6201/11-2

General

Well 6201/11-2 was designed to drill the Oksen prospect in the southwestern corner of block 6201/11. A prominent NE-SW trending ridge complex occupies the southern part of this block, separating the Møre Basin from the northern North Sea along the Møre Trøndelag fault complex. The reservoir rocks of the Oksen prospect were interpreted as synrift submarine fan deposits of Kimmeridge age located in a half graben between two Triassic Highs. Trapping mechanism were stratigraphically dependant on sealing faults towards rotated Triassic rocks in southeast. The objectives of the well were to test the hydrocarbon and reservoir potential of the Late Jurassic play-concept (Magnus Sand) and to test the geophysical and structural interpretation of the area and give valuable information on palaeontology and geochemistry.

Shallow gas warnings were given for two levels.

Operations and results

Wildcat well 6201/11-02 was spudded with the semi-submersible rig Deepsea Bergen on 8 January 1991 and drilled to TD at a total depth of 3778 m in the Jurassic Heather Formation. The well was drilled with seawater/CMC/viscous plugs down to 780 m, with KCl/polymer mud from 780 m to 3335 m, and with gel/lignosulfonate mud from 3335 m to TD. The well was drilled without major problems, except for 3 days lost rig-time due to low leak-off value at the 20" casing shoe.

Top Late Jurassic was encountered at 3339 m, which is 24 m lower than prognosed. No potential reservoir rocks were encountered in the Late/Middle Jurassic. The biostratigraphic breakdown was difficult to interpret from approximately 3650 m and to TD with Triassic shale overlying the Late Jurassic Heather Formation towards TD. It is thus possible that the Jurassic and Triassic sequences in this well represent slumped/slided sediment packages similar to the situation in well 33/5-2 not very far to the south. The only shows recorded were cut fluorescence in claystones in the in