This study will provide a physically-based description of the mass transfer process in multi-fluid porous media. By developing a pore-scale miscible transport model and coupling it with existing pore-scale models for fluid-fluid displacement, a complete and self-consistent mathematical description of capillary displacement, fluid motion, interphase mass transfer, and miscible contaminant transport will be obtained. With this model, mass transfer coefficients will be predicted as functions of interfacial areas, which will be directly related to fluid saturations. comparison of model results to a number of reported laboratory experiments involving non-aqueous phase liquid (NAPL) dissolution will be used to validate the model. Correlations between predicted mass transfer coefficients and capillary pressure-saturation-relative permeability relations will be explored. The model will be used to investigate the functional dependence between dispersivities and fluid saturations, including examination of possible hysteresis. Finally, the influence of material heterogeneity will be explored, with an emphasis on determination of effective mass transfer coefficients and macrodispersivities. The practical utility of the results will be demonstrated by coupling the continuum-scale transport properties predicted by the pore-scale models to more traditional continuum-scale multi-phase simulators.
