Two‐phase flow in heterogeneous porous media: 2. Model application

The migration of a dense, nonaqueous phase liquid through heterogeneous porous media is examined using numerical simulation. Laboratory measurements of capillary pressure‐saturation curves were performed on samples obtained from a sand aquifer and scaled to permeability to provide a data base of model input parameters. Numerical simulations incorporating 25,200 finite difference cells are carried out in a spatially correlated, random permeability field to illustrate the influence of fluid properties on the migration of a nonwetting liquid below the water table. The simulation results are characterized by spatial moments to reflect the relative degrees of lateral spreading exhibited by the migrating nonwetting body in the presence of lenses of differing permeability. In addition, numerical simulations were performed in a solution domain containing a single lens of lower permeability material in order to examine the local‐scale sensitivity to porous media and fluid properties. The results of the study show the migration of a nonwetting liquid to be extremely sensitive to subtle variations in the capillary properties of the porous medium and to be influenced strongly by the fluid physical properties.