A property characterising agility of the fluid -phase under pressure gradient with account of relative permeability and dynamic fluid viscosity:

M_{r\alpha}(s) = \frac{M}{k_{air}} = \frac{k_{r \alpha}}{\mu_\alpha}

where

	relative formation permeability to fluid -phase
	dynamic viscosity of fluid -phase
	phase mobility
	absolute permeability to air
	reservoir saturation

In most practical case of a 3-phase fluid model this will be:

See also