This research justifies the improvement of the oil recovery by using the water alternating CO2 flooding method for the right candidates, also indicates the importance of considering relative permeability hysteresis effects in WAG numerical simulations.
Good reservoir candidates for water alternating CO2 injection have been prepared in this study considering different wettability characteristics (oil-wet and water-wet) and different oil viscosities. In addition, some simulations have been performed on the models with severe permeability distribution in their layers.
First, it was shown that CO2-WAG (water alternating gas) results in much higher oil production in all the simulations compared to water flooding or CO2 flooding.
Then CO2-WAG simulations were conducted with and without considering the relative permeability hysteresis effects. It was concluded that the models with the hysteresis effects have higher oil production for different scenarios of oil viscosity and reservoir wettability.
Moreover, including hysteresis effects has bigger impacts on the oil production in the cases of low viscosity oil and a severe permeability reservoir.
Finally, water flooding and CO2 flooding worked differently with respect to the rock and fluid properties such as reservoir permeability distribution and oil viscosity.