30/6-17 R

General

Well 30/6-17 was drilled on the Alpha structure on the western side of the Oseberg Field in the northern North Sea. The structure is a tilted and rotated fault block with a Jurassic sequence dipping towards the east. The main objective was to prove hydrocarbons in the Statfjord Formation. Prognosed depth was 200 m into the Statfjord Formation with TD at ca 2682 m. Well 30/6-17 was drilled by Vildkat Explorer to a depth of 615 m where it was temporary abandoned due to technical problems. The re-entry 30/6-17 R was made to fulfil the original objectives.

Operations and results

Wildcat well 30/6-17 was re-entered with the semi-submersible installation Treasure Hunter on 14 August 1985 and drilled to TD at 2650 m in the Early Jurassic Statfjord Formation. The well was drilled without significant technical problems, but about one third of the time was counted as downtime. The main contribution to the excessive downtime was waiting on weather. The well was drilled with KCl/polymer mud from 615 m to 2409 m and with NaCl/polymer mud from 2409 m to TD.

Oil shows were recorded on limestone and dolomite stringers in the Tertiary and Late Cretaceous, beginning at 1650 m and all the way down to near BCU at 2290 m. These oil shows were most frequent, and strongest, in the interval 1750 to 1810 m in the lower part of the Tertiary Hordaland Group. Two gas bearing sandstones units, possibly reworked Brent Group, were found at the BCU (2296 - 2300 m and 2303 - 2308 m).

The prognosed target for the 30/6-17 well was the Statfjord Formation. The well was, however, drilled ca 600 m east of the proposed location at a structurally down flank position. At this position also the Cook Formation was p