## Model for Residual Saturations and Capillary Imbibition and Drainage Pressures

A pore saturation model expresses the capillary pressure as a function of a characteristic pore pressure and the wetting phase saturation. Singularity analyses of the total energies of the wetting and nonwetting phases give the residual saturations for the two phases. The total energy consists of a potential term and a work term associated with the effective pressure gradient for each phase. The derived residual wetting saturation is 0.236, and the derived residual nonwetting saturation is 0.884. The model includes separate pressures for imbibition and drainage to account for capillary hysteresis. In the model, the pressure gradient for the wettingmore »