34/10-15

General

Well 34/10 15 was drilled as a wildcat on a horst block in the south-eastern part of the Gullfaks Field. The primary purpose of the well was to test hydrocarbon accumulations in the Jurassic and Brent sands. Secondary objectives were the Early Jurassic Statfjord sands and to test shallow gas accumulations in Pliocene sands.

Operations and results

Appraisal well 34/10-15 was spudded with the semi-submersible installation Neptuno Nordraug on 16 October 1982 and drilled to TD at 2400 m in Late Triassic sediments in the Statfjord Group. A 12 1/4” pilot hole was drilled from 250 m to 950 m to check for shallow gas. The well was situated ca 90 m south of the location for the well 34/10-10, which was abandoned due to gas flow from a gas filled sand at 428 m. The same sandlense was penetrated in the well 34/10-15 from 444-447 m. The well was drilled with spud mud down to 250 m and with gel/seawater/lignosulphonate mud from 250 m to TD.

Weak shows on cuttings, mostly on limestone, were recorded intermittently from 1220 m in the Hordaland Group to 1630 m in the Lista Formation. The Brent Group sands were not encountered. Late Triassic Statfjord Group sands were found water wet without shows. The Cook Formation sands contained residual oil.

Ten cores were cut. Cores 1 to 5 were cut from 1870 m to 1945 m in the Cook Formation with recoveries varying from 34% to 75%. Cores 6, 7, and 8 were cut from 2170 m to 2213 m in the Amundsen Formation with recoveries varying from 87% to 93%. Cores 9 and 10 were cut from 2301 m to 2323 m in the Statfjord Group with 90% and 85% recoveries, respectively. An RFT fluid sample was taken at 1875.5 m in the Cook Formation residual oil zone. The sample co