Compositional Simulation of a Gas-Cycling Project, Bonnie Glen D-3A Pool, Alberta, Canada

Abstract

Black-oil and multicomponent compositional models were used to simulate a gas-cycling scheme. Reservoir fluid sample data were carefully matched to ensure realistic predictions of phase behavior during cycling. The study indicated that cycling was technically feasible and that an additional 64,906,000 bbl of hydrocarbon liquid would be recovered over the life of the cycling and blowdown. Introduction The Bonnie Glen D-3A pool, discovered in Jan. 1952, is situated approximately 43 miles southwest of Edmonton, Alta. The reservoir, which forms part of the prolific Leduc reef chain, is one of the most capable prolific Leduc reef chain, is one of the most capable producing fields in Canada. The original oil in place producing fields in Canada. The original oil in place is estimated to be 657,138,000 STB, with an original gas cap of 444,900 MMcf. The recovery mechanism is primarily gas cap expansion and natural water influx with excellent gravity segregation, which will effect an estimated recovery of 452,226,000 bbl of oil, or 68.8 percent of the original oil in place. Since simultaneous production of the gas cap during the life of the oil column could be detrimental to oil recovery, gas cap production would normally be deferred until depletion of the oil column. Gas cycling, however, can be carried on while the oil column is depleting, with a beneficial effect on the over-all recovery of hydrocarbon liquids. Reservoir Properties and Performance The Bonnie Glen pool is a dolomitized, biotherm reef in the Leduc member of the Upper Devonian Woodbend formation and is completely underlain by the Cooking Lake formation. The reef, which forms part of the Leduc D-3 reef trend, is approximately 7 miles long, 21/2 miles wide at the original oil/water contact and less than 1 mile wide at the original gas/oil contact, Maximum original net pay thickness of the reef is 701 ft, of which 402 ft is gas cap and 299 ft is oil column. The Cooking Lake formation is an active aquifer extensive in all directions except to the west, where it pinches out almost immediately. The aquifer is common to other oil- and gas-bearing accumulations in the same reef trend (Fig. 1), and interpool interference is evident by past pressure trends of the D-3 pools. Fig. 2 presents a structure contour map of the top of the pool, based on the gross reef section, and Table 1 presents a summary of important reservoir properties. The original composition of the gas cap and oil column is presented in Table 2. Since discovery of the field, 166 wells capable of production have been drilled, most of them on production have been drilled, most of them on 40-acre spacing. Currently, 58 wells produce the field allowable of approximately 40,000 BOPD. Cumulative production to Dec. 31, 1971, was 154,078,000 bbl of oil, 114,500 MMcf of solution gas, and 1,204,000 bbl of water. The reservoir pressure at datum has declined from the original 2,477 psi to a current 2,005 psi. Fig. 3 presents the production and reservoir pressure history of the Bonnie Glen pool, and Fig. 4 shows a transverse cross-section of pool, and Fig. 4 shows a transverse cross-section of the reservoir, illustrating original and current gas/oil and oil/water interfaces. Interfaces were calculated by a combination of material balance and a knowledge of cumulative reservoir pore volume as a function of reservoir depth. Calculations agreed very closely with semiannual field measurements. JPT P. 1285