Experimental and simulation studies for optimization of water–alternating-gas (CO2) flooding for enhanced oil recovery

Abstract

The paper deals with the screening of injection of water-alternating-gas (WAG) to tap the residual oil saturation left in the reservoir by over and above the water flooding. The detailed mineralogical composition has been studied by X-ray diffraction (XRD) method along with the petrophysical parameters to see their impacts of flow on Himmatnagar (India) sandstone. Saturates, aromatics, resins, and asphaltenes present in the crude oil were determined by ASTM procedure. Minimum miscibility pressure of CO2 with the crude oil was determined and it has been found at 1254 psi based on thermodynamic software. Different WAG ratios of 1:1, 1.5:1 and 2:1 have been applied for EOR during studies. Simulation on water injection followed by CO2 has been performed for investigation of the WAG process efficiency. A total 2 cycles of WAG injection was done with water flow rate of 1 ml/min and gas injection pressure around 1250 psi to achieve the better contact miscibility. The experimental data has been generated, compiled and interpreted during different cycles of WAG process. It was observed that WAG ratio 2:1 exhibits highest additional oil recovery around 34% of original oil in place. Increasing WAG ratio yields more additional oil recovery.