A property characterising agility of the fluid $\begin{array}{l}\alpha\end{array}$ -phase under pressure gradient with account of relative permeability and dynamic fluid viscosity:

(1)	$\begin{array}{l}\displaystyle M_{r\alpha}(s) = \frac{M}{k_{air}} = \frac{k_{r \alpha}}{\mu_\alpha}\end{array}$

where

$\begin{array}{l}\displaystyle k_{r\alpha}(s)\end{array}$	relative formation permeability to fluid $\begin{array}{l}\alpha\end{array}$ -phase
$\begin{array}{l}\displaystyle \mu_\alpha\end{array}$	dynamic viscosity of fluid $\begin{array}{l}\alpha\end{array}$ -phase
$\begin{array}{l}M\end{array}$	phase mobility
$\begin{array}{l}k_{air}\end{array}$	absolute permeability to air
$\begin{array}{l}s = \{ s_{\alpha}\}\end{array}$	reservoir saturation $\begin{array}{l}\sum_\alpha s_{\alpha} = 1\end{array}$

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

$\begin{array}{l}s = \{ s_w, \, s_o, \, s_g \}\end{array}$	$\begin{array}{l}s_w + s_o + s_g =1\end{array}$
$\begin{array}{l}\displaystyle M_{ro} = \frac{k_{ro}}{\mu_o}\end{array}$	relative oil mobility
$\begin{array}{l}\displaystyle M_{rg} = \frac{k_{rg}}{\mu_g}\end{array}$	relative gas mobility
$\begin{array}{l}\displaystyle M_{rw} = \frac{k_{rw}}{\mu_w}\end{array}$	relative water mobility

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See also