16/1-10

General

Well 16/1-10 was drilled on the eastern margin of the South Viking Graben on the south-western part of the Utsira High in the North Sea. It was drilled to confirm the northern extent of the Luno oil discovery in Early Jurassic conglomerates made by well 16/1-8. The oil-water contact at 1965 m TVD RKB should be confirmed and a production test of the clean sand facies and conglomeratic facies should be conducted.

Operations and results

Appraisal well 16/1-10 was spudded with the semi-submersible installation 16/1-10 on 13 November 2008 and drilled to TD at 2151 m in conglomeratic sandstones of Early Jurassic age. As the site survey revealed a number of possible shallow gas zones the well started with a 9 7/8" pilot hole to check for shallow gas down to 400 m, TD of planned 26" section. No gas was seen in this interval. Due to a leak in the 20" casing the casing programme was significantly revised, with 13 3/8" casing set at 589 m, above a potential shallow gas zone at 634 m, and the 12 1/4" hole was drilled down into top Shetland Group. This slimmer-than-planned hole turned out to give easier drilling than in the previous well on the prospect (16/8-1). The amount of down time was however comparatively large, due mainly to wait-on-weather. Additional coring also added to a longer than planned time for this well. The well was drilled with seawater and hi-vis bentonite sweeps down to 411 m, with KCl/glycol enhanced mud from 411 m to 1860 m, and with Performadril water based mud with 5% glycol from 1860 m to TD.

The Utsira, Skade and Grid sandstone formations were penetrated by the well, all water bearing. The top of the Jurassic reservoir sequence was encountered at 1898 m (1872.9 m TVD MSL), 11.4 m TV