Modelling of the Stability of Highly Inclined Boreholes in Anisotropic Rock Formations

Abstract

Simulators have been developed to study fracture and collapse behavior around boreholes. To take into account the directional properties of real rocks, an anisotropic stress model is used. In addition to take into account anisotropic elastic properties, directional shear and tensile strengths are also included. The orientation of the borehole, the in-situ stresses and the bedding plane can all be arbitrarely oriented relative to each other to model field situations. This paper presents some of the results of this model. It is shown that by neglecting the anisotropic effects, an error is introduced. Also, by studying the anisotropic model, further insight into the behavior of the borehole is gained.