33/12-9 S

General

Well 33/12-9 S was drilled about seven kilometres south of the 33/12-8 S oil/gas discovery on Skinfaks Sør, between the Gullfaks Sør field and the UK border in the northern part of the North Sea. Skinfaks Sør was proven in 2002 and consists of several smaller structures. The main objective of the well was to explore a possible commercial oil leg in the Jurassic Tarbert Formation of the Brent Group, with the secondary objective of proving commercial volumes of hydrocarbons in the Ness and Etive/Rannoch Formations of the Brent Group.

Operations and results

Well 33/12-9 S was spudded with the semi-submersible installation COSL Pioneer on 28 October 2011 and drilled to TD at 3812 m (3746 m TVD) in Middle Jurassic sediments of the Drake Formation. The well was drilled vertical down to 2400 m and deviated from there. The deviation from vertical was built to ca 19 deg at 3100 m. This deviation was kept to TD. The well was drilled with hi-vis/bentonite sweeps down to 947 m, with Glydril mud from 2078 m to 3340 m, and Versatec oil based mud from 3340 m to TD.

Top of primary target, Tarbert Formation sandstone, was encountered at 3420 m (3375.2 m TVD). The Tarbert Formation contained light oil from top and down to 3501 m (3452 m TVD) with a most likely OWC just one meter deeper than that. Oil shows with petroleum odour continued down to 3538. Weaker shows on sandstones, typically patchy moderate bright yellow direct fluorescence and slow streaming/blooming blue white-yellow white cut fluorescence with blue white residual fluorescence, continued down to 3795 m. No oil shows were recorded above top reservoir level.

No cores were cut. MDT oil samples were taken at 3428.6 m and 3498.5 m. The