) with a slightly lower
angle (50 deg) than in the initial well bore (55 deg). The chalk stratigraphy
in the two well bores was very similar apart from the angle/depth shift. The
well tested oil in the Tor / upper Hod formations and in the lower Hod
Formation. Seven conventional cores were cut from
3693 to 3741 m in the initial well bore before side tracking. The cores were
cut in the Late Cretaceous Chalk. The total recove General Exploration well 3/5-1 is located near
the Coffee Soil Fault Complex on the northeast border of the Søgne Basin. The
main objective of the well was to test the hydrocarbon potential of
Rotliegendes sands on the crest of a tilted fault block, which was thought to
mark the local eastern edge of the Central Graben of the North Sea. A secondary
target was the basal Zechstein, where it was hoped that any dolomites present
might have developed the secondary porosity exhibited in the Auk and Argyll
Fields lying on the Western side of the Central Graben. There was no mappable
closure at any post Zechstein horizon. Operations and results Wildcat well 3/5-1 was spudded with the
semi-submersible installation Odin Drill on 3 May 1978 and drilled to TD at
3426m in basal conglomerates of the Permian Rotliegendes Group. While drilling
at 2561 m the string twisted of at the jars, costing some six days lost time. A
salt-water flow occurred while drilling at 2918 m, but was controlled by
increasing the mud weight from 11.3 to 12.4 lb/gal. During abandonment 2.3 days
were spent cutting and retrieveing of the well head. The well was drilled with
seawater and hi-vis slurry down to 466.3 m and with lime/Drispac mud from 466.3
m to ca 2228 m from where it was gradually displaced to a Spersene/Resinex mud
system. This mud was in turn displaced to a salt saturated mud from ca 3058 m
after it became clear that massive salt was being drilled. The salt saturated
mud was used to drill the rest of the well to TD. Schlumberger's CPI log showed almost 23 m
of reservoir quality sands in the Late Jurassic (average log porosity 24 %),
and almost 259 m in the Rotliegendes (average log porosity 23 %). A thick salt
section covered the Zechstein carbonates. It is probable that the salt-water
flow at 2918 m came not from this salt but from the overlying Jurassic
sandstones. Shows were recorded while drilling the Late Jurassic Kimmeridgian
"Hot" Shale (M General Exploration well 3/5-2 is located in the
eastern part of the Søgne Basin. The main objective was to test the hydrocarbon
potential of northeasterly dipping Jurassic sands, which appeared to be
truncated up dip by erosion at a Late Kimmerian unconformity. The exact age of
the beds above and below the unconformity could not be predicted with certainty
with the seismic evidence available. There was no capable closure at any post
unconformity horizon higher than that mapped as Late Kimmerian unconformity
just above a possible Jurassic Sand. Well 3/5-2 is Reference well for the
Middle to Late Jurassic Haugesund Formation Operations and results Wildcat well 3/5-2 was spudded with the
semi-submersible installation Odin Drill on 29 June 1978 and drilled to TD at
3826 m in the Triassic Skagerrak Formation. The well was drilled without
significant problems. After drilling 164 m of 36" hole the pipe was stuck,
but after spotting two 60 Bbl LCM pills followed by an 85 Bbl pill of Pipe Lax
the string pulled free without significant lost time. Drilling went on through
the 26" section to 462 m using viscous gel mud. From 426 m to TD the well
was drilled using a Drispac/Spersene mud system, adding Resinex from ca 3080 m. Reservoir potential was encountered in
the Late Cretaceous Chalk (Maastrichtian 2708.5 m to 2726.5 m) and in Late
Jurassic (3174 m to 3185 m) and Triassic (3575 m to 3823.5 m) sandstones.
Geochemical analyses proved oil prone shale, marginally mature (%Ro = 0.6 û
0.7), in the Late Jurassic Kimmeridge Clay with TOC measured up to2.1 %. Also
the Middle Jurassic Haldager Formation contained shales with potential for gas
and possibly some oil. Vitrinite reflectance in one sample from this Formation
was %Ro = 0.85. Small quantities of C1 to C4 were recorded in the Late Jurassic
Kimmeridge Clay Formation (3143 m to 3163 m) and in even smaller amounts in
shales at the top of the Middle Jurassic (3331 m to 3359 m General Well 3/7-1 was drilled in the Søgne Basin
in the North Sea, about 1400 m north of the border to Danish waters. The well
location is near the top of a large anticline whose axis trends northwest with
a 200 km2 closure at the pre-Zechstein horizon. The structure was considered as
a north-western extension of the Fynn Falster High. The expected reservoirs
were Danian and Maastrichtian chalky limestone, Jurassic sandstone, Rotliegend
sandstone, and Carboniferous or Devonian sandstone. It was supposed that all or
none of these reservoirs could be encountered. Basement could be found at
different depths, owing to the difficulties in identifying main seismic
horizons below the top of the chalky limestone. Operations and results Wildcat well 3/7-1 was spudded with the jack-up
installation Ocean Tide on 1 August 1973 and drilled to TD at 3227 m, 9 m into
basement rock. The Paleocene and Maastrichtian horizons
were encountered at 2690 m and 2852 m respectively, which was 41m and 28 m low
to the geologic prognosis estimated depths. The basement (chloritic gneiss) was
encountered directly underlying Turonian limestone. Only the middle part of the chalky Maastrichtian
section had some reservoir characteristics with inferred porosity from the BHC
log about 12% from 2852 m to 2951 m and about l8% from 2951 to 2984.5 m. The Maastrichtian
reservoir was water wet based on the IES log. The underlying Turonian -
Campanian limestone was very tight. No hydrocarbon shows were reported from the
well other than traces of dry gas. One core was cut in basement at TD from
3221 - 3227 m. No fluid samples were obtained. The well was permanently abandoned on 13
September 1973 as a dry well. Testing No drill stem test was performed. General Well 3/7-3 was drilled on a salt diapir in
the southern part of the Søgne Basin in the North Sea. The primary target of
the well was Danian/Late Cretaceous chalk, which had been found hydrocarbon
bearing in the Ekofisk area and in the Danish well Lulu 1. Secondary target was
Middle Jurassic sandstones, which had been found hydrocarbon bearing in well
2/6-2. The TD was planned below the top of the Zechstein salt in order to test
possible Early Jurassic and/or Triassic sandstones. Operations and results Wildcat well 3/7-3 was spudded with the
semi-submersible installation Dyvi Alpha on 21 June 1981and drilled to TD at 3540
m in the Late Permian Zechstein salt. At 1968 m, in the Late Eocene, a drilling
break was experienced and the well started to flow. The flow was killed with a
mud weight of 1.55 g/cc. After setting the 13 3/8" casing shoe at 1961 m,
the well was controlled after gains and losses with a mud weight of 1.58 g/cc. No
other problems were encountered while drilling. The well was drilled with
seawater and bentonite down 666 m, with seawater/SST 202/FCL mud from 666 m to
1970 m, and with seawater/FCL/LC mud from 1970 m to TD. Tertiary sands with a thickness of 37.5 m
were encountered in the Paleocene. They were water bearing. The chalk, which
was the main target, was relatively tight and water bearing. At 3325 m a 107
meter thick water bearing sandstone of Latest Jurassic - Earliest Cretaceous
age (Kimmeridgian - Berriasian) was encountered. Below this sandstone Kimmeridgian
shales rested directly on the Zechstein anhydrite. No shows were noted in the
well. Three cores were cut; one from 2830 to
2848 m in the Danian chalk (60% recovery) and two in the Beriasian Sandstones
from 3337.5 to 3339 m (67% recovery) and from 3339 to 3348 m (100% recovery). No
wire line fluid samples were taken. The well was permanently abandoned on 31
August 1981as a dry well. Testing N The 7/8-2 (Cero) well was drilled on a
domal structure approximately 6 km long by 6 km wide, situated on the Jæren
High in the North Sea. It was estimated that at Paleocene depth there would be close
to 40 square km of closure with 140 m of vertical relief and at Early
Cretaceous depth 27 square km of closure with 150 m of vertical relief. The
principal objective horizons were Paleocene, Jurassic and Triassic sands with
the Danian-Cretaceous limestone as a possible secondary objective. Operations and results Wildcat well 7/8-2 was spudded with the
semi-submersible installation Ocean Viking on 24 July 1973 and drilled to TD at 3006 m in anhydrite of the Zechstein Group. No significant problems are
reported from the operations. The well had no hydrocarbons or shows of
hydrocarbons. In the Paleocene no sand beds were developed, although sand was
present as a loose, unconsolidated constituent in most of the clays and shales.
The Danian and Late Cretaceous limestones were tight. The Late Cretaceous
section was 150 m thinner than anticipated due to erosion of the Coniacian to
Cenomanian formations at the base. The Jurassic succession was encountered at
2808 m and top Triassic at 2883 m. Two Triassic sands were encountered at 2911
- 2937 m and at 2972 - 2996 m. The Triassic section was thinner than expected,
being truncated at 2996 by the Permian Zechstein Group. No cores were cut and no wire line fluid
samples were taken in the well. The well was permanently abandoned on 29 August 1973 as a dry well. Testing No drill stem test was performed. General Well 7/12-2 was drilled on a salt induced
structure on the east side of the Cod Terrace in the North Sea. The primary
objective was to evaluate potential Upper Jurassic and Triassic reservoirs The well is Type well for the Ula Formation
and Reference well for the Farsund Formation. Operations and results Wildcat well 7/12-2 was spudded with the
semi-submersible installation Norskald on 4 July 1976 and drilled to TD at 3676
m in the Early Jurassic Gassum Formation. The well was drilled with
seawater/gel down to 158.5 m and with seawater/lime Drispac mud from 158.5 m to
TD down to 495 m and with a lime/Drispac mud from 495 m to TD. Well 7/12-2 penetrated a major Late
Jurassic reservoir (Ula Formation) and was terminated within a hydrocarbon
bearing sequence of poor quality sands and interbedded shales in the Gassum
Formation. Core analysis and log interpretation indicate an Ula Formation
sandstone reservoir of 128 m net thickness (154 m gross) with porosities
ranging from 14 to 28%, permeabilities from a few millidarcy to over two darcy
and water saturations from 5 to over 50%. The Ula Formation was oil bearing
from top to base at 3532 m in an oil down-to setting. The Gassum Formation
sandstones have a porosity between 11 and 19%, average permeability of 1 md and
water saturation generally in excess of 70%. Eleven cores were cut in the well. Cores
one to ten were cut in succession from 3385.75 m (3380.95 m logger's depth) to
3476.9 m (3470.9 m logger's depth) in the Ula Formation. The overall core
recovery for this section was 97.3%. Core no 11 was cut in the Early Jurassic from
3634.2 to 3652.3 m with 100% recovery. The core-l General Well 7/12-3 was drilled as an appraisal
well on the western flank of the 7/12-2 Ula Discovery in the North Sea. Operations and results Appraisal well 7/12-3 was spudded with
the semi-submersible installation Norskald on 5 April 1977 and drilled to TD at
3710 m in Late Jurassic sediments. The drilling, coring and logging of the well
were of a routine nature. Plugging of the flow lines and screens by hydrating
clays while drilling the 17-1/2" hole caused delays and the loss of considerable
quantities of mud. Rates of penetration were less than anticipated in the Lower
Cretaceous and Upper Jurassic mudstones/ shales. Ninety-four hours were lost
through weather delays during the course of the well. The well was drilled with
fresh water and gel down to 471 m and with Lime/Drispac mud from 471 m to TD. Core, log and R.F.T. analyses proved the
well to have penetrated the Jurassic reservoir discovered in well 7/12-2
beneath the oil water contact. One core was cut in the Jurassic section,
from 3612.2 to 3628.6 m. An RFT water sample was taken at 3683 m The well was plugged back for sidetracking
on 3 June as a dry well. Testing No drill stem test was performed. General Well 7/12-3 A is a geological sidetrack
to 7/12-3 on the western flank of the 7/12-2 Ula discovery in the North Sea. The
primary objective was to establish the oil-water level in the Ula structure. The well is type well for the Mandal
Formation. Operations and results On 4 June 1977 appraisal well 7/12-3 A was
kicked off from below the 13 3/8” casing shoe in well 7/12-3 at a depth of 1720.
The semi-submersible installation Norskald drilled the well to TD at 4191 m
(4011 m TVD) in the Permian Zechstein Group. Well 7/12-3A penetrated the reservoir at
3638.5 (3506.8 m TVD). The cores showed oil staining, cut and fluorescence.
Wire line logs and testing showed this to be immovable oil, and indicated an
oil water transition zone to a depth of 3693.5. (3555.3 m TVD). One hundred and
eighty-nine meters of Ula Formation reservoir were encountered representing a
true thickness of 168.9 m, and a net to gross ratio of 0.83 assuming a 10%
porosity cut off on the computer-processed log. Seven full hole cores were cut from 3642.0
to 3730.0 m. RFT fluid samples were taken at 3675.5 m (salt water and mud
filtrate) and 3688.5 m (salt water with traces of gas and oil/oil-water
emulsion). The well was permanently abandoned on 6
September 1977 as a dry well with shows. Testing DST 1 tested the interval 3771.0 to
3715.5m. The test flowed 192 m3 saline formation water /day through a 32/64
choke. The DST temperature was 146.7 °C.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 7/12-4 was drilled as an appraisal
well on the Ula Field in the North Sea. The main objective was to evaluate the
extent and hydrocarbon potential of the Late Jurassic sands in the south
eastern flank of the structure. Operations and results Appraisal well 7/12-4 was spudded with
the semi-submersible installation Nordskald on 11 September 1977 and drilled to
TD at 3623 m in Early Jurassic sediments of the Bryne Formation. Operations
proceeded without significant problem. The well was drilled with fresh
water/gel down to 498 m and with lime/Drispac mud from 498 m to TD. The target reservoir Ula Formation was
encountered at 3445 m, while the underlying Bryne Formation came in at 3529 m. Net
sand in the reservoir was 73 m with porosity from 10 to 23%, permeability from
a few millidarcy to 1750 millidarcy, and water saturation from 5 to over 60%. The
reservoir was oil-bearing with a possible OWC at 3551 m in the Bryne Formation based
on disappearance of oil shows; however, drill stem tests showed that the producible
contact between oil and water was between 3530 and 3536 m. Seven cores were cut from near top Ula
Formation at 3447.5 m to 3556.7 m in the Bryne Formation. The recovery was 100%
in core one to six and 96% in core seven. RFT fluid samples were taken at 3458
m (oil, emulsion and water), 3467 m (emulsion) and at 3528 m (water) The well was suspended on 12 December
1977 for possible use as a producer at a later stage. It is classified as an oil
appraisal well. Testing Production test General Well 7/12-5 was drilled ca 4 km northwest
of the Ula Field in the North Sea. The objective was to test the hydrocarbon
potential in Late Jurassic Sandstones. Secondary objectives were Early Jurassic
and Triassic sandstones. Operations and results Wildcat well 7/12-5 was spudded with the
semi-submersible installation Borgsten Dolphin 6 February 1981 and drilled to
TD at 4440 m in the Late Permian Zechstein Group. There were some problems with
drilling the section from 2851 to 3741 m due to junk in hole, otherwise
operations proceeded without significant problems. The well was drilled with sea
water and hi-vis pills and gel down to 467 m and with
gypsum/lignosulphonate/CMC mud from 467 m to TD. The Mandal Formation was penetrated at 3731
m, while the Farsund Formation was penetrated at 3763 m. The Ula Formation was
penetrated at 3831 m and consisted of a 69.5 m thick homogenous sandstone, very
fine to fine grained with poor reservoir characteristics (porosities from 7 to
14 % and permeabilities from 0.3 to 3 mD). All attempts to obtain reservoir
pressures and fluid samples failed due to tight formation. Oil shows were
recorded in the upper half of the reservoir and an oil water contact was
established at 3872. Log analysis indicated that no significant hydrocarbons were
present below the Ula formation where all porous zones calculated high water
saturations. Weak shows were recorded in sandstone in the interval 3940 to 3960
m in the Skagerrak Formation. Weak shows were recorded also in siltstone in an
isolated sample from 2235 m in the Hordaland Group. Four cores were cut from 3844.5 to
3912.15 m in the Ula, Fjerritslev, and Skagerrak formations. Core depths are
4.8 m deeper General Well 6506/12-7 was drilled as an
exploration well on the Northeast Smørbukk structure. The primary purpose was
to find hydrocarbon accumulations of significant amounts in the Middle and
Early Jurassic sandstone reservoirs. Secondary objectives were to check for
hydrocarbon accumulations deeper than the structural closure of the main field.
The well should also verify the geophysical and structural interpretation and improve
the geological, paleontological and geochemical understanding of the area.
Total depth was to be in rocks of Triassic age or 4000 m in order to satisfy
the licence commitment. Operations and results Well 6506/12-7 was spudded with the
semi-submersible installation Dyvi Delta on 7 April 1987 and drilled to TD at 4840 m in the Early Jurassic Tilje Formation. Drilling proceeded without
significant problems. The well was drilled with spud mud down to 597 m, with
gypsum/polymer mud from 597 m to 4427 m, and with a pre-hydrated
Bentonite/Lignosulphonate mud system from 4427 m to TD. No shallow gas was
encountered. The first show appeared in the Lange
Formation at 3791 - 3794 m. During coring there were oil shows in Garn and Ile
Formations, while Ti1je only contained small traces of oil. Both cores and logs
indicated that Garn and Ile Formations were hydrocarbon bearing down to ca 4538
m, while Ti1je Formation was indicated to be water bearing. The porosity was
assumed to be between 8 and 12 %. Mobil wanted to test the Ti1je Formation to
get a fluid sample to understand the logs better. This was a wise decision
because the formation produced oil at very good rates. The Garn Formation on
the other hand did not produce any formation fluid when tested. The oil/water
contact in the Tilje Formation was not found because the logs did not give
clear data. Eight cores were cut in the well with a
total recovery of 62.6 m core. One core was cut in the interval 4053 - 4058 m
(Spekk Formation), two cores from 4 General Exploration well 8/1-1 is situated in the
Danish-Norwegian Basin in the North Sea. The Primary objective of the well was
Jurassic to Triassic sands with estimated 380 m gross and 76 m net sand.
Secondary targets were seen in Paleocene sands, Danian - Late Cretaceous
limestones, and Early Cretaceous sands. The well is Reference Well for the Sauda,
Tau, and Flekkefjord Formations. Operations and results Wildcat well 8/1-1 was spudded with the
3-leg jack-up installation Ocean Tide on 2 December and drilled to TD at 2973 m
in the Late Permian Zechstein Formation. Paleocene shales were penetrated at 1378
m without sand development. The dark grey shales of the Paleocene continued into the Danian. The interval from 1507 m o 1535 m in the Danian was
described as a light to medium grey calcareous marl grading to shale. The
sequence from 1535 m to 1899 m was composed of white chalky limestone. A bed of
medium grey to light green-grey shale was recorded from 1899 m to 1932 m. The
Early Cretaceous consisted of shale and clay. Late Jurassic shales of the Sauda
and Tau Formations were penetarated from 2425 m to 2606 m. The primary target
sands were encountered from 2606 m to 2704 m. Sand and sandstone, clear, white
and light grey, fine medium and coarse grained, angular to sub-rounded and
anhydritic, dominate the lithology. Lesser amounts of medium to dark grey shale
occur in the form of erratically spaced interbeds. Red-brown, silty, soft,
anhydritic shale characterizes the major portion of the Triassic. Interbedded
with the shale are occasional relatively thin zones of both clear and red
hematitic stained, fine to medium grained, sand. No shows of hydrocarbons were
encountered in either the Jurassic sand or the Danian - Late Cretaceous carbonate.
No conventional core was cut and no fluid samples were taken. The well was permanently abandoned on 17
February 1972 as a dry hole. Testing No General Wildcat well 8/4-1 is located in the
Danish Norwegian Basin of the North Sea. The primary objective was to test the
hydrocarbon potential of Middle Jurassic sandstones, expected at 2430 m with a
122 m thickness. A secondary objective was seen in the Late Cretaceous chalk.
Planned TD was at 2850 m in the Permian Zechstein Group. Operations and results Wildcat well 8/4-1 was spudded with the
semi-submersible installation Norjarl on 21 June 1977 and drilled to TD at 2632
m, 50 m into the Permian Zechstein Group. The well was drilled with lime and
Drispac down to 1757 m and with, and lignosulphonate from 1757 m to TD. The well encountered a 116 m thick Middle
Jurassic sandstones sequence (Bryne Formation) with top at 2397, fairly close
to prognosis. The secondary target was also encountered close to prognosis, at
1664 m (Tor Formation). Early Cretaceous Cromer Knoll Group was found
unconformable on Late Jurassic shales. The Upper part of the Boknfjord Group
was not present in the well. The well was electrically logged from 85 m to 2623
m and no pay was present in the well to this depth. Trace residual oil shows
were seen in sidewall cores at 2417 m and 2462 m. Total gas averaged 5 to 10
units throughout the course of drilling with no significant gas peaks. Shows of
the heavier hydrocarbon gases C2 to C4 were present in the interval 2355 m to
2466 m. Three pressure regimes exists in this well. The first includes the Late
Tertiary sediments and is only very slightly overpressured reaching approximately
9.2 ppg at its base at 899 m. This is the top of the second regime and marks
the unconformity between the Late Tertiary and Eocene sediments. The Eocene and
the Paleocene below, exhibit an increasing pore pressure with depth reaching a
maximum of approximately 12.6 ppg EMW above the Paleocene/Late Cretaceous
unconformity at 5261 ft. (1604 m). The third regime extends to TD and is
assumed to be near normally pressured. Organic geo General Well 8/9-1 is located in the Åsta Graben.
It was designed to test a salt structure in the central part of the
Norwegian-Danish basin. The primary objective was to penetrate Basal Jurassic
unconformity sands in a crestal position of the closure. The sands were
estimated to have an approximate gross thickness of 60 m and were expected to
be Late Jurassic in age. The well is Reference Well for the
Fiskebank Formation. Operations and results Wildcat well 8/9-1 was spudded with the
semi-submersible installation Ocean Viking on 22 December 1975 and drilled to
TD at 2376 m in the Late Permian Zechstein salt. The well was drilled with salt
gel down to 411 m and with a lignosulphonate / gypsum mud from 411 m to TD. The well penetrated fine-grained silty
sandstone very rich in glauconite in the interval 1316 m to 1376 m in
Paleocene. Net sand for the interval was 60 m and porosities derived from the
density log and corrected for clay effects were in the range 16 % to 24 %. In
the interval 2124 m to 2149 m in the Late Jurassic a series of interbedded
claystones, siltstones and sandstones were penetrated. The only true sandstone
interval here existed between 2147 m and 2149 m where porosities ranged from 7
% to 14% calculated from density - neutron cross plot. All other low GR and
permeable intervals in the Late Jurassic section indicated porosities
substantially less than this and corresponding sidewall cores showed tight
siltstones. In the Middle Jurassic the interval 2168.7 m to 2222.6 m was found
to contain a sequence of predominantly interbedded sandstones, siltstones, and
claystones with occasional thin carbonaceous beds. The caliper indicated a net
sand of approximately 25 m out of a gross interval of 54 m. The porosities in
this interval were exceedingly variable from one sandstone unit to the next and
ranged from 5 % to 26 %. The sands with the highest porosities occurred near
the top of the section between 2171 m a General Well 8/11-1 is located on the
Sørvestlandet High towards the Åsta Graben. It was drilled on a crestal
position of an elongated faulted anticline approximately 11 km long and 5 km
wide. The primary objective horizon was the Jurassic Sandstone section, which
from seismic information was expected to have closure of 39 km2 with a maximum
of 66 m of vertical closure. Late Cretaceous limestone, Paleocene sandstone and
Triassic Sandstone were secondary objectives. Operations and results Wildcat well 8/11-1 was spudded with the
semi-submersible installation Ocean Viking on 24 April 1975 and drilled to TD
at 3810 m in the Triassic Red beds. The well was drilled with seawater and
Attapulgite clay down to 458 m, with seawater/Drispac and 3% diesel oil from
458 m to 1219 m, and with seawater/Drispac/lime/4-5% diesel oil from 1219 m to
TD. The formation tops and thicknesses agreed
well with the geological prognosis with Paleocene coming in at 1968 m, top
Cretaceous at 2143 m, the Jurassic at 2807 m, and top Triassic in the interval
2855 m to 2900 m. In the Paleocene, no sands were developed and in the Upper
Cretaceous the limestone was tight. The Jurassic section consisted of 27.4 m of
dark grey shale of Portlandian - Late Kimmeridgian age. The total sand section
had been eroded away by the Kimmeridgian unconformity. After drilling 975 m of
barren Triassic section the well was terminated at the prognosed depth of 3810
m without the Zechstein salt having been encountered. The well had no shows and
thus no testing was carried out. No conventional core was cut and no fluid
sample taken. The well was permanently abandoned on 29
June 1975 as a dry well. Testing No drill stem test was performed General Well 9/4-4 is located east of the
Flekkefjord High on the western flank of the Egersund Sub-basin, which forms a
part of the Danish-Norwegian Basin. The main objective of drilling 9/4-4 was to
test the middle Jurassic sands on the western flank of the Egersund sub-basin.
Alternating porous and nonporous sands of Late Triassic and possible minor Late
Jurassic sands were considered secondary objectives. Operations and results Wildcat well 9/4-4 was spudded with the
semi-submersible installation Deepsea Saga on 19 July 1977 and drilled to TD at
2902 m, 57 m into the Triassic Skagerrak Formation. No significant problems
were encountered in the drilling operations. The well was drilled with
high-viscosity spud mud down to 405 m, with gypsum mud from 405 m to 1300 m,
and with lignosulphonate mud from 1300 m to TD. At 2807 m the pipe stuck and
was freed by adding "Pipefree" and diesel to the mud. The Middle Jurassic sands with a gross
thickness of 117 m were found as postulated. Secondary objective reservoir
sands in Late Triassic and Late Jurassic were not encountered. No oil shows
were encountered in any section of the well and no hydrocarbons could be
inferred from logs. The most likely reason for the lack of hydrocarbons is
immaturity of the Jurassic source beds. Organic geochemical source rock
screening of the interval 250 m to TD showed good to excellent source rocks in
the Late Jurassic shales and the Middle Jurassic (Bryne Formation) coals. The
analyses showed that the Bryne coals were immature for petroleum generation and
that the Late Jurassic shales were immature, possibly marginally mature. No
conventional core was cut and no fluid samples taken. Fourteen sidewall cores
were recovered from the interval 2673 m to 2850 m. The well was permanently abandoned on 20
August 1977 as a dry hole. Testing No drill stem test was performed. General Well 10/5-1 was designed to test a tilted
fault block with an overlying pinch out trap in the eastern part of the
Norwegian-Danish basin. The primary objective was Rotliegendes sands. A
probable 460 m gross thickness was anticipated. A secondary objective was
Middle Jurassic sandstones with an estimated gross thickness of 61 metres.
Other possible objectives were the Early Cretaceous sandstones and Basal
Zechstein carbonates. The well is Illustration Well for the
Børglum Unit of the BoknFjord Group. Operations and results Exploration well 10/5-1 was spudded with
the semi-submersible installation Norjarl on 31 May 1976 and drilled to TD at
1843 m in crystalline granite dated by the potassium-argon method to apparently
689 ± 21 My (Late Precambrian). After drilling the 36" section to 189 m
the hole had washed out under the temporary guide base. The guide base sank 26
feet below the mud line and the 30" casing could not be stabbed through
the guide base. The rig was moved 38 m and the hole was respudded. The well was
drilled with seawater / gel down to 501 m, with Inpac polymer mud from 501 m to
1768.2 m, and with lignosulphonate mud from 1768.2 m to TD. The well penetrated a gross thickness of
67 metres of Middle Jurassic (Sandnes Formation) sandstones from 1472 m to 1539
m. Porosity was good, but there were no hydrocarbon indications while drilling,
and subsequent log analysis confirmed that the objective horizons were water
wet. Triassic sandstones were also encountered, but these were extremely
shaley, and had no clean sandstone sections. Rotliegendes sandstones were not
present at the 10/5-1 location. The base of the Zechstein interval was
represented by a clear, white, light brown, hard, very angular sandstone,
cemented with siliceous cement and extremely tight. Organic geochemical
analyses found fair to rich TOC (1 - 5%) in the Early Cretaceous and Late
Jurassic and possibly in some Permian sha General Well 11/9-1 is located in the Horn Graben
far to the east in the North Sea towards the Skagerrak Sea, ca 15 km from the
Danish border. It was located near the top of a saliferous structure in order
to explore the whole Triassic series in the most favourable structural
position. The structure is potentially large, but since all horizons above the
Jurassic level were expected to crop out on the seabed the objective horizon
was Lower Middle Triassic carbonaceous shales. These shales were seen both as
source rock and seal for hydrocarbons in underlying sandstones (basal Triassic
Brockelschiefer). No other objectives were defined for this well. Operations and results Wildcat well 11/9-1 was spudded with the
semi-submersible installation Deepsea Driller on 16 January 1976 and drilled to
TD at 1972 m, 42 m into Late Permian Zechstein salt. The well was drilled water
based with spud mud down to 660 m and with ferrochrom lignosulphonate mud (FCL)
from 660 m to TD. Drilling was without returns to 145 m.
From there red sandstones and variegated shales made up a very thick Triassic
interval (1785 m). The Triassic contained reservoirs as usual but no obvious
sealing intervals were seen. Moreover, no potential source rocks were
encountered. No shows of gas or oil were recorded during drilling and the
different reservoirs were water bearing from the logs. No conventional core was
cut and no fluid sample taken. Forty sidewall cores were retrieved in two runs
in the interval 737 m to 1962 m. The well was permanently abandoned on 28
February 1976 as a dry hole. Testing No drill stem test was performed. General Well 15/2-1 was drilled in the Vilje
sub-basin in the Viking Graben in the North Sea, ca 1.5 km from the UK border.The objective of the well 15/2-1 was to
test the Upper Jurassic, Middle Jurassic, and Triassic sandstone reservoirs
northwest of and down dip of the salt diapir encountered in the well 15/5-3. The
well was planned to be drilled ca 200 m into the Triassic with a total depth of
ca 4525 m. Operations and results Wildcat well 15/2-1 was spudded with the
semi-submersible installation Nortrym on 26 September 1981 and drilled to TD at
4600 m in the Late Permian Zechstein Group. No significant problems were
encountered in the operations. The well was drilled with seawater and hi-vis
pills down to 665 m and with Shaletrol polymer mud system from 665 m to 2750 m.
At 2750 m the mud was converted to a dispersed mud system by adding
lignosulphonate and this was used for the remaining well bore down to TD. There
was 0 - 3% oil in the mud below 1168 m. The well penetrated a number of sandstone
Formations in the Tertiary (Skade, Grid, Intra Balder sandstone, Heimdal, and
Ty Formations). All these were entirely water wet. The Hugin Formation (4356 - 4493
m) consisted of massive very fine grained sandstones with beds of coal on top. The
Sleipner Formation (4493 - 4554.5 m) had a 10 m thick coal layer on top
underlain by siltstones grading occasionally to very fine sandstones, interbeds
of sandstones, and stringers of coal. The well did not penetrate any Early
Jurassic or Triassic rocks, but encountered evaporites of Permian age at 4554.5
m, unconformably underlying the Sleipner Formation. Good hydrocarbon shows were reported from
both the Hugin and Sleipne Well 15/3-1 S was drilled west of the
Gudrun Terrace on the east flank of the North Sea Central Graben. The primary
objective was to test sands in the Middle Jurassic (Dogger sands). Secondary objectives
were the Early Tertiary, Danian, Early Cretaceous sands. Triassic sandstones
and Zechstein dolomites down to the "economic basement" were also
possible targets. The well is reference well for the Ty,
Draupne, and Heather formations. Operations and results Wildcat well 15/3-1 S was spudded with
the semi-submersible installation Deepsea Driller on 27 November 1974 and
drilled without significant problems to 4400 m. While circulating before
logging the pipe stuck and the hole started to kick. After unsuccessful efforts
to free the pipe the well was plugged back and sidetracked from 3985 m. The
sidetrack was drilled without further significant problems to final TD at 5129
m in the Middle Jurassic Hugin Formation. The well penetrated water-bearing Hermod,
Heimdal and Ty formation sandstones from 2215 to 2715 m. The Ty Formation from
2556 m was reported as the best of these with a main body of clean sand from
2599 to 2711 m. Top Viking Group, Draupne Formation was encountered at 3947 m.
The Draupne Formation contained many oil and gas bearing Intra-Draupne
Formation sandstones. Of these the best reservoirs were found in the intervals
4083 to 4317 m with OWC at 4218 m, and 4442.5 to 4610 m with OWC at 4486 m.
Total net pay in these two intervals together were 32 m with 22 - 19 %
porosity. Geochemical analyses indicated good source rock properties in the
shale interbeds, with a maturity ranging from early to late oil window
(vitrinite reflectance from 0.6 to 0.9 %R General Well 15/3-2 was drilled in the Vilje
sub-basin structural element of the south Viking Graben of the North Sea. The
objectives of well 15/3-2 were all Jurassic sands. The well was planned in two
phases. Phase 1 (15/3-2) was to be drilled with the Polyglomar Driller down to
top Jurassic. Phase 2 (15/3-2 R) was to be drilled with the Pentagone 84, a rig
with a 15.000 psi wellhead equipment, necessary for testing of the high-pressure
Jurassic reservoirs. Operations and results Well 15/3-2 was spudded with the
semi-submersible installation Polyglomar Driller on 29 October 1976 and drilled
to TD at 4258 m in the Late Jurassic Draupne Formation. When pulling out of the
hole to set the 9 5/8" casing the drill string parted at 138 m, but was
fished out. Otherwise, no significant technical problem occurred in the
operations. The well was drilled with seawater and hi-vis pills down to 186 m,
with prehydrated bentonite in fresh water from 186 m to 784 m, with LFC/Dextrid
mud from 784 m to 2875 m, and with LFC+LC in seawater from 2875 m to TD. Up to
3% oil was added to the mud from 3953 m to TD. Down to 4236 m (Tertiary and Cretaceous
sections) no significant shows were observed except in Coniacian and Turonian
limestones where some brown-yellow fluorescence was observed. Electric log
analysis did not indicate any hydrocarbon-bearing reservoirs in these
limestones. No cores were cut and no wire line pressure
points or fluid samples were taken. A 9 5/8" casing was set at 4248 m
and the well was suspended on 24 January 1977 for later re-entry and drilling
and testing of General Well 15/3-2 R is a re-entry of well
15/3-2 in the Vilje sub-basin structural element of the south Viking Graben of
the North Sea. The primary well 15/3-2 was drilled by "Polyglomar
Driller", which was equipped with 10.000 psi WP 18 3/4" BOP-stack.
This well was suspended on 24 January 1977 with 9 5/8" casing set at 4248
m, in the Late Jurassic Draupne Formation. The re-entry was drilled with the
Pentagone 84, equipped with a 15000 psi WPI 11" BOP stack, necessary to drill
and test high-pressure Jurassic reservoirs. The objective of well 15/3-2 R was
to test the Jurassic reservoirs, including the Dogger - Lias sections. Operations and results Well 15/3-2 was re-entered with the
semi-submersible installation Pentagone 84 on 26 July 1977 after some initial
problem with connecting to the wellhead on the sea floor. An 8 11/32" hole
was drilled down to 4990 m when the drill string parted. In spite of an
extensive fishing operation, the fish had to be left in hole. Top fish is at
4742 m. A sidetracking operation was performed trying to bypass the fish, but
also this operation failed and 4990 became TD of the well. The well was drilled
water based with LFC-LC mud from re-entry point to TD. The Draupne Formation extended from 4236
m down to 4352 m, making up a total of 116 m. Geochemical analyses proved TOC
from 3 to 7 %wt and vitrinite reflectance analyses indicated middle oil window
maturity (%Ro = 0.75). Four Intra Heather Formation sandstone reservoirs were
drilled in the Jurassic section, varying in gross thickness from 15 to 112 m. According
to logs the two upper ones, 112 and 64 m thick, were hydrocarbon-bearing, but
with bad characteristic General Well 31/4-8 was drilled on the Brage
field in the North Sea to appraise the Statfjord Group oil discovery made in
well 31/4-7. The Cook Formation of the Dunlin Group was the secondary target.
This sandstone was found water bearing in well 31/4-7. Chances for finding
hydrocarbons in well 31/4-9 were good since the formation would be penetrated
in a structurally higher position. Prognosed TD was 2565 m or 50 m into
Triassic rocks. Operations and results Appraisal well 31/4-8 was spudded with
the semi-submersible installation Treasure Hunter on 11 May 1986 and drilled to
TD at 2611 m in the Late Triassic Lunde Formation. The 13 3/8" casing got
stuck at 1855 m. Diesel and spot fluid was pumped down the hole and the casing
was worked free. The well was drilled with spud mud down to 900 m and with
KCl/polymer mud from 900 m to TD. From 2030 m to ca 2400 m the KCl/polymer mud
contained 1% diesel as a result of the problem with the stuck casing. The well 31/4-8 encountered hydrocarbon
bearing sandstones and siltstones in the Viking Group, the Statfjord Group and the
Lunde Formation. Of these, only the Statfjord reservoir is produceable. The
Viking Group consisted of a thin Draupne Formation from 2085 m to 2088 m and a
29 m thick Fensfjord Formation with poorly developed, generally very fine-fine
sandstones grading into and interbedded with siltstones and claystones. Some
residual hydrocarbons were encountered in the best sands. Net pay in the
Fensfjord Formation was 0.61 m, water saturation was 59.9% and the average porosity
was 25.5%. The Cook Formation was found water bearing without traces of shows. Average
porosity in the Cook sand was 17.7%. The Statfjord Group had a gross oil column
of 60 m from 2346 to the OWC at 2406 m. General Well 15/3-3 was drilled west of the
Gudrun Terrace on the east flank of the North Sea Central Graben, about 4.5 km north-east
of the 15/3-1 S discovery. The main objective of the 15/3-3 well was to appraise
the complete Jurassic series up-dip of well 15/3-1 S drilled on the same
structure in 1975. Well 15/3-3 is type well for the Grid
Formation. Operations and results Appraisal well 15/3-3 was spudded with
the semi-submersible installation Pentagone 84 on 5 January 1979 and drilled to
TD at 5115 m in the Triassic Skagerrak Formation. Several water bearing sands with high
porosity were encountered in the Tertiary section including the Grid, Heimdal
and Ty formations. The Cretaceous had no reservoir sections and was drilled
without gas shows. The Late Jurassic Draupne Formation was encountered at 4017
m. The Draupne Formation was 208 m thick and consisted of shales with only a
few < 1 m sandstone beds. The Heather Formation was penetrated from 4225 to
4522 m and contained a main Intra Heather Formation sandstone from 4260 to 4369
m. This sandstone was gas and condensate bearing in the upper part down to a
GOC at 4272 m. The Hugin Formation came in at 4522 m and then the Sleipner
Formation at 4545 m. The Hugin Formation contained gas filled sandstone from
4522 to 4527 m. Several thinner sandstones with gas followed down to a main gas
filled sandstone in the Sleipner Formation from 4588 to 4632 m. A second hydrocarbon
filled Sleipner Formation sandy interval was penetrated from 4679 to 4693 m.
The upper part down to 4687 m consisted of good sandstone, further down it was
cemented. The only oil shows in the well was rare
pa General Well 15/3-4 was drilled on the Gudrun
Terrace, east of the 15/3-1 S Gudrun Discovery in the North Sea. The main objective
of the well was to test sandstones of the Late and Middle Jurassic, which were
found to contain gas and condensate in wells 15/3-1 S and 15/3-3. The secondary
target was the Eocene sands where oil shows were encountered in well 15/5-3. Operations and results Wildcat well 15/3-4 was spudded with the
semi-submersible installation Borgsten Dolphin on 3 October 1981and drilled to
TD at 4259 m in the Triassic Skagerrak Formation. After the 13 3/8" casing
had been cemented drilling was interrupted for 13 days due to a combination of
bad weather and repairs on the BOP stack. When running in hole at TD the drill string
stuck leaving a fish with top at 4098 m. Hence, no logs were run between 4098 m
and TD. The Eocene sands from 1628 to 2025 m
(Grid Formation sands) were found water bearing. The Brent Group was
encountered with top Hugin Formation at 3786 m and top Sleipner Formation at
3856 m. Sandstones in the Brent Group contained oil and gas in four different intervals:
3786 to 3817 m, 3819.5 to 3826.5 m, 3849.9 to 3854.8 m, and 3872.2 to 3876.4 m.
The four zones were in different pressure regimes. The interval from 3819.5 to
3826.5 m had a low hydrocarbon saturation based on the logs, but the cores from
this section had good shows with a similar bulk hydrocarbon composition as in
the uppermost interval. Triassic sands below 4050 m were found water bearing. Good
oil shows were seen on all cores from the Hugin Formation, otherwise no shows
were reported from the well. Five cores were cut in the well. Core 1
was cut in the Grid Formation from 1678 to 1694 m wit General Well 15/5-1 was drilled on the Ve
Sub-basin north of the Sleipner Vest Field in the North Sea. The main objective
of the well was to test sandstone reservoirs of Middle Jurassic age. In the
nearby Sleipner field (in block 15/6 and 15/9) gas had been found previously in
reservoirs of the same age. The well was located down flank on the structure at
the Kimmerian level. This position was chosen to penetrate reservoirs believed
to be wedging both above and below a strong seismic marker ("Red
Marker"). Operations and results Wildcat well 15/5-1 was spudded with the
semi-submersible installation Treasure Seeker on 26 November 1977 and drilled
to TD at 3775 m in Late Triassic sediments belonging to the Hegre Group. This
was the first well drilled by Treasure Seeker, which was outfitted in
Stavanger. About 25% of total rig time was counted as lost time, mainly due to
wait-on-weather or equipment problems caused by rough weather in wintertime.
The well was drilled with seawater and gel down to 1225 m, with
seawater/gel/CMC/Spersene from 1225 m to 1910 m, and with a freshwater-based Spersene/gel/chrome-lignosulphonate/Drispac
mud from 1910 m to TD. The 15/5-1 well encountered gas
condensate-bearing sandstones of Late and Middle Jurassic age (Callovian and
Bathonian) from top at 3558 m down to 3614 m where a Bathonian/Bajocian deltaic
series with up to five m thick coal beds appeared. From wireline log evaluation
the sandstone section with a gross thickness of 56 m, has been subdivided into
four separate pay zones, each zone being separated by thin impermeable layers,
resulting in a net sand pay of 42.1 m. Average porosity was calculated to 14%
and the average water-saturation to 14%. Sands were water wet below the coal
bed General Well 15/5-2 was drilled in the Ve Sub-basin
in the North Sea, north of the Sleipner Vest Field and 15/5-1 Gina Krog
Discovery. The main objective of the well was to test possible hydrocarbon
accumulations in Middle to Late Jurassic Bathonian/Callovian transgressive
sandstones and Middle Jurassic Bajocian deltaic sandstones. The well was
located in a purposely off-crestal position on an approximately 16 km2 large
structure some 7 km north-west of the 15/5-1 discovery. The well was planned to penetrate into
the Triassic with a projected total depth of 4500 m. Operations and results Wildcat well 15/5-2 was spudded with the
semi-submersible installation Treasure Seeker on 16 August 1978 and drilled to
TD at 4322 m in the Triassic Hegre Group. At 1267 m, the string unscrewed in a
tight section, but it was fished without problems. After drilling to 2293 m,
the string stuck when pulling out of hole. This time the fish was not recovered
and a sidetrack was performed with kick-of at 1775 m. Heavy weather caused
further delays, otherwise the drilling went forth without significant problems
to TD. The well was drilled with seawater mud mixed with gel and Spersene down
to 454 m, and with a Spersene/XP-20 (lignosulphonate) mud from 454 m to TD. At
2232 m 1% Diesel was added to the mud. Two hydrocarbon bearing sandstone
intervals were penetrated by the well. In the Jurassic, only a thin Early to
Middle Bathonian sandstone development was penetrated between 4035 m and 4055 m.
Interbeds of siltstones and shales reduced the 20 m gross pay to a net pay of
7.3 m from wireline log interpretation. Average porosity and average water
saturation over the pay interval was calculated to 14.3 and 41 General Well 15/6-2 was drilled in the Ve
Sub-basin in the North Sea, ca 5 km north of the Sleipner Field. It is the
replacement well for 15/6-1, which was junked for technical reasons. The objective
was to evaluate a deep-seated structure in the Scottish-Norwegian Graben. The
target was Eocene to Paleocene sandstones. Operations and results Wildcat well 15/6-2 was spudded with the drill
vessel on 9 September 1971 and drilled to TD at 3131 m in the Shetland Group. No
drilling problems were encountered, however, due to deviation problems around 1311
m a planned FIT was aborted, as the tool would not go beyond this depth. Initial
drilling from the sea floor to 1330 m was with seawater and gel. Below 1330 m,
a fresh water Spersene XP-20 mud system was used. The Paleocene section contained abundant
potential sandstone reservoirs (Heimdal Formation) with thin beds of clay
becoming marly below 2390. Significant shows were encountered in the interval 2223
to 2236 m in the upper Heimdal Formation. The cuttings, sidewall and
conventional cores corroborated the shows. Weak shows were recorded also on
numerous sidewall cores between 2303 and 2604 m. However, other evidence did
not substantiate these shows and the reservoir was assumed water wet below 2236
m. The Danian (2676 to 2735 m, Våle Formation) consisted of a sequence of
thinly interbedded sandstones, clays, shales and chalky limestones. No shows
were reported in this section. The Late Cretaceous section, from 2735 m to 3106
m, was predominantly limestone with thin interbeds of shale. Thin interbeds of
sandstone were also noted. There were no shows in the Late Cretaceous. Three cores were cut. Core 1 was cut from
2236 to 2242 m with 10 General Well 15/6-3 was drilled in the Ve
Sub-basin in the south Viking Graben in the North Sea. The primary objective
was to test the Dogger Sands (Middle Jurassic), which were gas bearing in
15/6-2 R, at a structurally higher position on a large north south trending
anticline. Operations and results Wildcat well 15/6-3 was spudded with the semi-submersible
installation Drillmaster on 5 September 1974 and drilled to TD at 3795 m in
Late Triassic sediments of the Skagerrak Formation. A lignosulphonate seawater
mud was used to drill the well. The Dogger sand from top at 3488 m to 3579
m was hydrocarbon bearing. The resistivity log indicate gas down to a massive
coal layer at ca 3562 m. The true gas/water contact was not established. There was
63 m of net gas bearing sand with average porosity 21% and average water
saturation 21.%. The Triassic was not a viable reservoir. The only major shows in
the well were in the Dogger reservoir sands. A total of 125.8 m core was recovered
(90.7 % overall recovery) in ten cores in the interval 3512.2 to 3650.9 m. FIT
fluid samples were taken at 3505 m (gas, water, mud and trace oil), 3553 m
(gas, water, mud and trace oil), 3557 m (gas, mud filtrate and mud), and 3575 m
(mud filtrate and mud). The well was permanently abandoned on 19
December 1974 m as a gas/condensate discovery. Testing Two production tests were run. The first was between 3601.2 and 3604.3 m,
this failed to flow.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 15/6-4 was drilled on the southern
end of the Gudrun Terrace in the North Sea. The objective was to test the
hydrocarbon potential of Middle Jurassic (Dogger) sandstones. Operations and results Wildcat well 15/6-4 was spudded with the
semi-submersible installation Norjarl on 28 June 1976 and drilled to TD at 3505
m in the Triassic Smith Bank Formation. The well was drilled water based with
lignosulphonate/CMC/lignite below 3097 m Top Draupne Formation was encountered at 3157
m. The target sandstone unit was encountered at 3222 m and was found to be
water bearing. Four cores were cut. Cores 1 and 2 were
cut from 3226.3 m to 3247.6 m and cores 3 and 4 were cut from 3271.5 m to 3308
m. FIT fluid samples were taken on wire line at 3312 m (small amounts of gas
and 10.2 l water) and at 3222.5 m (small amounts of gas and 10.2 l water). The well was permanently abandoned on 16
August as a dry well. Testing No drill stem test was performed. General Well 15/6-5 was drilled in the north-eastern
part of the Sleipner Field (Sleipner West). The objective was to confirm
structural and stratigraphic interpretations as well as define the hydrocarbon
content and contacts and the reservoir properties in this part of the Field. The well is reference well for the Hugin
Formation. Operations and results Appraisal well 15/6-5 was spudded with
the semi-submersible installation Drillmaster on 10 October 1977 and drilled to
TD at 3824 m in Triassic sediments. No significant problems were encountered
during the drilling of the well. Initial drilling from the sea floor to 166.5 m
was with fresh water and lignosulphonate. Below this depth and down to 1197.5 m
a seawater gel with carboxymethyl-cellulose (CMC) mud system was used. Below
1197.5 m the above mud with lignosulphonate was used. The Hugin Formation (Upper Dogger
Sandstone) was encountered at 3627 meters. This was six meters below the lowest
gas seen in the main Sleipner reservoir to that date, 3597 m MSL in 15/9-1. The
Hugin Formation is 53 meters thick in the well and essentially 100% sandstone. Electric
log analysis and RFT pressure data show the section to be water bearing,
although the presence of residual hydrocarbons down to 3655 m was indicated by
bleeding gas and excellent liquid hydrocarbon shows in the cores. No
hydrocarbon indications were present below 3655 m. The Sleipner Formation
(Lower Dogger) came in at 3580 m with several massive coals beds. The well established
that the potential lower limit of hydrocarbons in the main Sleipner reservoir was
3627 m (3603 m MSL). Four conventional cores were cut from
3629 m to General Wildcat well 15/8-1 was drilled west of
the Sleipner field, ca 2 km from the UK border. The well was designed to test
possible hydrocarbon accumulation in the sandstones of middle Jurassic age. Operations and results Wildcat well 15/8-1 was spudded with the
semi-submersible installation Glomar Biscay II on 18 July 1981 and drilled to
TD at 4300 m in the Middle Jurassic Fladen Group. Drilling operations were
performed without significant problems in the 36", 26" and 17 1/2"
holes. Pipe stuck in the 12 1/4" hole at 2254 m and several times in the 8
1/2" hole. Miscellaneous technical problems occurred while drilling the
6" hole and a gas kick was at 4265 m while tripping. The well was drilled
with seawater and gel down to 500 m and with gypsum mud from 500 m to 2890 m.
Lignosulphonate was added from 1570 m, and from 2890 m to TD the gypsum mud was
gradually depleted and replaced with a gel/lignosulphonate mud. The well 15/8-1 proved gas and condensate
in sandstone of Middle Jurassic age. The gas/water contact was indicated at
3698 m from the Formation Multi Tester. Oil shows were recorded from 3065 m to
3075 m in the Hod Formation. Five conventional cores were cut in the interval
3658 m to 3705.5 m in the Hugin Formation. Three samples were attempted taken
during FMT runs. Due to technical malfunctions only 1 sample (from 3668 m) was
obtained. The well was permanently abandoned on 7
January 1982 as a gas/condensate discovery. Testing One drill stem test was performed in the
Sleipner formation and three in the Hugin Formation. The procedure of the tests
was similar; after initial flow and build up the well was flowed for
approximately 660 min. producing gas/condensate. Test no. 4 was only flowed for
480 minutes. CO2 was produced in all tests, in concentrations ranging from 4%
to 15%, and up to 8 ppm H2S was recorded in DST2. Two sets of PVT samples were
taken General Well 15/9-1 is located in the Sleipner
Field. It was drilled on a seismic structure in order to evaluate the Dogger
sandstone (Hugin and Sleipner Formations) of Middle Jurassic age. Operations and results Wildcat well 15/9-1 was spudded with the
semi-submersible installation Ross Rig on 24 February 1977 and drilled to TD at
3734 m in the Late Triassic Skagerrak Formation. Severe weather occurred on 31
March, at 3539 m, when the drill string was hung off in the wellhead and the lower
marine package disconnected. Drilling commenced on 2 April. When
washing/reaming back to TD at 3675 m with a bit to open up the rat hole the
pipe stuck at 3647m. Jarring/fishing action was unsuccessful and the string was
backed off at 3507 m. The hole was then plugged back, sidetracked and drilled
to TD. The well was drilled with seawater and hi-vis pills to 415.5 m and with
a seawater/conditioned bentonite/spersene mud system from 415.5 m to TD. Top of the Dogger sandstone (Hugin
Formation) was encountered at 3530 m. Log evaluation gave a net productive pay
of 56 m, of which 38 m was gas bearing and 18 m was oil bearing. Lowest
producible hydrocarbon depth was top of coal bed at 3672 m. Good shows were
recorded on cuttings in the interval 3633 m to 3687 m, and in porous sandstones
on cores from 3545 m to 3667 m. The Jurassic sandstone was cored in nine cores
between 3521 m and 3675.5 m. RFT fluid samples were taken at 9 depths in the
interval 3525.5 m to 3701 m. Most of them recovered traces of condensate or oil
together with mud filtrate and gas. Only three samples recovered measurable
quantities of fluid hydrocarbons: 3528.8 m (5 - 15 ml condensate), 3596.5 m
(500 ml condensate), and 3621 m (5 - 15 ml oil). The well was permanently abandoned on 30
May 1977 as an oil and gas appraisal. Testing Two DST's were performed. DST 1 perforated the interval 3660 m to
3655 m and flowed 1330 STBOPD (211.5 General Well 15/9-2 was drilled on the Sleipner
Vest Field in the North Sea. The primary objective was to test the "beta
closure" on the 15/6-3 Sleipner Vest discovery. The target was Middle
Jurassic sandstones. Operations and results Well 15/9-2 was spudded with the semi-submersible
installation Ross Rig on 12 April 1978 and drilled to TD at 3764 m in Late
Triassic sediments in the Skagerrak Formation. The main problem in operations
was the discovery of a washout in the well head 18 3/4" ax seal area after
setting 9 5/8" casing. This was repaired so that drilling could proceed,
but it was decided not to do the planned DST due to possible leak. Otherwise,
operations proceeded without significant problem. The well was drilled with seawater
and gel down to 644 m and with gel and lignosulphonate from 644 m to TD. The Vestland Group, Hugin Formation was
encountered at 3483 m. The Hugin Formation contained gas/condensate down to the
OWC between 3652 and 3654 m based on logs and pressure gradients. Weak shows
continued down to 3659 m, 2 meters into top Sleipner Formation. Two spots of
dead oil and fluorescence on limestone/siltstone cuttings at 2788 and 2812 m in
the upper Shetland Group were the only other shows described in the well. A total of 186.3 m core was recovered in
11 cores from the interval 3498 m to 3692 m. RFT fluid samples were taken at
3490 m ((gas, condensate, water), 3535,7 m (gas and condensate), 3601.6 m (gas,
condensate, water), 3640.4 m (gas, condensate, water), 3641 m (gas, condensate,
water), 3641.5 m (gas, condensate, water), 3644 m (gas, condensate, water),
3652 m (gas, condensate, water), and 3654 m (water). The condensate gravity in
th General Well was drilled on the northwestern part
of the Sleipner Vest structure in the Viking Graben of the North Sea. The
objective was to test hydrocarbons in the “Alpha structure” of the Sleipner
field. The target was Middle Jurassic sandstones. Operations and results Appraisal well 15/9-3 was spudded with
the semi-submersible installation Ross Rig on 17 December 1978 and drilled to
TD at 3796 m in the Triassic Skagerrak Formation. Many problems were
encountered in the operations. When drilling the 26" interval, the
circulation was lost several times. Pumping lost circulation material pills and
cement into the formation solved this. The main problem arose when drilling the
8 1/2” interval. At 3375 m on top of Upper Jurassic, an abnormally pressured
impermeable zone was penetrated. Due to a series of technical problems that
followed this incident, the well was finally plugged back and sidetracked from
1213 m. Furthermore, the well was drilled in the wintertime and the cold was
quite severe. Because of this, the hydraulic control system for the BOP stack
froze on one occasion. Functional problems with the BOP pods were experienced,
consequently, the time and cost estimates, were seriously exceeded. The well
was drilled with spud mud down to 402 m, with gel/lignosulphonate from 402 m to
2680 m and with gel/lignosulphonate/lignite mud from 2680 m to TD. The Middle Jurassic Vestland Group, top
Hugin Formation, was encountered at 3498 m. Well 15/9-3 proved very poor
reservoir qualities in these strata and the well was hence not production
tested. A cluster of RFT pressure data points suggested a light hydrocarbon gradient
of 0.11 - 0.25 psi/ft. between 3600 m and 3612 m. Between 3650 m and 3682 m a good
"heavier" hydro General Well 15/9-4 was drilled on in the southeastern
part of the Sleipner Vest area in the Viking Graben of the North Sea. Previously
four wells had been drilled on the Sleipner Alpha structure in the north. Two
of these showed significant gas-condensate accumulations (15/6-3 and 15/9-1) in
the middle Jurassic while in the western part of the Alpha structure the sand
had shaled out (15/9-3). In the northeast, the sand was penetrated below the
hydrocarbon/water contact (15/6-5). The first well drilled on the Beta prospect
(15/9-2) showed a significant gas-condensate column in the middle Jurassic
sand. The primary objective for well 15/9-4 was to test possible hydrocarbons
in Middle Jurassic sandstones in the southeast extending Delta structure. Operations and results Well 15/9-4 was spudded with the semi-submersible
installation Ross Rig on 4 April 1979 and drilled to TD at 3716 m in the
Triassic Skagerrak Formation. Very few problems were encountered during
drilling of this well, with the exception of lost circulation in the 26"
interval. This problem was solved by pumping cement into the formation. The
main problem arose only after drilling the 8 1/2” interval. The 7" liner
was run and cemented sucessfully. When pressure was applied in order to test
the liner lap, the 9 5/8" casing burst. The well was drilled with spud mud
down to 415 m and with gel/lignosulphonate mud from 402 m to TD. Top of the Middle Jurassic Vestland
Group, Hugin Formation was penetrated at 3441 m. The section contained
sandstones with good reservoir properties interbedded with some thin shale
beds. The sandstones were hydrocarbon bearing with a gas-water contact at ca
3570 m, 7 m into the Sleipner Formation. Weak oil shows were described
t General Well 15/9-5 was drilled in the Sleipner
Vest area in the Central Graben of the North Sea. The objective was to test
hydrocarbons in Middle Jurassic sandstones in the Beta structure of Sleipner
Vest. The well is Reference Well for the Heimdal and Våle formations. Operations and results Appraisal well 15/9-5 was spudded with
the semi-submersible installation Norskald on 19 November 1979 and drilled to
TD at 3946 m in the Triassic Skagerrak Formation. Operations met with many
problems, but the well objectives were fulfilled in the end. Excessive drag
when pulling core barrel out of reservoir was a severe problem, and
consequently frequent reaming and circulating trips was needed. Having finished
logging in the 8 1/2” section, and just started testing the BOP stack, one of
the riser tension sheaves broke and fell down. Also several problems with the
hydraulic BOP control system and the ball joint made nearly 12 days rig repair
necessary. After this delay the hole required extensive reaming before the 7”
liner could be ran and the final 6” section could be drilled. Testing
operations were hampered and delayed by bad weather and test equipment
breakdown. The well was drilled with spud mud down to 426 m and with
seawater/lignosulphonate mud from 426 m to TD. The well proved gas in sandstones of Middle
Jurassic age from top Hugin Formation at 3526 m down to a true gas/water
contact at 3662 m, based on logs and RFT samples. The Sleipner Formation was
encountered at 3693 m. Logs and RFT pressure gradient proved Sleipner water
filled, and ca 3 bar overpressured compared to the Hugin Formation. Shows were
described on cores all through the hydrocarbon bearing reservoir. Abundant
spots of fluorescence described on cuttings below ca 2000 General Well 15/9-8 was drilled on the Delta
structure in the southeastern part of the Sleipner West Field in the North Sea.
The primary objective was to delineate the hydrocarbon accumulation
encountered in the 15/9-4 well on the same structure, and to get further
information about the sand distribution in the area. The primary target was Callovian
sandstones. Paleocene sandstone was the secondary target. Operations and results Appraisal well 15/9-8 was spudded with
the semi-submersible installation Nortrym on 5 March 1981 and drilled to TD at
3730 m in the Triassic Smith Bank Formation. Operations proceeded without
significant problems. The well was drilled with seawater and hi-vis pills down to
495 m, with gypsum/polymer mud from 495 m to 2845 m, and with a
gel/lignosulphonate mud from m 2845 m to TD. The sandstones in Paleocene were water
bearing. Top of the Callovian sandstone, Hugin Formation, was encountered at
3446 m, while top Sleipner Formation was encountered at 3493 m. Bothe formations
proved to be gas/condensate bearing with a gas-water contact at 3564 m based on
pressure gradients and well logs. No shows were recorded outside of the
hydrocarbon bearing Hugin and Sleipner Formation. A total of 46.5 m core was recovered in
four cores from the interval 3448 to 3499 m. Segregated RFT fluid samples were
taken at 3460 m (gas, condensate and mud filtrate), 3561.5 m (gas, condensate
and mud filtrate), and 3566.5 m (mud filtrate and a smaller quantity of gas). The well was permanently abandoned on 25
May 1981 as a gas/condensate appraisal well. Testing
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 15/9-9, was drilled on the Sleipner
Terrace in the North Sea. The primary objective was to test possible hydrocarbons
in Jurassic sandstones on the 15/9-Gamma structure and to get more information
about the sand distribution in the area. Operations and results Wildcat well 15/9-9 was spudded with the semi-submersible
installation Nordraug on 4 May 1981 and drilled to TD at 3044 m in the Early-Middle
Permian Rotliegendes Group. No significant problems were experienced in operation,
logging or testing of the well. The well was drilled with seawater and pre-hydrated
gel down to 501 m, with gel/lignosulphonate from 501 to 1155 m, with
gypsum/polymer mud from 1155 m to 2540 m, and with gel/lignosulphonate from 2540
m to TD. The primary objective, the Jurassic, was
thinner than expected and consisted of Late Jurassic Viking Group shales only.
The well, however, proved gas and condensate in the Heimdal Formation. The
Heimdal Formation was reached at 2322 m. It consisted of sand of fairly good
reservoir properties interbedded with some thin shale beds. The whole sand
interval was hydrocarbon bearing and no water contact was located. In addition,
the well proved residual hydrocarbons over the interval 2648 to 2738 m on cores
from the Triassic Skagerrak Formation. Seven cores were cut. The interval 2648
to 2756 m was cored in six cores with 98 - 100% recovery. A seventh core was
cut from 3032 to 3043.5 m with 96% recovery at TD. RFT segregated samples were
taken at 2323 m (condensate and mud filtrate) and 2648 m (water and mud
filtrate, no gas or condensate). Repeated attempts to sample in the interval
2401 to 2414 all failed due to plugging of probe by unconsolidated sand.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 15/11-9 was drilled to appraise the
15/9-9 Sleipner Øst discovery in the south Viking Graben area of the North Sea. The primary objective was to delineate
the hydrocarbon accumulation found in the Heimdal Formation of the 15/9-Gamma
structure. The secondary objective was to test for possible hydrocarbons in
Triassic sandstones. The well is Reference well for the Lista Formation,
the Meile Member, and the Heimdal Formation Operations and results Appraisal well 15/9-11 was spudded with
the semi-submersible installation Ross Rig on 18 September 1981 and drilled to
TD at 2950 m in the Triassic Hegre Group. A total of 99 days including a strike
was spent on this well. Apart from the strike, which amounted to 22 days of
lost operation, there were no severe problems during drilling and testing
operations. The well was drilled with sea water and bentonite down to 585 m and
with gel/lignosulphonate/seawater mud from 585 m to TD. The well proved gas and condensate in
Heimdal formation and verified thereby the results from the 15/9-9 well. The
gas- water contact was found at 2442 m. Hydrocarbons were found also in the Jurassic
Hugin Formation sandstones with a gas-water contact at 2825 m. The TD for the
well was then extended from 2650 to 2950 m. No hydrocarbons were found in
Triassic sandstones Eleven cores were cut in the well. Cores
1 and 2 were cut from 2364 to 2379 m in the Lista Formation. Cores 3 to 11 were
cut from 2395 to 2514 m in the Heimdal Formation. The RFT tool was run on wire
line and the pressure data supported communication with the 15/9-9 discovery
well within the Heimdal Formation, while the Hugin Formation was in a separate
pressure regime. Segregated fluid samples were taken at 2387.5 m, in the
Heimdal Formation, and at 2812 and 2825.8to 2826.5 m in the Hugin Formation. The well was permanently abandoned on 23
December 1981 as a gas/condensate appraisal well. General Well 15/9-12 was drilled as an appraisal
well on the saddle area between the Alpha and Beta structures on the Sleipner
Vest field in the North Sea. The main objective was to test the Middle Jurassic
sandstones. Operations and results After setting anchors on 8 November 1981
the spud was delayed two weeks due to strike by the maritime and drilling crews.
Appraisal well 15/9-12 was spudded with
the semi-submersible installation Nordraug on 22 November 1981 and drilled to
TD at 3740 m in the Middle Jurassic Sleipner Formation. The 36" hole was
drilled to 195 m but due to bad weather the hole was lost and the well was re-spudded
on 26 November. Drilling of the 26" and 17 1/2" holes went forth
without significant problems other than tight spots in the lower part of the 17
1/2" hole. When setting the 9 the 5/8" casing shoe at 2755 m 64 m3 mud
was lost to the formation. The well was drilled with seawater and gel slugs
down to 501 m, with gel-lignosulphonate mud from 501 m to 1135 m, with lignosulphonate/gypsum/CMC
mud from 1135 m to 2771 m, and with gel-lignosulphonate mud from 2771 to 3740
m. A 251 m thick Heimdal Formation was
penetrated from 2374 m to 2625 m. The Heimdal Formation was water bearing
without shows. The primary target reservoir Hugin Formation was penetrated at
3510 m and proved to contain gas-condensate with a gas-water contact at 3654
according to RFT pressure gradients. Weak shows continued on the cores down to
3665 m. The underlying Sleipner Formation was dry without shows. A total of 168.8 m core was cut from top
to base of the Hugin Formation. The depth for cores 1 - 9 should be sh General Well 15/12-2 was drilled in order to
evaluate Jurassic formations on a seismic structure located in the eastern part
of block 15/12. The principal objective of the 15/12-2 well was to test the
Dogger (Hugin Formation) sandstone, where oil shows had been encountered in the
15/12-1 well. A secondary object was a possible sand in the Paleocene. Operations and results Wildcat well 15/12-2 was spudded with the
semi-submersible installation Ross Rig on 7 January 1976 and drilled to TD at
2924 m in Late Permian Zechstein anhydrite. The well was drilled with a
lignosulphonate mud system. No sand was found in the Paleocene. The
Hugin Formation sandstone was found 304 meters higher than in the 15/12-1 well.
The sandstone proved to have very good reservoir qualities, but was completely
water bearing. There were sandstone stringers in the lower part of the Heather
Formation. The Hugin Formation sand was cored from 2823 m to 2835.4 m, with no
show. No fluid sampling was attempted in the well. The well was permanently abandoned as a
dry well on 27 February 1976. Testing No drill stem test was performed General Well 16/1-2 is located on the eastern
side of the Gudrun Terrace, towards the Utsira High in the North Sea. The well
was designed to test all potential reservoirs through the Permian on a closure
on a large, rotated fault-block. Primary objectives were Jurassic sandstones
and secondary objectives were Paleocene sandstones. Operations and results Wildcat well 16/1-2 was spudded with the
semi-submersible installation Ross Rig on 4 July 1976 and drilled to TD at 2919
m in granite basement. Loss of circulation in high-porosity Zechstein
carbonates was the only significant problem encountered during the drilling of
16/1-2. Initial drilling from the sea floor to 1286 meters was with sea water
and gel. Below this depth a fresh water and lignosulphonate mud system was
used. The well penetrated several sands in the Tertiary
including the Utsira, Skade, and Grid formations. The Heimdal Formation was
encountered at 2098 m with a 10 m zone of strong oil shows. The zone was
however judged by log analysis to be water-productive and the shows not of
sufficient quality to warrant testing. Triassic sandstones were originally interpreted to be water-filled. Later reinterpretation have confirmed the presence of oil in the Triassic interval. There were no shows from either the Zechstein or the Rotliegendes
sandstone. No cores were cut and no wire line fluid samples
were taken. The well was permanently abandoned on 7
August 1976 as a dry well with shows. Testing No drill stem test was performed. General Wildcat well 30/6-16 was drilled on the
Theta structure, immediately northwest of the main Oseberg Alpha North
structure. The main objective of the well was to prove hydrocarbons in the
Statfjord Formation. Planned TD was ca 3150 m or ca 225 m into the Statfjord
Formation. Operations and results Wildcat well 30/6-16 was spudded with the
semi-submersible installation Treasure scout on 9 November 1984 and drilled to
TD at 3300 m in the Triassic Hegre Group. Drilling proceeded without
significant problems. The well was drilled with spud mud down to 613 m and with
KCl/polymer mud from 613 m to TD. Good oil shows were reported on dolomite
and limestone beds and stringers from 1993 to 2333 m in the Rogaland and
Shetland groups. From 2605 to 2853 (Shetland Group) good oil shows were
recorded in sandstones and siltstones as well as in limestones. The Brent Group
was encountered at 2856 m and consisted of 12 m Etive Formation only. The Etive
Formation was found to be oil bearing over the entire interval. The net pay was
6.3 m with average log porosity of 19.1%. Also the 26 m thick Cook Formation
with top at 2920 m was oil bearing all through. Net pay here was 12.6 m with
average log porosity of 19.0%. No oil/water contacts could be established. The
Statfjord Formation had weak shows in the top 10 m, but was found to be water
bearing. RFT pressure recordings and sampling were recorded in 5 runs.
Different pressure regimes were proved for the Etive Formation, the Cook
Formation and the Statfjord Group. Four cores were cut in the Etive and
Drake Formations (2856 - 2909 m), two in the Cook and Amundsen/Burton
formations (2923 - 2949 m) and one in the Statfjord Formation (2982 - 2990 m) General Well 16/3-2 was drilled 40 m east of
16/3-1 on the Utsira High in the North Sea. The objectives were to investigate
Paleocene sand pinch out, the weathered top of the Cretaceous chalk and
Jurassic sandstone. The 16/3-2 well is a replacement for well 16/3-1, which was
junked for technical reasons. Operations and results Wildcat well 16/3-1 was spudded with the
semi-submersible installation Polyglomar Driller on 11 February 1976 and
drilled to TD at 2019 m in granite basement. No significant problems were
reported from the operations. The well was drilled with spud mud (gel and lime)
and pre-hydrated bentonite down to 440 m, and with lignosulphonate mud from 440
m to TD. Around the well there was a 3 m deep and 15 m wide crater. Gas was
observed leaking from 2 main openings and 1 minor. The gas flow from one of the
major openings was about 400 l/hour. The gas was practically pure methane
(99.98%), probably coming from layers near the surface. There were no sands in Paleocene and the Cretaceous
chalk was tight. A 20 m thick immature Draupne shale was encountered at 1955 m.
The well then encountered a 31 m thick late Jurassic sandstone from 1975 m to
2006 m. Below this sandstone was a 9 m thick layer of weathered basement
overlying the solid granite. The well proved to be water wet all through, and
no shows were recorded. Three cores were cut. Core 1 gave no
recovery, while core recovered 3.5 m core from the interval 1998 m to 2000.6 m
in the Late Jurassic sand. Core no 3 was cut from 2017.5 m to 2019 m in
basement rock. No fluid sample was taken in the well. The well was permanently abandoned on 8
March 1976 as a dry well. Testing No drill stem test was performed General The well was located to test a
thrust-faulted structure in a NE-SW trending sub-basin to the southeast of the
Utsira High. The primary objective was the basal Late Jurassic sand. This sand
was estimated to have an approximate gross thickness of 71 metres. Operations and results Wildcat well 16/8-1 was spudded with the
semi-submersible installation Nordskald on 25 September 1976 and drilled to TD
at 2301 m in the Triassic Smith Bank Formation. The well was drilled with
seawater and gel down to 172 m and with Drispac and seawater from 172 m to TD. No reservoir sands were encountered in
either the Paleocene or the Triassic. From 1769 m to 1820 m in the Late
Cretaceous Tor and Hod Formations chalks with calculated porosities from 17% to
34% were encountered. At 2073 the well penetrated a gross thickness of 43 m of
Late Jurassic Intra Draupne sand. This sand was of high porosity but water
bearing. No evidence of hydrocarbons was encountered while drilling, and log
analysis confirmed all intervals with significant porosity to be water bearing.
Canned samples for source rock/maturity analysis by Robertson Research were
collected every 100 m from 1000 m and every 30 m from 2000 m to TD. This study
shows that the penetrated sections are immature. Samples from the Draupne
Formation show good source characteristics with TOC from 3% to 7% and one
extract from this section contained minor amounts of probably locally generated
hydrocarbons. No conventional cores were cut and no fluid samples taken. The
well was plugged and abandoned as a dry hole on 29 October 1976. Testing No drill stem test was performed General The Anchovy (16/11-2) well was drilled on
a semi-domal structure, about 5 miles long and 4 miles wide situated in the
Danish-Norwegian Basin. It was estimated that at Paleocene depth there would be
12 square miles of closure with 150 m vertical relief and at Jurassic depth, 9
square miles of closure with 370 m vertical relief. The principal objective
horizons were the Jurassic and Paleocene sands. Operations and results Wildcat well 16/11-2 was spudded with the
semi-submersible installation Ocean Viking and drilled to TD at 2378 m in Late
Permian Zechstein salt. No Paleocene sands were encountered. As
expected the Danian Chalk section was missing in the well. The Upper Cretaceous
Limestone was tight with no shows. The Jurassic sand top was encountered at
2202 m with the main sand development beginning at 2207 m. The net sand
thickness was 35 m, but on testing was found to be tight and unproductive. The
total Jurassic section was about 244 m thinner than anticipated. The Triassic was
missing. An 11.5 m Dolomite section was developed from 2250 m to 2261.5 m at
the top of the Permian succession. This was also tested, but found to be tight
and unproductive. Thus the well was terminated in the Zechstein higher than
planned. Except for the reduced Jurassic sequence and absence of Triassic
sediments causing the higher position of the Zechstein, the structure and
stratigraphy were as predicted in the prognosis. Geochemical analyses of shales
from the Late Jurassic Tau Formation proved excellent source potential, but the
kerogen is immature to marginally mature in the well location. No cores were
cut. The well was permanently abandoned as a dry well on 23 July 1973. Testing Two intervals in the Sandnes Formation
were perforated and tested, 2261 m to 2251 m and 2242 m to 2231 m. Both
intervals were found tight and unproductive and no hydrocarbons were produced
during the tests. General Well 17/9-1 is located in the Åsta Graben
in the North Sea, ca 30 km north of the 17/12-1R Bream Discovery well. The
primary objective was to evaluate sands at the base of the Jurassic sequence.
The structure is not associated with mobile salt, which is the case for the
Bream Discovery. The well is Reference Well for the
Fjerritslev Formation. Operations and results Wildcat well 17/9-1 was spudded with the
drill ship Glomar Grand Isle on 16 September 1973. Initial drilling from the
sea floor to 423 m was with seawater and gel. From the 20-inch casing shoe at
409 m to TD a fresh water Spersene XP-20 mud system was used. The well was
drilled to 2816 m in Early Jurassic sediments when drilling operations were
suspended due to a severe storm. During this storm on November 6, the riser was
dropped from the drill ship. During subsequent efforts the riser was broken
leaving a riser stub approximately 13 m above the ocean floor. Due to this logs
were not run below 2616 m. No good reservoir sequence was
encountered in the well. Some porosity was noted in cores from the formation
underlying the Sandnes Formation. No shows were recorded during drilling, and
the lack of hydrocarbons in 17/9-1 was confirmed by logs run in the re-entry.
Organic geochemical analyses showed excellent source rock quality in the Late
Jurassic interval from 2120 m to 2210 m with TOC in the range 2.5 % to 9.4 %
and hydrogen index from 130 to 490 mg HC/g rock. The well is immature (%Ro
<0.5) all through. Two conventional cores were cut in the intervals 2268 m
to 2276.8 m and 2286 m to 2294.8 m. No fluid samples were taken. The well was secured and temporary
suspended on December 23 as a dry hole. Testing No drill stem test was performed. General The prospect lay in the Egersund Basin
West of Phillips' marginal Bream and Brisling discoveries. Well 17/11-2 was
located to penetrate Middle Jurassic/Triassic sands on the west flank of a
NNE-SSW piercement salt wall. A pair of prominent west-dipping growth faults
marks the western edge of the salt wall. The well is reference well for the Åsgard
Formation and Ran sandstone units. Operations and results Wildcat well 17/11-2 was spudded with the
semi-submersible installation Chris Chenery on 12 April 1976 and drilled to TD
at 2644 m in the Triassic sediments. The well was drilled without significant
problems with bentonite/seawater spud mud down to 436 m and with Lime/PAC
(Drispac)/seawater from 436 m to TD. Top chalk was picked at 1323 m. Dipmeter
evidence indicated several faults within the Early Cretaceous sequence, at 2025
m, 2244 m and 2382 m. Apart from minor gas shows while drilling in the Early
Cretaceous/Late Jurassic shales, no hydrocarbon indications (shows and logs) were
seen in the well. Dark grey to black carbonaceous Kimmeridgian shales were
penetrated from 2495 m to 2521 m. The top of the target ?Triassic sandstone at
2521 m was marked by a sudden increase in penetration rate and sand grains in
the cuttings. A total of 35 m net sand with 17 - 30 % porosity was evaluated,
the thickest single sand unit was 7.5 m. One conventional core was cut from
2532.7m to 2540.4 m. No fluid samples were taken. The well was permanently abandoned on 24
March 1969 as dry hole. Testing No drill stem test was performed. General Exploration well 17/12-1 is located on
the northern margin of the Egersund Basin in the North Sea, towards the Åsta
Graben. Its primary target was Jurassic sands (Bream prospect) with estimated
top at 2161 m (7090 feet) and with 61 m (200 feet) thickness. Sand developments
within the Early Cretaceous and Triassic sections were regarded as secondary
objectives. Planned TD was 8 m (25 feet) into the Zechstein salt. Operations and results Well 17/12-1 was spudded with the 3 leg
jack-up installation Mærsk Explorer on 27 October 1971 and drilled to TD at 458
m in the 26" section where it was suspended on 1 November for later
re-entry with a different rig, Ocean Viking. Testing No drill stem test was performed. General Well 17/12-2 is located on the
northwestern margin of the Egersund Basin in the North Sea, ca 14 km southwest
of the 17/12-1R Discovery. The primary objective was to test Middle Jurassic
and/or Triassic sands. Both had been found present in the 17/12-1R well where
the Middle Jurassic sand was oil-bearing (Bream Discovery). The Triassic sands
could be oil-bearing, especially if overlain by Jurassic shale. A secondary
objective was seen in the Late Cretaceous limestones. Planned TD was at 3658 m
(12000 ft) or 100 m into Zechstein salt. Operations and results Wildcat well 17/12-2 was spudded with
Ocean Viking on 31 August 1973 and drilled to TD at 2334 m in Devonian sand. No shows were present in the Late
Cretaceous Limestone. An oil-bearing Jurassic sand 13 m thick (7 m net pay) was
encountered at 2157 m. The Triassic was absent and the Jurassic Sandnes and
Bryne Formations rested directly on a 50 m thick layer of Permian salt at 2243
m. Below the salt was a 7 m thick Rotliegendes sequence. Sandstone of possible
Devonian age was encountered at 2300 m. This remnant Paleozoic feature caused
the well to be terminated higher than originally anticipated. One conventional core was cut at TD from
2330.8 m to 2333.9 m. No wire line fluid samples were taken. The well was permanently abandoned on 9
October 1973 as an oil Discovery. Testing Two drill stem tests were carried out.
DST1 from 2166 m to 2169 m produced 16 m3 water cushion and 1 m3 oil. After the
final flow period water cushion and formation fluid was reversed out. DST2 from
2157 m to 2162 m produced at maximum 366 m3 oil and 31800 m3 gas / day. Gas-oil
ratio was 87 m3/m3 and oil gravity was 27.9 °API. General Well 17/12-3 is located on the northern
margin of the Egersund Basin in the North Sea, ca 3 km west of the 17/12-1R
Bream Discovery well. The Bream structure is a domal (salt-induced) anticline.
The pay zone is the Middle Jurassic sands at a sub-sea depth of 2377 m (7800
feet). The 17/12-1R well was drilled on the crest of the Bream structure. Here
Late Jurassic black marine shales with excellent source rock potential overlie
a 156 m thick Early - Middle Jurassic sequence of interbedded sands and shales
in which net sand thickness totals 38 m. Two 8 m thick sands near the top of
the Middle Jurassic section tested oil. The Upper sand was oil saturated and
the lower sand contained an oil/water contact between 2337.2 m and 2344 m (2310.4
m and 2317 m MSL). Two overlying sands, however, contained only water, which
indicates that individual sands possess independent hydrodynamic
characteristics and, therefore, probably are lenticular and laterally
discontinuous. It was expected that on the flank of the structure potential
reservoir sands would be thicker, and additional sands would be encountered. Hence, primary objective was Middle
Jurassic sands. Estimated top and thickness of the sand was 2313 m (7590 ft)
and 91 m (300 ft), respectively. Planned TD was at 2591 m (8500 ft), 120 m into
Triassic sediments Operations and results Wildcat well 17/12-3 was spudded with the
semi-submersible installation Nortrym on 12 December 1979. Due to technical
problems it was re-spudded 19 December. The well was then drilled without
significant problems to TD at 2730 m in m in the Triassic Skagerrak Formation. Top Cretaceous (Tor Formation) came inn
at 817 m, 28 m deeper than prognosed. The target Middle Jurassic reservoir sand
(Sandnes and Bryne Formations) came in at 2370 m (2345 m MSL), which was 57 m
deep to prognosis and ca 30 m MSL deeper than the OWC indicated by the DST's in
17/12-1R. No significant shows were encountered in t General Well 18/10-1 is located in the Egersund Basin in the North Sea, ca 16 km southeast of the 17/12-1R Bream Discovery. It was
designed to test a seismic structure on the same trend as the Bream discovery.
The primary target was to test possible hydrocarbon accumulation in Jurassic
sandstones on. Planned TD is about 150 to 200 m below Jurassic sandstone in a
shaly-sandy sequence of Early Jurassic or top of Triassic. Operations and results Well 18/10-1 was spudded with the
semi-submersible installation Dyvi Alpha on 19 October 1979 and drilled to TD
at 2800 m in the Triassic Skagerrak Formation. A thick Late Jurassic shale sequence with
limestone stringers was penetrated before reaching the target Middle Jurassic
sands. The sands (Sandnes and Bryne Formations) were encountered at 2405 m,
close to prognosis. The reservoir consisted of two zones separated by a thin
shale barrier between 2427 and 2433 m. Based on FMT and DST pressure
measurements the upper zone appeared slightly overpressured relative to the
lower, suggesting a compartmentalized reservoir. The reservoirs were found
hydrocarbon bearing and an OWC was found at 2437 m in the lower zone. The
lithology below the target reservoir section, from 2483 m to TD, was
predominantly sandstone, fine in the upper part, becoming medium to coarse
downwards. Frequent thin interbeds of shale and marl, occasionally also thin
stringers of limestone were encountered. The sequence was entirely water
bearing. Weak direct fluorescence and cut appears at 2420 m, becoming very good
in the intervals 2423 m to 2430 m and 2433 m to 2440 m, then the shows get
weaker and disappear below 2444 m. Organic geochemical analyses showed an
immature well all through (%Ro = 0.5 at TD). TOC in the Late Jurassic shale
increased gradually from ca 0.8% at top Jurassic to ca 1 % at 2200 m. A peak
TOC is reached in the Tau Formation with 4.5 % TOC in cuttings and 6.9 % in a
sidewall core. The hydroge General Well 18/11-1 is located on the Stavanger
Platform, ca 25 km north of the Yme Field in the North Sea. The primary
objective was to test possible hydrocarbon accumulation in Middle Jurassic
sandstones in a seismic structure interpreted on the same trend as the 17/12-1R
Bream Discovery. Secondary objectives were possible Triassic or Rotliegendes
sandstones in a faulted triangular block tilted southwest. Planned TD was 150
-200 m below the primary target, prognosed at 2365 m. The well is Reference Well for the
Sandnes Formation. Operations and results Wildcat well 18/11-1 was spudded with the
semi-submersible installation Deepsea Driller on 17 February 1974 and drilled
to TD at 2086 m in Pre-Devonian Basement rocks. Late Cretaceous limestones from 498 m to
985 m had excellent reservoir properties. Limestones below this level became
harder; more compacted, and had poor reservoir properties. The well penetrated
top Sandnes Formation at 1878 m with fine, argillaceous cemented, well sorted sandstone
down to 1919 m, and a Bryne Formation sequence with fine to coarse, angular
grained, sandstones with variegated shale from 1964 m to 2060 m. The Jurassic
sands rested directly on basement at 2060 m. No noticeable shows were recorded
in the well. Organic geochemical analysis proved a thermally immature well all
through down to basement (%Ro < 0.36). Good source potential (TOC in the
range 1.3 % to 6 % and Hydrogen Index from 30 to 230 mg HC/g rock was seen in a
ca 80 m thick Kimmeridgian shale sequence from 1735 m. High TOC in the range
1.3 % up to 6.9 % was seen also below 1919 m in Callovian claystones, but
Hydrogen Index in the range 30 - 180 mg HC/g rock suggested a more inertinitic,
gas prone kerogen in this sequence. One conventional core was cut at TD from
2082 m to 2086 m. No fluid samples were taken. The well was permanently abandoned on 31
March 1974 as dry hole. Testing General Wildcat well 24/9-1 is located in the
Vana Sub-basin in the Southern Viking Graben, about 11 km east of the border to
British sector. The well was drilled to test a large, dip-closed structure
located in the centre of the Viking Graben. The target was Late Jurassic
sandstones. Two sandstone intervals were expected in the well, with a possible
gross thickness of about 250-300 m. The prognosis was based on a correlation
with the UK wells 16/7-1, 16/8-1 and the Norwegian well 15/3-1 which are
situated in a similar position as 24/9-1 relative to the eastern boundary fault
of the Viking Graben. The well is Reference Well for the
Svarte, Tryggvason, Kyrre, and Jorsalfare Formations. Operations and results Well 24/9-1 was spudded with the
semi-submersible installation Ross Rig on 29 February 1976 and drilled to TD at
4907 m in the Late Jurassic Heather Formation. Below the 20" casing at
758.3 m the Formations drilled contained abundant sand and was drilled
extremely fast. This created problems as the solids removal system on the rig
was incapable of removing the sand as fast as it was drilled. In addition the
polymer mud system chosen did not provide sufficient fluid loss control in the
porous formation and large amounts of fluids were lost to the formation. From
ca 2440 m to TD at 2752 m in the 17 1/2" hole low penetration rates was a
problem. Of 126 rig days 20 % was counted as lost time, but the total time
spent on the well was still less than the originally estimated 139 days. Problems
related to tight/sloughing hole and down hole tool failure accounted for
roughly half of the lost time. The well was drilled with seawater down to 256
m, with lime / lignosulphonate from 256 m to 3983 m, with Dextrid /
Lignosulphonate from 3983 m to 4613 m, and with lime / lignosulphonate from
4613 m to TD. Tertiary sandstones were encountered in
the Grid Formation (1131 m to 1420 m), The Heimdal Formation (2202 m to 2497
General Well 24/9-2 was drilled in the Vana
Sub-basin in the Southern Viking Graben of the North Sea. The well was located
to test Danian and Early Paleocene sands. Dip closure at this level was
enhanced by a seismic anomaly of a "build-up" shape within the
Middle-Late Paleocene Heimdal sands. Operations and results Wildcat well 24/9-2 was spudded with the
semi-submersible installation Borgny Dolphin on 13 June 1977 and drilled to TD
at 2743 m in the Late Cretaceous Tor Formation. A total of 9.8 days was lost on
various mechanical hole problems during. The well was drilled with seawater and
gel down to 1554 m and with lignosulphonate / CMC / gel / seawater from 1554 m
to TD. The well penetrated a gross interval of
439 m of Paleocene sands. No sands were found in the Danian, which was of a
marl and limestone lithology. Hydrocarbons in commercial quantities were not
encountered. While drilling the gas detector showed two slight increases, one
within the Late Paleocene (a thin intra-Sele Formation sandstone) and one
within the Early Paleocene Sand. Fluorescence was observed in the samples from
the Late Paleocene Sand. Log analysis proved a 3-meter hydrocarbon bearing interval
in the Late Paleocene sand between 2101.5 and 2104.5 metres, and sidewall cores
proved the presence of oil in this interval. No cores were cut, and no wire line fluid
samples were taken. The well was permanently abandoned on 22
July 1977 as a well with shows. Testing No drill stem test was performed. General Exploration well 24/9-3 was drilled by
Conoco for the Conoco/Statoil/Norsk Hydro/Hudbay PL 039 partnership. The well
lies in the west-central part of block 24/9, close to the Norway/UK median
line. The location was chosen to test an apparent sand build-up, observable on
seismic lines, in the Lower Tertiary part of the section. The sand build-up was
thought to correspond to the Lower Eocene Frigg Sand Formation, which forms the
reservoir in the Frigg Field. Operations and results Well 24/9-3 was spudded with the
semi-submersible installation SEDCO 704 on 28 January 1981 and drilled to TD at
3051 m in the Late Cretaceous Jorsalfare Formation. The duration of the well
was 81 days, 20 of which were spent testing. A 36" hole was drilled to
207.6 m / 681 ft and 30" casing set to same depth. A 17 1/2" pilot
hole was drilled to 518.2 m, logged, and then opened to 26". 20" x-56
casing was set at 503.2 m. A 17 1/2" hole was drilled to 1600.2 m, logged,
and 13 3/8" N-80 casing was set at 1587.1 m. A 12 1/4" hole was
drilled and cored to 2049.8 m, logged, and 9 5/8" N-80 casing was set then
drilled to TD and logged. The well was drilled with spud mud to 518 m, with
Dextrid/gel from 518 m to 853 m, with gel/lime from 853 m to 1067 m, with
seawater/gel/Dextrid from 1067 m to 1600 m, and with seawater/lime/Dextrid mud
from 1600 m to TD. The Lower Eocene sands (Frigg Formation)
were encountered 141 m high to prognosis at 1739 m. This shows that the sands
correspond to a higher and less distinct build-up on the seismic. The build-up
originally mapped corresponded to the Paleocene Tuff level and contained shales
and water-wet Paleocene Sands. A gross interval of 92 m of Early Eocene Sands
was penetrated. The uppermost 70 m, from 1739 m, were hydrocarbon bearing down
to an OWC at 1809 m, while the lowermost 22 m (1809-1831m) were water bearing.
Patchy oil shows were observed down to 1870 m, no sho General Well 24/12-1 is located on the Gudrun
Terrace ca 15 km east of the border to British sector. The purpose of the well
was to evaluate a seismic closure, named Gamma, in the southern part of the
Block. The main target was the Middle Jurassic sands. Well 24/12-1 was the
first of two phases in drilling the borehole, and this first phase was planned
to reach the Early Cretaceous only. The main target was planned to be reached
in a later re-entry with a different rig than was available at the time when
the well was scheduled. The well is Type Well for the Skade
Formation and Reference Well for the Grid Formation. Operations and results Wildcat well 24/12-1 was spudded with the
semi-submersible installation Ross Rig on 16 January 1978. At the time when the
well was to be spudded, Statoil did not have available a rig equipped with a
15000 psi BOP stack and associated equipment. The well was therefore spudded
with Ross Rig, which was equipped with a 10000 psi BOP. Ross Rig drilled the
well down to 3966 m in the Early Cretaceous Sola Formation. The 9 5/8"
casing was set and the well was temporarily plugged and abandoned. The problems
experienced during PHASE I were primarily related to weather (anchor chain
breakage and WOW), BOP-stack, and items lost into the hole and the sea. The
well was drilled with seawater and gel from down to 771 m, with lignosulphonate
mud from 771 m to 2874 m, and with lignosulphonate/lignite/CMC from 7874 m to
TD. From 2870 m 1 % to 8% oil was added to the mud. Tertiary sandstone intervals were
encountered in the Utsira Formation (497 m to 730 m), the Skade Formation (825
m to 1007 m), the Grid Formation (1502 m to 1660 m), and in the Paleocene
Heimdal Formation (2326 m to 2700 m). No shows were encountered during drilling,
but post-well organic geochemical analyses showed one cuttings sample from 2860
m to 2890 m to contain significant amounts of light hydrocarbons combined with
a comparati General Wildcat well 24/12-2 is located in the Vana Sub-basin in the Southern Viking Graben, about 11 km east of the border to British
sector. The well was drilled on structure (Alpha) in the northeastern part of
the block. Target was Late Jurassic sandstones. The well is Reference well for the Sola
and Grid Formations Operations and results Well 24/12-2 was spudded with the
semi-submersible installation Dyvi Delta on 23 June 1981 and drilled to TD at
5100 m in the Late Jurassic Heather Formation. Operations on both 36" and
26" sections went smooth. During drilling of the 17 1/2" section the
drill pipe broke off at 2044 m. This was recovered and drilling continued to
2445 m. One stand was left in the hole at this depth and fishing was unsuccessful.
Both fish and open hole were cemented up to 2160 and the well was sidetracked
from 2220 m. After setting the 13 3/8" at 2886 m casing the Kelly bushing
elevation was changed from 32 m to 30 m. The 8 1/2" hole was drilled to
4306 m when a 21-day strike occurred. The well was drilled with seawater and
gel down to 1005 m, with gypsum / lime / polymer from 1005 m to 2866 m, and
with a Spersene / XP-20 / Resinex mud from 2886 m to TD. Tertiary sandstones were encountered in
the Grid Formation (1282 m to 1397 m), the Heimdal Formation (2202 m to 2407
m), and the Ty Formation (2567 m to 2617 m). The main target Late Jurassic
sandstones were found (Intra Heather Sandstone Formation) in the intervals 4739
m to 4749 m and 4955 m to 4978 m. These sands had poor reservoir properties.
Oil shows were recorded in the Heimdal Formation. Ca 380 m of Draupne Formation
was penetrated by this well. The dark shales in this formation had TOC
typically in the range 4 % to 7 %, but with relatively low Hydrogen Index (50 to
110 mg/g HC). The Kerogen in the shales appeared to be mostly type III with
some Type II towards the top. Measured vitrinite reflectance varies somewhat
be General Well 25/1-3 was drilled to appraise the eastward
extension of the 25/1-1 Frigg Discovery on the Frigg Ridge in the North Sea. The
primary objective was to test the Eocene sandstones that were gas bearing in
well 25/1-1. Operations and results Appraisal well 25/1-3 was spudded with
the semi-submersible installation Pentagone 81 on 14 November 1971 and drilled
to TD at 2872 m in the Late Cretaceous Shetland Group. The well was drilled
with seawater down to 405 m and with a seawater/LFC mud from 405 m to TD. The target Eocene sandstones (Frigg
Formation) was penetrated at 1952 m. The gross thickness was 217 m and the N/G
was 0.82 with porosities ranging from 28 to 33%. It was gas bearing down to the
GOC at 1973 m and oil bearing down to the OWC at 1982.5 m. Good oil shows on
cores were recorded throughout the hydrocarbon-bearing reservoir. Weaker oil
shows on cores were described ("fluo but salty taste") below the OWC. Three cores were cut from 1951 to 2005 m
in the Frigg reservoir. Total recovery for these three cores was 42.25 m (78.2%
recovery). A fourth core was cut from 2563 to 2568 m with 50% recovery. FIT
fluid samples were attempted at 2550.5 m and 2576.3 m but only mud and filtrate
was recovered. The well was permanently abandoned on 27
January 1972 as an oil and gas appraisal well Testing Six drill stem tests were conducted. DST 1, 2 and 3 tested the interval 1985
to 1987 m. All three tests produced water. General Exploration well 25/1-4 was located on a
lower Eocene structure straddling the 25/1 and 30/10 blocks limit, north-east
of the main Frigg Field. It was drilled to explore additional gas reserves in
the Frigg area. A "Bright spot" phenomenon interpreted as a gas/oil
or water table is clearly visible on all the seismic sections crossing the
structure. Possible Danian and Maastrichtian reservoirs were considered
secondary objectives. Operations and results áWell 25/1-4 was spudded with the
semi-submersible installation Deepsea Driller on 1 April 1974 and drilled to TD
at 2795 m in Maastrichtian marls. The top of the Eocene reservoir (Frigg
Formation) at 1967.8 was detected by C1 traces (maximum 3%). Based on shows on
cores and electrical logs gas/oil and oil/water contacts were found at 2005.6 m
and 2009 m, respectively. The contacts were not the same as on the Frigg Field,
implying that this discovery was not in communication with the main Frigg
Field. Background gas was weak to nil below 2010 and cuttings or sidewall cores
below this depth showed no direct fluorescence or cut. Paleocene was penetrated
at 2058 m with well-developed sand bodies as is usual in the area. Hence, the
Paleocene contained 190 m net sands of which 25 m consisted of calcareous
sandstone and 90 m of shaly sands. All Paleocene sands were water wet. In the
Maastrichtian chalk some gas shows were recorded on the section 2757 m to 2763
m. Some hydrocarbon saturation was inferred by logs, but an FIT at 2760 m
recovered 2.750 l of mud with only oil traces after a 25 minutes flow period. Coring started at 1922 m, 45.8 m above
the Eocene sands. Eight conventional cores were cut from this point down to
2028 m. Two wire line tests were conducted in the oil-bearing zone at 2006.5 m
and 2007.5 m. The latter recovered 5.15 l of oil and 4.75 l of mud filtrate. The well was permanently abandoned on 30
May 1974 as an oil and gas discover General Well 25/1-5 was drilled southeast flank
of the main Frigg structure in the North Sea, about 2.25 km from the discovery
well 25/1-1. The objectives were to provide data for development of the Frigg
Field and calibrate the seismic model. Operations and results Appraisal well 25/1-5 was spudded with
the semi-submersible installation Deepsea Driller on 24 July 1975 and drilled
to TD at 2259 m in the Paleocene Balder Formation. The well was drilled with spud
mud down to 464 m, with KCl mud from 464 to TD. The Frigg sands were encountered at 1907
m. It was 275 m thick with 225 m net sandstone. The Frigg Formation was gas
bearing down to the GOC at 1976 m, oil bearing down to an an oil/water
transition zone down to 1982 m and the oil/water contact at 1987 m. The only
shows described in the well were in the Frigg reservoir: "First
significant gas increase in drilling was recorded at 1908 m. Sand on cores
showed a gas bearing facies, i.e. dry outlook, faint direct yellow fluo but
strong cut. Gas ground began to decrease below 1970 m, becoming nil after 2010
m. Strong direct fluo on cuttings and side wall cores was observed from 1970 m
to 2010 m." Two cores were cut in the Frigg
Formation. Core 1 was cut from 1914 to 1923 m and core 2 was cut from 1928 to
1937 m. cores were cut. FIT fluid samples were taken at 1979.6 m (oil and
filtrate), 1981 m (oil and filtrate), 1937 m (gas and filtrate), and 1945.5 m
(gas and filtrate). The well was permanently abandoned on 12
September 1975 as an oil and gas appraisal well. Testing General Exploration well 25/1-6 is located 12 km
southwards of the 25/1-1 well and 6 km south of the Frigg Field boundary. The
main objective was a Paleocene seismic structure underlined by a strong
discontinuous flat seismic event. Geological correlations and geophysical
studies indicated a detritic sand body belonging to the Heimdal formation. The
Cod or Heimdal clay layer could be the closure of this structure.á The
structurally closed Frigg, Cod, and Danian Sands, and Late Cretaceous chalk
were secondary objectives. Operations and results Well 25/6-1 was spudded with the
semi-submersible installation Pentagone 84 on 26 January 1978 after spending 10
days on the location waiting on weather. No significant problems were
encountered during the drilling to TD at 2895 m in Late Cretaceous limestone.
The well was drilled with spud mud to 192 m, with CMC/Bentonite from 192 m to
468 m, and with Lignosulfonate/Dextrid mud from 468 m to TD. The first interval of interest was the
Eocene Frigg Formation from 2107 m to 2150. This interval turned out to be
shaly with thin sand layers up to 3 meter thick only. Some oil shows were
recorded in the sands. In the lower part of the Frigg Formation a core was
taken with four thin interbeds of sandstones medium to fine grained and weakly
cemented. These sandstones were fluorescent (light yellow) and gave a
fluorescent, light yellow extract. Massive Heimdal Formation sand was
encountered from 2249 m to 2563 m. The unit has good reservoir characteristics
with translucent fine to coarse, subrounded to subangular, mostly well-sorted
sand. The porosity of the sandy levels varies from 20 to 25% and net sand
thickness is about 226 m. The unit was water bearing. No shows were encountered
during the drilling or on the lab. The lower part (2675 m to 2799 m) of the
Danian sequence (Ty Formation) was composed of many intercalations of sandy
levels and shaly beds. The sandy intervals had poor porosit General The 25/2-1 well was drilled on the top of
the eastern structure on the WSW-ENE trend of the Frigg Field. The objective of
this well was the lower tertiary sands, especially Eocene, which are equivalent
to the gas - bearing sand section in the western Frigg wells. Their thickness
range around 100 m according to the seismic. Sandy interbeds in the upper part
of the cretaceous chalk were considered secondary objective. Operations and results Well 25/2-1 was spudded with the
semi-submersible installation Neptune 7 on 4 August 1973 and drilled to TD at
2740 m in the Late Cretaceous Hardråde Formation. Top Frigg sand was found at 1915 m, only
8 meters above the average seismic estimate. As expected, the Frigg sand body
was found underlying the Eocene green and brown-red shales. The net sands are
88 m thick with excellent reservoir qualities (30 % to 24 % on the cores). The
top of the reservoir stands 7 m deeper than in well 25/1-1. The net pay zone in
the Frigg Formation includes 56 m of gas bearing and seven m of oil bearing
sand. The gas/oil interface at 1971 m was found exactly at the same depth as in
the Frigg Field. Two wire-line tests were performed in the gas-zone at 1973 m
and 1974 m. The second of these was plugged by sand. A Third wire line test in
the transition zone at 1985 m produced some oil with 70% salt water (35 g/l).
Paleocene reservoirs below Frigg were of very good quality too, but all Sands
below the Frigg Formation were found water wet.á Only very weak shows were recorded
in the Paleocene (Hermod Formation), the Danian (Ty Formation) and
Maastrichtian (HardrÕde Formation). Two cores were cut in the Frigg Formation,
the first in the interval 1950 m to 1968 m, and the second in the interval 1973
m to 1991 m. Testing An open hole test was carried out from
1926 to 1938 m Just after setting the 9" 5/8 casing at 1907 m in order to
check a new type of sand screen to be used in furthe General Well 25/2-2 is located east of the Frigg
Field and south of the Frigg Øst Field, on the top of an E-W trending
structure. The well was drilled to appraise the 25/2-1 Øst Frigg Discovery made
in September 1973. The main target was lower Eocene sands where seismic
sections displayed a bright spot in the western part of the closure just below
the Frigg sand horizon. Secondary targets were Danian and Maastrichtian sands. Operations and results Appraisal well 25/2-2 was spudded with the
semi-submersible installation Deepsea Driller on 31 May 1974 and drilled to TD
at 2740 m in the Late Cretaceous Shetland Group. Top Early Eocene sands (Frigg Formation)
were encountered at 1949 m, 23 m lower than prognosed. The Hermod Formation
came in at 2269 m while Danian sand (Ty Formation) was encountered at 2563 m
and chalky limestone (Shetland Group) at 2703 m. Hermod and Ty were water wet.
An increase in C1 and C2 at around 1950 m during drilling marked the top of the
Frigg Formation reservoir. From electrical logs, FIT's and the DST Gas/oil and
oil/water contacts were set at 1964.2 m and 1974.4 m, respectively. Three cores
were cut from 1991 to 2012.5 m. The cores consisted almost entirely of sand
with only some thin interbeds of silt in core number 2. Down to 2011 m the
cored sands were brown coloured from oil stain, and direct fluorescence and
cuts were very strong. No shows were observed from 2011 m to 2015.5 m in the
base 1.5 m of core number 3. The DST carried out in the cored interval produced
only water. Weak shows were recorded in the Ty Formation sands. Two FIT's at
1952 and 1968.2 in the Frigg Formation reservoir sampled gas and oil and
recorded formation temperatures of 57.6 °C and 57.9 °C, respectively. The well was permanently abandoned on 11
July 1974 as an oil and gas appraisal. Testing DST 1 carried out from 1983 to 1996 m
produced 5.1 m3 of salt water (53 g/1). General Well 25/2-3 was drilled southwest of the
East Frigg Field on a Paleocene structure with the objective to increase Frigg
area gas reserves. The main target was sand channels in the Paleocene Balder
Formation. Early Eocene and Danian sands were considered as secondary targets. Operations and results Exploration well 25/2-3 was spudded with
the semi-submersible installation Deepsea Driller on 1 September 1974 and
drilled to TD at 2795 m in the Late Cretaceous Shetland Group. Eocene sands (Frigg Formation) were
encountered at 2073 m, 27 m deeper than expected. The top of the tuff (Balder
Formation) was encountered at 2211 m, 85 m deeper than expected. Both the
Hermod (153 m thick) and the Ty (144 m) Formations were well developed in the
well. The top of the chalk (Shetland Group) was encountered at 2726 m. All the
sandstone sequences encountered in the well were water bearing. No shows were
reported from the well. No cores were cut and no fluid samples taken. The well was permanently abandoned on 9
October 1974 as a dry hole. Testing No drill stem test was performed General Well 25/2-4 was drilled in the north west
corner of block 25/2. It lies on the eastern flank of the Viking basin in the
Viking Graben and to the east of the Frigg Field and Frigg Kitchen. The main
targets was the Jurassic with a mapped seismic structure of 30 ms vertical
closure and 30 square km acreage spreading on the Shell block 30/11. Well
25/2-4 was located on the west flank near the top of the structure. Agreement
with Shell management was signed for a bottom hole contribution with obligation
for the operator to reach the Triassic red shales or to set TD at 3360 m. The well is Reference Well for the Drake
Formation. Operations and results Exploration well 25/2-4 was spudded with
the semi-submersible installation Neptune 7 on 14 may 1975 and drilled to TD at
4384 m in the Triassic Smith Bank Formation. The well was drilled water based
with salt/gel/Flosal/seawater down to 733 m and with FCL/LC mud from 733 m to
TD. At 3375 m the well kicked due to an under balanced hydrostatic mud
pressure. The well penetrated Danian, Paleocene and
Eoceneá sandstone sequences (Frigg Formation, Intra Balder Formation
Sandstones, Hermod and Ty formations). All these sands were water wet without
shows. In the Late Cretaceous limestones were found fairly well developed
overlying a thick shaly and marly sequence with some more limestone levels,
particularly in the Campanian and Turonian. The latter limestones contained
significant shows, but a production test proved tight formation. The Kimmerian
unconformity was penetrated at 3632 m with 8 m Draupne shale. In the Jurassic
two reservoir sandstone sequences were encountered: the Vestland Group and the
Statfjord Formation. The Vestland sequence was first interpreted as oil and gas
bearing from 3640 m to 3708 m (Hugin Formation) with a probable gas/oil
contact 3660 m and an oil/water contact between 3704 m to 3708 m. Net pay in
the 25/2-4 Hugin reservoir was estimated around 40 m w Well 25/2-5 is located on the north-west
rim of the Stord Basin and to the north of the main part of the Utsira High in
the North Sea. The main target was Jurassic sandstones, which appeared
promising after the discovery made in well 25/2-4 where Mid Jurassic (Dogger)
sandstones were found to be hydrocarbon bearing, and also after the positive
results of 25/4-1. Operations and results Wildcat well 25/2-5 was spudded with the
semi-submersible installation Polyglomar Driller on 8 March 1976 and drilled to
TD at 4000 m in the Triassic Smith Bank Formation. As anticipated, good reservoirs were
encountered in the early Tertiary, but without any shows (no structural
closure) Jurassic sandstones present two main reservoirs: The upper reservoir
"Brent sands" (3336 - 3489 m) was oil bearing in 3 zones (3339 m -
3388.5 m, 3448.5 - 3481 m, and 3487 - 3489 m), with a net oil pay of 40 m. Tests
of the upper Brent showed a good productivity. The lower reservoir
"Statfjord sands" (3652 - 3847 m) was oil bearing in two zones (3652
- 3692 m and 3706 - 3763 m), with a net oil pay of 44.5 m, but with lower
porosities than in the "Brent sands". The pressure of the Jurassic
reservoir was hydrostatic (equivalent density = 1.08). Five cores were cut in the Vestland
Group. Four were cut from 3339.5 to 3372 m in the Hugin Formation and one was
cut from 3476 to 3485 m in the Sleipner Formation. Ten FIT tests were carried
out in the Vestland Group sands. Five were carried out while drilling from 3354
to 3384 m. Of these, oil was recovered in two FITs at 3357.2 and 3382.5 m (density
= 0.804 g/cm3 = 44 deg API). The others were unsuccessful. Another five FITS were
carried out during DST3. Of these, oil was recovered in FIT no 15 at 3383.8 m and
gas in the 4 others. Nine FITs were carried out in the Statfjord Formation.
None of these recovered any oil or gas. The well was permanently abandoned on 4
August as an oil and gas General Exploration well 25/2-6 was located in
the Viking Graben on the same main structure as well 25/2-5 targeting the
Jurassic were oil bearing, while the Statfjord sands gave good oil shows.
25/2-6 was drilled on the northwestern flank of a structure that was about ten
years later discovered as the Frøy Field. The well is Type Well for the Hermod
Formation. Operations and results The well was spudded with the
semi-submersible installation Polyglomar Driller on 1 August 1977 and drilled
to TD at 3750 m in the Triassic Smith Bank Formation. The well penetrated two Paleocene sands,
the Hermod Formation from 2221 m to 2361 m and the Ty Formation from 2563 m to
2631 m. No shows were recorded in these sands. The Jurassic contained two major
sandy but somewhat heterolithic sequences in the Vestland Group and Statfjord
Formation. Four conventional cores were cut in the
well, one from 3159.6 m to 3165 m in the Heather Formation, two from 3253.4 m
to 3271.8 m in the Hugin and Sleipner formations, and one from 3509 .7 m to
3518.9 m in the Statfjord Formation. Good oil shows were recorded on the lower
part of the Statfjord core. An extensive pressure and fluid sampling programme
was carried out in the Jurassic with 19 RFT samples from the interval 3242.5 m
in the Vestland Group and 24 RFT samples and four FIT samples from the interval
3505.1 m to 3648 m in the Statfjord Formation. Fluid samples were taken from
four depths in the Sleipner and Hugin formations (3243.3 m, 3257.8 m, 3267.5 m,
and 3286 m). Only one of the samples (3286 m) recovered fluid that was
representative for the formation and this sample contained water with dissolved
ga General Well 25/4-1 is the discovery well on the
Heimdal Field. The primary objective was Paleocene sand development (which was
confirmed by the well), while Jurassic sands were regarded as a secondary
objective. Planned depth was 3500 m. The well is Type Well for the Heimdal
Formation. Operations and results Wildcat well 25/4-1 was spudded with the
semi-submersible installation Neptune 7 on 1 July 1972 and drilled to TD at
4060 m in the Triassic Smith Bank Formation. From 2600 m to 3580 m the well
built some angle (maximum 5 deg), resulting in a 3 m deviation between measured
and true vertical depth at 3580 m. In addition, logger's depth is 6 m deeper
than driller's depth from seabed to 3525 m. Below 3525 m driller's depth is
equal to logger's depth. This history quotes logger’s depth if not otherwise
stated. While drilling at 3178 m the well started to flow and a lost
circulation situation followed. The situation was adequately dealt with. The
well was drilled water based all through. The well penetrated a 356 m thick Heimdal
Formation from 2067 m to 2423 m. The reservoir was composed of more or less
unconsolidated sands with interbedded shales and carbonates. The formation was
gas filled down to a gas/oil contact at 2173 and contained oil in a thin zone
down to a shale at 2177 m. The OWC could not be seen in the well. The upper
Cenomanian rested unconformably on a 14 m thick Oxfordian/Callovian Draupne
Formation sequence, which in turn rested unconformably on the Middle Jurassic
Vestland Group at 3185 m. Several permeable reservoirs were penetrated from
3185 m to 3512.5 m (3179 m to 3506.5 m drillers depth) in the Middle Jurassic
to Late Triassic. Four of these were hydrocarbon bear General Well 25/4-2 was drilled ca 6 km ENE of
the 25/4-1 Heimdal Discovery well, which encountered 106 m gas-bearing sands
gas in the Paleocene Heimdal Formation and several thin sands with gas and oil
in the Jurassic and late Triassic. The aim of well 25/4-2 was to explore the
Heimdal sand section on a separate closure. Operations and results Wildcat well 25/4-2 was spudded with the
semi-submersible installation Neptune 7 on 18 October 1973 and drilled to TD at
2775 m in the Late Cretaceous Jorsalfare Formation. The well penetrated a 405 m thick section
with Heimdal Formation sands from 2156.5 m to 2561 m. The reservoir
characteristics were quite the same as in well 25/4-1: clean sands with
occurrence of only small shale-sand laminae and a few carbonaceous stringers. A
nine-meter thick oil column was found from top of the reservoir down to an OWC
at 2165.5 m, which was estimated to be 8.5 m higher than in 25/4-1. Other
reservoirs were water-wet except a very thin bed of calcareous sand between
2591 and 2597 m (Våle Formation) with some residual oil according to the log
interpretation, and where a small methane kick occurred. One conventional core was cut in the
interval 2159 m to 2172 m. Only 2166.6 m to 2167.4 m was recovered. Good shows
with bleeding oil was observed on the recovered piece of core. Three Formation
Interval Tester samples were taken. FIT 1 and 3 were taken at 2162.5 m. The FIT
1 fluid was transferred under bottom hole pressure for PVT studies. FIT 3
recovered 4.15 1itre of oil, 5.75 litre of filtrate + mud and 136 litre of gas.
FIT 2 at 2165.8 m produced 9.9 1itre of water, filtrate, and mud with some
traces of oil. The well was permanently abandoned on 6
December 1973 and has been classified as a minor oil discovery. Testing No drill stem test was performed in the
well. General The well 25/4-3 is located SW of the
Heimdal field on a Paleocene structure which trends NE-SW and stretches
southwards over the block 25/7. The Heimdal sand formation was the main
objective with a bright spot phenomenon clearly visible on all the seismic
sections through the structure. Seismic mapped vertical closure was assumed to
be less than 50 m. Danian sands was the secondary target. Operations and results Wildcat well 25/4-3 was spudded with the
semi-submersible installation Deepsea Driller on 13 October 1974 and drilled to
TD at 2714 m in the Late Cretaceous Jorsalfare Formation. The tuff marker was encountered at 1974
m, 20 m lower than prognosed. Heimdal sands expected around 2075 m were found
at 2125 m. The Heimdal sand contained 3 m gas down to a gas/oil contact at 2128
m and 5 m oil down to a oil/water contact at 2133 m. A 94 m thick sequence of
Danian sands (Ty Formation) was encountered at 2550 m overlying Late Cretaceous
chalky limestones. Three cores were cut in the Heimdal sands
from 2128 m to 2144 m. Three Formation Interval Tests were conducted on the
interval 2125 - 2133 m. FIT 1 and 3 at 2126.2 and 2126.4 m were unsuccessful
due to mechanical failures. FIT 2 at 2129.7 recovered oil and mud filtrate. The well was permanently abandoned on 22
November 1974 as an oil and gas discovery. Testing No drill stem test was performed in the
well. General Well
25/4-4 was drilled on the NW flank of the structure of the Heimdal structure,
north of well 2 5/4-1. The objective was to appraise the Heimdal reservoir
extension, to assess its characteristics, and to sample it. Operations
and results Appraisal
well 25/4-4 was spudded with the semi-submersible installation Odin Drill on 16
May 1975 and drilled to TD at 2681 m in the Early Paleocene Våle Formation. The well
encountered 323 m of Heimdal sands with top at 2133 m, and 157 m of Ty sands at
2517 m. The Heimdal Formation consisted of sand with shale interbeds. The sand
was generally clean, with a few sand-shale laminae. It was hydrocarbon bearing
with a gas/oil contact at 2172 m, and the oil/water contact at 2175 m in
accordance with what was expected. The Ty sand was water bearing. Four
cores were cut from 2142 m to 2170 m in the Heimdal Formation. The recovery
varied from 0.5 m to a full 9 m barrel. Poor recovery was mainly due to very
unconsolidated sand. Three Formation Interval Tests were conducted. FIT1
sampled oil from 2173.5 m, FIT2 sampled gas from 2171.4 m, and FIT3 sampled
salt water from 2190 m. The well
was permanently abandoned on 7 July as a gas and oil appraisal. Testing A drill
stem test was conducted from the interval 2134 m to 2143 m in gas zone of the
Heimdal Formation. It produced 676300 Sm3 gas and 95.8 Sm3 condensate/day. General Well 25/8-2 was drilled on the Heimdal
Terrace in the North Sea.The objective
was to test Jurassic and Paleocene age sands located within a structural
closure. Operations and results Wildcat well 25/8-2 was spudded with the
semi-submersible installation Ross Rig on 9 September 1975 and drilled to TD at
2578 m in Late Triassic sediments of the Statfjord Formation. No significant
drilling problems were encountered. Initial drilling from the sea floor to 1268
m was with sea water and gel. Below 1268 m sea water and lignosulphonate mud
system was used. The well penetrated good reservoir sands
as predicted, but they were water bearing. No Danian or Cretaceous sediments
were present. Paleocene sediments (Ty Formation) lie unconformable on the Middle
Jurassic Sleipner Formation in the well. A small gas show (methane) was found
in the top of the Miocene (Utsira Formation) and scattered oil stained sand
grains were found in the upper part of Paleocene. No other shows were encountered
in the well. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 1
October 1975 as a dry well. Testing No drill stem test was performed. General Well 25/8-3 was drilled in the northern
part of the Utsira High in the North Sea. The main purpose was to establish the
presence of a thick accumulation of Paleocene oil sand, and evaluate the Paleocene
sand-shale distribution and reservoir quality in the area. The top of the
reservoir was anticipated to be at 1668 m subsea. Operations and results Wildcat well 25/8-3 was spudded with the
semi-submersible installation Glomar Biscay II on 20 March 1981 and drilled to
TD at 1868 m in the Danian Ekofisk Formation. A total of 159.25 hours, or more
than 23% of the total time spent on this well, were lost due to downtime in the
categories of: Subsea and Surface BOP Equipment Repairs and Casing and
Wellhead. The well was drilled seawater and hi-vis pills down to 219 m and with
seawater/gel/Lignosulphonate from 219 m to TD. The top of the Paleocene reservoir (Hermod
Formation) was encountered 64.5 m lower than predicted at 1757.5 m and the net
oil sand was 9.5 m thick, which is close to what was found in the 25/8-1 well
to the southwest. The results were disappointing as there was much less sand
than had been anticipated. However, shows of hydrocarbons were found in thin
sand stringers throughout the interval 1667-1784 m, suggesting that the OWC
might be at 1784 m (1759 m TVD SS), about the same as in the Balder field. One core was cut from 1859 m to 1868 m in
the Ekofisk Formation Chalk/Limestone and recovered 90%. Reservoir data was
limited to mud logs and electric logs. No wire line fluid samples were taken. The well was permanently abandoned on 17
April 1981. It is classified as an oil appraisal of the 25/8-10 S Ringhorne
General The 25/10-5 well was drilled to establish
the presence of an accumulation of Eocene oil sand in the western part of the
Balder Field, and evaluate the geologic concept of sand-shale distribution and
reservoir quality. Operations and results Wildcat well 25/10-5 was spudded with the
semi-submersible installation Glomar Biscay II on 15 June 1981 and drilled to
TD at 2011 m in the Late Jurassic Viking Group. The well was drilled with sea
water/gel/lignosulphonate. The top of the Early Eocene reservoir
was encountered at 1733 m (1708 m sub sea), as prognosed.
The reservoir consisted of thin sandstone beds interbedded with shale and was
oil bearing. A 49.5 m gross oil column was found down to an OWC at 1782.5 m.
The net oil sandstone thickness was 18.2 m. Late Eocene Grid Formation
sandstone was penetrated at 1398 m to 1443 m and Paleocene Heimdal Formation
sandstone from 1905 m to 1929 m. These were both water wet without shows. Four cores were cut in the Lower Eocene
reservoir sequence. No wire line test or fluid sampling was carried out. The well was permanently abandoned on 17
July 1981 as an oil appraisal well. Testing Two drill stem tests were performed in
the Early Eocene reservoir. DST 1 perforated the interval 1756 m to 1753 m and
produced 171 Sm3 oil/day. The oil gravity was 25.3 deg API and the gas/oil ratio
was 59 m3/m3. DST2 perforated the intervals 1732 - 1740 m and 1756 - 1763 m. It
produced 515 Sm3 oil/day. The oil gravity in DST2 was 25.5 deg API and the gas/oil
ratio was 59 m3/m3. General Well 25/11-5 was drilled ca 4 km north
west of the 25/11-1 Balder discovery well on the Utsira High in the North Sea. The
well was designed to evaluate a sand build up and/or structural closure at the
Middle Paleocene horizon top. The location was mapped structurally high to the
adjacent wells 25/11-1, 25/11-2, 25/10-1, and 25/10-3. Operations and results Appraisal well 25/11-5 was spudded with the
drillship Drillmaster on 3 April 1974 and drilled to TD at 2164 m in Triassic red-grey
clays, and grey-green shale. Sloughing shale was the only drilling problem and
this was overcome by converting the Drispac mud system to a ligno-gel seawater
mud system. The well was drilled with Drispac from approximately 1000 to 1400
m, and with lignosulphonate/gel/seawater from ca 1400 m to TD. The well penetrated the Utsira Formation
and a Skade Formation sand and then entered a ca 700 m thick section of shales
belonging to the lower Hordaland Group before top Balder formation was
encountered at 1661 m. Significant oil bearing sands in the interval from 1714 to
1771 m were confirmed by sidewall cores and Schlumberger electric logs. The
lower part of this interval tested oil at good rates. Additional shows in traces
of sand in cuttings at 1838 - 1847 m were believed to be sloughings from the
oil sand above. One conventional core was cut from 1723.3
to 1725.5 m. Six attempts at FIT's were attempted with one successful at 1744.1
m. This test recovered 0.33 Sm3 gas, 4.5 l oil, 2.3 l filtrate and 0.8 l mud. The well was permanently abandoned on 8
May1974 as an oil appraisal. Testing< General Well 25/11-6 was drilled ca 1 km west of
the 25/11-1 Balder discovery well on the Utsira High in the North Sea. The
primary objective was to delineate the Paleocene E-70 oil sand and older sands
which are developed as topographic mounds (stratigraphic traps) in the Balder
Field area. A secondary objective was Danian sand which had oil shows in an
offset well. Operations and results Appraisal well 25/11-6
was spudded with the semi-submersible installation Norskald
on 20 August 1978 and drilled to TD at 1948 m in the Early Cretaceous Cromer
Knoll Group. The well was drilled with seawater/gel/lignosulphonate. The well penetrated the Utsira Formation,
a Skade Formation sand and a Grid Formation sand and then penetrated a ca 175 m
thick section of shales belonging to the lower Hordaland Group before top
Balder formation was encountered at 1646 m. An 8 m thick shaly Intra Balder
Formation sand at 1664 m had some shows and appeared to be oil bearing on the
logs. Two Paleocene Heimdal Formation sand units with tops at 1717.5 m and
1763.0 m were found oil bearing down to a clear oil-water contact at 1785.3 m
in the lower sand unit. This defines the OWC of the Balder field at 1760 m MSL.
The Danian sand (Ty Formation) was encountered at 1877 m, but was water wet. Five cores were cut in the Lista and
Heimdal Formation, recovering a total of 25.5 m core from the interval 1713 to
1797 m. Wire line fluid samples were attempted, but with no success. The well was permanently abandoned on 1
October 1978 as an oil appraisal. Testing
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 25/11-7 was drilled ca 3 km
west-south west of the 25/11-1 Balder discovery well on the Utsira High in the
North Sea. The primary objective was to delineate topographic mounds developed
in the Paleocene sands of the Balder Field. The primary targets were the Zone
II sand (E-70 sand) which was found oil-bearing in the 25/11-5 and the Zone I-B
sands which were found oil-bearing in the 25/11-6. Operations and results Appraisal well 25/11-7 was spudded with
the semi-submersible installation Norskald on 3 October 1978 and drilled to TD
at 1944 m in the Late Cretaceous Tor Formation. The well was drilled with Seawater/Gel/Lignosulphonate. The well penetrated the Utsira Formation
and several Skade Formation sands and then penetrated a ca 600 m thick section
of shales belonging to the lower Hordaland Group before top Balder Formation
was encountered at 1697 m. The Balder Formation contained some shaley sands
with poor to no oil shows. The massive I-B sand at 1750.3 m (Heimdal Formation)
was the only significant oil sand in the well. The well proved 36 m of net oil
sand with a clear oil-water contact at 1786.5 m (1761.5 m MSL), in reasonable
agreement with the Balder Field contact at 1760 m MSL established in 25/11-6. The
Zone II (E-70) sand was absent, or possibly an unrecognizable part of the I-B
Sand. A total of 20.35 m core was recovered in
four cores from the interval 1748.6 to 1772.3 m in the Lista and Heimdal
Formations. No wire line fluid samples were taken. The well was permanently abandoned on 27
October 1978 as an oil appraisal well. Testing General Well 25/11-8 was drilled ca 3 km
west-north west of the 25/11-1 Balder discovery well on the Utsira High in the
North Sea. The primary objective was to establish the presence of, and closure
on, the thick accumulation of Paleocene zone IB sand in the central part of the
Balder Field, evaluate the geologic interpretation of sand distribution and
reservoir quality in this field and test the flow potential and nature of the
hydrocarbons present. Operations and results Appraisal well 25/11-8 was spudded with
the semi-submersible installation Dyvi Alpha on 8 September 1979 and drilled to
TD at 1950 m in the Early Paleocene Ekofisk Formation. The well was drilled
with Seawater/Gel/Lignosulphonate. The well penetrated the Utsira Formation
and several Skade Formation sands and then penetrated a ca 600 m thick section
of shales belonging to the lower Hordaland Group before top Balder Formation
was encountered at 1655 m. The well encountered two massive sand units in the Paleocene
Heimdal Formation at 1721.5 m and 1743.8 m (dinoflagellate zones IB and II,
respectively), interpreted as sand lobes deposited from sand-rich turbidity
currents in the Balder Deep Sea Fan Complex. Both sands were oil bearing down
to an OWC at 1785 m (1760 m MSL). Some thin sands from about 1705 m to 1720 m,
overlying the massive sands, also appeared to be oil-bearing, and there were
good shows on a core three meter below the OWC. Nine cores were taken in the interval
1722.5 m to 1800.4 m in the Heimdal Formation. Cores 1 and 4 had no recovery;
the remaining cores retrieved a total of 41.7 m. No wire line fluid samples
were taken. The well was permanently a General Well 25/11-10 was drilled to appraise the
Balder Field on the Utsira High in the North Sea. The objective was to
establish the presence of a thick accumulation of oil sand in the southern part
of the Balder Field, and evaluate the geologic concept of sand-shale
distribution and the reservoir quality of the Paleocene sands. Operations and results Appraisal well 25/11-10 was spudded with
the semi-submersible installation Glomar Biscay II on 20 January 1981 on and
drilled to TD at 1988 m (1985 m logger's depth) in the Danian age chalk of the Ekofisk
Formation. The well was drilled with seawater/gel/Lignosulphonate mud. The Paleocene Heimdal Formation reservoir
sands anticipated to be present in this well were found at 1786 m, significantly
deeper than prognosed and below the field oil-water contact. Gross thickness of
the sands was 128.2 m with an average porosity of 31.4%. They were water wet. The
sands were found similar to those found in 25/11-7 to the north. Only thin
stringers (2.5 m totally) with shows between 1757 m and 1785 m were found in
the Sele and Lista formations. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 17
February 1981 as a dry well with shows. Testing No drill stem test was performed. General Well 25/11-11 was drilled to appraise the
Balder Field on the Utsira High in the North Sea. The objective was to
establish the presence of an accumulation of oil sand in the western part of
the Balder Field, and evaluate
the geologic concept of sand-shale distribution and reservoir quality. The top
of the reservoir was anticipated to be at 1708 m MSL. Operations and results Appraisal well 25/11-11 was spudded with the
semi-submersible installation Glomar Biscay II on 18 February 1981 and drilled
to TD at 1960 m in the Danian age chalk of the Ekofisk Formation. The well was
drilled with seawater and gel/lignosulphonate. One main oil sand of Paleocene age (Heimdal
Formation) was encountered at 1754 m (1729 m TVD MSL). It was 141.5 m thick and
was oil-bearing in the upper 29 m down to an OWC at 1783 m (1758 m TVD MSL).
This OWC was in agreement with the general field OWC in the area. Average
porosity in the oil sand was 32.6%. Shows of hydrocarbons were also present in a
16 m thick Intra Balder Formation Sandstone with top at 1698 m, and in thin
sand stringers within the Sele Formation. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 18
March as an oil appraisal. Testing No drill stem test was performed. General Well 25/11-12 was drilled to appraise the
Balder Field on the Utsira High in the North Sea. The objective was to
establish the presence of a thick accumulation of oil sand in the north-eastern
part of the Balder Field, and evaluate the geologic concept of sand-shale
distribution and the reservoir quality of the Paleocene sands. The top of the reservoir was anticipated to
be at 1717 m TVD MSL. Operations and results Appraisal well 25/11-12 was spudded with
the semi-submersible installation Glomar Biscay II on 18 April 1981 on and
drilled to TD at 1918 m in the Danian age chalk of the Ekofisk Formation. The
well was drilled with seawater/gel/Lignosulphonate mud. The Sele Formation had thin stringers of
sand with oil shows, but no significant Paleocene sands were developed above
the Heimdal Formation in this well. Massive Paleocene Heimdal Formation sands
were encountered at 1784.5 m (1759.5 m TVD MSL) and 1860 m (1835 m TVD MSL).
The upper sand is 65 m thick and had oil shows evident by sidewall cores at
1785 m and 1786 m. The lower sand is 20 m thick and was entirely water-bearing
with no shows. The Balder Field oil/water contact is generally thought to be at
1785 m (1760 m). No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 7
May 1981as a dry well with shows. Testing No drill stem test was performed. General Well 25/11-13 was drilled to appraise the
Balder Field on the Utsira High in the North Sea. The objective was to
establish the presence of a thick accumulation of oil sand in the southern part
of the Balder Field, and evaluate the sand-shale distribution and the reservoir
quality of the Paleocene sands. Top of the Paleocene reservoir sands was
anticipated at 1702 m MSL. Operations and results Appraisal well 25/11-13 was spudded with
the semi-submersible installation Glomar Biscay II on 10 May 1981 and drilled
to TD at 1932 m in the Late Cretaceous Tor Formation. The well was drilled with
seawater and bentonite down to 500 m and with
seawater/bentonite/lignosulphonate mud from 500 m to TD. Shows of hydrocarbons were present in
three 1-2 m thick Intra-Balder Formation sand beds between 1723 and 1743 m. The
main oil-bearing Paleocene reservoir sand (Hermod Formation) was encountered between
1768.8 m to 1816.8 m. It contained oil down to the OWC at 1783 m (1758 m MSL),
which is close to the regional Balder Field OWC. The average porosity in the
oil zone was 33.5 %. Poorly developed 4 m thick Heimdal Formation sand was
penetrated at 1858 m, and then a massive Ty Formation sandstone was penetrated
from 1875 m down to the Shetland Group at 1908 m. No cores were cut and no wire line fluid
samples were taken. The well was permanently abandoned on 29
May 1981 as an oil appraisal. Testing No drill stem test was performed. Well 25/12-1 is located on the Patch Bank
Ridge between the Utsira High and the Stord Basin in the North Sea. The well
was designed to test Paleocene sand and late Cretaceous chalk prospects (found
oil bearing in the adjacent Esso blocks). Additional objectives were the
Mesozoic and possibly older sands, which formed part of a monocline, east
dipping subcrop below this structure. The well was programmed to investigate
the entire sedimentary sequence down to igneous/metamorphic basement,
interpreted to occur at approximately 2743 m. Operations and results Wildcat well 25/12-1 was spudded with the
semi-submersible installation SEDCO 135 G on 3 October 1973 and drilled to TD
at 2865 m in rocks of possible Devonian age. The spud was delayed due to rig
repairs in Hamburg. This resulted in the well being drilled during the worst of
the winter weather. Due to adverse weather and bad anchoring conditions, 14.5
days were spent anchoring the rig. A total of 19.7 days was lost directly due
to weather during drilling and abandoning. A further 8.7 days were lost
repairing underwater equipment, much of which was also due to weather damage.
The well was drilled with seawater and bentonite down to 463 m and with a
seawater / lignosulphonate mud from 463 m to TD. The Oligocene-Eocene sands of the
Hordaland Group were water bearing and the Paleocene sands absent. The Chalk
section (Tor and Hod formations) showed poor reservoir characteristics and was
also water bearing. Below the Late Jurassic shale sequence sands and
conglomerates of Middle Jurassic age and older were penetrated. The sands were
penetrated in a down dip position on a monoclinal structure rising towards
block 25/11. Middle Jurassic (Vestland Group) sands were encountered at 2244 m
with porosity up to 30 %, averaging 18 %. Conglomerates were encountered at
2425 m and extended down to 2671 m. From this point down to TD at 2865 m the
well drilled a thick water bearing sand sequence. This possible Devonia General Well 29/6-1 was drilled ca 2 km west of
the UK border on the eastern margin of the East Shetland Basin. The primary
objective was the Brent Group in a fault block separate from the Hild structure
some few km to the southwest. The secondary objective was the Statfjord
formation. Operations and results Wildcat well 29/6-1 was spudded with the
semi-submersible installation SEDCO 707 on and drilled to TD at 4832 m. The well was spudded by "Sedco
707" on 12.10.81. When drilling the 17 1/2" pilot hole (with 1.1 sg mud)
in the 24" section, mud losses occurred at 870 m. The hole was displaced
to seawater and operations continued down to 1205 m where the 24" casing
was set. Further drilling went with increasing mud weights due to tight hole
problems, to a point where the overbalance considerably reduced penetration
rate. Due to high deviation the pipe became differentially stuck at 4664 m. The
well was planned to be vertical, but ended up severely deviated. From 3973 m to
4097 m hole inclination increased from 5 degrees to 10.5 degrees, increasing to
15.5 degrees by 4155 m, as a result of the increased dip of the bedding planes.
At 4155 m a pendulum drill assembly was used but the hole inclination continued
to increase to 19.5 degrees. By 4211 m the angle had reduced to 17 degrees but
again increased to a maximum of 21 degrees by 4457 m, and then decreased to
20.25 degrees by 4570 m. Below this depth, surveys were not possible due to the
hole conditions with overpull and stuck pipe on the connections and tight hole
on trips. Keyseating, washout in the sandstones and the swelling nature of the
clays in the Dunlin formation added to the problem caused by hole angle. At TD Schlumberger
HDT log was run and the General Well 30/3-1 is located just north of the
Huldra Discovery. It was planned to be drilled in two phases and the primary
objective was to test sandstones of the Brent Group. Secondary objectives were
sandstones in the Paleocene and in the Lower Jurassic, Cook and Statfjord
formations. Operations and results Well 30/3-1, Phase I was spudded with the
semi-submersible installation Nordskald and drilled to 3718 m in claystone and
marls of the Early Cretaceous Cromer Knoll Group. Phase I was drilled without
serious problems but the 12 1/4" hole section had to be cut shorter than
originally planned due to lost circulation and possibly higher pore pressures
than prognosed. The mud gas readings were relatively high through the 17 1/2"
section causing long periods of circulation. The well was drilled with seawater
and hi-vis pills down to 212 m, with a gel mud from 212 m to 985 m, and with a
Spersene XP 20/Magcogel/nut plug mud from 985 m to TD. The Paleocene did not contain good
reservoirs. Shows and live oil in the mud were however recorded in predominant
claystone lithology from 1910 m to 2470 m. No conventional cores were cut and
no fluid samples taken. The well was suspended on 7 September as
a dry hole after the 9 5/8" casing was run. The plan was to re-enter the
well later, using a rig equipped with a 15000 psi BOP stack and drill through
the Jurassic sandstones. Testing No drill stem test was performed General Well 30/4-1 is located north of the Hild
Discovery and west of the Oseberg Field. The main target was Middle Jurassic
sandstones in a complex fault and dip-controlled closure. Secondary targets
were Palaeogene sands (Balder and Sele Formations) and possible Late Jurassic
sands, both in simple dip closures. Operations and results Wildcat well 30/4-1 was spudded with the
semi-submersible installation SEDCO 707 on 1 November 1978 and drilled to TD at
5454 m in the Early Jurassic Dunlin Group. The well penetrated a mainly argillaceous
Palaeogene section. However, a distinct interval of interbedded thin
argillaceous water-bearing sandstones (beds 1 - 3 m thick) with thicker
mudstone intervals was drilled between 2116.5 and 2162.5. The net/gross ratio
of this interval was about 0.2 (20%) and the sandstone porosities average
around 30% (from Schlumberger logs). The well then penetrated a thick
argillaceous Cretaceous and Late Jurassic interval. No Late Jurassic sandstones
were developed. Water bearing, Middle Jurassic sandstones of the Brent
Group were encountered at 5181.5 m. This target group was 218.2 m
thick, had a net/gross ratio of about 0.66 (66%) and had sandstone porosities
ranging from around 4-16% (from Schlumberger logs). Shows were recorded in
limestones in the interval 2545 m to 2570 m, with weaker shows extending down
to 2630 m. Weak shows were also noted in the interval 2900 m to 3000 m.
Geochemical analyses of cuttings confirmed migrant "medium gravity oil"
in the interval 2570 m to 2630 m. No conventional cores were cut. Wire line RFT
samples were attempted but all failed. The well was permanently abandoned as dry
on 14 May 1979. Testing No drill stem test was performed General Well 30/4-2 was drilled test an easterly
dipping fault block on the western margin of the Viking Graben. The primary
target was the Brent Group, which had already been proven to contain gas
condensate by well 30/7-6 located 3 km to the South on the same structure.
Secondary objectives were to test Palaeocene and Lower Eocene sandstones, and
the Statfjord Formation. Well 30/7-2 had earlier encountered a hydrocarbon
column with dry gas overlying heavy oil in the uppermost part of the Eocene
Frigg Formation. Operations and results Well 30/4-2 was spudded with the
semi-submersible installation SEDCO 707 on 16 November 1979 and drilled to TD
at 4775 m in the Triassic Hegre Group. Bad weather caused some delay, and on 12
March, the drill string was hung-off due to adverse weather conditions. Whilst
retrieving the running assembly an influx from the well was observed. The
influx was bull-headed and it took five days before the well was in stable
conditions again. Otherwise, no significant incident happened in the
operations. The well was drilled with seawater and gel down to 1096 m, with
lignosulphonate/Drispac/Gypsum mud from 1096 m to 2530 m, and with
lignosulphonate/Poly-rx from 2530 to TD. The Frigg Formation was encountered
water-wet without shows at 1820 m, 36.5 m below the OWC defined in the 30/7-2
Frigg discovery. The Brent Group was encountered at 3779 m. Brent contained
gas/condensate and had excellent poroperm characteristics. The gas-water
contact established between 3876.5 m and 3893.5 m in the Ness Formation. The
Statfjord Formation was encountered water-wet at 4337 m with only some poor
shows in the top. Pressure analysis showed that it was not communicating with
the Brent Group. General Well is located centrally in the northern
Viking Graben of the North Sea. It was the most northerly well drilled in
Norwegian waters of the North Sea when it was drilled. Primary objectives of
30/5-1 were Paleocene sands, thought to be productive in the Frigg Field and the
recently discovered Heimdal Field, and potential sand or carbonate reservoirs
in the Early Cretaceous. The Late Cretaceous
Chalk found so prospective in the south was considered to be a secondary
objective in view of the possible northward shaling out of that formation. Operations and results Wildcat well 30/5-1 was spudded with the
semi-submersible installation Transworld 61on 17 May 1972 and drilled to TD at 4124
m in the Early Cretaceous Åsgard Formation. The well was drilled with seawater
and Lignosulphonate with additions of a total of 329 bbls of diesel oil. In the main Paleocene objective a few
thin water-bearing sand-streaks were present, and in the secondary Upper
Cretaceous objective, the Chalk Formation, as expected, had virtually shaled
out. Between a depth of 3475 and 3604 m four streaks of limestone occur,
ranging in thickness from 1 - 3 m. The mud became gas cut while drilling the
interval. From petrophysical logs the limestone streaks appeared to be gas bearing
with porosities from 9 to 20% and water saturations in the range 20 - 60%. They
were the only intervals recognisable from logs containing hydrocarbons. The
total thickness of these limestone stringers was insufficient to justify a
test. No One core was taken at TD from 4114.8 to 4123.9
m with a recovery of 5.6 m (62. 5%). No wire lin General Well 30/6-1 was drilled on the Oseberg
Fault block in the North Sea. The primary objective was to penetrate sandstones
of Middle Jurassic age and to evaluate their possible content of hydrocarbons.
Secondary objectives were sandstones of Lower Jurassic and Paleocene age. The
well is Reference well for the Statfjord Group. Operations and results Wildcat well 30/6-1 was spudded with the semi-submersible
installation Deepsea Saga on 18 June 1979 and drilled to TD at 3175 m in the
Triassic Lunde Formation. Problems with setting the 9 5/8” casing at 2443 m
caused an 8 days delay in the drilling phase. Also gumbo problems were
encountered in the interval 1000 – 1600 m and 4 days rig time as lost due to
this. Otherwise operation proceeded without significant problems. The well was
drilled with spud mud down to 895 m and with a lignosulphonate/bentonite mud
from 895 m to 2456 m and with chromium-lignosulphonate/bentonite mud from 2456
m to TD. Diesel was added at 1720 m to reduce problems with sloughing shales. A
6% to trace levels of oil was recorded in the mud from this depth to TD. The Cretaceous Jorsalfare Formation had
6.75 m of net pay gas in thin sandstones with average porosity of 29% and water
saturation of 39.3%. The Brent Group was encountered at 2285 m and was
gas/condensate filled in 38.75 m of net pay sandstones with average porosity of
22.5% and water saturation of 29.2%. The hydrocarbon/water contact was not
encountered in the well. The Dunlin Group was water bearing with 45 m of net
sand with an average porosity of 24.6%. The Statfjord Group was water bearing
with 235 m of net sand with an average porosity of 21.4%. Weak shows were
described on conventional and sidewall cores in sandstones from below the
hydrocarbon General Well 30/6-2 was drilled to appraise the
30/6-1 Oseberg discovery. Well 30/6-1 found gas in the Brent Group and water-filled
reservoirs in the Dunlin and Statfjord groups. The primary objectives were to
test the Dunlin and Statfjord sandstones in a structurally higher setting on
the Oseberg Alpha structure. Secondary objective was appraisal of the Brent
Group hydrocarbons. Operations and results Appraisal well 30/6-2 was spudded with
the semi-submersible installation Deepsea Saga on 24 September 1979 and drilled
to TD at 2890 m in the Triassic Hegre Group. Tight hole became a serious
problem at 1313 m. This was cured with salt water and diesel addition. Five
days were counted as non-productive due to bad weather and fishing for lost
objects in hole. The well was drilled with spud mud down to 736 m, and with Chromium-Lignosulphonate/bentonite
mud from 736 m to TD. After the diesel addition at 1313 m the mud contained 8%
diesel. The diesel content became slowly diluted to 0.25% at TD. The Brent Group was penetrated from 2191
to 2237. It is 46 m thick and gas bearing. The hydrocarbon/water contact was
not seen in the well. The underlying Dunlin and Statfjord groups were both
water bearing. Oil shows were described on cuttings and 39% water saturation
was calculated, from top Brent and all through the Shetland Group up to 2165 m.
Further oil shows on cuttings and core were described at 1945 to 1955 m in the
Balder Formation, on cores and cuttings in the Dunlin Group, and on the
Statfjord core. A total of seven cores were recovered in
the interval from 2202 to 2238.5 m in the Brent Group, 2435 m to 2437.5 m, and
2444.5 to 2454.5 m in the Dunlin Group, and 2571 to 2577 m in the top of General Well 30/6-3 was drilled on the Alpha
structure situated in the south-western part of block 30/6. The objective of
the well was to penetrate sandstones of Middle Jurassic age and to evaluate
their possible content of hydrocarbons. Operations and results Appraisal well 30/6-3 was spudded with
the semi-submersible installation Deepsea Saga on 16 December 1979 and drilled
to TD at 2940 m, 56 m into the Statfjord formation. No significant problem was
encountered in the operations, but 13.5 days were lost due to bad weather. The
well was drilled with spud mud down to 1757 m and with chrome
lignosulphonate/bentonite mud from 1757 m to TD. Oil shows were recorded in
claystone/siltstone cuttings at 1993 to 2023 m, in siltstone cuttings at 2095
m, and in limestone cuttings from 2253 m to 2296 m and 2317 m to 2350 m. Top
Brent Group came in at 2421 m. It consisted of sandstone interbedded with shale
and coals with a main reservoir sand from 2480 to 2513 m. Gas/condensate was
proven all through the reservoir. The hydrocarbon/water contact could not be
defined, but the presence of hydrocarbons down to the base of the reservoir
indicated the contact to be located down flank on the structure. The sandstones
of Early Jurassic age ("Intra Dunlin Sand" and the Statfjord Group) were
water bearing. Four cores were cut in the interval from
2421 to 2458 m. An RFT fluid sample was taken at 2499 m. FIT fluid samples were
taken at 2279 m (traces of gas), 2422 m (gas), 2451 m (small amounts of 32.6
deg API oil), and 2463 m (gas). The well was permanently abandoned on 7
March 1980 as a gas/condensate appraisal.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 30/6-4 was drilled on the Alpha
structure on the Gullfaks fault block in the North Sea. The primary objective
was to test hydrocarbon accumulations in Middle Jurassic sandstones and to
define the hydrocarbon contacts. Gas was the expected hydrocarbon phase. Operations and results Well 30/6-4 was spudded with the
semi-submersible installation Deepsea Saga on 17 February 1981 and drilled to
TD at 2942 m in the Early Jurassic Amundsen Formation. Total depth for the well
was reached 10 days before prognosed although 5 days were spent on rig repair
when the heave compensator fell down. Apart from this accident no major
problems were encountered in the drilling phase. The well was drilled in
favourable weather condition. The well was drilled with spud mud down to 962 m,
with KCl/polymer mud from 962 m to 1862 m, and with gel/lignosulphonate mud
from 1862 m to TD. Sporadic fluorescence was recorded on
cuttings from limestone/siltstone stringers in the Paleocene and Cretaceous.
Top Cretaceous had good shows on cuttings and sidewall core in the interval
2300 - 2305 m, and two valid RFT pressure points indicated a gas gradient over
the interval. Top Brent Group, Ness Formation was
encountered at 2597 m with an oil-filled Etive Formation from 2630 m to 2686 m.
No oil/water contact was found, but combined pressure data from the well and
three previous wells on the structure indicated a gas/oil contact at 2528 m. Four cores were cut from 2638 m in the
Etive Formation to 2692.5 m, a few meters into the underlying Drake Formation. One
RFT oil sample of good quality was taken at 2633 m.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 30/7-1 was drilled in the eastern
part of the East Shetland Basin in the North Sea. The well location is due west
of the Oseberg Field and ca 3.5 km from the UK Border. The primary objective was
to investigate structural closure at Eocene and Paleocene with possible sand
development. Operations and results Wildcat well 30/7-1 was drilled with the
semi-submersible installation Polyglomar Driller. Polyglomar Driller was
accepted in Verdal on June 28, and left for its first location on June 30, 1975
at 1500 hrs. The rig was on location ready to spud on July 4, after a period of
4 days for movement to location and for anchoring. During the drilling of the
36" hole the drilling template tilted and the entire assembly had to be
picked up. The rig was moved 50 ft due east and a new spudding attempt was made
on July 5, 1975. Drilling then proceeded without significant problems to 1007 m,
which became TD of the well. While pulling out of the hole to set the 13
3/8" casing the pipe stuck in the hole with the bit at 420 m. Numerous
attempts to free the pipe were unsuccessful and it was decided to abandon the
well. The well was drilled with seawater/sweeps and gel from surface to TD. The penetrated sediments are interpreted
as recent to Miocene in age. No logs were run in the well. No cores
were cut and no wire line fluid samples were taken. During abandonment the drilling template was
found to be stuck and the attempts to recover it were unsuccessful. Divers were
jumped to inspect the drilling template and they reported the template had sunk
10 ft below the sea bed. Permission was obtained to fill the cavity above the
ba General Well 30/7-2 was drilled from a location
150 ft (46 m) east of well 30/7-1, which was junked for technical reasons. The
well is located in the eastern part of the East Shetland Basin in the North
Sea. The well location is due west of the Oseberg Field and ca 3.5 km from the
UK Border. The primary objective was to investigate structural closure at
Eocene and Paleocene with possible sand development. Operations and results Well was spudded with the semi-submersible
installation on 6 August 1975. While drilling the 36" hole at 167 m, the
drill string stuck. After several unsuccessful attempts to free the pipe, a
string shot was run and the hole was plugged. The well was re-spudded on 9
August 9 after having moved the rig 200 ft (61 m) south-southeast. From 28
August up to 10 September operations were more or less suspended at a depth
between 991 and 1001 m due to technical problems with the BOP. The well was
drilled with gel/seawater mud down to 485 m, with seawater/gel and Drispac from
485 m to 1001 m, and with seawater/gel/Drispac and Lignosulfonate (Unical) from
1001 m to TD. Two minor shows were reported from Late
Eocene. The first, at 1226 m, is a sandstone with patchy yellow to whitish fair
to weak fluorescence with a medium to slow cut. There was no visible oil stain
on the sample. The second, in a thin sandstone stringer, at 1525 m, gave a dull
gold fluorescence with a slow streaming cut. At approximately 1700 a thin
sandstone gave a gold fluorescence and a white, milky, streaming cut. The
samples had a slight oil stain. The well penetrated the Frigg Formation
from 1748 to 1909m. It was hydrocarbon bearing with a gas/oil contact at 1762.8
m and an oil/water contac General Well 30/7-3 was drilled in the Fensal
sub-basin south-southeast of the Hild Discovery and north of the Odin
Discovery. The main objective of the well was to
test a mapped seismic anomaly below the "Ml" marker, prognosed to be
a possible porous carbonate development at Cenomanian level. The location of
the well gave a test of the anomaly on the western edge, according to the
seismic mapping. Secondary objectives were possible Early Cretaceous
sand/limestone pinch-outs and Late Jurassic sands. Operations and results The well 30/7-3 was spudded with the
semi-submersible installation Polyglomar Driller on 6 August 1976 and drilled
to TD at 4044 m in the Early Cretaceous (Albian - Aptian) Cromer Knoll Group.
When drilling the 12" hole at 3001 m, a leak was discovered in the
wellhead. A groove was cut in the sealing area between the wellhead and the
collet connector. A wellhead extension was run in the damaged wellhead with
four o-rings as seal towards the original wellhead. The drilling was continued
and 9 5/8"casing was set at 3782 m. While drilling 8-3/8" hole at
4044 m circulation was lost. When the mud weight was reduced in an attempt to
re-establish circulation the well started to flow. A barite plug was set at
bottom, and this finally stabilized the well. The well was drilled with
freshwater gel to 700 m and with lignosulphonate mud from 700 m to TD. A comparison of the results from the
seismic velocity survey and the seismic interpretations identify the interval
between 3795 m and 3918 m as the target seismic anomaly. In this interval a
sequence of limestone, marlstone and shale was found. The limestone is composed
of mainly calcite with recognisable coccoliths. In the lower part minor
terrigenous components of quartz sand and silt, and mica flakes were
encountered. In places the limestone became very argillaceous grading to
marlstone and shale. No visible porosity or any hydrocarbon s General Well 30/7-4 is located in the eastern
part of the East Shetland Basin in the North Sea. The well location is due west
of the Oseberg Field and ca 2.5 km from the UK Border. The main objective of
the well was to test Middle and Early Jurassic sandstones (Brent Group and
Statfjord Formation) Secondary objectives were possible lower Cretaceous
carbonate development, and possible Late Jurassic sandstones. Operations and results Well 30/7-4 was spudded with the
semi-submersible installation Polyglomar Drilling on 25 January 1977. A 17
1/2" pilot hole was drilled to 192 m. The operation had to be suspended
for two days due to bad weather. When the operation was continued, the 17
1/2" pilot hole could not be found and a new 36" hole was drilled. The
30" casing was set and cemented at 193 m. The weather conditions made it
necessary to set piggy backs on five anchors. A 17 1/2" hole was drilled
to 778 m in assumed Miocene sediments. This was the planned setting depth for
the 20" casing. While reaming out the 17 1/2" hole to 26" prior
to running 20" casing, the drill string parted. An overshot was worked
over the fish but attempts to pull the fish were unsuccessful. The string was
backed off at 538 m in the x-over above the overshot and the hole was given up.
The well was drilled with seawater and gel. No cores were cut, no logs were run, and
no wire line fluid samples were taken. The well was permanently abandoned on 5
February as a junk well and the rig was prepared for spudding replacement well
30/7-5. Testing No drill stem test General Well 30/7-5 was a replacement of the well
30/7-4 which was lost due to "twist off" of the drill pipe. The well is
located in the eastern part of the East Shetland Basin in the North Sea. The
well location is due west of the Oseberg Field and ca 2.5 km from the UK
Border. The main objective of the well was to test Middle and Early Jurassic sandstones
(Brent Group and Statfjord Formation) Secondary objectives were possible lower
Cretaceous carbonate development, and possible Late Jurassic sandstones. Operations and results The semi-submersible installation
Polyglomar Drilling was skidded over from the junked 30/7-4 well to the
position for 30/7-5 by regulating the length of the anchor chains. Well 30/7-5 was
spudded with on 5 February 1977 and drilled the 26" section to TD at 805 m
in Miocene sediments. When running the 20" casing, the string parted and
18 joints of casing were left in the hole. Attempts to catch the fish failed
and the well was given up. The well was drilled with seawater and gel. No cores were cut, no logs were run, and
no wire line fluid samples were taken. The well was permanently abandoned on 13
February 1977 as a junk well, and the rig was prepared for spudding replacement
well 30/7-6. Testing No drill stem test was performed. General Well 30/7-6 was drilled on the East
Shetland Basin in the North Sea close to the UK border. It was drilled as
replacement well for wells 30/7-4 and 30/7-5, which were both junked for
technical reasons. Well 30/7-6 (Phase I) was planned to be suspended after setting
the 9-5/8" casing at ca 3800 m. The well would then be re-entered as
30/7-6 R (Phase II) and drilled to a TD of ca. 5000 meters employing the
11" 1000 bar BOP system. The main objective was Middle Jurassic
sandstones, and this was planned to be penetrated in the re-entry. The exploration
targets in the 30/7-6 well were the secondary ones: possible lower Cretaceous
carbonate development, and possible Late Jurassic sandstones. The
hydrocarbon-bearing Eocene sands (Frigg Formation) tested by the 30/7-2 well
were also expected to be encountered within the same structural closure by this
well. Operations and results Wildcat well 30/7-6 was spudded with the semi-submersible
installation Polyglomar Driller on 15 February 1977. At 3784 m, on April 14, a
massive gas kick occurred and circulation was lost. The well was killed and
plugged back into the 13 3/8" casing. A sidetrack was kicked off from 2619
m. The sidetrack proceeded with the 12 1/4" hole to 3252 m and the 8
3/8" hole to 3711 m. A 7" liner was set down to 3707. The cement
flash set around the running string for the liner and 18 days were spent
cleaning out the hole. At this point, the well was plugged back and suspended. The
well was drilled with a gel/lignosulphonate mud system. The top of the Eocene sands were
penetrated at 1783.5 m and were found to be water wet. This agrees with the
observation made in 30/7-2, in which the oil water contact was defined at 1783
m. No res General The main objective of the well was to
test the SE prospect on the 30/7 block. The objective of the well was to test
possible sandstone reservoirs of Jurassic age, which were predicted to occur-in
a large structure (150 km2) at the Kimmerian unconformity) located on the
eastern flank of the Viking basin. The specific targets were possible
turbiditic sandstone deposits within a thick Late Jurassic sequence, Middle
Jurassic Brent Formation sandstones, and Early Jurassic Statfjord Formation
sandstones. The well was planned to penetrate 50 m into the Statfjord Formation
to approximately 5250 m. The well is Reference Well for the Cook
Formation. Operations and results The well 30/7-7 was drilled between
December 16th 1978 and May 30th 1979 with the rig Treasure Seeker. It reached
TD at 5127 m in the Early Jurassic/Late Triassic Statfjord Formation. 34.5% of
the total rig time was lost time due to fishing, waiting on weather, waiting
for replacement of equipment, and hole problems. The problem that had most
serious consequences for the geological program occurred while reaming from
5114 m to 5125 m where the string got stuck. After 9.5 days of fishing for the
drill string it was finally backed of at 4804 m. At this point it was decided to
abandon the well leaving the fish in the hole. Before this happened the well
had been logged down to 5122 m, but the fish made it impossible to test the
Statfjord Formation sandstone. The well was drilled with Seawater/gel/hi-vis
pills spotting LCM pills as needed down to 763 m and with a
Spersene/XP20/Drispac mud with 0 % to 4% oil and LCM pills as needed from 763 m
to TD. Sandstone levels interbedded with shales
were encountered below 2187 m in the Tertiary. They were mainly developed
between 2216 and 2320 m. Some calcareous levels in the Maastrichtian limestones
between 2531 and 2575 m could be considered as reservoirs. Limestone stringers
in the Turonian calcareous section from General Well 30/10-1 is located on the Northern
apex of the Frigg field. The well was drilled as a wildcat, primarily to
evaluate the Lower Eocene sand ("Frigg Field Clastic Tongue") in the
area. Secondly, the well should evaluate the Paleocene sands and the Late
Cretaceous limestone. The plan was to set the 9 5/8 inch casing in the top of a
high-pressure zone (Cretaceous Shale) prior to moving the rig Saipem Due to
another location. The hole should then be re-entered with another rig and drill
deeper to evaluate a deep-seated structural closure. Operations and results Well 30/10-1 was spudded with the vessel
Saipem Due on 5 May 1973 and drilled to TD at 2917 m in Late Cretaceous
(Maastrichtian) shale. Initial drilling from the sea floor to 1067 m was with
seawater and gel. Below 1067 m a fresh water Spersene XP 20 (lignosulphonate)
mud system was used. The thickness of the pay section of the
Frigg Clastic Tongue (Primary objective) was disappointing in that it was very
thin. A green shale unit replaced the expected pay section. Formation interval
test and logs indicate that approximately 4 m of the Frigg Clastic sand
contained gas and approximately 6 m could possibly be oil bearing. No other
good hydrocarbon shows were encountered below the Frigg Clastic Tongue. in the rogaland Group almost
200 m of sand were present, however, the sand was void of hydrocarbons,
with the exception of some scattered fluorescence in the upper portion. Five
cores were cut in the Frigg sand in the interval 1974 m to 2010 m. No sidewall
cores were taken. Four Formation Interval Tests (FITs) were taken in the Frigg
sand. FIT No 1 at 1960.5 m recovered, 29 cubic feet of gas, 5 litres water and
0.5 litres mud. FIT No. 2 at 1989.5 m recovered 10 litres water. FIT No. 3 at
1974.5 m recovered 7 litres liquid (mud and water) and 100 cc oil. FIT No. 4 at
1966 m recovered 6.5 cubic feet gas, 2.25 litres oil, 300 cc mud, and 4.75
litres of water. Oil g General Well 30/10-2 was the discovery well for
the Odin field, located North of the Frigg Field. The primary objective of the
well were to evaluate the Early Eocene sands ("Frigg Field Clastic
Tongue") predicted at 1954 m. Secondary objectives were to evaluate the
Paleocene sands and the Danian / Late Cretaceous limestone prognosed from ca
2187 m to ca 2713 m. Operations and results Exploration well 30/10 2 was spudded with
the semi-submersible installation Drillmaster on 24 December 1973 and drilled
to TD at 2755 m in Late Cretaceous (Maastrichtian) Hardråde Formation. The mud
programme used was a seawater/Lignosulphonate system. Some drilling problems
were encountered due to shale cavings. After drilling to 2026 m it was
necessary to condition the hole several days due to caving shales. While
drilling at 2147 m three cones were lost in the hole and when attempting to
recover these, six feet of the bottom drilling string was left in the hole. The
fish was recovered after several attempts. Later after setting 9 5/8"
casing the hole was drilled to TD with some minor shale caving problems. The Late Cretaceous consisted primarily
of interbedded tight micritic limestone and shale. No reservoir beds were
present and no significant shows were recorded. However, traces of dead oil
were noted between 2722 m and 2743 m (Ekofisk Formation). The Danian section
consisted of detrital and skeletal limestone. No reservoir beds were noted and
no shows recorded. The Paleocene contained 235 m of potential sandstone
reservoirs. The sands were water wet and no significant shows were recorded.
However traces of dead oil was again noted in an upper massive sand and in
silty shales (Lista Formation) from 2457 m to 2472 m and from 2527 m to 2594 m.
The Eocene section contained a good sand reservoir (Frigg Formation) from 1997
m to 2067 m. The formation was gas-filled down to 2048 m. The sand is white,
medium to coarse grained, fine to ver General Well 30/10-3 was drilled on the Odin
Discovery just north of the Frigg area. The main objective was to evaluate the
Early Eocene sand ("Frigg Field Clastic Tongue") and appraise the
30/10-2 Odin gas Discovery. Operations and results Appraisal well 30/10-3 well was spudded
with the semi-submersible installation Drillmaster on 8 August 1974 and drilled
to TD at 2255 m in sands of the Paleocene Hermod Formation. Some anchor
problems were experienced due to the sandy sea floor; otherwise no drilling
problems were encountered during the operations. The mud used was a seawater,
lignosulphonate system. Cuttings from 177 m to 704 m
(Pliocene-Miocene undifferentiated) consisted of sand and shells (coquina).
From 704 m to 1213 m (Oligocene) the section consisted of sand, coquina and
traces of lignite between 780 m and 1213 m. From 1213 m to 1594 m the section
is grey shale with stringers of thin micritic limestone. From 1594 m to 1823 m
the section is predominantly grey shale with minor traces of micritic
limestone. From 1824 m to 2030 m a green shale unit is present. At 2030 m (Top
Frigg Clastic Tongue) the lithology changed to sand and continued to a depth of
2073 m. From 2073 m to 2182 m the section consisted of red brown shales and
sands. From 2182 m to TD (Paleocene) the section is predominantly sand with
some thin grey shales. The Paleocene sand was void of
hydrocarbon shows. The Frigg Clastic Tongue was 43 m thick. Logs and cores
indicated approximately 24 m of this interval contained oil and gas down to an
oil-water contact at 2054 m. Net pay was 18 m of which 14 m was good clean gas
sand and 4 m oil sand. Six cores were cut from 2010 m in the
"Green shale unit" down to 2064 m, 34 m into the Frigg sand. Eight
Formation Interval Test (FIT) fluid samples were recovered from four different
depths in the Frigg sand. A sample from 2068.1 m 9.75 l water and 0.5 l mud; a
sample from 2052.8 m General Well 30/10 4 was drilled on the northern
tip of the Frigg Field. Its main purpose was to explore a deep-seated closure
at Middle Jurassic level. This was a secondary target in the 30/10-1 well, but
it was not reached in this well, which was terminated in the Late Cretaceous
due to high-pressure problems. Operations and results Well 30/10-4 was spudded with the
semi-submersible installation Neptune 7 on 11 September 1974 and drilled to TD
at 758 m. At this point the drill string was lost in the hole. Fishing was
unsuccessful and the well was plugged back and junked. The well was abandoned
on 25 September 1974. Testing No drill stem test was performed General Well 30/10-5 was drilled on the northern
tip of the Frigg Field. Its main purpose was to explore a deep-seated closure
at Middle Jurassic level. This structure was targeted already in the 30/10-1
and 30/10-4 wells, but it was not reached because well 30/10-1 was terminated in the Late
Cretaceous due to high-pressure problems and well 30/10-4 became junked in the Miocene due to an unrecoverable fish. Operations and results Exploration well 30/10-5 was spudded with
the semi-submersible steel installation Neptune 7 on 25 August 1974 and drilled
to TD at 5185 m in the Late Triassic Hegre Group. Reaming of the 12 1/4"
hole to17 1/2" for setting the 13 3/8" casing was delayed due to
several twist-offs, junk in hole, pod trouble and weather. After setting the13
3/8" casing drilling was resumed. At 2943 m, lost circulation was
encountered, however; after setting a cement plug, drilling was continued
without difficulties. Drilling from the sea floor to 747 m was with seawater
and gel. Below 747 m a fresh-water Spersene XP 20 (lignosulphonate) mud system
was used. The Oligocene section consisted entirely
of siltstone and clay. The Eocene, section contained a sandstone reservoir
(Frigg Formation, first informally termed "Frigg Clastic Tongue")
from 1964 m to 2150 m. Good gas shows were present from 1965 m to 1974 m and
good oil shows from 1974 m to 1978 m. Below 1978 m the section was water wet.
The Rogaland Group contained 159 m of potential sandstone reservoirs but no shows
were encountered. The Danian consisted of silty limestone and dark grey shale.
The Late Cretaceous consisted primarily of interbeds of tight micritic
limestone, marl and shale. Numerous gas shows were noted in limestone stringers
in the uppermost part of this section. The limestone section between 2917 m and
2943 m was sandy and contained some gas. A second zone between 3628 m and 3534
m also contained some gas. Log analysis indicated General Well 30/11-1 was drilled in the Fensal
Sub-basin between the Frigg area and the Stord Basin in the North Sea. The
primary objective was the Eocene Frigg sand, which was gas bearing in the
Frigg, East Frigg, Northeast Frigg, Odin and Heimdal fields to the west and
south. Secondary objectives were sands of Paleocene age. Operations and results Wildcat well 30/11-1 was spudded with the
semi-submersible installation Ocean Voyager on 5 February 1975 and drilled to
TD at 2682 m in the Late Shetland Group. No significant problem was encountered
in the operations. The well was drilled with seawater and viscous slugs down to
469 m, and with a lignosulphonate mud from 469 m to TD. Four zones of interest were encountered
in the well, namely the Frigg sand, Cod sand, Danian sand and Late Cretaceous
limestone. All four intervals were interpreted as being water bearing. From petrophysical analysis the Frigg
Formation had 68 m net sand (N/G = 0.9) in the interval 1952.5 to 2026.9 m. The
average porosity is 32%. The "Cod sand" (Sele and Hermod formations)
from 2211.0 to 2354.3 m had 102 m net sand (N/G = 0.71) with 36% average
porosity. The "Danian sand" (Ty Formation) from 2586.8 to 2638.7 m) had
43 m net sand (N/G = 0.83) with 25% average porosity. The Late Cretaceous
limestone was described as shaly in parts, but clean limestone intervals had
porosities from 4.5 to 7%. Gas readings were low in the well, and the only oil
show described was "very, very faint solvent cut fluorescence" in the
Frigg Sand. Two cores were cut in the interval 1978.2
to 1994.9 m. No fluid sample was taken.
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 30/11-2 was drilled on the Bjørgvin
Arch between the Stord Basin and the Frigg Field in the North Sea. The primary objective
was a potential stratigraphic trap, formed by a shale-out of the Early Eocene
"Frigg Sand" equivalent. Secondary objectives were sand bodies in the
under-lying Paleocene (Cod and Danian Sands). Operations and results Wildcat well 30/11-2 was spudded with the
semi-submersible installation Ocean Vanguard on 18 March 1975 and drilled to TD
at 2590 m in the Late Cretaceous Shetland Gp. A shallow gas incident occurred
at 343 m where the total mud gas increased to more than 30% for 5 minutes. The
mud weight was increased to 490 psi. No further significant problem was
encountered in the operations. The well was drilled with seawater and viscous slugs
down to 215 m, with H921 Polymer/lignosulphonate/Gel and Ferrobar weighting
material from 215 m to 1158 m, and with Dextrid/gel/lignosulphonate and Ferrobar
weighting material from 1158 m to TD. All targets including the Frigg sand were
water bearing. The Frigg Formation was encountered at 2052 m and was 86 m
thick. Based on petrophysical analysis it contain 58 m net sand (N/G = 0.69)
with 33% average porosity. The Cod and Danian Sands were absent, or represented
only by thin sandstone streaks and tight siltstones. Apart from the shallow gas,
all gas readings were low throughout the well. The only oil show described was
"a very faint solvent cut fluorescence" on a sidewall core from
2120.2 m in the Frigg sand. No cores were cut and no fluid sample was
taken. The well was permanently abandoned on 16
April 1975 as a dry well. General Well 31/2-1 is the Troll West gas and oil
Discovery well. The purpose of the well was to establish the basic stratigraphy
in the area, and to evaluate the prospectivity of the Jurassic sequence. The
structure is formed by a tilted Jurassic fault block on the Sogn Spur High
between the North Viking Graben and the Horda Basin. A migration path from the
Viking Graben kitchen area is provided by monoclinal fault blocks. The most
dominant characteristic of the structure was the presence of a
"flatspot", which was believed to be associated with a present
hydrocarbon/water contact. Sealing of the potential Jurassic reservoir is
provided by Cretaceous and Paleocene Claystones, overlying the reservoir
sandstones. The well is Type Well for the Johansen,
Krossfjord, Fensfjord, and the Sognefjord Formations, and Reference Well for
the Amundsen, Cook, and Drake Formations. Operations and results Wildcat well 31/2-1 was spudded with the
semi-submersible installation Borgny Dolphin on 17 July 1979 and drilled to TD
at 2433 m in the Late Triassic Hegre Group. Severe problems with setting the
30" casing led to abandoning of the first hole and re-spudding on 24 July,
50 m to the south of the original spud position. The well was drilled with gel
polymer down to 793 m, and with gypsum/lignosulphonate mud from 793 m to TD. The well 31/2-1 proved the existence of a
Late - Middle Jurassic gas bearing reservoir sequence in the Flathead A
structure (block 31/2). A gross commercial gas column of 134.5 metres with top
at 1439.5 m was encountered in good-moderate quality coastal - shallow marine
sands. Good oil shows with oil bleeding from cores were encountered from 1567 m
to 1597 m, below the gas. It is possible that both a gas-oil contact and an
oil-water contact occur in this zone, however, data available suggested tight
formation. From the pressure data the plausible interpretation is t General Well 31/2-6 is located in a fault block
north-east on the main Troll structure, approximately 8 km NNE of 31/2-3. The
main objective of the well was to test the north-eastern margin of the Troll
structure and to prove hydrocarbon communication between block 31/2 and 31/3.
The well location was picked to test the oil zone in a good sand reservoir. A
second objective was to get reliable geologic tie to the seismic reflectors to
allow for accurate lateral extrapolation of well data. Planned TD was 2500 m in
Triassic sediments. The well is Reference Well for the Sele
Formation. Operations and results Appraisal well 31/2-6 was spudded with
the semi-submersible installation Borgny Dolphin on and drilled to TD at 1760 m
in the Late Jurassic Formation. The 9 5/8" casing collapsed at 771 m and
was cut and retrieved from 760 m. As a result of this, well 31/2-6 was not
deepened to the Triassic. The well was drilled with seawater gel down to 614 m
and with KCl polymer mud from 614 m to TD. Well 31/2-6 proved a similar hydrocarbon
accumulation in this northern fault block area to that of the main field
accumulation tested by wells 31/2-1,2,3 and 4. The well encountered the
Sognefjord Formation at 1492 m. The Formation held a 79.4 m gross gas column
underlain by a 10.3 m oil column. The GOC at 1571.4 m and the OWC was at 1582.2
m. Well 31/2-6 confirmed the overall interpretation of the flatspot as a direct
hydrocarbon indicator. Oils shows were recorded on cores from 1504 m to 1601 m.
In addition, cuttings gave patchy shows in the interval from 1710 m to 1758 m.
Sidewall cores from this interval did not confirm shows in the latter interval. Coring commenced at 1504.4 m and
terminated at 1632.05 m, within the Sognefjord Formation. Thus 127.65 m of core
was cut from which 123.65 m (97%) was recovered. An RFT gas sample was taken at
1518 m as a backup until samples could be obtained from the subs General Well 31/4-1 is located on the Brage Horst
between the Oseberg and Troll Fields in the Northern North Sea. The primary
objective was Middle Jurassic sandstones of the Brent Formation. A "flat-spot"
was seen on the seismic sections and tentatively interpreted to represent a gas
fluid contact in these sandstones. A secondary objective was sandstones in the Early
Jurassic Statfjord Formation. Sandstone intervals of upper Early Jurassic age
(Dunlin Formation) and of Triassic age (Hegre Group), were also expected to be
penetrated, but were not considered to be prospective. The well was planned to
be drilled to a depth of 2930 m RKB (+/- 90 m), 100 m into the Triassic. Operations and results Well 31/4-1 was spudded with the semi-submersible
installation Norskald on 9 September 1979 and drilled to TD at 1000 m in Late
Oligocene - Miocene sediments of the Hordaland Group. None of the objectives were tested due to
technical problems; the well was plugged and abandoned due to lack of cement support
around the 30" casing, experienced when landing the 20" casing. No
cores were cut and no wire line fluid samples were taken. The well was permanently abandoned on 25 September 1979 as a junk well. The rig was moved over 100 - 150 m in a direction 213
degree N to spud replacement well 31/4-2. Testing No drill stem test was performed. General Well 31/4-2 is a replacement for junk
well 31/4-1. The well is located on the Brage Horst between the Oseberg and
Troll Fields in the Northern North Sea. The primary objective was Middle
Jurassic sandstones of the Brent Formation. A "flat-spot" was seen on
the seismic sections and tentatively interpreted to represent a gas fluid
contact in these sandstones. A secondary objective was sandstones in the Early
Jurassic Statfjord Formation. Sandstone intervals of upper Early Jurassic age
(Dunlin Formation) and of Triassic age (Hegre Group), were also expected to be
penetrated, but were not considered to be prospective. The well was planned to
be drilled to a depth of 2930 m RKB (+/- 90 m), ca 100 m into the Triassic. Operations and results Wildcat well 31/4-2 was spudded with the
semi-submersible installation Norskald on 26 September 1979 and drilled to TD
at 2900 m in the Triassic Lunde Formation. There were some problems with
keeping position and anchor movements in rough weather, but otherwise
operations went forth without significant problems. The well was drilled with Seawater
and pre-hydrated bentonite down to 990 m, with Seawater/Drispac/pre-hydrated
bentonite from 990 m to 1712 m, and with seawater/prehydrated
bentonite/ligcon/Unical mud from 1712 m to TD. Good oil shows were recorded on sidewall
cores from thin sandstone stringers at 2061 to 2069 m in the upper part of the
Shetland Group. The well penetrated top Draupne Formation at 2146 m and top
Heather Formation at 2171 m. The Heather Formation contained a 49 m thick very
fine to silty water-bearing sandstone interval from 2190 to 2239 m. The well
penetrated two hydrocarbon bearing sandstone intervals at 2325 to 2329 m and
2344.5 to 2354 m within a 29 m thick Mi General Well 31/4-3 was drilled on the Bjørgvin
Arch in the North Sea, east of the Oseberg main field. Near-by well 31/4-2 on
the southern part of the Brage Horst had recently found live oil and gas in
small quantities in the Brent Group. The primary objectives were sandstones
within the Early Jurassic Dunlin and Statfjord Formation. They were thought to
be separate reservoirs with different hydrocarbon/water contacts. A secondary
objective was to penetrate a deep seismic marker assumed to be a Paleozoic
unconformity. Accumulation of hydrocarbons in Early Triassic and pre-Triassic
sandstones were considered possible if adequate seal and source rocks were
present. Operations and results Wildcat well 31/4-3 was spudded with the
semi-submersible installation Treasure Seeker on 24 December 1979 and drilled
to TD at 4981 m in rocks of Triassic/Permian age. The well was drilled with
seawater and hi-vis sweeps down to 906 m, with XP-20/Spersene/Drispac mud from
906 m to TD. Two separate hydrocarbon-bearing
sandstone intervals were encountered in the Late Jurassic Heather Formation. The
Oxfordian to Kimmeridgian "Intra Heather Sand I" from 2018 m to 2082
m had gas down to a gas/oil contact at ca 2035 m and oil down-to 2048 m. The
section below 2048 had silty to shaley sand with 82% water saturation. The OWC
could be somewhere in this section between 2048 and 2054 m. The Callovian "Intra
Heather Sand II" (Fensfjord Formation) from 2136 to 2246 m had oil (57.7%
average water saturation) down to a possible OWC at 2172. This section was a
silty/shaley sand and the net pay was 24 m. Below this the well penetrated 45 m
of Middle Jurassic Brent Group sandstones, a 291 m thick Dunlin Group with sandstone
in the Cook Formationa General Appraisal well 31/4-5 was drilled on the
31/4-3 Discovery on the Bjørgvin Arch in the northern North Sea. The primary
objective was to test "Intra Heather Formation" sands on the "B
structure" in a crestal position, up dip from the discovery well 31/4-3. The well was planned to delineate known
hydrocarbons in the "Intra Heather Sand I" (Sognefjord Formation) and
to test the prospect for additional up dip oil and gas reserves in the "Intra
Heather Sand II" (Fensfjord Formation). The well was planned to enter the
"Intra Heather Sand I" reservoir approximately 20 m below the OWC in
order to provide evidence of the extent of the reservoir. The lower oil bearing
zone ("Intra Heather Sand II") was prognosed approximately 20 m
higher than in well 31/4-3 and significant amounts of up dip oil were thought
to exist. The Brent, Dunlin and Statfjord Groups were secondary objectives,
possibly prospective in an up dip position. Operations and results Wildcat well 31/4-5 was spudded with the
semi-submersible installation Nortrym on 27 May 1981 and drilled to TD at 2930
m in the Triassic Hegre Group. The well was drilled without significant
problems. It was drilled with seawater and hi-vis pills down to 926 m, with KCl
mud from 926 m to 1966 m, and with a lignosulphonate/XC polymer/Drispac mud
from 1966 m to TD. The well penetrated the Sognefjord
Formation at 2070 m and the Fensfjord Formation at 2104 m. The Sognefjord
Formation was 8.5 m thick and water bearing, but with good oil shows. The
Fensfjord Formation was hydrocarbon bearing with a net sand of 60 m and a net
pay of 37 m. The oil/water contact was not possible to define exact General Well 31/6-4 was drilled in the southern
part of the Troll East gas province. The main purpose was to appraise and test
possible oil and gas accumulations in sandstones of Late to Middle Jurassic
age. Operations and results Appraisal well 31/6-4 was spudded with
the semi-submersible installation Deepsea Bergen on 5 March 1984 and drilled to
TD at 820 m in Eocene sediments. After setting of the 30" casing a 12
1/4" pilot hole was drilled. When opening the pilot hole to 26" hole,
the hole holed kicked off from the pilot hole and deviated to 12.75 deg. at 662
m. Because of the deviation it was decided to junk the well. The well was
drilled with spud mud. No cores were cut and no fluid samples
taken. The well was junked and abandoned on 16
March as a dry well. Testing No drill stem test was performed General The prime objective of the well 33/5-2
was to test a Late Jurassic sandstone reservoir. The Middle Jurassic Brent
Group and the Early Jurassic Statfjord Formation were considered secondary
objectives. The Late Jurassic (Early Kimmeridgian) sandstone was assumed to be
a continuation of the same deposits recorded at the Magnus Field and in the
wells 211/8-1 and 211/13-3. These deposits constitute the oil reservoir at the
Magnus Field and were also hydrocarbon bearing in 211/13-3. This objective was
considered a high-risk prospect since the "Magnus Sandstone Member"
had previously not been recorded on this side of the 211/13- 33/5- (Makrell-)
horst. The Brent Group was expected to be as in the wells 211/13-2 and -6 where
it is oil bearing. It was thought to be a typical shallow to marginal marine
sandstone sequence, deposited during shoreline progradation. The location far
down flank from the crest of the closure was considered to make hydrocarbon
occurrence in the 33/5-2 Brent Group less likely. This was also the case for
the Statfjord Formation. It was expected to consist of fine to coarse,
occasionally pebbly sandstones with some shale interbeds of fluvial to marginal
marine origin. The well was planned to drill approximately 50 m into the
Statfjord Formation with an expected total depth at 4525 m. Operations and results A number of "pockmarks"
typically 40 m across and 2 m deep were seen in the northern and eastern part
of the area of the well location. To get some more information about the
uppermost meters of soil, seafloor sampling and analysis were conducted by
IKU. The seabed was found to consist of a fine sand, normally firm with shell
fragments, plastic, silty clay and below greyish green sand. Wildcat well 33/5-2 was spudded with the
semi-submersible installation Nortrym on 31 July 1981 and drilled to a total
depth of 4520 m in the Triassic Lunde Formation. The well was drilled with
sea General Well 33/6-1 is located in the Marulk
Basin northwest of the Snorre Field in the southeastern sector of block 33/6.
The location was selected on the crestal area of the most attractive feature in
the licence: a fault bounded, tilted block. The closure was considered
dependent upon the sealing properties of the NE-SW fault to the south of the
prospect. The primary objective of the well was to test the Middle-Early
Jurassic Brent-Statfjord reservoirs. Planned TD was in the Late Triassic Hegre
Group Operations and results Exploration well 33/6-1 was spudded on
April 9, 1979 in 306 m water depth, the deepest drilling location to that date.
Semi-submersible installation Fernstar was used to drill the well. Due to soft
bottom conditions and problems with stabilizing the temporary guide base on the
sea floor the well was re-spudded twice, the last and successful attempt on
April 15. The well reached TD at 3900 m in the Early Jurassic Statfjord
Formation. The well was drilled with seawater and pre-hydrated bentonite down
434 m, with seawater/HPD polymer/bentonite from 434 m to 695 m, with
KCl/Dextrid/seawater from 695 m to 1690 m, and with lignosulphonate/fresh water
from 1690 m to TD. The most significant horizons, the top of
the Paleocene Seismic Marker and top Cretaceous, came in 13 meters lower and
37,5 meters higher than expected, respectively. The pre-Cretaceous section
deviated significantly from prognosis. This was caused by a very crude depth
conversion model due to lack of well control in the area and a much thinner
Brent thickness than prognosed. All pre-Cretaceous targets were found however.
The Late Kimmerian unconformity was encountered 133.5 m high to prognosis. The
Late Jurassic shale was 65.5 m thick, 35 meters thicker than prognosed and
consisted of 30 m of Draupne Formation plus 35.5 m of Heather Formation. The primary target Brent Group was
penetrated at 3603 m, 97 meters higher than prognosed, and on General Well 33/9-1 was drilled on the Statfjord
structure. It was the first appraisal well on the structure after well 33/12-1
had discovered oil there in 1973-1974. The primary objective was to test
sandstones in the Middle Jurassic Brent Group. The well is reference well for the
Amundsen, Burton, Cook, Drake, Broom, Rannoch, Etive, Tarbert, Heather, and
Draupne formations. Operations and results Wildcat well 33/9-1 was spudded with the semi-submersible
installation Norskald on 2 April 1974 and drilled to TD at 3126 m in Late
Triassic sediments of the Statfjord Group. The target Middle Jurassic Brent Group,
Tarbert Formation came in at 2464 m and was oil-bearing down to the OWC at 2584
m in the Etive Formation. The Brent reservoir has 145 m gross pay and 124 m net
oil pay. Porosities range from 13.0 to 35.9 percent with the overall average
porosity being 25 percent. Average water saturation is 18 percent. Cores taken
near top of the reservoir showed porosities up to 37% and permeabilities as
high as 4.1 darcy. The Statfjord Group sandstone was penetrated at 2923 m. Statfjord
Group sandstone was water wet as expected from the structural position of this
well. The sands, however, had very good reservoir qualities with average
porosity of 22 percent as calculated from the CPI log. Two cores were cut in the Tarbert
Formation from 2469.2 to 2499.4 m with 18 m recovery (60%) of the total cored
interval. No fluid samples were taken on wire line. The well was permanently abandoned on 4
June 1974 as an oil appraisal. Testing
wlbHistoryDateUpdated: 2016-07-06T00:00:00 General Well 33/9-2 was drilled on the Statfjord
structure on Tampen Spur in the northern North Sea. The primary objective was
to provide seismic velocity control for detailed field mapping and to provide
additional reservoir data for the Statfjord Field development. Operations and results Appraisal well 33/9-2 was spudded with
the semi-submersible installation Norskald on 27 August 1974 and drilled to 940
m in Oligocene sediments of the Hordaland Formation. The well was abandoned at
this depth due to irreparable damage to the subsea equipment. No cores were cut and no fluid sample was
taken. The well was abandoned as a junk well on 14
September 1974. Replacement well 33/9-2 was initiated to fulfil the well
objectives. Testing No drill stem test was performed. General Well 33/9-4 was drilled on the Statfjord
structure on Tampen Spur in the northern North Sea. The primary objective was
to test the northern extension of the Statfjord discovery in the Brent Group. Operations and results Appraisal well 33/9-4 was spudded with
the semi-submersible installation Norskald on 30 July 1975 and drilled to TD at
3076 m in the Triassic Hegre Group. No significant problem was encountered in
the operations. The well was drilled with seawater and spud mud down to 488 m and
with Lignosulphonate mud from 488 m to TD. The objective Brent Group was encountered
at 2554.5 meters, 33.9 meters high to prognosis. Measured core porosities in
the Brent Group averaged 26 percent. Horizontal liquid permeability ranged from
0.05 to 1100.5 milliDarcy and averaged 2155 milliDarcy. The Brent Group was oil
filled down to the oil-water contact at 2611.5 m. This is 2 m deeper than on
the southern part of Statfjord Field and constitute an in-well gross oil column
of 57 m of which 37 m was calculated as net reservoir with 25.4% average
porosity and 24.2% average water saturation. Apart from shows in the oil
bearing section an oil show was described on a sidewall core at 2618 m. Continuous coring was carried out from
within the overlying Middle Jurassic shales through the base of the oil/water
contact in the Brent sands, from 2547.2 to 2612.5 meters. Of the 56.7 meters
cut by nine cores, 50.7 meters (89 percent) was recovered. No fluid sample was
taken on wire line. The well was permanently abandoned on 17
September as an oil appraisal well. Testing General Well 33/9-5 was drilled on the northern
part of the Statfjord structure on Tampen Spur in the northern North Sea. The objective
was to appraise the northern extension of the Statfjord Field with the Brent
Group as primary target. The Brent Group had previously proved oil bearing in
wells 33/9-3 and 33/9-4 on the northern part of the structure. The well was
positioned to penetrate the upper Brent reservoir at 2522 m MSL, 62 meters
above the known field water level. The Statfjord Group was a secondary
objective. Operations and results Appraisal well 33/9-5 was spudded with
the semi-submersible installation Ross Rig on 27 October 1975 and drilled to
TD at 3157 m in Late Triassic sediments of the Statfjord Group. Top Brent Group (Tarbert Formation) was
encountered at 2605 m, 57.8 m low to prognosis. As with other Brent Group oil
wells in the Statfjord Field, high total gas readings (70 000 ppm) were
encountered when the reservoir was penetrated. Using the field pay cut off
value of 65% water saturation, the oil/water contact depth as measured from the
CPI log is 2616.4 m (2591.4 MSL), which is 7.3 meters deeper than the main
field water level. The resulting gross pay interval is 11.6 meters of which
100% is net pay using CPI field cut off values of 65% water saturation, 40%
v-clay or 12% porosity. Average CPI measured porosity in the pay section is
22.1% and water saturation is 37%. The Statfjord Group was penetrated at
2998 m and was found water wet. One core was cut from 2611.5 to 2628.35 m
with 88.7% recovery. The core to log depth shift was estimated to be -2.3 m. FIT
fluid samples were taken at 2624.5 m (failed test), 2617. General Well 33/9-6 was drilled ca 3 km east of
the UK border on the 9-Delta prospect located on the regional Murchison structural
trend, which extends across the northern portion of block 33/9. The well was the first wildcat in the Norwegian
sector of the Murchison trend. The
primary objective was the Brent Group sand, which is oil reservoir of the
adjacent Murchison Field. The well was drilled near the crest of the structure
with a planned total depth of 3300 m, approximately 30 m into the Early
Jurassic Statfjord Formation. Operations and results Wildcat well 33/9-6 was spudded with the
semi-submersible installation Dyvi Alpha on 23 June 1976 and drilled to TD at 3354
m in the Early Jurassic Statfjord Formation. The Tertiary consisted primarily of
clays, siltstones, and minor sands. The tuffaceous red claystone typical of the
Paleocene was encountered slightly above the log pick at 1669.5 m. The sandy
basal portion of the Paleocene was not well developed in 33/9-6. Oil and gas
shows have occurred in this zone in both Statfjord and Murchison Field wells;
however, no-shows were observed in 33/9-6. The objective Brent Group was encountered
at 2995 m, 7.5 m low to prognosis. The sand was described as clear to white,
fine grained and very micaceous. Porosity was poor to fair; and poor to fair
oil shows and scattered thin zones of bleeding oil were described down to 3023 m.
No shows occurred below 3023 m. Schlumberger Coriband Log analysis and core
data indicated 24.5 meters of gross pay and 13.5 meters of net pay, and an
oil/water contact of 3019.5 m. Based on this reserves for the horst block alone
were estimated at only ca 900000 Sm3 oil Well 33/9-7, was drilled on the 33/9-Alpha
prospect, 2.5 km east of the Statfjord Field in the Tampen Spur area in the
northern North Sea. The primary objective was to test a part of the
Brent-Statfjord trend separated from the Statfjord Field to the west by a
structural saddle. The primary target was the Brent Group sandstones.
Sandstones within the Statfjord Group was a secondary target. Operations and results Wildcat well 33/9-7 was spudded with the semi-submersible
installation Dyvi Alpha on 11 September 1976 and drilled to TD at 3127 m in the
Statfjord Group. Good oil and gas shows seen in a 50-meter
thick sequence of interbedded sands and claystones in the lower portion of the
Paleocene from 1770-1820 m. The sands although not apparently continuous, were
oil stained and had good gas shows throughout the interval. Log evaluation was
not practical due to washing out resulting in excessive hole sizes. The Brent
Group sandstones came in sandstones at 2461 m. There was 160 m net sand with
average 27% porosity. The sands were oil-filled down to a section of
claystones, coals and minor sands at 2520 m. An OWC was inferred at 2533 m. No
shows were observed in the Statfjord sands, but the logs indicated scattered
residual oil. A total of 103.33 m core (86% recovery)
was cut in nine cores in the interval 2465 to 2597 m in the Brent Group. No fluid
samples were taken on wire line. The well was permanently abandoned on 7
November 1976 as an oil discovery. Testing Three drill stem tests were car General Well 33/9-8, was drilled on a prospect
north of the main Statfjord Field in the Tampen Spur area in the northern North
Sea. The primary objective was to test sandstones in the Brent Group. Secondary
objective was the Statfjord Group Operations and results Wildcat well 33/9-8 was spudded with the semi-submersible
installation Deepsea Bergen on 11 November 1976 and drilled to TD at 3085 m in
the Statfjord Group. The original hole was abandoned at 2974 with stuck pipe. A
technical sidetrack was kicked off from 2533 m. Top Brent Group is 6 m deeper
in the sidetrack compared to in the original hole. The sand and sand stringers generally
associated with the lower portion of the Paleocene in the area were not
developed in 33/9-8. An oil filled Intra-Draupne Formation sandstone was penetrated
at 2670 m. This was the first encounter of Late Jurassic sandstone in the 037
License area. The gross thickness of this sandstone is 45.8 m. Net sand was
found to be 34.8 m with 27% average porosity, based on log analysis. The whole
sand was oil filled down to top Heather Formation at 2716 m. The Brent Group
sandstones was encountered at 2740 m with oil down to the OWC at 2741.5 m.
Gross thickness of the Brent Group sandstones was 140.3 m. Net sand was found
to be 124 m with 22% average porosity. The secondary objective Statfjord Group
was water wet without shows. Three cores were cut in Late Jurassic
Viking Group the interval 2670 to 2724.8 m (54.8m). The core recoveries were
2670 to 2671.27 m (7%), 2688.5 to 2706.26 m (97%), and 2706.8 to 2724.5 m (98%)
for cores one, two, and three, respectively. The cores were cut in the original
hole. Add six meters to the core depths to match with the we General Well 33/9-9 was drilled in the northern part
of the Statfjord field, about 1.6 km southeast of 33/9-3 well on the Tampen
Spur in the northern North Sea. The objectives were to provide structural and
stratigraphic control on the Brent reservoirs, and to provide stratigraphic
control and to establish an oil/water contact for the Statfjord reservoir. Operations and results Appraisal well 33/9-9 was spudded with
the semi-submersible installation Borgny Dolphin on 27 July 1977 and drilled to
TD at 3100 m in Late Triassic sediments in the Statfjord Formation. The well
was drilled with seawater down to 486 m and with a seawater/lignosulphonate mud
system from 486 m to 1993 m. At 1993 m, TD in the 17 1/2" section, the
hole was displaced to a freshwater/Lignosulphonate mud system. At the same
point diesel was added to free the 13 3/8" casing which had become
differentially stuck. After that the mud contained initially 5% diesel
decreasing to traces of diesel at to 2489 m. From 2489 m to final TD the
freshwater/Lignosulphonate mud system was without measurable diesel. No hydrocarbon shows were reported above
the Brent Group. The Brent Group was found at 2413 m, 77.5 m deeper than
prognosed 44.0 m thinner than anticipated in comparison to 33/9-3. Good oil
shows were encountered at the top of the Brent Formation and continued
throughout the reservoir down to top Dunlin Group at 2504 m. The entire Brent Group
was oil-filled and it was above the field oil/water contact of 2609.1 m (2584.1
MSL). Log calculations showed that of the 87.0 m of gross oil section 84.6 m was
net sand with 27.5% average porosity and 13.1% average water saturation. The
Dunlin Group came in at 2504 m and log interpretation indicated a 23.2 m gross oil
bea General Wildcat well 33/9-10 is located on the Tampen Spur North of the Murchinson Field.
The Middle Jurassic Brent sand was the primary objective with the Early Jurassic
Statfjord sand as a secondary objective. Planned TD was 3695 m, interpreted to be 30 m
into the Statfjord Formation. Operations and results Wildcat well 33/9-10 was spudded with the semi-submersible installation Fernstar
on 7 April 1978 and drilled to TD at 3715 m in the Early Jurassic Statfjord Formation.
The well was drilled with Spud down to 516 m, with seawater/FCL polymer mud
from 516 to 1820 m, with lignosulphonate/fresh water from1820 to 3491 m, and with
Qbroxin/CC-16/fresh water from 3491 m to TD. Spots of diesel and protectomagic
(water or diesel-dispersed asphalt) was added to the mud, beginning at 1820 m.
From 1820 m, oil in the mud was reported at contents varying between 3% and 20%. The electric log pick of the top of the Early Cretaceous Cromer Knoll Group was
taken at 3113 m, giving an Early Cretaceous thickness of 146.8 m. The Early Cretaceous
consisted of 20.3 m of Barremian limestone at the base with red marl interbedded with
the overlying claystone section. Top Late Jurassic Viking Group was picked at 3259.8 m, 15.7 m high to prognosis.
The thickness was 88.2 m of which the upper 69.2 m was the Draupne Formation and the
lower 19 m was the Heather Formation. The lithology of the Viking Group was grey to
dark grey, silty claystone. The primary objective Brent Group was penetrated at 3348 m, 37.5 m high to prognosis.
The sandstone was argillaceous, medium grained, and had fair to poor porosity.
Of the expected 140 m of Brent Group, only 67.5 m was found. Of this 37 m was net sand.
The Brent Group was water bearing. No shows were seen in the ditch samples. One core
was cut from 3358 m to 3376 m. Very poor shows were observed in the core, but electric
logs and Schlumberger Coriband analysis indicated the Brent Formation to be water wet. General Wildcat well 33/9-11 was drilled to test
the 33/9-Epsilon prospect 6 kilometres north of the 33/9-Beta oil discovery and
10 kilometres northeast of the Murchison Field (UK). The Epsilon structure is a
northwest tilted fault block and is expressed as a topographic high at the
Kimmerian Unconformity surface. The primary objective was to test the hydrocarbon
potential in the Middle Jurassic Brent Sand. The Early Jurassic Statfjord Sand was
secondary objective. Operations and results Exploration well 33/9-11 was spudded with
the semi-submersible installation Fernstar on 17 June 1978. The spud location
turned out to be in a 25 m diameter crater in the sea floor. Due to problems
with tilting of the temporary guide base two unsuccessful spuds were made
before the third and successful spud was made with a modified guide base on 24
June 1978. Final position refers to this hole. The well was drilled with
seawater and gel down to 820 m, with KCl polymer mud from 820 m to 1870 m, and
with a fresh water/lignosulfonate mud from 1870 m to TD. Diesel and
Protectomagic was spotted below 820 m, and from this depth the mud is reported
to contain between 4 and 12 % oil. The well was drilled to TD at 3528 m, 91 m
into the Early Jurassic Statfjord Formation. Grey clays and claystone dominated the
Tertiary except for the sands in the intervals, 989 to 1034m and 1205 to 1225m.
In the Paleocene Balder Formation typical tuffaceous grey and red claystone
were present and were also observed above and below the Balder. The Late
Cretaceous Shetland Group was comprised of grey and brown claystone and
siltstones with only minor sands and carbonates. The electric log pick of the
top of the Early Cretaceous Cromer Knoll Group was taken at 3037.8 m. The Early
Cr General Well 33/12-1 is the Statfjord Field
discovery well. The well was drilled ca 400 m east of the UK boundary. The
Statfjord Field is located in the Tampen Spur area of the North Sea. The
drilled structure is a west tilted fault block, forming part of a structural
trend extending across the U.K. - Norway boundary. The trapping mechanism for
the prospect was westerly dipping Jurassic beds bevelled at the Late Kimmerian
regional unconformity. Cretaceous mudstones and marls provided the seal. The
Brent Field is located on the southwestern U.K. portion of the same structural
complex. The primary objective of the well was the Middle Jurassic sandstone
section known to be productive in the U.K. Brent Field. Secondary objectives
were Lias (Early Jurassic) and Triassic sands. The Paleocene section, which is
structurally high, was an additional objective although nearby wells did not
have reservoir rocks in this section. Operations and results Well 33/12-1 was spudded with the semi-submersible
installation Waage Drill I on 1 December 1973 and drilled to TD at 3060 m in
the Triassic Lunde Formation. After drilling to 466 m, TD in 26" section,
47 days were spent due to rough weather and problems with tensioners and riser.
After this operations proceeded without significant technical problems, but the
weather caused much interruptions and WOW. There were oil shows with relatively high
gas readings in the interbedded siltstones and sandstones in the Paleocene
section and throughout the Maastrichtian. The Brent Group was encountered at
2409 m and was oil filled down to top Dunlin Group at 2570 m. The oil-water
contact was not present in this well. From log analysis, 148 m of net sand with
an overall average porosity of more than 28 General Well 33/12-2 was drilled in the Tampen
Spur area as one of the first wells in the Statfjord Field area. Primary target
of the well was the Early Jurassic Statfjord Group, which was known to be
productive in Brent Field located about 20 km to the southwest in the U.K.
offshore. The Statfjord Formation was water wet in the 33/12-1 and 33/9-1
tests. The 33/12-2 wildcat was located to encounter the Statfjord Formation
approximately 200 m high to the 33/12-1 well. The Middle Jurassic Brent
Formation was prognosed to be erosionally thin or absent. Triassic, Permian and
Devonian reservoirs were secondary targets. Planned total depth was 4572 m
(15000 ft.), believed to be sufficient to reach Devonian age rocks or
"Petroleum Basement". The well was one of the three deep tests called
for by the License 037 work obligation. The well is type well for the Alke and
Lunde formations of the Hegre Group and the Raude and Eiriksson formations of
the Statfjord Group. It is reference well for the Nansen Formation. Operations and results Wildcat well 33/12-2 was spudded with the
semi-submersible installation Nordskald on 6 June 1974. Drilling proceeded to 4354
m in Early Triassic sediments of the Lomvi Formation. At this depth the drill
string twisted off leaving a fish with top at 4157 m. Attempts to remove the
fish were unsuccessful so 4354 m became TD of the well. No wire line logs were
run below 4145 m. The well was drilled with water-based mud. Below 2716 m the
mud contained from 2% to 8% oil. As predicted, the Middle Jurassic Brent Group
was thin (17.5 m) and oil bearing (12 m net). Test data and log correlation
indicated that the upper reservoir in the 33/12-2 well is a sectio General Exploration well 34/2-1 is located a
northwestern part of the Tampen Spur area. It was intended to be the first well
to test the reflections below the Base Cretaceous (Kimmeridgian) Unconformity
on a seismically defined, northerly trending west-northwest dipping fault
block. The well was located near the apex of the structure at the Base
Cretaceous level, but down-dip with respect to deeper stratigraphy. Primary
targets were the Middle Jurassic Brent Formation and the Early Jurassic/Triassic
Statfjord Formation. Secondary targets were possible Early Tertiary and Late
Jurassic sandstones. Planned TD was 4300 m Sub Sea. Operations and results Wildcat well 34/2-1 was spudded with the
semi-submersible installation Byford Dolphin on 29 December 1979. Due to
problems with the guide line and instability of the temporary guide base three
unsuccessful spuds were made before a successful spud was made on 23 January
1980. The well was drilled to TD at 807 meters in the Tertiary. Being unable to
latch the BOP onto the 20-inch wellhead, 34/2-1 was permanently abandoned on 23
February 1980 as a junked well. A total of 68 days was spent on the well. Testing No drill stem test was performed. General Block 34/2 lies at the very northern end
of the Tampen Spur and is located at the convergence of pre-Cretaceous Highs
trending through Block 34/4 from Brent/Statfjord, from Dunlin/Murchison, from
the 34/10 area and from a similar high trend through Block 34/5 from Block
34/8. The block was awarded in License 56 in 1979. The first well in the
License (34/2-1) was spudded on 29 December 1979 and junked and abandoned on 19
February 1980 at 850 m, due to technical problems. As the first well did not
satisfy License commitments, it was agreed among the partners that Well 34/2-2
would be drilled at the same location with the same objectives. This well was
drilled to 4074 m and plugged and abandoned after having found poor reservoir
conditions and no hydrocarbon accumulations. Well 34/2-3 was drilled 3.25 km to
the northwest of Well 34/2-2 on the northern end of the Tampen Spur. The main
objective was to test the sedimentary section below the Base Cretaceous
Unconformity in a seismically defined northeasterly trending horst block. Operations and results The well was spudded with the
semi-submersible installation SEDCO 703 on 15 May 1981. Due to boulder beds at
the location the first 36-inch interval was unsuccessful. The well was
respudded on 17 May 1981 and drilled to TD at 3742 m in the Late Triassic Lunde
Formation. The well was drilled with spud mud down to 815 m, with
gypsum/lignosulphonate from 815 m to 3340 m, and with
gel/chemtrol/lignosulphonate from 3340 m to TD. While drilling between 820 m and 890 m
shallow gas was encountered, giving readings of up to 7% total gas. However,
this caused no drilling problems. The well penetrated Tertiary and
Cretaceous sediments down to the Barremian Rødby Formation, which was found
unconformably overlying Late Triassic Lunde Formation. No significant reservoir
zones were encountered above Top Trias. The Lunde Formation consisted of
interbedded shales, siltstones, sandsto General Wildcat well 34/4-1 was drilled on the
rotated fault block systems on the Tampen Spur area of the Northern North Sea. The
objective of the well was to test the stratigraphic sequence below the Base
Cretaceous Unconformity. The primary target was the Intra Triassic
"Carnian Sandstone", which was known from two wells in block 33/12
where it constitutes more than 100 m silty, argillaceous, partly calcareous
cemented sandstone. The secondary targets were possible reworked Late Jurassic
sandstones immediately below the Unconformity, and by possible sands associated
with stratigraphically undefined seismic reflectors between Base Cretaceous and
Carnian level. Operations and results Well 34/4-1 was spudded with the
semi-submersible installation Byford Dolphin on 11 July 1979. The well was
first drilled to 2961 m. When pulling out of hole to change bit it got stuck.
The bit could not be worked free and the drill string was eventually backed off
and left in the hole. A sidetrack was made from 2484 m and drilled to final TD
at 2916 m in the Triassic Teist Formation. The well was drilled with seawater
and viscosity slugs down to 844 m, with Drispac/Unical/gypsum mud from 844 m to
1988 m, and with Drispac/Unical mud from 1988 m to TD, including sidetrack. The well penetrated Tertiary, Cretaceous
and Triassic rocks with a hiatus ranging from Late Triassic to Early Cretaceous Secondary target for the well was
reworked Late Jurassic sediments immediately below Base Cretaceous. Such
deposits were not established. The Triassic sandstones (Lunde Formation) were
encountered at 2508 m and contained oil over a column of more than 100 m. No
definite OWC was seen, but it could be estimated to be at 2618 m. Numerous
shows on sandstone stringers were observed in the Cretaceous from ca 2025 m
(top Kyrre Formation) and down to top of the Triassic reservoir. No shows were
observed below 2622 m. Eleven cores were cut in General Exploration well 34/4-3 is located in the
Marulk Basin north-northwest of the Snorre Field. It was drilled as the third
well on the Gamma Structure and had a wedge structure between the Base
Cretaceous Unconformity and the Late Jurassic Unconformity as primary target.
Secondary objectives were to penetrate the Brent Equivalent and the Statfjord
formation. The well is located on the downthrown side of a NE-SW trending major
fault, and the sealing nature of this fault was critical for a closure of the
reservoir. Operations and results Wildcat well 34/4-3 was spudded with the
semi-submersible installation Dyvi Alpha on 16 October 1981 after waiting on
location for two weeks due to bad weather. The 26" section was drilled
with a 21 1/4" BOP installed but after pulling the riser and the BOP a
26" bit was run in the hole since the underreamer did not perform.
Drilling of the 17 1/2" section was delayed by nearly two weeks due to the
18 3/4" BOP not meeting requirements. During drilling of the 12 1/4"
section electrical problems on the draw works as well as mud pump breakdowns
and high pressures was experienced. Drilling the 8 1/2" section included 4
core runs, killing a water/methane kick at 3555 m, changing leaking seals on riser
and two intermediate log runs. TD was reached at 4460 m in Late Triassic
sediments. The well was drilled with seawater/bentonite/gel down to 516 m, with
gel/gypsum from 512 m to 1019 m, with gypsum/polymer from 1019 m to 2209 m, and
with lignosulfonate mud from 2209 m to TD. A methane gas/water kick occurred at 3550
m when the first Late Jurassic sandstone stringer was entered, giving 21 %
total gas. A more continuous Late Jurassic sand was drilled into at 3565 m. Two
cores (18 m) were cut in this 27 m thick sandstone sequence. The cores consist
of shallow marine laminated shale/silt/sandstone. The sandstone is grey, very
fine to fine grained with average porosity 10%
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