ID: 633
OBJECTID: 633
wlbNpdidWellbore: 1302
wlbName: 34/10-33
wlbHistory:

General

Well 34/10-33 was the sixth well drilled to reservoir level on the Gullfaks South structure. The main objective of the well was to appraise the oil and gas reserves in the Brent Group on the northern part of the structure. The gas/oil and oil/water contacts were to be confirmed at 3324 m and 3395 m MSL respectively. Secondary objective was to penetrate 50 m of the Statfjord Formation to obtain data to better understand the structural development in the area, and also update the geological model for the upper part of the formation. A positive result would lead to the drilling of a horizontal testing well as a sidetrack from this well.

Operations and results

Well was spudded with the semi-submersible installation West Delta on 25 September 1988 and drilled to TD at 3870 m in the Early Jurassic Statfjord Formation. There was some shallow gas at 477 - 478 m. Due to this the 20" casing was set at 450 m. There was a problem with a leakage in the BOP. The drill string got stuck when setting the 13 3/8" casing and the MWD and drill bit had to be changed. The well was close to vertical down to ca 2500 m. From there the well built inclination gradually up to 20 deg at TD. At TD true vertical depth is estimated to be ca 20 m less than measured depth. The well was drilled with spud mud down to 483 m, with gypsum/polymer mud from 483 m to 3161 m, and with gel/lignosulphonate/lignite mud from 3161 m to TD.

Top Brent Group, Tarbert Formation came in at 3186 m with gas and oil. FMT data showed a gas/oil contact at 3268 m, 85 m higher than prognosed. Approximately 150 m of oil was found vertically down to top Dunlin Group at 3424 m, much more than expected. No oil/water contact was seen. There was a pressure shift of 1.5 - 2 bar at
wlbHistoryDateUpdated: 2016-07-06T00:00:00