3-FLUID RETENTION IN POROUS-MEDIA INVOLVING WATER, PCE AND AIR

A classical way to obtain three-fluid retention curves in porous media from measured two-fluid retention curves is based on the Leverett con cept, which states that the total volumetric liquid content in a water -wet porous medium, containing water, a nonaqueous-phase liquid (NAPL) and air, is a function of the capillary pressure across the interface between the continuous NAPL and air. This functional relationship res ults from the assumed condition that in a three-fluid porous medium, t he intermediate wetting fluid spreads over the water-air interface. Ap plication of Leverett's concept may not be valid, however, for nonspre ading NAPLs Like perchloroethylene (PCE). This paper discusses measure ments of both PCE-air and water-PCE-air retention curves using a long vertical column in conjunction with a dual-energy gamma radiation syst em. The data indicate that the Leverett concept was applicable only un til a critical PCE saturation had been reached. (C) 1997 Elsevier Scie nce B.V.