7122/7-4 S

Well 7122/7-4 S was drilled 1.8 km northeast of well 7122/7-3 on the Goliat Discovery. The purpose was to prove the OWC and additional oil reserves down dip in the Kap Toscana Group deeper than the ODT in 7122/7-3 and to confirm the up dip oil and gas reserves (GOC) in the Kobbe Formation. The 7122/7-4 S well is the fourth appraisal well on the Goliat discovery.

Operations and results

Well 7122/7-4 S was spudded with the semi-submersible installation Polar Pioneer on 21 September 2006 and drilled to TD at 2550 m in the Early Triassic (Griesbachian age) Havert Formation. The well was drilled vertical down through the Kap Toscana Group and then deviated to TD. No significant technical problems were encountered during the operations. The well was drilled with sea water and hi-vis sweeps down to 1050 m. Formate mud previously used for drilling the 7122/7-1, -2 and -3 wells was re-used in this well from 1050 m to TD.

Top Kap Toscana reservoir was penetrated at 1177 m, 14 m deeper than the prognosis. The reservoir consisted of very fine to fine sandstone and was water-bearing, but shows were recorded on cores from the upper part of the Kap Toskana Group. Top Snadd Formation was penetrated at 1244 m, 26 m deeper than prognosis. The reservoir consisted of sandstone interbedded with siltstone and claystone and was water bearing, but with weak, scattered shows in the interval 1260 to 1370 m. The third reservoir, in the Kobbe Formation, was found at 1793 m (1737 m TVD RKB), 5 m deeper than prognosis. The Kobbe Formation reservoir had a gas cap with the GOC at 1856 m (1790.5 m TVD RKB). The OWC was not clear-cut, but was estimated at 1957 m (1876 m TVD RKB). The upper part of the Kobbe Formation consisted of clean light grey, very fine to coarse Sandstone bodies. The sandstone bodies varied from 1 to 18 m thick with the thickness of the beds decreasing with depth. The Sandstone porosity was between 20 % and 30 % and permeability up to 4000 mD. The sandsto