Carbon dioxide - heavy oil systems: Thermodynamics, transport and interfacial stability

Conventional oil recovery leaves behind around 67% of original oil in place for light oils and all of it for heavy oils. The carbon dioxide flooding process is the cheapest among the recovery methods for the next stage. The interest here lies in recovering heavy oil. When CO2 dissolves in oil, it increases the volume of oil, squeezes it out of narrow capillaries and the viscosity of oil drops by up to an order of magnitude. Starting with the available data with and without CO2 in heavy oil, the free volume theory is used to predict these physical properties. Specific volume CO2 in the solution is obtained from the swelling data. The viscosity data show us how to obtain the free volumes of CO 2 in oil and hence allow prediction of the diffusivity of CO2. Separately, an analysis of the displacement process has been undertaken in a single cylindrical pore ~ 1 micrometer in diameter where the disjoining pressure is included and added to the Laplace pressure, besides the correlations obtained earlier. Numerical solutions have been obtained to provide the results: profile shapes, capillary numbers, and the thickness of thin oil film left behind the drive and net mass transfer rates across the interface. Finally, the viscosity of heavy crude is much higher than the viscosity of CO 2 because of which the displacement process can be unstable leading to fingering or channeling. Linear stability analysis of the displacement process which is that of immiscible displacement but includes mass transfer has been investigated. We are able to provide results that lead to a stabilizing effect overcomes a large destabilizing effect of the adverse mobility ratio. The results show that in the limit that the solubility of CO2 in oil drops to zero, the above window of instability becomes infinite.