30/6-25 S

General

The main objectives of well 30/6-25 S was to test the potential, fluid types, and reservoir quality of the Brent Group on the Kappa structure, north of the Omega Nord structure in the Oseberg Sør area. The Kappa structure is located in a down faulted position to both the Oseberg Gamma and the Omega Nord structures. The main target was the lower Brent Group, with Oseberg Formation as the main reservoir. The well should furthermore acquire vital pressure data in order to identify likely pressure cell boundaries.

Operations and results

The exploration well 30/6-25 S was spudded on 26 November 1998 with the semi-submersible installation "Transocean Leader" and drilled deviated to a TD of 2988 m (2935m TVD RKB), 63 m TVD into the Early Jurassic Drake Formation. The well was drilled water based with bentonite down to 1046 m and with &AQUACOL& KCl/polyalkylene-glycol mud from 1046 m to TD. The Oseberg Formation was thinner and of poorer reservoir quality than expected, based on log data. The log quality was considered to be good. The Brent Group was penetrated twice which reveals that the well penetrates, at least, one fault. Both Ness and Oseberg Formations were remarkably thinner than expected. Oil shows were pointed out in the lower part of Tertiary and uppermost part of the Cretaceous. In the Brent Group only weak oil shows were observed, and consequently no movable hydrocarbons were stated. The formation pressure data indicate a water gradient similar to the gradient in ORELN on northern part of the Omega Nord structure. There is a water gradient of approximately 1 g/cc throughout the Oseberg, Rannoch, Etive and LN2 (ORELN2) Formations. The relative overpressure in the ORELN2 Formations is around 30 Bar. The water pressure in the Upper Ness sands is 2-3 bar less than the water gradient interpreted in the ORELN2 Formations. In the hydrocarbon filled Upper Ness Sands in well 30/9-3 A the pressure is approximately 10 bar lower