7/11-1

General

Well 7/11-1 was drilled on eastern side of the Breiflabb Basin in the southern North Sea, ca 3km from the UK Border. The main objective was to test the hydrocarbon potential of the Tertiary and the Mesozoic sediments. Specific objectives were Paleocene sandstone, the Late Cretaceous carbonate section, and the Jurassic. Sandstones in the Early Cretaceous and Triassic were seen as possible secondary targets.

Operations and results

Wildcat well 7/11-1 was spudded with the semi-submersible installation Ocean Viking on 26 February 1986 and drilled to TD at 3974 m in Late Permian Zechstein Salt. The only significant drilling problem encountered was sloughing of shale between ca 1675 m and 2315 m. Deviation was negligible above 3500 m, from where it increased from 4.5 deg to 11.5 deg at approximately 3960 m. The true vertical depth therefore probably is 4-5 m short of measured depth at TD. A Drispac-Flosal-Desco mud system was used to a depth of 3290 m. At this depth the system was converted to a sodium chloride saturated Drispac-Flosal-Desco system. The salt saturated system was used to total depth.

The well proved gas and condensate in three tests in a 5 m thick intra-Balder Formation sand (DST 5) and the Forties Formation from top at 2904 m down to 2989 m (DST 3 and 4). Below this depth DST 1 and 2 produced only minor amounts of hydrocarbons due to tight formation. Top salt came in under the Late Cretaceous Hidra Formation at 3740 m.

Three cores were taken in the Paleocene sandstone in the intervals 2922.7 - 2932.8 m, 2932.8 - 2949.9 m, and 2952.9 - 2966.9 m. A fourth core at TD had no recovery. No wire line fluid samples were taken.

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