Simultaneous measurement of capillary pressure, saturation, and effective permeability of immiscible liquids in porous media

In many studies involving a liquid and air, the effective permeability of the wetting phase ( k w ) is determined from the capillary pressure ( P c )–saturation ( S ) relation and a corresponding, measured k w value. The movement, and therefore the effective permeability, k nw , of air in an air‐liquid system is often ignored, especially by those who consider only the flow of water in soils. However, if a wetting and a nonwetting liquid coexist (two immiscible liquids), the effective permeability function of the nonwetting liquid must be determined as well. Rather than using some indirect method to determine the k nw ( P c ) or k nw ( S ) relationship of the nonwetting liquid, we propose a direct measurement technique by using a permeameter which allows for steady state flow of the nonwetting liquid over a range of P c and S values. During each steady state flow condition of the nonwetting liquid, P c and S are constant and uniform throughout the permeameter, while the wetting liquid is at rest. The nonwetting liquid can either be a dense non–aqueous phase liquid (DNAPL) or a light non–aqueous phase liquid (LNAPL). The k nw values are calculated as a function of P c and S from the measured flow rates and the density difference between the wetting and nonwetting liquid. The proposed technique can be applied during drainage as well as imbibition. The S values are determined by recording the amount of water being displaced from the cell each time the P c is changed. Results are discussed for the DNAPL perchloroethylene (PCE) and the LNAPL Soltrol.