34/10-41 S

General

Well 34/10-41 S was drilled west of the Gullfaks Field and slightly south of the Tordis Field on the Tampen Spur in the North Sea. The primary objective was to test the hydrocarbon potential in the "A-prospect" at Middle Jurassic Brent Group level. The secondary objective was to test the Early Jurassic Statfjord Group.

Operations and results

Wildcat well 34/10-41 S was spudded with the semi-submersible installation Deepsea Trym on 13 July 1997 and drilled to TD at 3420 m in the Early Jurassic Statfjord Group. At 3098 m problems with steering and hole angle made it necessary to sidetrack in order to reach the planned secondary target at top Statfjord Group. The well was plugged back ca 270 m and sidetracked (34/10-41 S T2) from 2913 m. The well was drilled with spud mud down to 1050 m and with Quadrill KCl/glycol mud in both well tracks below 1050 m to TD.

The top of the Brent Group was penetrated at 2553 m, approximately 18 m above the prognosed depth, and proved to be dry. The seismic anomaly in top of the prospect turned out to be a lithology effect. From the claystone in the Heather Formation, a very calcareous sandstone was penetrated in the Tarbert Formation. It is believed that this transition to a high velocity layer is the cause of the amplitude. The Statfjord Group was penetrated at 3367.5 m and was also proven dry. Except for occasional fluorescence and cut in claystones between 2472 m and 2775 m there were no shows in the well. The lack of migrated oil was in agreement with post-well organic geochemical analyses, where extracts proved to be more or less contaminated by the mud and devoid of typical migrated hydrocarbons.

No cores were cut and no wire lin