A New Model for Two Phase Multicomponent Displacements Honouring Ganglia and Droplets

Abstract

Abstract During two-phase flow through porous media, a non-wetting phase may be present simultaneously as a continuous phase and as trapped isolated ganglia. Mass exchange between these two parts of the non-wetting phase is going on by dissolution and diffusion of components through the wetting phase, the compositions of the non-wetting phase in both parts being different. Nevertheless, the traditional mathematical model for two-phase multicomponent transport through porous media assumes that the distribution of all components in the overall non-wetting phase is homogeneous. This paper derives a new set of equations governing two-phase, three-component flow through permeable media that honours the isolated nature of a trapped residual phase. The solutions of these equations compare favourably to the results of laboratory tests. An analytic solution of the equations of the displacement of oil and water by the mixture ‘water-miscible gas’ (water-alternating-gas process) shows that a significant amount of oil remains after a miscible displacement. This observation is in contrast to the ‘traditional’ fractional flow model that predicts complete recovery of oil from the portions of the medium swept by the solvent.