The Brent Field, A Reservoir Engineering Review

Abstract

Abstract The Brent Field, found by well 211/29-1 in August 1971, was the first discovery in the Northern North Sea and is one of the largest hydrocarbon accumulations in the United Kingdom. It is located in about 140m (470 feet) of water approximately 160 km (100 miles) northeast of the Shetland Islands. The field has two major separate accumulations: one in the Middle Jurassic (Brent reservoir) and the other in the Lower Jurassic (Statfjord reservoir). Estimated recoveries are 250 million m3 (1600 million barrels) of oil and 100 billion m3 (3.6 trillion cubic feet) of gas, with roughly two-thirds coming from the Brent reservoir and the remaindeĩ from the Statfjord reservoir. Brent reservoir oil is volatile and its properties vary with depth. The paper discusses the problems that arose when modelling this fluid system on the computer for development planning studies. Fluid samples taken at various depths by the Formation Interval Tester served to define the position of the gas/oil contact in the Brent reservoir. Production started in 1976 from the first of four platforms. The production build-up continues and a pipeline has been laid to transport the oil to the terminal at Sullom Voe in the Shetland Islands. Starting in 1981 gas will be piped to Scotland where it will be processed and the dry gas stream sold to the British Gas Corporation. Production is from rows of wells completed in single zones. These wells will subsequently be recompleted in the next higher zone when the existing completion waters out. Reservoir pressure is being maintained by water injection. Computer model studies were used to optimise well positioning, pressure levels, recoveries and production planning. Numerous Repeat Formation Tester pressure measurements have been taken and are an invaluable aid in defining the zones and monitoring reservoir performance. Several wells have high gas-oil ratios or water cuts: however, well performance has generally been good with individual well rates of up to 4800 m3/d (30, 000 b/d).