Theoretical prediction of poroelastic properties of argillaceous rocks from in situ specific storage coefficient

Abstract

An integrated and theoretical approach is proposed to determine poroelastic properties of isotropic or transversely isotropic argillaceous rocks from conventional mechanical and hydraulic field tests. It uses values of specific storage coefficient, “undrained” elastic parameters, and porosity. No special hydromechanical test is required. In the isotropic case, a simple binomial equation is derived, whereby the poroelastic properties can be rapidly obtained. An application to deep argillaceous formations has shown that calculated poroelastic property values are in satisfactory agreement with direct experimental measurements. In the transversely isotropic case, which is more representative of sedimentary rocks, the approach is generalized from a theoretical relationship between the specific storage coefficient and the anisotropic poroelastic properties. Nevertheless, in both cases, sensitivity analyses have shown that the method is very sensitive to input data, especially the specific storage coefficient and the “undrained” mechanical parameters, which have to be measured with accuracy.