A modified percolation approach to simulating three-fluid capillary pressure-saturation relationships

A computational model was developed for simulating capillary pressure-saturation relationships for porous media systems containing two or three mobile fluids. The model is based on describing fluid displacement on a pore-by-pore basis over a large number of pores to produce bulk saturations in the medium. The computational approach utilizes percolation and network theories to describe fluid movement within the pore space. Percolation theory calls for a set of displacement rules to determine the movement of the fluids under capillary-driven transport. A comprehensive set of rules appropriate for either two-fluid or three-fluid systems is described. These rules account for a variety of processes affecting displacement, such as wetting films, hysteresis, trapping of fluids, and gravity. The model is shown to reproduce the basic characteristics of a two-fluid capillary pressure-saturation curve, and model predictions are shown to agree with both two- and three-fluid experimental data.