ID: 120
OBJECTID: 120
wlbNpdidWellbore: 122
wlbName: 7120/12-2
wlbHistory:

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
wlbHistoryDateUpdated: 2016-05-19T00:00:00