Relative permeability has important implications for flow of reservoir fluids. A number of models have been developed to relate relative permeability to other reservoir properties. This page provides an overview of those models. In 1954, Corey combined predictions of a tube-bundle model with his empirical expression for capillary pressure to obtain expressions for gas and oil relative permeabilities. In 1964, Brooks and Corey extended Corey's results using Eq. 1 for capillary pressure to obtain the following expressions for oil and gas relative permeabilities: Eqs. 2 and 3 apply to a porous material that is initially fully saturated with oil and then invaded by gas.