30/6-7

General

Well 30/6-7 is an appraisal well on the Oseberg Field, discovered by well 30/6-1 in 1979.The primary objective was to test for hydrocarbon accumulations in the Late Jurassic sandstones of the Brent formation and the Late and Early Jurassic sandstones of the Dunlin and Statfjord formations in the Alpha north structure. Secondary objectives were to establish the type of communication between the Alpha and Alpha North structures and to define the oil/water contact on Alpha North. The well was planned to reach total depth at 3225 +- 50 m, 75 m into the Statfjord Formation.

The well is Type well for the Oseberg Formation and Reference well for the Amundsen, Cook, Drake, Etive, Ness, and Tarbert Formations.

Operations and results

Well 30/6-7 was spudded with the semi-submersible installation Nortrym on 20 May 1982 and drilled to TD at 3236 m in Early Jurassic rocks of the Statfjord Formation. The 26" section was initiated by a 17 1/2" pilot hole. One small pocket of shallow gas was detected at 358 m (5.6% C1). The well was drilled with seawater and hi-vis pills down to 952 m and with KCl/polymer mud from 952 m to 2285 m. At 2285 m the 13 3/8" casing got stuck and a pill of EZY spot and diesel was pumped in the hole, without effect. The drilling fluid used in the 12 1/4" section from 2285 m to 2915 m the well was drilled with a Dextrid/KCl mud. From 2915 m to TD the mud was converted to a dispersed system by adding lignosulfonate.

The Brent Group was encountered at 2631.5 m. The Brent Group was hydrocarbon bearing with a total gross thickness of 154.5 m and a net sand interval of 106.9 m. The net pay was 50.7 m. Sandstone intervals were also encountered in