A Single Pore Model for Displacement of Heavy Crude Oil With Carbon Dioxide

Abstract

Summary The present problem analyzes displacement of heavy crude oil in a capillary by carbon dioxide (CO2) as seen in enhanced oil recovery (EOR). In immiscible displacement of viscous liquid in a tube by a gas with lower viscosity than the liquid, a gas bubble moves steadily and leaves behind a thin liquid film of thickness h∞ which is known as the Bretherton problem. With the recovery of crude oil in mind, the analysis was confined to cylindrical pores of diameter ≈1 µm, and hence disjoining pressures are included and added to the Laplace pressures. It is observed that, at small capillary numbers, the effect of disjoining pressure dominates, and at large capillary numbers, the Laplace pressure dominates. The key contribution here is the solutions to the mass-transfer problem in the form of CO2 dissolving in oil. We included the changes of the physical properties of heavy crude oil on carbonation on the basis of a real system. The thickness of thin residual oil film decreases in the presence of mass transfer, leading to an increase in oil recovery, but lowers the carbonation because of the convection in the reverse direction. The opposite is true of displacements at low capillary numbers in which the disjoining pressure dominates. The numerical solutions were obtained with ANSYS® FLUENT software for the profile shapes, capillary numbers, the thicknesses of thin oil films left behind, and the net mass-transfer rates. The capillary pressure dominates the net pressure drop that one can lower by lowering the surface tension.