17/3-1

General

Block 17/3 is situated approximately in the center of a broad, elongated Triassic rift basin composed of the Stord and Egersund basins. The well is located on a well-defined horst structure (Bark Prospect) in the northern part of the block, in an almost unexplored area in the southern part of the Stord Basin. Due to the "wildcat" nature of the well there were many unknowns and "worst case scenarios" had to be planned for. The well was designed for two objectives with different pressure regimes: The primary objective was the Late Jurassic Sandnes Formation at 1.20 sg. The Permian Rotliegendes Group at 1.55 sg was a secondary objective. This necessitated an expensive deep 13 3/8" casing (2312 m) to ensure that the 2 objectives could be properly evaluated and that the well could be completed in the 8 1/2" section. The expected hydrocarbon phase was oil. The prognosed TD of the well was 3300 m RKB, 309 m below the supposed Top Rotliegendes. This was in order to reach the highly dipping markers of assumed Paleoz

Operations and results

Wildcat well 17/3-1 was spudded with the semi-submersible installation "Wildcat Explorer" on 29 June 1995 and drilled to a total depth of 2852.15 m in metamorphic basement rock, dated 410 My. The well was drilled with seawater down to 949 m and with water based gypsum mud from 949 m to TD. The well came in under budget and almost 14 days ahead of schedule. A major contributing factor to the latter was the shallower than expected TD, 2852 m (basement) as opposed to 3300 m, due to the Permian section being non-existent. The primary objective Sandnes Formation was encountered at 2387 - 2409 m, about 50 m shallower than prognosed, with a hydrostatic pore pressure (1.05 sg emw from RFT and MDT) and only ~2 m of gas was found at the top of the reservoir. The Permian series were not present, as the Triassic Smith Bank Formation was directly deposited on metamorphic basement. The secondary objective, the Rotliegendes Group, was never encountered