Enchant Arcs AB CO2 Pilot Project

Enhanced oil recovery using Carbon Dioxide as miscible flooding injectant (CO2 EOR) can improve oil recovery from certain conventional oil fields in Alberta.

The applicant wishes to implement a CO2 EOR flood, with alternating water and CO2 at a VRR of 1 and average WAG ratio of 1.3 in the Enchant Arcs A&B pool, which has been on waterflood since 1993. The pool contains 1 injection well and 3 producers, which is essentially one-quarter of a nine-spot pattern on 80 acre spacing. Extensive laboratory testing for this project indicated that a significant increase in recovery could be realized by lowering the interfacial tension in a near-miscible displacement, and the applicant intends to operate at a pressure of 1610 psi, which is the pressure required to lower the interfacial tension indicated by laboratory testing.

The applicant plans to inject initially 0.96 MMCFD (51 tonnes/day) of pure CO2 (98%) into the current waterflood injector at 10-22-13-15W4, which will be converted to water-alternating-CO2 injection. Although the well is structurally the lowest in the pool, the applicant believes that it is the best candidate for CO2 injection due to low oil saturation after 10 years of water injection coupled with the fact that CO2 will be injected at near-critical fluid, with a density of 621 kg/m3, therefore mitigating any gravity override concerns. The source of the CO2 to be injected is from the sweetening unit at the 11-31-13-14W4 Hays gas plant, which is operated by the applicant and is located 6 km NE of the proposed CO2 scheme. The plant processes associated and non-associated Arcs gas production from the Enchant and hays Fields, and the gas has unusually high CO2 content for Alberta (10-20%). The gas plant is currently venting 3.5 MMCFD of 98% CO2, and the applicant proposes instead to use the CO2 stream available at the gas plant for injection. To compress the CO2 to a discharge pressure of 2239 psi for EOR injection, the applicant plans to install compression and dehydration facilities at the plant.

The OOIP for the pool is 8.3 million barrels with a small gas cap of 0.45 bcf. The ultimate recovery for the existing waterflood is estimated at 2.37 million barrels, which corresponds to 28.6%. The applicant estimates the ultimate recovery with CO2 EOR to be 3.3 million barrels, or 39.8% after 50 years of WAG injection entailing injection of total CO2 slug size of 69% HCPV, and resulting in incremental CO2 EOR recovery of 11.3% OOIP.

If this project proves successful, the Enchant-Taber regions (and other suitable regions in Alberta) contain numerous small oil pools with medium gravity type crude which would be candidates for CO2 EOR; hence replication of this project would only be limited to the volume of CO2 available for injection. This would also be a good example of using CO2 from a local source for CO2 EOR and sequestration of CO2 in Alberta.

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