33/12-6

General

Well 33/12-6 was drilled on Tampen Spur in the North Sea between the Gullfaks Sør Field area and the UK border. The objective was to test a large structural feature in the southeastern part of Block 33/12, located across a major regional fault bounding the eastern flank of the Brent and Statfjord Fields. The targets were sands in the Early and Middle Jurassic sandstones of the Statfjord and Brent Groups.

Operations and results

Wildcat well 33/12-6 was spudded with the semi-submersible installation Norskald on 2 March 1976 and drilled to TD at 4612 m in the Triassic Hegre Group.

The Middle Jurassic Brent Group was encountered at 2973. Gross thickness was 312 meters. Only rare fluorescence with minor gas readings were noted in the sands. Higher gas readings encountered were associated with coal beds. Using cutoffs of 40 percent clay volume and 12.5 percent porosity, Schlumberger’s coriband analysis indicates 103 meters of net sand with an average porosity of 20 percent. The coriband analysis showed the sands to be water wet with only 6 m of net pay with water saturations less than 65 percent, scattered throughout the unit. The Early Jurassic Statfjord Group sands were topped at 3721 meters. Gross thickness was 309.5 meters. Using the same cutoff parameters as for the Brent formation, log analysis indicated 149 meters of net sand with an average porosity of 16 percent and showed the sands to be water wet. Only 3 m of scattered thin zones had water saturations less than 65 percent. No shows were seen in the samples. However, the core in the Statfjord sands had residual oil saturation over the 6.51 meters recovered indicating earlier oil migration through the section.

The core w