A method for characterizing properties of a sample that employs a test apparatus including an isolated sample cell and pressure sensor where the isolated sample cell is loaded with the sample and gaseous test fluid to perform a number of different tests to derive properties of the sample. The tests can be performed over different parameters, such as different applied pressures of the test fluid to derive parameters related to apparent gas permeability of the sample as a function of applied pressure, different gaseous test fluids to characterize dependence of permeability of the sample on mean free molecular path or pressure, with both adsorptive and non-adsorptive test gases to characterize at least one property related to adsorptive interaction between the adsorptive test gas and the sample, and with samples of varying saturation levels to derive a measure of at least one property of the subsamples at corresponding saturation levels.