Pore-scale simulations of drainage of heterogeneous and anisotropic porous media

A numerical model, based on smoothed particle hydrodynamics, was used to simulate pore-scale liquid and gas flow in synthetic two-dimensional porous media consisting of nonoverlapping grains. The model was used to study the effects of pore-scale heterogeneity and anisotropy on the relationship between the average saturation and the Bond number (strength of the gravitational field acting on fluid density differences relative to capillary forces). Pore-scale anisotropy was created by using co-oriented nonoverlapping elliptical grains, and heterogeneity was created by inserting a microfracture in the middle of the porous domain consisting of nonoverlapping circular grains. The effect of the wetting fluid properties on drainage was also investigated. It is shown that pore-scale heterogeneity and anisotropy can give rise to saturation/Bond number relationships and entry (bubbling) pressures that depend on the flow direction, suggesting that these properties should be described by tensor rather than scalar quantities.