Permeability of shale by the beam-bending method

The beam-bending method permits measurement of liquid permeability in the nanoDarcy range in a few minutes to a few hours. This technique has been applied successfully to determine the permeability, as well as the viscoelastic properties, of isotropic materials with low permeability, such as gels, porous glass, and cement paste. The method has been extended to measure transversely anisotropic materials, such as sedimentary rock, to find the permeability parallel and perpendicular to the bedding. In this study, measurements have been made on a set of shales from varying depths and locations in the continental United States. The measured permeabilities range 0.009–400 nanoDarcies (nD=10−21 m2). The permeability in the direction parallel to the bedding orientation was larger than that perpendicular to the bedding orientation, by a factor ranging from 1.2 to 6. This is the first instance of using the beam-bending method to measure the permeabilities of shale in different orientations.The measured permeabilities were compared to the Kozeny–Carman and Katz–Thompson models. The pore geometry parameters used in the models, such as the pore size distribution, characteristic pore diameters, porosity, and tortuosity were measured using mercury intrusion porosimetry (MIP), gravimetry, and electrical conductivity, respectively. The measured permeability values match better with the predictions from the Katz–Thompson equation.

► Permeability of shale measured using beam-bending method. ► Technique permits rapid measurement of anisotropic samples. ► Elastic modulus and viscoelastic stress relaxation function also obtained. ► NanoDarcy permeability reported for wide variety of shale types. ► Pore size distribution by MIP and tortuosity from electrical conductivity also found. ► Measured permeability shows order-of-magnitude agreement with Katz–Thompson model.