Critical Gas Saturations : the lowest gas saturation in the reservoir rock at which gas will flow. When the gas saturation is less than the critical value, the permeability to gas is zero. (RP 44)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}