Improved Reservoir Description: Swan Hills Unit No.1

Abstract

Abstract Oil production in the Swan Hills A & B Pools is taken from the Swan Hills Formation of the Beaverhill Lake Group of Devonian age. The reservoir rock is a carbonate formed ill a bioherm. The rock mass is rather complex, with at least seven major porous zones having been identified. Tile field was discovered in 1957 and steady oil production commenced ill January, 1959, after a pipeline became available. Swan Hills Unit No.1 was formed ill January, 1963. About 80% of the pool's oil in place and about 40% the developed area are contained within the unit limits. Water injection commenced in August. 1963. The reservoir description used in the early engineering studies was rather simple and bore scant resemblance to the complex reservoir geology. As the water-flooding operation has become more mature, it has been necessary to use increasingly more complex geologic models in order to reconcile reservoir performance prediction with observed reservoir performance data. Introduction The Swan Hills Field was discovered in the spring of 1957 by Home Regent Swan Hills 08-l1-068-10 W5M, which encountered 12 feet of pay in a gross interval of 124 feet in a limy carbonate section in the lower portion of the Beaverhill Lake Group. In the fall of 1957, a confirmation well, Home Regent Edith Lake 11-19-067-10 W5M, drilled 6 miles to the southwest, encountered 141 feet net pay in a gross interval of 312 feet in the same zone. This pay interval is now known as the Swan Hills Formation of the Beaverhill Lake Group of Devonian age. For administration purposes, the Alberta Energy Resources Conservation Board (ERCB) defines the producing formation as the Swan Hills Beaverhill Lake A & B Pools. The A & B Pools designation dates back to the carly history of the field development, when it was demonstrated that the lowermost porous interval (Coral Zone) was a separate hydrocarbon accumulation the "B" Pool. The remainder of the vertical sequence of oil productive intervals was defined as the "A" Pool. This pool separation move was carried out in an attempt to gain an allowable advantage. The advantage disappeared with prorationing rule changes and the ERCB subsequently approved commingling production from the two pools; however, the A & B definitions still persist. (Sec Figure 1 for position of Coral Zone.) Steady oil production commenced in January, 1959 after a pipeline was laid to Edmonton, a distance of 125 miles to the southeast. Commencement of steady production caused reservoir pressure to decline rapidly because of the undersaturated nature of the reservoir fluid. It became obvious that pressure maintenance would be needed in order to effectively recover the oil in place. The Swan Hills Unit No.1 was formed in January, 1963, and water injection commenced in August. 1963. About 80% of the pool's oil in place and 40% of the developed area are contained within the unit outlines. The reservoir description used in the early engineering studies was oversimplified and bore scant resemblance to the complex: reservoir geology.