30/9-9

General

Well 30/9-9 was drilled on the J-South structure in the Oseberg Sør Field complex in the North Sea. The first well on J-South, well 30/9-5 S some 3.5 km to the north, encountered a highly eroded Brent Group with gas shows in the Brent, a gas bearing Cook Formation and a water bearing Statfjord Group. The primary objective of well 30/9-9 was to prove oil in the Brent Group and the Cook Formation, and define the oil-water contact.

Operations and results

Wildcat well 30/9-9 was spudded with the semi-submersible installation Polar Pioneer on 26 September 1989 and drilled to TD at 2809 m in the Early Jurassic Eiriksson Formation. No significant problem was encountered in the operations. The well was drilled with seawater and hi-vis pills down to 919 m and with KCl/polymer mud from 919 m to TD.

The Tarbert Formation and the uppermost part of the Ness Formation were found oil bearing down to 2319 m. The net pay was estimated to be 13.5 m and average water saturation calculated to 30.1%. Average porosity was 20.8%. The Ness Formation (2307 - 2412 m) was found oil bearing from 2391.5 to 2412.5 m. No oil water contact was proved, leaving oil down to base reservoir. The net pay was estimated to be 15.5 m and average water saturation calculated to 24.3%. Average porosity was 24.9%. RFT results showed no pressure communication between the hydrocarbon bearing intervals in the Tarbert and Ness Formations.

The Etive-Rannoch Formations and the Oseberg Formation were not present in the well, most likely due to faulting. The lower Jurassic Cook Formation and the Statfjord Group were found water bearing. Oil shows were described on claystones and sandstones from 2115 to 2175 m, throughout the