30/6-1

General

Well 30/6-1 was drilled on the Oseberg Fault block in the North Sea. The primary objective was to penetrate sandstones of Middle Jurassic age and to evaluate their possible content of hydrocarbons. Secondary objectives were sandstones of Lower Jurassic and Paleocene age. The well is Reference well for the Statfjord Group.

Operations and results

Wildcat well 30/6-1 was spudded with the semi-submersible installation Deepsea Saga on 18 June 1979 and drilled to TD at 3175 m in the Triassic Lunde Formation. Problems with setting the 9 5/8” casing at 2443 m caused an 8 days delay in the drilling phase. Also gumbo problems were encountered in the interval 1000 – 1600 m and 4 days rig time as lost due to this. Otherwise operation proceeded without significant problems. The well was drilled with spud mud down to 895 m and with a lignosulphonate/bentonite mud from 895 m to 2456 m and with chromium-lignosulphonate/bentonite mud from 2456 m to TD. Diesel was added at 1720 m to reduce problems with sloughing shales. A 6% to trace levels of oil was recorded in the mud from this depth to TD.

The Cretaceous Jorsalfare Formation had 6.75 m of net pay gas in thin sandstones with average porosity of 29% and water saturation of 39.3%. The Brent Group was encountered at 2285 m and was gas/condensate filled in 38.75 m of net pay sandstones with average porosity of 22.5% and water saturation of 29.2%. The hydrocarbon/water contact was not encountered in the well. The Dunlin Group was water bearing with 45 m of net sand with an average porosity of 24.6%. The Statfjord Group was water bearing with 235 m of net sand with an average porosity of 21.4%. Weak shows were described on conventional and sidewall cores in sandstones from below the hydrocarbon