The Schrader Bluff Pool in the Milne Point Unit, Alaska, is estimated to contain 1.5 billion bbl of heavy oil. Due to the lack of any significant primary recovery mechanism, enhanced oil recovery methods are considered for early stage application. Availability of hydrocarbon gases and CO2 on the Alaskan North Slope makes a miscible solvent injection process attractive. Therefore, the objective of this study was to experimentally investigate the performance of CO2 injection and miscible WAG processes for enhanced recovery of Schrader Bluff heavy oil. From slim tube experiments, CO2 was found to be immiscible with Schrader Bluff oil at reservoir conditions. Prudhoe Bay gas (PBG) enriched with at least 50% natural gas liquids (NGL) achieved dynamic miscibility with the crude oil. Coreflood experiments in 4 ft long sandpacks were conducted using CO2, and a mixture of 50% PBG and 50% NGL as the solvents to study the effects of slug size and WAG ratio on displacement of Schrader Bluff oil at reservoir conditions. These experiments showed that there was no significant improvement in the incremental oil recovery (IOR) for PBG/NGL slug sizes larger than an optimum value, however, the highest IOR per unit slug size occurred for a much smaller slug size. On the other hand, a single, small CO2 slug resulted in almost same IOR as a large PBG/NGL slug. Thus, CO2 had the highest IOR per unit slug size although it was immiscible with the oil. The IOR from PBG/NGL multiple slug WAG decreased asymptotically with increasing WAG ratio and a single slug WAG resulted in highest IOR per unit slug size. Thus, in coreflood experiments, a small single slug of 50% PBG and 50% NGL mixture, or of CO2 appears to be most efficient in improving oil recovery.

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