Mixed wettability: a numerical study of the consequences of porous media morphology

Four types of 2-D numerical networks have been used as models of porous media, in order to derive capillary pressure curves in the case of two immiscible fluids competing for the possession of the porous space under mixed-wetting conditions. The porous networks were constructed using a variation of the dual site bond model (DSBM) framework, which allows a substrate to have an adequate geometrical and topological distribution of its pore elements. For the same pore-size distribution, the DSBM can provide simulated porous media of different topological structures. Just taking into account thermodynamics aspects, it is possible to calculate some wetting indices for the special case involving spontaneous water imbibition, forced water drive, oil imbibition, and forced oil drive within each one of the above topologically different substrata, i.e. the main flooding sequences characteristic of wettability experiments have been studied in a variety of porous media. In this work, Amott–Harvey and US Bureau of Mines wetting indices are calculated from simulated capillary pressure curves describing the water–oil and oil–water immiscible displacements occurring in these topologically different porous structures.