35/8-5 S

General

Well 35/8-5 S was drilled on a location ca 15 km west of the Gjøa Field on the western margin of the Måløy Slope in the northern North Sea. The main objective was to test the presence and type of hydrocarbons in Oxfordian turbidites in the J10 Prospect. A secondary objective of the well was to test the hydrocarbon potential of the Brent Group Sandstones. The well was targeted in the W-segment of the prospect, close to the eastern boundary fault, in order to enable a possible sidetrack towards east and into the C-segment. To meet these criteria, the well was designed as a deviation well to follow the dip of the eastern boundary fault plane of the W-segment in a proper distance from the fault. Sidetracking was only to be performed in case of discovery in either the primary or the secondary target.

Operations and results

Wildcat well 35/8-5 S was spudded with the semi-submersible installation Deepsea Delta on June 1 2003 and drilled to TD at 4000 m (3831.8 m TVD) in the Middle Jurassic Rannoch Formation. It was discovered after spud that the spud position of the well was placed 105 m east of the planned spud location. The deviation was adjusted during drilling and the reservoir was penetrated within the planned target tolerance. The resulting well path was vertical down to 2315 m, and then deviated with variable inclination down to ca 3300 m, then keeping a fairly constant inclination of 36 deg throughout the last 700 m to TD. A drilling hazard was given due to possible water flow from over-pressured sand interval in the Skade Formation at 673.5 - 794 m. This sand was considerably thicker than prognosed. There was no overpressure in the interval, but two thinner sands above, at 570 m and 590 m, where water flow occurred, were over