FRACTAL APPLICATIONS - WETTABILITY AND CONTACT-ANGLE

A theromodynamic expression is derived fro the equilibrium contact angle on fractal surfaces in which the welted surface area is a function of the contacting fluid. The correlation for fractal surfaces can be decomposed into an areal contribution analogous to Wenzel's roughness ratio, which alway enhances the natural wettability characteristics of the material, and a wettability alteration factor due to fluid adsorbate size differences. Reported fractal properties of reservoir materials suggest that for most fluid pairs, such porous media will appear perfectly wetted by one of the fluids. Fractional and mixed wettability states are not prohibited by the theory but exist as combinations of perfectly wetting and perfectly nonwetting domains. © 1990.