Brent Field Reservoir Modelling: Laying the Foundations of a Brown-field Redevelopment

Abstract

Abstract The Brent field was discovered in 1971. It is now a mature asset and, in order to increase oil and gas ultimate recovery, will commence depressurisation in 1997. The redevelopment of the field has been underpinned by extensive static and dynamic modelling studies. Developments in geological computing and the numerical processing power of reservoir simulation platforms significantly improved the quality of the Brent field static and dynamic models. The static models have been used for a range of studies including gas cap volumetrics and bypassed oil investigations. Their functionality provides significant scope for target sizing as a basis for selecting the appropriate reservoir access well technology. Introduction The Brent field, located 100 miles north east of Lerwick, Shetland Islands (Fig. 1) was discovered by well 211/29–1 in 1971. With total hydrocarbons initially in place of some 3.8 MMMbbl oil and 7.5 Tscf gas the Brent field ranked as one of the largest fields in the northern North Sea. Following 20 years of production remaining reserves are estimated to be some 400 MMbbl oil and 2.6 Tscf gas and in these terms the Brent field continues to rank as the largest field in the U.K. Sector of the North Sea. The Brent field is a mature asset. Facilities comprise four platforms providing a total of 154 well slots. Oil export is via the Brent systems pipeline to Sullom Voe and gas export via the FLAGS line to St. Fergus. Production from the extensive West Flank area commenced in 1976 and by January 1997 cumulative production amounted to 1.6 MMMbbl oil, some 80% of anticipated waterflood ultimate recovery, and 3.2 Tscf gas. In order to significantly increase ultimate recovery through field depressurisation an extensive brown-field redevelopment project, costing 1.3 billion, was initiated in 1994. This is now reaching completion with depressurisation commencing in 1997 and low pressure operation in the year 2000. This project has extended the life of the field and increased ultimate recovery. The redevelopment of the Brent field involved extensive static and dynamic reservoir modelling studies which will continue to guide reservoir management during depressurisation. This paper reviews the development of the current generation of static reservoir models and illustrates their use, not only as the basis for dynamic studies but also in delineating areas of bypassed oil and monitoring gas cap volumetrics.