Absolute permeability is a rock property no matter what fluid is saturating the rock; it is strongly related to the pore size and the pore size distribution. Having said that, lab test measurements using any displacing fluid (liquids or gases) should yield the same absolute permeability value for the same rock sample. This holds true if the fluid being used during the test (liquid or gas) is non-reactive with the rock components; water for example is not usually used in lab tests since it might react with authigenic clays, changing the pore structure of the rock and thus yielding erroneous absolute perm values. For lab measurements, gases are preferred since they are not reactive with the rock minerals, however, gas-derived absolute perm values should be corrected for gas slippage (Klinkenberg correction).