Permeabilities of tight reservoir cores determined for gaseous and liquid CO2 and C2H6 using minimum backpressure method

Permeability is the most important parameter for characterizing fluid flow though porous media and determined experimentally using a gas or liquid. For most porous materials the values of permeability determined with gas and liquid are the same. For tight rocks, however, the permeability obtained with liquid is much lower than that with gas. Such difference has been ascribed to uncertainties involved in the measurement, including the inaccuracy of the gas permeability extrapolated from Klinkenberg correlation, or the effects of liquid polarity and fine particle movements on liquid permeability when the liquid is present. In this paper, we report a noticeable difference between the gas and liquid permeability determined after all the above uncertainties are excluded by using a novel-designed experiment. The results show that the permeability of the same fluid varies as its state changes from gas to liquid in low-permeability porous media. This indicates that the gas behaves differently from liquid of the same fluid in low-permeability porous media.