Simplified Mechanistic Simulation of Foam Processes in Porous Media

Summary The mechanisms controlling transport and mobility of foam in porous media are complex, but in some cases the mechanisms that dominate foam properties can be represented in simple models. For instance, fractional-flow methods can reproduce the predictions of more-complex foam simulators while highlighting the mechanisms controlling foam behavior. Fractional-flow methods indicate that the effectiveness of foam processes that alternate injection of liquid and gas ("SAG" processes) depends on foam strength at extremely high foam quality, conditions difficult to control in the laboratory. A numerical simulator that incorporates the relation between capillary pressure and foam stability extends simplified foam modeling to cases where fractional-flow methods do not apply. Applications of this simulator to one-dimensional (1D) foam displacements match predictions of analytical models based on laboratory data and illustrate the numerical artifacts that challenge foam simulation. Applications to 2D flow through layers in capillary contact show that the interplay between capillary crossflow and foam collapse depends on both the dimensions of the layers and the relative magnitudes of the capillary and viscous pressure differences.