The Thistle Field, Blocks 211/18a and 211/19, UK North Sea

Abstract

Abstract The Thistle Oilfield is located on the western margin of the North Viking Graben in UK Blocks 21l/18a and 211/19. The field was discovered in 1973 by the Halibut Group, operated by the Signal Oil Company. The discovery well was drilled in 1973 and the field was declared commerical before completion of the first two appraisal wells. The extension of the field into Block 211/19 was confirmed by well 211/19-1 drilled in 1974 and the field was subsequently unitized. The Middle Jurassic Brent Group forms the oil-bearing reservoir sequence. The structure is an easterly dipping, rotated fault block divided into five main compartments by N-S normal faults and E-W cross faults. A 60 slot drilling and production platform was installed in 1976 and production began in February 1978. It is now connected by pipeline to Sullom Voe and production through this link commenced in late 1978. Due to only limited aquifer support, injection wells have been drilled on the east flank of the field, in order to maintain reservoir pressure. In addition, several wells in partly isolated fault blocks are produced by gas lift completions. The current STOIIP is estimated at 794 MMBBL of which 396 MMBBL will ultimately be recovered. Cumulative production to the end of 1988 was 334 MMBBL from 34 production wells, with support from 13 injection wells.