6407/8-5 S

General

Well 6407/8-5 S and the sidetrack 6407/8-5 A were drilled on the Gygrid prospect situated 7 km west of the Draugen Field in the Norwegian Sea. The main objectives of the wells were to prove hydrocarbons in the Upper and Lower Åre Formation. A secondary objective was to test the prospectivity of the Late Jurassic Rogn Formation. The structure was expected to be gas filled with a thin oil leg. Total Depth of the wells was planned 100 m TVD under prognosed HC/water contact in the Åre Formation or maximum 2308 m TVD RKB in both S and A wells.

Operations and results

Wildcat well 6407/8-5 S was spudded with the semi-submersible installation West Alpha on 2 May 2009 and drilled to TD at 3240 m (2368.7 m TVD) in the Triassic Grey Beds. The well was drilled vertical down to 1375 m, building angle to ca 70 deg at 2170 m, and keeping ca 70 deg from 2170 m to TD. It was drilled with Seawater/WBM down to 926 m and with Versatec oil base mud from 926 m to TD.

The well penetrated rocks of Quaternary, Tertiary, Cretaceous, Jurassic, and Triassic age. Contrary to the pre-drill interpretation a full Jurassic stratigraphy was encountered, with the Viking Group coming in at 2100 m (1979.2 m TVD), the Fangst Group (Garn Formation) at 2252.5 m (2035.5 m TVD), and the Båt Group at 2487.5 m (2114.5 m TVD). The Spekk and Melke Formation contained several thin sandstones, but no massive Rogn Formation. Instead the Ile Formation at 2346.5 m (2067 m TVD) and the Tilje Formation at 2549 m (2135.3 m TVD) proved to be the main reservoirs, with oil proven in the Tilje Formation. No gas cap was seen. A Tilje ODT was encountered at approximately 2148 m TVD with water up to approximately 2151 m TVD. In addition, a thin gas zone was encountered in a condensed