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

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

where

	total fluid mobility
	relative phase mobility of -phase
	absolute permeability to air
	reservoir saturation

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

M_{r}(s) = M_{r o}(s) + M_{r g}(s) + M_{r g}(s)

See also