Physics of Desaturation in Porous Materials

Previous investigations of the hydraulic properties of porous materials have been primarily empirical, i.e., correlations have been based upon experimental data. A physical description of the desaturation process in porous media is developed by analyzing both discrete and continuous desaturation mechanisms. The desaturation process is characterized by three distinct phases: the boundary-effect zone, the transition zone (primary and secondary), and the residual desaturation zone. Mathematical relationships are developed to related saturation to capillary pressure and to entry pressure which corresponds to a characteristic dimension of the medium.