Numerical Simulation of Foam Transport in Porous Media.

Amendment solutions with or without surfactants have been used to remove contaminants from soil. However, they have drawbacks in that amendment solutions often mobilize the plume, and its movement is controlled by gravity and preferential flow paths. Foam is an emulsion-like, two-phase system in which gas cells are dispersed in a liquid and separated by thin liquid films called lamellae. The potential advantages of using foams in sub-surface remediation include providing better control on the volume of fluids injected, uniformity of contact, and the ability to contain the migration of contaminant-laden liquids. The transport of foam in porous media is complicated in that the number of lamellae present governs flow characteristics such as viscosity, relative permeability, fluid distribution, and interactions between fluids. Three major approaches to modeling foam transport in porous media are the analytical fractional flow method, the empirical and mechanistic numerical methods. Mechanistic approaches can be complete in principle but may be difficult for obtaining reliable parameters, whereas empirical approaches can be limited by the detail used to describe foam rheology and mobility. Mechanistic approaches include the bubble population-balance model, the network/percolation theory, the catastrophe theory, and the filtration theory.  All these methods were developed for modeling polyhedral foam, with the exception that the filtration theory method was developed for modeling ball foam (microfoam).