6406/1-2

General

Well 6406/1-2 was drilled on the Sklinna prospect in the Norwegian Sea ca 10 km west of the Kristin Field. The Sklinna prospect is a faulted structural closure within a huge structure at Base Cretaceous level on the Sklinna High. The area closure was about 60 km2; crestal depth at ca 4160 m msl, and structural relief of more than 600 m. Structural closure was observed on all levels from The Lysing Fm and deeper. Therefore all possible reservoir levels like the Lysing and Lange sandstones were possible targets, but the primary target was the hydrocarbon potential in the Early Jurassic sandstone reservoirs of the Båt Group.

Operations and results

Wildcat well 6406/1-2 was spudded with the semi-submersible installation Deepsea Bergen on 26 June 2003 and drilled to TD at 4500 m in the Triassic Red Beds. The well was drilled with seawater/ high viscous sweeps with seawater/PAC spud mud down to 1205 m, with a water based silicate mud (Sildril) from 1205 m to 2415 m, and with Versapro oil based mud from 2415 m to TD. In addition to Versapro, Versatrol, VersaVert, and EDC99-ESCAID were used in intervals in the oil-based section. No shallow gas was observed.

No significant sand development was encountered above the Lange Formation. The well encountered Hydrocarbon bearing sandstone of Turonian age in the Lower Lange Formation from 4163 m - 4185 m (4157 - 4181 m TVD). The Early Jurassic Båt group was not present in the well as the Early Cretaceous rested unconformably on Triassic sediments. The reservoir hydrocarbon samples taken at 4178 m were all found to have more than 90 % mud contamination. A number of different petroleum-like products were used in the oil-based drilling mud, including Versatrol, which is a trade name for Gilsonite, a natural petroleum asphalt. Due to this strong contamination the PVT program was reduced and of all the geochemical analyses only the optical analyses (e.g. vitrinite reflectance), the gases and t