7/4-2

General

Well 7/4-2 was drilled on the Nemo prospect on the Jæren High in the North Sea. Two wells had previously been drilled for the evaluation of the Nemo structure. The 7/7-2 was drilled by Statoil in 1992 and discovered 19.5 m oil filled Ula Formation. No OWC was detected and no reliable pressure measurements were retrieved in the underlying Triassic Smith Bank Formation. Well 7/7-3 was drilled down flank to the SSW in 1993 and penetrated a 16.5 m Ula Formation which was water bearing with oil shows. The primary objective of the 7/4-2 Nemo well was to appraise the 7/7-2 oil discovery. This objective included determination of the OWC deeper than 3372 m (3371.1 m TVD RKB) oil down to in well 7/7-2; to verify the seismic interpretation and geological model for the Nemo discovery, including facies changes in the Farsund Formation; and finally to obtain fluid samples (oil and formation water). The secondary objective was to test the reservoir potential of the Triassic Smith Bank Formation.

The well was designed as a potential future water injector.

Operations and results

Appraisal well 7/4-2 was spudded with the jack-up installation Mærsk Giant on 15 December 2007 and drilled to TD at 3459 m in the Late Permian Zechstein Group. A 9 7/8" pilot hole was drilled from the 30" conductor shoe at 208 m and down to 236 m when losses were discovered. A passage through the cement from the 30" conductor shoe to seabed allowed the pumped seawater to escape from the circulating system. While monitoring the losses when pumping at 3000 l/min, 42 m3/hr travelled unhindered behind the conductor to the seabed. Due to the severity of the losses a cement stinger was run in to 207 m and 37 m3 cement pumped to seal the passage and