34/8-8

General

Well 34/8-8 was drilled to appraise the N-1 segment of the 34/8-1 Visund discovery on Tampen Spur in the Northern North Sea. The N-1 segment is estimated to contain approximately 30% of the resources in the Brent-North area. Confirmation of these resources was critical for reservoir management and production layout in future development plans. The primary objectives of the well were thus to confirm the resources in the Brent Group and to obtain data that could be used in reservoir engineering studies on improved oil recovery. Secondary objectives were evaluations of the Statfjord Formation and the Lunde B/C Formation. The well design and location was chosen primarily to evaluate the Brent target with respect to defining fluid contacts in clean sands, avoid faults, and penetrate as close as possible to the erosion edge of the top of the Brent Group.

Operations and results

Appraisal well 34/8-8 was spudded with the semi-submersible installation Transocean 8 on 30 June 1992 and drilled to TD at 3625 m in the Late Triassic Lund Formation. After drilling to 1430 m in the 12 1/4" section the drill string got stuck. 16.55 m of the BHA was left in the hole and the hole was plugged back to 1354 m where a minor technical sidetrack was performed. After setting the 30" casing an industry strike caused ca 5 days downtime. The well was drilled with spud mud down to 1364 m, and with Anco 2000 glycol mud from 1364 m to TD.

The Brent Group was encountered at 2921 to 3077 m. It was oil bearing and wire line logs confirmed an OWC at 2971 m, while RFT pressure tests suggested a free water level between 2973.4 m and 2976.8 m. From a gross Brent Group thickness of 156 m, a net pay thickness of 97 m was identified. An average porosity of