35/11-5

General

Well 35/11-5 was drilled on the "D" West prospect on the northwestern part of the Horda Platform, and ca 18 km north of the Troll Field. The primary objective for 35/11-5 was the Middle Jurassic Brent Group. Reservoirs were expected in the Tarbert, Ness, Etive, and Oseberg Formations. Secondary there was a possibility for reservoir development in the Late Jurassic Sognefjord Formation. Similar sands are the main reservoir in the Troll area, and were expected to be well developed in the eastern part of the block. No shallow gas warnings were given. Boulders might be encountered in the interval 395 - 532 m. The well was planned to be drilled to a total depth of 3678 m.

Operations and results

Wildcat well 35/11-5 was spudded with the semi-submersible installation Sovereign Explorer on 27 June 1991 and drilled to TD at 3769 m in the Early Jurassic Statfjord Formation. The well reached a depth of 1118 m before technical problems caused the well to be plugged back and sidetracked. Further problems in the sidetrack caused the well to be abandoned and re-spudded on 18 July 1991, 50 m northwest of the original location. The first well bore was drilled with seawater and hi-vis pills. The second and final well bore was drilled with seawater and hi-vis pills to 1010 m, and with KCl/polymer mud from 1010 m to TD

Water bearing sandstones were drilled in Palaeocene. The Draupne Formation was penetrated at 2657.5 m. The Sognefjord Formation came in at 2875 m and consisted predominantly of claystones with some sandstone interbeds. Shows were observed in cuttings, and RFT samples recovered contained oil and gas. However, reservoir quality of the sandstones was generally poor and there was less than 5 m of net pay. In the Middle Jurassic Brent Group, shows were observed in cores from 3208 m down to 3305 m. Light oil/condensate and gas was recovered from an RFT sample taken at 3214 m. Reservoir quality was however poor with only 5.