Relative permeability

In multiphase flow in porous media, the relative permeability of a phase is a dimensionless measure of the effective permeability of that phase. It is the ratio of the effective permeability of that phase to the absolute permeability. It can be viewed as an adaptation of Darcy's law to multiphase flow.

For two-phase flow in porous media given steady-state conditions, we can write

where ${\displaystyle q_{i}}$ is the flux, ${\displaystyle \nabla P_{i}}$ is the pressure drop, ${\displaystyle \mu _{i}}$ is the viscosity. The subscript ${\displaystyle i}$ indicates that the parameters are for phase ${\displaystyle i}$.

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