35/1-2 S

General

Well 35/1-2 S was drilled on the Soleie Graben Prospect on the Tampen Spur between the Knarr and Peon discoveries in the northern North Sea. The main objective was to prove commercial hydrocarbon accumulation in the Early Jurassic Cook Formation. Secondary objectives were to drill through leads in the Paleocene Lista Formation and in the Cretaceous Kyrre Formation. The well commitment was to drill 50 m into the Statfjord Formation.

Operations and results

Drilling was performed with the semi-submersible installation Transocean Leader. A pilot hole 35/1-U-1 was drilled first to check for shallow gas. No gas was seen. The main well was spudded 15 m south-east of the pilot and drilled to TD in 26" section. Casing and conductor were run, but due to a leak in the casing the well was abandoned and re-named 35/1-U-2. Wildcat well 35/1-2 S was spudded 15 m north-east of the abandoned on 12 September 2010 and drilled to TD at 4202 m (4122 m TVD) in the Early Jurassic Statfjord Formation. The Lista Formation was drilled with a 17" hole and opened up to 20" after the wire line logging was performed. Due to interbedded clay and hard limestone layers 8 runs were necessary to under ream the section. The well was drilled with sea water down to 1293 m, with Performadril mud from 1293 m to 2358 m, with XP-07 oil based mud from 2358 m to 3698 m, and with Low ECD-HTHP oil based mud from 3698 m to TD.

The tops in the overburden came in within the given uncertainties. Bigger differences were seen below the BCU. Five meters of Cromer Knoll Group were drilled before the Heather Formation was encountered at 3624 m. The Viking Group was thinner than expected and no Brent Group Equivalent was identified, therefore the Heather was dir