Oseberg Field

Abstract

The Oseberg field is located in the Norwegian North Sea in Blocks 30/6 and 30/9, approximately 140 km northwest of Bergen, Norway. The field came on stream December 1988. The field comprises three major easterly tilted fault blocks called Alpha, Gamma, and Alpha North. The hydrocarbons are contained in the sandstones of the deltaic Middle Jurassic Brent Group. The Brent Group exhibits excellent reservoir properties with porosities around 20-30% and permeabilities ranging up to several darcys. The gross Brent thickness ranges mainly between 50 and 190 m. The maximum extension of the field is 27 km, and the maximum width is about 6.5 km. The structural dip is normally 6-10{degree} east-northeast. The presence of gas caps has been proven by wells both on the Alpha and Gamma structures. The vertical gas column on Alpha is 380 m and the oil column is 210 m, thus giving a total hydrocarbon column of about 600 m. Reservoir engineering studies have shown that the ultimate oil recovery will be larger by gas flooding compared to water flooding. Consequently, pressure maintenance by gas injection has been chosen as the production mechanism for the Alpha and Gamma structures. To get sufficient gas for injection, largemore » quantities of gas have to be imported from the huge Troll field via a 48-km-long pipeline. The Alpha North structure is planned to be produced mainly by water injection. On the Oseberg field itself, the development comprises a field center in the southern part of the field (on stream), a production platform in the northern part (in construction), and three subsea wells. The reserves estimate for the field is currently 209 {times} 10{sup 6}Sm{sup 3} of oil and 92 {times} 10{sup 9}Sm{sup 3} of gas.« less