Suction-saturation and relative permeability functions are two essential constitutive relationships for solving problems in multiphase flow. A reliable and convenient experimental method is needed for the determination of these relationships for engineering applications where a large number of samples may have to be tested. An automated technique using flow pump has been previously developed for unsaturated flow. In this study, we extend this technique to a two-phase system containing water and a Non Aqueous Phase Liquid (NAPL). The automated flow pump technique provides complete control over the test conditions and is capable of detecting all the important elements of the suction-saturation curve in multiphase flow. In particular, it is capable of defining continuous drying and wetting curves, the point of NAPL occlusion, and the hysteretic behavior.

An inverse problem solution technique has been adopted to obtain the relative permeability function. Since the flow pump technique not only measures the suction-saturation curve but also records the response of a multiphase flow system, the measured suction response is used in conjunction with inverse modeling to obtain the relative permeability function. The inverse problem solution technique provides an independent solution for the determination of the relative permeability function while traditional methods use fitted parameters of the retention function to obtain the relative permeability function, empirically. This paper presents the experimental technique and analytical procedures used in this automated testing method for water-NAPL systems.