Simulation study on the effect of gravity ratio on viscous fingering and gravity segregation in water-alternate-gas process

Abstract

The recovery of residual oil using Carbon Dioxide (CO2) flooding has received great attention over worldwide to maintain and prolong oil supply. The major problem in applying this process is to control the mobility of CO2 due to its low viscosity as compared to oil. Therefore, water is suggested to be injected alternately with gas to overcome the mobility problem. The use of Water Alternate Gas (WAG) is simulated using ECLIPSE software to validate the experimental result on the effect of Viscous Gravity Ratio (VGR), which is the ratio of horizontal force to vertical force on gravity segregation and viscous fingering. The study also looks into effect of different perforation injection strategy on ultimate oil recovery. The simulation results agree with experimental result by Nguyen (2000) where the viscous fingering is significant in high VGR value while the gravity segregation is significant at low VGR value. The ultimate oil recovery is found increase with VGR value increase, where at VGR 4.5, 33 and 300, the ultimate recovery is 41.4%, 77.9% and 80.5%. With different perforation injection strategy, ultimate oil recovery is found to be highest when water injection is at top and gas injection is at bottom, and at high VGR, where the ultimate recovery is 83.8% at VGR 300.