Capillary-pressure saturation relation derived from the pore morphology method.

A computationally efficient method to calculate the capillary pressure-saturation relations of immiscible multiphase flow on two-dimensional pore morphologies is presented. The method is an extension of the porous morphology method that includes the wetting angle and trapped mechanism of the displaced fluid, and calculation of material properties using density functional theory. After the method was validated with microchip fluid injection experiments, it was used to relate pore morphology to the capillary pressure-saturation relation using square-lattice pore morphologies. Because the method uses only morphological binary operations, it is more efficient than well-established high-resolution voxel dynamics methods such as lattice-Boltzmann methods and level-set computational fluid dynamics. Apart from pore morphology, only the material parameters related to the contact angle (wettability) and interfacial tension are required to connect the pore-saturation relation and pore throat distribution. We investigate the effects of interfacial tension, wettability, sample size, and pore throat distribution on entry pressure and residual saturation.