AN INVESTIGATION OF SATURATION-CAPILLARY PRESSURE RELATIONS IN 2-FLUID AND 3-FLUID SYSTEMS FOR SEVERAL NAPLS IN DIFFERENT POROUS-MEDIA

Lack of constitutive data has impeded efforts to model the subsurface transport of organic-liquid contaminants. To help fill this need, functional relationships between fluid saturations and capillary pressures were obtained using a unique fluid-retention cell. The functional relationships between water saturations and NAPL-water capillary pressures, and between total-liquid saturations and air-NAPL capillary presures in two- and three-fluid phase systems were measured directly during monotonic drainage of a fine quartz sand and a nonswelling loam soil. Additionally, measurements were made between water saturations and air-water capillary pressures for an air-water fluid system in both porous media. The NAPLs investigated were Soltrol 170(R), toluene, and trichloroethylene (TCE). Following the:measurements, the two- and three-fluid retention relations were compared to test the validity of extending two-phase saturation-pressure (S-P) relations to three-fluid systems. Good agreement was observed between the two- and three-fluid data for Soltrol 170(R), toluene, and TCE in both porous media. An S-P scaling format for two- and three-phase systems was also evaluated. Results indicate that a single multiphase retention function is suitable for describing two- and three-phase S-P relations in similar porous media; however, it is unclear whether the scaling factors can be predicted a priori from ratios of interfacial tensions.