Investigation of the Poromechanical Behavior of Shales in the Elastic Domain

Abstract

Abstract In order to study the poroelastic behavior of shales, a set of experiments have been performed in an uniaxial strain setup. The shales were cored at a depth about 450m. Assuming Biot's poroelastic theory, the Biot coefficient was determined in a uniaxial strain loading system. At several steps of the mechanical loading in the plastic domain, the poroelastic properties are determined, A particular attention is paid to the evaluation of the Biot tensor by combining the results of 2 different mechanical unloadings. One consists in decreasing the total stress, the other consists in increasing the pore pressure, Since the shales are anisotropic rocks, measurements have been performed on samples cored perpendicular to the bedding plane or parallel to the bedding plane. Three different rock samples have been tested and measurements have been performed in both directions, The Biot coefficient is shown to change while loading is increased, on the other hand no significant difference is observed as a function of the orientation with regard to the bedding plane. P. 515