Fundamentals of Fluid Flow in Porous Media
Three Phase Relative Permeability: Drainage and Imbibition Relative Permeabilities
Many people believe that in strongly wetted systems, the relative permeability of the wetting phase is usually a function of its own saturation, which means that it is not a function of saturation history. Anderson reported that the wetting phase relative permeability is very similar for both two and three-phase in strongly wetted systems at a specific wetting phase saturation. This implies that the wetting phase distribution in two-phase is very much similar to the one in three-phase systems. Therefore the hysteresis between the drainage and imbibition of the wetting phase is very small. In three-phase systems, many people assumed that gas is almost always a nonwetting phase.
There were other experiments, which show that there was hysteresis for the wetting phase in both water wet system and oil wet system. It is possible that for the cases where hysteresis was seen in the relative permeability of the wetting phase, the medium was not strongly wet. In general, the majority of the results show that there is little or no relative permeability hysteresis in the wetting phase.
Most of the results that show significant hysteresis in the wetting phase relative permeability were obtained from unsteady state methods. Craig and others believe that there are problems with the unsteady state relative permeability measurement in strongly wetting systems