25/6-2

General

The well 25/6-2 is located in the southern part of block 25/6, approximately 175 km Northwest of Stavanger on the northern part of the Utsira High. Utsira High forms the southern part of western rim of the Horda Platform and lies between the South Viking Graben to the west and Stord Basin to the east.

The main objectives for the well 25/6-2 were to test the hydrocarbon potential of the Paleocene Ty Formation in the Delta and Beta prospects and the extension of the Middle Jurassic Vestland Group discovery in well 25/6-1. The Ty Formation prospects were anticipated to comprise of clastic, gravity fan deposits. The well location was in a position that would test both a mapped simple closure at this level and a larger stratigraphic trap interpreted to be characterised by sands pinching out to the south.

Operations and results

The well 25/6-2 was spudded with the semi-submersible installation Treasure Saga the 26 April 1992 and drilled to TD at 2392 m in the Early Jurassic Drake formation. The well was drilled with seawater and gel down to 1046 m and with KCl mud from 1046 m to TD.

The Nordland, Hordaland and Rogaland Groups consisted mainly of clays and claystones with minor sandstones. The Cromer Knoll Group consisted of limestone interbedded with claystones and marls, while the Viking Group consisted mainly of claystones as expected. The tops prognosed for the well were within the expected margin of error for the Top Balder and Top Shetland seismic markers. However, the depths prognosed for the Top Ty Formation, base Cretaceous, top Vestland, and top Dunlin markers were off by as much as 65m. Therefore, the top of the Vestland Group was encountered 39.5 m below the oil water contact in the Vestland discovery at 25/6-1. No hydrocarbons were encountered in any of the prospective intervals, and only one show was described from a single cutting sample recovered from the Vestland Group. No cores were cut and no fl