ESTIMATING INTERFACIAL-AREAS FOR MULTI-FLUID SOIL SYSTEMS

Knowledge of the fluid-fluid and fluid-solid interfacial areas is impo rtant to better understand and quantify many flow and transport proces ses in porous media. This paper presents estimates for interfacial are as of porous media containing two or three fluids from measured capill ary pressure (P-c)-saturation (S) relations. The thermodynamic treatme nt of two-fluid P-c-S relations presented by Morrow (1970) served as t he basis for the predictions. In media containing two fluids (air-oil, air-water, oil-water), the solid-nonwetting interfacial area (A(sN)) equaled zero when the solid was completely wetted by the wetting flui d. The area under the P-c-S curve was directly proportional to the non wetting-wetting interfacial area (A(NW)). If the solid surface was no t completely wetted by one fluid, A(NW) and A(sN)* were estimated by weighed partitioning of the area under the P-c-S curve. For porous med ia with fractional wettability, the procedure was applied separately t o water- and oil-wet regions. The values of A(NW) and A(sN)* were hig hest and lowest, respectively, in systems that were strongly wetted. I n three-fluid media the wetting and spreading behavior of the liquids greatly affected the estimated interfacial areas. For a water-wet medi um with a continuous intermediate oil phase, the interfacial areas wer e predicted from P-c-S data in a similar manner as for two-fluid media . The oil-water and oil-solid interfacial areas were estimated from th e oil-water P-c-S curve, while the air-oil interfacial area was obtain ed from the air-oil P-c-S curve. For a fractional wettability or oil-w et medium there may be as many as six interfaces. These interfacial ar eas were estimated from three-fluid P-c-S relations based on previousl y developed methods for predicting three-fluid P-c-S relations from tw o-fluid data. (C) 1997 Elsevier Science B.V.