34/10-43 S

General

Wildcat well 34/10-43 S was drilled in a structure in the south-eastern part of the Tampen Spur area, on one of the westerly-rotated fault blocks east of the Beta Ridge. The structure is eroded at BCU level, successively deeper towards the east, and is limited by east-west faults towards north. Planned well trajectory was highly deviated in order to test several objectives in one well. Primary objective was to test the potential for hydrocarbons in Middle Jurassic sandstones of the Statfjord Formation. The secondary objective was the Brent Group, Cook and Lunde Formation. Tertiary objectives were to penetrate Paleocene in an optimal position for exploring the lowermost part for sand/hydrocarbons (Ty Formation) and at TD, a prospect of the Late Jurassic, Munin Member. The planned TD of the well was at 4505 m (2565 m TVD RKB) with an inclination of 67 deg .

Operations and results

Well 34/10-43 S was spudded with the semi-submersible installation Transocean Wildcat on 25 February 2001 and drilled deviated through Triassic sediments of the Lunde Formation as the oldest penetrated sediments, to TD at 5725 m (3219.9 m TVD RKB) in the Early Cretaceous Cromer Knoll Group. The drilling progress was very good down to the Lunde Formation. After logging of the reservoir sections in the Middle-Early Jurassic and Triassic objectives, the drilling continued to final tertiary objective in the Late Jurassic prospect in the Munin Formation. This part was significantly slower to drill, caused by places of tight hole and also because of hard lithology. Several bits had to be implemented before TD was reached with an inclination of approximately 101 deg . The well was drilled with KCl mud down to 709 m, and with oil based mud (Versavert) from 709 m to TD.

There were no sands in the Paleocene prospect, and the Shetland Group was therefore encountered more than 100 m shallower than expected. The Brent prospect was much more eroded at the well t