An Investigation of Saturation‐Capillary Pressure Relations in Two‐ and Three‐Fluid Systems for Several NAPLS in Different Porous Media

Abstract

AbstractLack 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®, 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®, 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.