On Values Characterizing the Degree of Elastic Anisotropy of Transversely Isotropic Rocks; Role of Shear Modulus

Resumo

The influence of the elastic constants of transversely isotropic rocks on the stress concentration values on the well contour is studied. It is shown that in the case of a uniform component initial stress state, the main parameter characterizing the deviation of the stress concentration on the well contour from the concentration characteristic of an isotropic body is the ratio of the independent shear modulus in the plane normal to the isotropy plane to the shear modulus characteristic of one of the subclasses transversally isotropic medium isolated by Saint-Venant, which is a combination of other elastic constants. With this ratio equal to one, stress concentrations for isotropic and anisotropic medium coincide. The well-known fact that this relationship is close to one for most transversely isotropic rocks allows us to use, to a first approximation, an elastic solution for an isotropic body. It is shown that the closeness to one of relation of the ratio of independent shear modulus to combinations of other elastic constants characteristic of other subclasses identified by Saint-Venant is also observed for most rocks, although with slightly less accuracy.