15/9-23

General

Well 15/9-23 was drilled in the southern Viking Graben, south of the Sleipner East Field in the North Sea. The primary objective was to test the Middle Jurassic Hugin and Sleipner formations and the Triassic Skagerrak formation within the Skardkollen prospect. The Early Paleocene Ty Formation was secondary objective.

Operations and results

Wildcat well 15/9-23 was spudded with the semi-submersible installation Bredford Dolphin on 18 November 2009 and drilled to TD at 3225 m in late Triassic sediments of the Skagerrak Formation. A 9 7/8" pilot hole was drilled from the 36" section to 714 m and a shallow gas zone was encountered at 674 to 678 m. The hole was opened to 26" down to 556 m, and 20" casing was set at 550 m. The well was drilled with seawater and hi-vis sweeps down to 556 m, with KCl/Glycol mud from 556 to 1520 m, and with XP-07oil based mud from 1520 m to TD.

The top of the first Frigg Formation sand was penetrated at 2092 m. The secondary target, the Ty Formation of the lowermost Rogaland Group was penetrated at 2524 m. The Ty Formation constituted excellent reservoir sandstones with a gross thickness of 24 m. GeoTap pressure measurements detected a pore pressure depletion of 105 bar compared to a normal hydrostatic gradient, most likely related to production at the nearby Sleipner East Field within the same stratigraphical unit. The primary reservoir target, the Middle-Jurassic Vestland Group, was penetrated at 3087.5 m, 45.5m deeper than anticipated. The Hugin Formation was absent, and the top of the Vestland Group consisted of the coal-bearing Sleipner Formation. Firm identification of red-brown Triassic mudstones of the Skagerrak Formation was penetrated at 3169 m, 5.5m shallower than progn