An analytical approach to the stress distribution around a cased borehole in an anisotropic formation

Abstract

We present an explicit analytical approach for calculating the distribution of stress around a circular cased borehole in a discontinuous anisotropic formation. The borehole model is built on a pure elastic model with the assumption of the generalized plane strain, in which casing and cement rings are assumed to be isotropic, while formation is anisotropic. Also the borehole model is subject to arbitrary far-field stress, whose inner boundary between cement and formation is nonwelded. The accuracy and robustness of the approach is validated through comparing its results with those calculated from the existing classical solution, such as the Amadei solution for an isotropic example and the solution for an anisotropic cased borehole example based on the welded contact. The numerical examples show that within a certain range of the contact compliance, the formation's stress changes obviously.