EFFECT OF SPREADING COEFFICIENT ON THE DISTRIBUTION OF LIGHT NONAQUEOUS PHASE LIQUID IN THE SUBSURFACE

We perform a series of three-phase gravity drainage experiments in col umns containing two different sands and for three different light non- aqueous phase liquids (LNAPLs) - hexane, iso-octane and n-decane. The fluid system is chosen to have different values of the equilibrium spr eading coefficient, which measures the tendency for LNAPL to spread on water. The final configuration of air, water and LNAPL in capillary/g ravity equilibrium is measured using gas chromatography. We find that the saturation of LNAPL in the top part of the column for the hexane s ystem could be as low as 0.1%, but that it increases with increasing s oil heterogeneity and with decreasing spreading coefficient. We also m easure the air/water distributions in capillary/gravity equilibrium to obtain the capillary pressure curve for each sand. Using a modified L everett J function scaling, we predict the distribution of continuous LNAPL, water and air from a single capillary pressure curve and compar e with our experimental results. The predictions match the measurement s in the regions where the NAPL saturation is greater than similar to 10%. (C) 1997 Elsevier Science B.V.