Three-dimensional poromechanical back analysis of the pulse test accounting for transverse isotropy: Fid-Bau Portal

Three-dimensional poromechanical back analysis of the pulse test accounting for transverse isotropy

Giot, Richard / Giraud, Albert / Guillon, Théophile / Auvray, Christophe

Abstract The pulse test is usually considered as an efficient test for measuring the permeability of weakly permeable porous media. It is generally interpreted by comparison of experimental and theoretical curves obtained by a simplified 1D analytical solution. In a previous work, we proposed an improvement for test interpretation, through fully coupled numerical modeling in 2D axisymmetric configurations. The numerical modeling took into account the poromechanical coupling and exhibited 2D effects that cannot be assessed with classical interpretation. The modeling was coupled with an inverse method permitting the assessment of intrinsic permeability, mechanical parameters such as Young’s modulus, and poromechanical coupling parameters such as Biot coefficient. The interpretation of the tests on argillites showed anisotropy of the material and revealed the fundamental importance of this anisotropy for further works. The present paper aims at taking into account the transverse isotropy of the rock samples in the poromechanical back analysis of the test. A transverse isotropic poroelastic constitutive law has been developed and implemented in Code_Aster (Edf), and 3D modeling is required to account for all possible orientations of the samples. The poromechanical modeling is still coupled with an inverse method, also implemented in the finite element code. The method was applied to laboratory tests on Meuse/Haute-Marne argillites, on cylindrical samples with axis either parallel or perpendicular to the isotropy planes, and the results were compared with isotropic interpretation. The 3D transverse isotropic modeling provides more consistent values of the parameters than the 2D modeling, particularly for the mechanical parameters.