A value of oil saturation  below which oil is not getting swept by gas:

k_{rog} (s_o < s_{rog}) =0

It usually depends on  absolute permeability  as:

s_{org} = s_{org,0} \cdot \left( 1 + k_a/k_{a,sorg} \right)^{-n_{sorg}} 

See also

Physics /  Fluid Dynamics / Percolation

Petroleum Industry / Upstream / Subsurface E&P Disciplines / Field Study & Modelling 

[ Petrophysics ] [ Basic reservoir properties ] [ Wettability ] [ Permeability ] [ Absolute permeability ]  [Relative permeability]  [ Oil permeability ] [ Oil relative permeability ] [ Oil-gas relative permeability (krog) ]