34/7-26 A

Appraisal well 34/7-26 A was drilled as a sidetrack from well 34/7-26 S in the in the "H-central" prospect in the Tampen area in the Northern North Sea. The H-Central is located between the Gullfaks and the Vigdis Fields. The well had two primary objectives. Firstly, to perform an optimum data collection programme in the Top Intra Draupne sandstone, and possible deeper Intra Draupne sandstone and also in possible base Cretaceous sandstone. Secondly, to perform a long term production test if the well was to encounter at least 20 m with Top Intra Draupne Formation sand. The two previous wells with this objective, 34/7-26 S and re-entry 34/7-26 SR, did not penetrate prognosed Top Intra Draupne sandstone in a position that fulfilled the test criteria.

Operations and results

Well 34/7-26A was kicked off from below 13 3/8" casing shoe in well 34/7-26 S, on 6 January 1998. The well was entered through slot J-3 on Tordis Extension Template and drilled deviated with the semi-submersible installation Scarabeo 5 to TD at 4290 m (2573 m TVD) in Late Jurassic sediments of the Heather Formation. Some problems were encountered getting the wire line tools to TD during final log runs, otherwise operations went without significant problems. The well bore was drilled all through to TD with a pseudo oil based mud (Ancotec with Novamul).

The Top Cromer Knoll Group was penetrated at 4115 m (2429 m TVD) and consisted of the Rødby Formation down to 4123 m, and the Mime Formation from 4123 m to 4129 m (2436 - 2441 m TVD). There were no sandstones in the Cromer Knoll Group.

The main reservoir interval, the Top Intra Draupne sandstone, came in at 4129 m (2441.1 m TVD) with a thickness of 50 m TVD. The underlying Draupne Formation shale was 20 m TVD thick. The top Intra Draupne Formation reservoir in well 34/7-26 A consisted of coarsening-upwards sandstones, which mostly were structureless, parallel bedded, and less frequent, graded bedded