A new measurement method for radial permeability and porosity of shale

Abstract

To more conveniently and accurately obtain the radial permeability of shale, a new measurement method was proposed for the pressure attenuation of radial permeability and porosity in shale. Through experiments, this method could be used to get the pressure attenuation curve in annular space between the core and inner wall of PVT vessel under the helium along shale radial flow. Accordingly, a mathematical model was established to obtain the semi-analytical solution between pressure and time in the radial model. Meanwhile, through fitting the experimental results, the concentration conductivity and porosity of shale were obtained, and their relationship was used to derive the radial permeability of shale. This method was adopted to measure the permeability and porosity of two cores under three sets of different initial pressures in the annular space. The permeability test results were compared with those obtained by the conventional Dicker method and Smits pressure-attenuation method, and the porosity test results were also compared with those obtained by the conventional porosimeter, thus the feasibility and superiority of this method were confirmed. In contrast to the conventional pressure-attenuation methods, this new model had advantages of simpler instruments and more convenient operation, and was also easy to measure the radial permeability and porosity of shale. Keywords: Radial permeability and porosity, Pressure attenuation, Annular space, Concentration conductivity coefficient, Shale