PERFORMANCE EVALUATION OF INTEGRATED CO2 HUFF-N-PUFF AND WAG IN LOW-PRESSURE HETEROGENEOUS RESERVOIR

Abstract

The integrated CO2 Huff-n-Puff and WAG is a novel technique to combine CO2 Huff-n-Puff technique that conducted at early state and followed by WAG technique until the end of operating time. This technique is effectiveness in term of increased oil recovery and reduced CO2 utilization. However, the integrated CO2 Huff-n-Puff and WAG process contains numerous adjustable operating parameters. Hence, numerical simulation study and sensitivity analysis become essential to investigate the effects of main operational parameters and evaluate the performance of the integrated CO2 Huff-n-Puff and WAG process in low-pressure heterogeneous reservoir to achieve the maximum benefits. According to simulation results, the highest sensitive parameter on oil recovery factor using CO2 Huff-n-Puff process is production time, followed by production rate. The lowest sensitivity is soaking time. Nevertheless, CO2 HCPV injection illustrates the highest sensitivity on CO2 consumption. In term of conducting integrated CO2 Huff-n-Puff and WAG, higher oil recovery factor with lower CO2 utilization can be obtained by injecting additional chasing water rate and extending CO2 Huff-n-Puff period. Last but not least, applying integrated CO2 Huff-n-Puff and WAG method has capability to extract up to 64% of OOIP beyond primary recovery. Finally, dominant EOR mechanisms of this technique are reservoir pressure maintenance, volumetric sweep efficiency improvement, and oil viscosity reduction.