Effects of Clay‐Solution Interactions on Water Retention

Capillary pressure‐saturation data were measured on unconsolidated porous media containing 40% montmorillonite, as a function of total electrolyte concentration and sodium adsorption ratio (SAR) of the wetting fluid. Data were also obtained with a nonpolar wetting fluid. The Su‐Brooks retention function was fit to the experimental data; the average R2 for all treatments was 0.9967. The liquid retention curves were scaled to account for differences in properties of the wetting fluids. The change in scaled liquid retention curves due to changes in solution concentration and SAR followed a pattern reported by earlier investigators, except at high solution concentrations. There were significant clay‐solution interactions affecting retention of solution at high electrolyte concentrations. Previous researchers assumed that at high solution concentrations clays did not swell sufficiently to affect hydraulic properties.