The Cormorant Field, Blocks 211/21a, 211/26a, UK North Sea

Abstract

Abstract The Cormorant Oilfield is located approximately 150 km northeast of the Shetland Islands in Blocks 211/2la and 211/ 26a of the UK sector of the North Sea, in water depths of 500-550 ft. The field was discovered in 1972 by exploration well 211/ 26-1 and consists of four discrete accumulations spread along a major, north-south trending fault terrace. Hydrocarbons are produced from Middle Jurassic (Bajocian) sands of the Brent Group, which was deposited in a wave-dominated delta system. The reservoir has a typical gross thickness of 250-300 ft, locally increasing to 550 ft over faults active during sedimentation. Reservoir porosity varies from 16-28%, with average permeabilities ranging from tens of md to 1300md. The accumulation contains under-saturated 34-36° API oil which was initially overpressured by some 1000-1270 psi. The stock tank oil initially in place and ultimate recovery are estimated at 1568 MMBBL and 623 MMBBL, respectively, reflecting a recovery factor of 39%. The reserves are produced through crestally-located wells supported by down-dip water injectors, and exported via two fixed platforms and an underwater manifold centre. To date, 59 wells have been drilled and 324 MMBBL (52%) of the estimated reserves have been produced.