34/7-17

General

Well 34/7-17 is located on the Vigdis Field on Tampen Spur in the Northern North Sea. It was drilled on the southern extension of the C-Plus prospect, on the eastern margin of a complete or non-truncated Brent Group sequence. Furthermore, the location is defined by the down dipping geometry to the northwest, and the proximity to a major fault zone to the south. The primary purpose of the well was to test the reservoir quality and fluid contacts in the prospect. The sequence was drilled in a structural position where a large range of oil-water contacts could be tested. A secondary objective was to test the pressure regimes in the Jurassic sequence, including possible depletion associated with pressure communication, previously identified in the nearby Tordis Field.

Operations and results

Well 34/7-17 was spudded with the semi-submersible installation Treasure Saga on 25 February 1991 and drilled to TD at 3115 m in the Late Triassic Lunde Formation. Due to leaks in the riser the 26? section was drilled riserless while the riser was sent onshore for repairs. First returns to the rig floor was at 897 m. From the MWD logs possible shallow gas was interpreted at 519 - 520, 576 - 576.5 and 692 -693 m, but flow checks performed proved negative. The well was drilled with spud mud down to 897 m, and with KCl mud from 897 m to TD.

In the Nordland, Hordaland, Rogaland and Shetland Groups, the well penetrated mainly claystones with minor sandstone intervals. Top of the Brent Group reservoir was reached at 2461 m (2458 m TVD), which was 38 m deeper than prognosed. The Jurassic section comprised a minor interval of the Viking Group, and a complete section of the Middle Jurassic B