2/7-15

General

Well 2/7-15 was drilled on the Eldfisk East structure in the Feda Graben of the southern North Sea. The well was an appraisal of the productive Danian - Late Cretaceous chalks found in 2/7-8. The well also had an explorative objective, namely to prove the existence of productive Jurassic sandstones on the East Eldfisk structure. Projected total depth was 14500 ft (4420 m).

The well is Reference well for the Ran Sandstone Units.

Operations and results

Well 2/7-15 was spudded with the semi-submersible installation Haakon Magnus (now Borgsten Dolphin) on 29 January 1980 and drilled to TD at 4423 m in the Late Jurassic Haugesund Formation. A 2.3 Sm3 influx was taken while drilling at 3667.7 m (3672.8 m logger's depth) in the Farsund Formation. The well was shut in. After shut-in the circulation was lost, probably because the formation broke down. The circulation was resumed by appropriate mud adjustments, and the return mud then contained 3% oil and was slightly gas-cut. The well was drilled with bentonite, Flosal and lime down to 503 m, with Drispac mud from 503 m to 1387 m, and with Drispac/lignosulphonate mud from 1387 m to TD.

The Danian - Late Cretaceous section tested small quantities of hydrocarbons. Shows were encountered, often in fractures, on cored siltstone and claystone in the Early Cretaceous Ran Sandstone Units and Åsgard Formation, but testing proved the section to be generally tight. The logs indicated a 2 m HC-bearing sandstone stringer at 3672.8 m (where the influx was taken while drilling), but no shows were reported from this depth. Isolated shows, in the form of dull yellow fluorescence, were reported also on cored claystone in the Farsund Formation at 403