34/7-4

General

Well 34/7-4 was drilled on the Snorre E structure in the northern part of block 34/7. The primary objectives were to further appraise the reservoir potential of the Statfjord Formation in the E-structure extension of the Snorre Discovery, to test the oil/water contact found in wells 34/7-1, and to test the reservoir quality in this area. A secondary objective was to test the reservoir potential in the upper Lunde Formation, which contain oil in an up-dip location.

Operations and results

Appraisal well 34/7-4 was spudded with the semi-submersible installation Treasure Saga on 19 November 1984 and drilled to TD at 3115 m in the Late Triassic Lunde Formation. No significant problems occurred during drilling of the well. The well was drilled with spud mud down to 963 m, with gypsum/polymer mud from 963 m to 2759 m, and with lignosulphonate mud from 2759 m to TD.

Except for the sandy Utsira Formation (Late Miocene/Pliocene) and an Early Eocene sandstone unit (1625-1664 m) in the lower part of the Hordaland Group, the well proved mainly claystones down to the Early Jurassic Statfjord Formation at 2535.5 m. The Statfjord Formation was 92 m thick and was oil bearing down to claystones in top Lunde Formation at 2627.5 m. No definite oil-water contact was seen. The N/G ratio in the Statfjord Formation was 0.26. The average porosity was 20 % and the average water saturation was 44%. The Lunde Formation proved mainly a claystone/siltstone sequence in the upper part, while the lowermost 265 m proved a sequence of alternating sandstones and claystones with limestone stringers. Of this sequence some 123 m can be considered as net. The Lunde Formation reservoir was water bearing.

Three co