Are existing three phase relative permeability models adequate in modeling heavy oil WAG processes?

Three-phase relative permeability for oil water and gas are very important input to the simulating of three phase flow processes in oil reservoirs. The existing models developed through the observation of recovery mechanisms in conventional oil, use both oil-water and oil-gas two phase relative permeability functions in generating three phase relative permeability functions. But given that the existing three phase relative permeability models were developed for conventional oil which has a different recovery mechanism from heavy oil, could they still be used in simulating three phase flow processes in heavy oil? This paper attempts to answer this question by examining the recovery mechanism in three phase flow processes in conventional oil vis-a-vis same process in heavy oil through micro-model experiments. A Water Alternate CO2 flood of a heavy oil sample in a core flood experiment was then simulated using the existing three phase relative permeability models. A comparison of the simulation and the core flood results shows that the existing three phase relative permeability models are inadequate in simulating three phase processes in heavy oil production. An alternative approach using an in-house three phase flow simulator was used in generating a three phase relative permeability curves was used. There is also a proposal of a new three phase relative permeability model for heavy oil. Experimental works have proved that the Water alternate Gas (WAG) flooding process is an effective enhanced oil recovery method for heavy oil production. The residual oil in a core/reservoir after a water flooding can be further reduced through a gas flooding or vice versa. A simulation of this process is very necessary for its optimization. Hence there is a need to have a robust three phase flow simulator for heavy oil.