COMPARATIVE PRODUCTION PERFORMANCE BETWEEN CONVENTIONAL WATER ALTERNATING GAS FLOODING AND WATER INJECTION ALTERNATING GAS DUMPFLOOD

Abstract

Although water alternating gas (WAG) injection provides incremental oil recovery, this process requires high expenditure for water and gas surface facilities. This study proposes a method that eliminates the use of gas injection facility via the process of gas dumpflood compares the performance of the proposed method of water injection alternating gas dumpflood with conventional WAG. Reservoir simulation is performed for a hypothetical oil reservoir with another gas reservoir underneath. In addition, the sensitivity of reservoir and fluid parameters on performance are investigated.

The best case of conventional WAG gives slightly higher oil production than the best case of the proposed water injection alternating gas dumpflood. Conventional WAG requires slightly lower water injection and less production time but needs tremendous amount of gas injection. In terms of operating conditions for both methods, the most suitable time to stop water injection is when water breaks through the producer. Well location at which injector to producer distance is 2,000 ft. gives the best results. In addition, increasing water injection rate slightly decreases total oil production in conventional WAG but slightly to moderately increases oil recovery in the proposed method. And, variation in slug size and ratio of water to gas injection duration has a minor impact on total oil recovery in both methods.

The sensitivity study shows that a decrease in kv/kh ratio moderately increases the recovery factor in the case of conventional WAG but highly increases the recovery factor in the case of the proposed method. Lower recovery factor is obtained when oil viscosity and residual oil saturation increases in both methods. As the thickness of source gas reservoir increases, the recovery factor moderately increases in the proposed method. The increase in depth difference between the oil and gas reservoir slightly increases the oil recovery in the proposed method.