ABSTRACT
A system of equations for miscible displacement in porous media was constructed by considering the limiting case of immiscible flow with zero surface tension. Yang et al. demonstrated that for miscible displacement the megascopic pressure difference between phases must be non-zero due to the effect of an average pressure drop between the displacing and displaced phases. The approach is based on the equilibrium thermodynamics of molecular mixtures, which does not apply to porous media. E. J. Koval noted that L. Handy, in some unreported experiments using radioactive tracers in miscible fluids, found that a given solvent saturation moved at constant speed. The equations of two-phase miscible flow with negligible molecular diffusion were derived from the equations of two-phase immiscible flowin the limit of zero interfacial tension. The dispersion that arises from the theory constructed here permits predictions of several features that arise in miscible displacement experiments.
