6406/11-1 S

General

The well 6406/11-lS was drilled on a truncational/fault seal trap structure on the western slope of the Frøya High near the southern end of the Halten Terrace. The main objective of the well was to test the hydrocarbon potential in the Early to Middle Jurassic Fangst Group. Secondary objectives were to test the reservoir properties the underlying Tilje Formation, as well as possible sand development in the Tertiary. The well should also evaluate the source rock properties in the Early Jurassic Åre Formation. Planned total depth was 4526 m RKB TVD beneath a seismic marker interpreted as Triassic Evaporite. The well was the first well on a new block and the pressure prognosis was uncertain. Formation pressures were to be watched closely while drilling.

Operations and results

Wildcat well 6406/11-1 S was spudded with the semi-submersible installation Treasure Saga on 19 October 1990 and drilled to TD at 4185 m in the Late Triassic Red Beds. To avoid shallow gas the well was spudded and drilled deviated from a location 260 m NNW of the planned target location. During drilling the Nordland Group, two shallow gas intervals were penetrated at 893 - 897.5 m and 1148 - 1150 m. To get back to vertical drilling the well was deviated from 1235 m to 2165 m MD. Only minor problems occurred while drilling down to the 12 1/4" section. After drilling the 12 1/4" hole down to 3395 m, the VSP tool become stuck at 3383 m. A total of 5 days were spent recovering the wire line and miring the fish down. Only minor problems with tight spots occurred while drilling to TD.

Formation pressure was hydrostatic down to ca 1520 m, from where a gradual pressure build up was indicated in the Hordaland Group down through the Rogaland Group, estimated to a maximum of 1.60 g/cc EMW at 2400 m in the upper part of the Shetland Group. From here a slight pressure depletion down to approximately 3000 m was indicated. From 3000 m down to the Jurassic