Relative permeability is the the ratio of effective permeability to a base permeability such as the absolute permeability of the porous medium.
kro - relative permeability for oil phase;
krw - relative permeability for water phase;
krg - relative permeability for gas phase;
ko - effective permeability for gas phase;
kw - effective permeability for gas phase;
kg - effectivepermeability for gas phase;
k - absolute permeability.