25/10-7 S

General

Well 25/10-7 S is located southwest of the Balder area. The primary objective of the well was to evaluate resource potential in the Paleocene Heimdal Formation in the Bjørn Prospect. Secondary objective was to evaluate resource potential in the Lower Eocene interval based on a high amplitude seismic response.

Operations and results

Exploration well 25/10-7 S was spudded with the semi-submersible installation "Vildkat Explorer" on 20 May 1996 and drilled to TD at 2617 m (2582 m TVD) in the Early Paleocene Ekofisk Formation. The well was drilled with seawater and bentonite down to 1102 m and with "ANCOVERT" oil based mud from 1102 m to TD. The well was drilled deviated to avoid shallow gas at a depth of 512-822 meters below sea level close to the proposed location. The surface location of 25/10-7 S was moved approximately 200 m south of the reservoir target location, and no shallow gas was seen at this location. The well was drilled vertically to 1165 m where angle was gradually built to max 25.8 degrees and then again reduced to 1& at 2000 m. Well time for 25/10-7 S was 19.78 days (vs. 31 days targeted) for $4.7 M (vs. an AFE of $6.7 M). A major contribution to the reduced time and cost was a reduction of the electric logging program from the planned 4 days to the actual of 0.6 days due to a labour dispute involving key service companies in Norway. A 233 m thick Heimdal Formation was penetrated by the well, starting at 2238 m. The secondary, Eocene target was a 22 m thick limestone. The plan was to cut one core in the top of the Heimdal sand, regardless of hydrocarbon shows. Coring continued after core no.2 based on shows described at well site. A total of five cores were cut from 2200-2378 m from the Lista Formation through a complete Heimdal sequence and into the Lista Formation again. Subsequent to the coring MWD logs reamed across cored interval showed reservoir to be water wet.