MEASUREMENT AND MODELING OF 3-PHASE SATURATION PRESSURE HYSTERESIS

A published hysteretic saturation-pressure (S-P) model, which predicts fluid distributions before and after subsurface contamination by a nonaqueous phase liquid (NAPL), is tested. To accomplish this, two-phase air-water and three-phase air-NAPL-water S-P measurements are conducted in two dissimilar porous media using a specially designed apparatus. Experimental boundary conditions are imposed to investigate hysteretic S-P scanning path behavior. Analysis of the data shows that fluid contents are not a unique function of capillary pressures; they are also a function of saturation path history (i.e. history-dependent movement of fluid interfaces through porous media). Close agreement is found between the experimental measurements and those calculated when the model was calibrated to the data. These results suggest that employing nonhysteretic S-P relations in computer codes to predict subsurface fluid distributions are likely to be inaccurate. In this paper the first version of the S-P model and a later amendment are outlined and consolidated.