2/8-7

General

Well 2/8-7 is located on the western side of the Piggvar Terrace towards the Feda Graben. The well was drilled to test the Late Cretaceous Limestone in the Trud structure. Structurally, the Trud anomaly is a high relief, salt induced, domal feature covering approximately 19 square kilometres. The structure was seen as highly faulted with a main fault trending north south, with the down-thrown side to the east. The displacement along this fault was estimated to approximately 150 m. No secondary objective was defined.

Operations and results

Wildcat well 2/8-7 was spudded with the jack-up installation Zapata Explorer on 23 July 1975 and drilled to a total depth of 2868 m in the Late Permian salt. The well was drilled without major problems. The well was drilled with seawater gel down to 375 m, and with a Lime/Drispac/seawater mud system from 375 m to TD. The mud weight was cut and LCM pills spotted at 2619 m to cure lost circulation problems.

The Tertiary section consisted predominantly of claystone and shale. The Paleocene ash markerá (Balder Formation) was encountered at 2511 m and was found to be 12 m thick. The Shetland Group chalk section (Ekofisk, Tor, and Hod Formations) was encountered at 2596 m. The Chalk section had a vertical thickness of 223 m, which compares to roughly 451 m in 2/5-4, 458 m in 2/9-1 and 280 m in 2/8-2. Oil shows were recorded in limestone stringers below 1548 m. The target Late Crataceous section had 12 m of oil shows from top of the Danian chalk (Ekofisk Formation), the core from this section was boiling gas and bleeding oil from vugs and fractures. Schlumberger logs were run before the 9 5/8-inch casing was set and after total depth was reached. Coriband log analysis estimated a water saturation around 60% in the top Ekofisk section. A core was cut from 8538 to 8554 feet (ca 2602 m to 2607 m) with 50% recovery. No fluid samples were taken. The well was permanently abandoned on 24 August as a well