CALCULATION OF TEMPERATURE EFFECTS ON WETTING COEFFICIENTS OF POROUS SOLIDS AND THEIR CAPILLARY-PRESSURE FUNCTIONS

We explored the notion that changes in wetting coefficients of porous solids contributed to the temperature sensitivities of capillary press ure functions (CPFs). A chemical-thermodynamic explanation for these c ontributions was developed. If the temperature sensitivities of CPFs w ere due to capillarity (i.e., due to temperature-induced changes in li quid-gas interfacial tensions or wetting coefficients), then for a giv en degree of saturation the ratios of capillary pressures to their tem perature derivatives should have been linear functions of thermodynami c temperature with slopes equal to 1. This indeed was the case for sam ples of both synthetic and natural porous media. Further, the estimate d intercepts of these linear functions indicated that changes with tem perature of these porous materials' wetting coefficients had pronounce d effects on temperature sensitivities of their CPFs. A simple model f or temperature effects on CPFs, which was derived from the linear rela tionship between temperature and the ratio of capillary pressure to it s temperature derivative, could be fitted precisely by nonlinear regre ssion to CPFs of two soils determined at four temperatures.