30/9-10

General

Well 30/9-10 was drilled in the Omega South segment on the Oseberg Fault Block in the North Sea. The primary objective was to test the hydrocarbon potential in the Tarbert Formation. Secondary objectives were to test the Cook Formation and the Statfjord Group.

Operations and results

Wildcat well was spudded with the semi-submersible installation Vildkat on 31 July 1990 and drilled to TD at 3649 m in the Early Jurassic Statfjord Group. An 8 1/2" pilot hole was drilled from 210 to 350 m to check a possible shallow gas zone at 329 m. No gas was encountered. No significant problem was encountered in the operations. The well was drilled with spud mud down to 1059 m and with KCl/polymer mud from 1059 m to TD.

The Draupne Formation was encountered at 2717 m and Intra Draupne Formation sandstone was penetrated from 2756 m to top Tarbert Formation at 2783 m. The Draupne Formation sandstone and the Upper Tarbert Formation were found to be oil bearing from 2756 - 2833 m. Poor to moderate oil shows continued down to 2858 m. No oil shows were recorded below this depth or above top Draupne Formation. The Middle Tarbert is poor or tight, and non-moveable hydrocarbons were present in the Lower Tarbert, which are interpreted from core analysis to be residual oil. The net pay was determined to be 55 m, with an average water saturation of 36.4% and average porosity of 17.5%. RFT data defines an oil gradient through Draupne and Upper Tarbert sandstones, which intersects with the Lower Tarbert water gradient at 2833 m in the Middle Tarbert. However, it is uncertain whether the oil gradient in the Upper Tarbert and the water gradient of the Lower Tarbert belong to the same pressure system. Consequently an oil-water contact was not proven in