15/5-2

General

Well 15/5-2 was drilled in the Ve Sub-basin in the North Sea, north of the Sleipner Vest Field and 15/5-1 Gina Krog Discovery. The main objective of the well was to test possible hydrocarbon accumulations in Middle to Late Jurassic Bathonian/Callovian transgressive sandstones and Middle Jurassic Bajocian deltaic sandstones. The well was located in a purposely off-crestal position on an approximately 16 km2 large structure some 7 km north-west of the 15/5-1 discovery.

The well was planned to penetrate into the Triassic with a projected total depth of 4500 m.

Operations and results

Wildcat well 15/5-2 was spudded with the semi-submersible installation Treasure Seeker on 16 August 1978 and drilled to TD at 4322 m in the Triassic Hegre Group. At 1267 m, the string unscrewed in a tight section, but it was fished without problems. After drilling to 2293 m, the string stuck when pulling out of hole. This time the fish was not recovered and a sidetrack was performed with kick-of at 1775 m. Heavy weather caused further delays, otherwise the drilling went forth without significant problems to TD. The well was drilled with seawater mud mixed with gel and Spersene down to 454 m, and with a Spersene/XP-20 (lignosulphonate) mud from 454 m to TD. At 2232 m 1% Diesel was added to the mud.

Two hydrocarbon bearing sandstone intervals were penetrated by the well. In the Jurassic, only a thin Early to Middle Bathonian sandstone development was penetrated between 4035 m and 4055 m. Interbeds of siltstones and shales reduced the 20 m gross pay to a net pay of 7.3 m from wireline log interpretation. Average porosity and average water saturation over the pay interval was calculated to 14.3 and 41