15/12-22

General

The15/12-22 Storkollen well was drilled south of the Sleipner East Field in the south Viking Graben of the North Sea. The objective was test the hydrocarbon and reservoir potential of the Storkollen prospect. Primary target was Oxfordian "Varg Equivalent sandstone" (Hugin Formation) of the Vestland Group, while the Early Tertiary Heimdal/Ty Formations was a secondary target.

Operations and results

Wildcat well 15/12-22 was spudded with the semi-submersible installation Bredford Dolphin on 17 April 2010 and drilled to TD at 3035 m in the Late Triassic Skagerrak Formation. A shallow gas influx occurred at 697-700 m while waiting on weather (low wind) after having drilled the 9 7/8" pilot hole to 744 m. The interval had an intermediate shallow gas warning. The gas influx was killed with 1.25 GS mud, and the pilot hole was plugged back for setting the contingent 20" casing with the shoe at 622 m. The well was drilled with seawater/bentonite and hi-vis sweeps down to 622 m, with KCl/polymer/GEM mud from 622 m to 1550 m, and with XP-07 oil based mud from 1550 m to TD.

Tertiary sands were penetrated in the Utsira and Skade formations, while the Frigg Formation sandstones were not encountered at the Storkollen location. The secondary target, the Paleocene Heimdal/Ty Formations was not present, and Top Shetland chalks were penetrated at 2320 m, which was 16 m shallower than prognosed. The primary reservoir target, the Hugin Formation of the Vestland Group, was penetrated at 2831 m, which was 22 m shallower than prognosed. The sandstone unit was 154 m thick and had excellent quality with a N/G ratio of 96% and an average porosity of 25%. It was water bearing. GeoTap pressure measurements within the Hugin Formatio