34/4-2

General

Well 34/4-2 is located in the northern North Sea, approximately 5 km west of the Snorre Field. The purpose of the well was to test the stratigraphic sequence below the Base Cretaceous Unconformity. The primary target was the Statfjord Formation, which was known from the license 037 area to contain porous sandstones of appreciable thicknesses.

The secondary target was possible Brent Group / Late Jurassic sands immediately below the Base Cretaceous unconformity. Thirdly, well 34/4-2 was a stratigraphic test of the Triassic deposits between the Statfjord Formation and the Middle to Late Triassic sequence penetrated in well 34/4-1.

Operations and results

Wildcat well 34/4-2 was spudded with the semi-submersible installation Byford Dolphin on 6 March 1980 and drilled to TD at 3599 m in the Late Triassic Lunde Formation. No significant incidents occurred during operations, but the well developed as much as 20 deg deviation towards TD, giving a TVD RKB of 3571 m, 28 m less than measured depth. The well was drilled with spud mud down to 816 m, with gypsum/lignosulphonate mud from 816 m to 1975 m, and with lignosulphonate mud from 1975 m to TD.

The well penetrated Tertiary, Cretaceous, Jurassic and Triassic strata as required in the work programme for License 057. More than 900 m of Triassic deposits were penetrated in order to obtain stratigraphic information. The Statfjord Formation was eroded and the reservoir characteristics here were on large negative. The exception was the upper seven meter thick Eiriksson Member with a net/gross-value of 1.00 and an average porosity of 24.3%. The underlying Raude Member had a high clay content, which reduced prospectiveness to a N/G value of 0.18 and porosities only rarely exceeding 20%. The Jurassic sequence proved to be different from the expected with Dunlin Group claystones directly underlying Barremian limestones. Hence, no Brent/Late Jurassic sands were present.

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