30/11-4

General

Well 30/11-4 was drilled north-east of the Frigg area in the Fensal Sub-basin in the North Sea. Previous well 30/11-3 was abandoned at top Statfjord Group for technical reasons, due to high pressures, without being production-tested. Well 30/11-4 was then proposed as a virtual re-drill, only some 400 m NE of 30/11-3. The objective of the well was to test the hydrocarbon potential of the Middle Jurassic Vestland Group sandstones and the Early Jurassic Statfjord Group sandstones in a westward tilted horst block

Operations and results

Wildcat well 30/11-4 was spudded with the semi-submersible installation Dyvi Delta on 25 January 1984 and drilled to TD at 5255 m in Late Triassic sediments belonging to the Statfjord Group . At 2179 m the drill string parted, leaving a 24 m fish in the hole. After unsuccessful fishing the well was sidetracked from 1918 m. The well was drilled with bentonite and brack water down to 813 m, with KCl/polymer mud from 813 m to 4205 m, with gel/lignosulphonate/lignite mud from 4205 m to 5059 m, and with gel/polymer lignite mud from 5059 m to TD.

Well 30/11-4 penetrated water bearing reservoir sands in the Tertiary Frigg and Heimdal formations. The Vestland Group was penetrated at 3434 m. This section had oil shows at 3434 m to 3470 m, where some oil emulsion was retrieved by RFT, at 3514 m to 3550 m, and at 3635 m to 3650 m. An anomaly in the reservoir pressure occurred at about 3580 m where a siltstone/claystone interval possibly acts as a seal/pressure barrier. A total of 615 m of sands and shales assigned to the Statfjord Group, between 4640 m and TD in the well. Log interpretation pointed towards the presence of at least 75 metres of sands with porosities up to 20% and water saturations as low as