7/7-2

General

Well 7/7-2 is located ca 8 km east of the UK border on the Jæren High in the North Sea. It was the second commitment well within the licence PL-148 and was designed to test the A-prospect, interpreted as a Late Jurassic channel sandstone. Planned TD was in Permian sediments or 3500 m, whichever came first.

Operations and results

Wildcat well 7/7-2 was spudded with the semi-submersible installation Deepsea Bergen on 20 January 1992 and drilled to TD at 3430 m in the Permian Zechstein Group. The well took 100 days to drill and test, 20 days more than planned. This was mainly due to a 25% higher pore pressure than prognosed in the reservoir, resulting in a plug-back and 9 5/8" casing above reservoir, and not at TD as programmed. Other contributing factors were re-spud after lost stinger in 30" casing, two occasions of pulling BOP due to leakage and leak on swivel stem on top drive. The DSTs experienced severe difficulties with leakage and operation of down hole valves resulting in two mis-runs with testing string and a shortened DST no. 2. The well was drilled with CMC EHV and seawater down to 904 m, with KCl/PHPA/PAC from 904 m to 2744 m, and with ANCOTEMP mud from 2744 m to TD.

The greater part of the prospect, the Late Jurassic Ula sandstone was encountered at 3327 m, and proved to be sandy. The Jurassic reservoir lithology consisted primarily of fine, well-sorted silica-cemented sandstone with poor visual porosity. Subsequent testing from 3348 - 3350 m showed a very tight formation, however testing from 3333 - 3342 m yielded oil. No oil-water contact was encountered, but organic geochemical analyses detected oil saturation in two intervals from the top of the reservoirs down to 3341, and from 3345 down to 3347 m.

Four and a half m of shaley core was recovered in two cores from 3242 m to 3247 in the Mandal Formation. Good oil shows were observed in these cores. Organic geochemical analyses proved them