Abstract: A mechanical model was built for stress distribution across a horizontal well in shale.Analytical solutions to the model were developed and used to study the distribution and the impacts of mechanical properties,including Young's modulus and Poisson's ratio,on the fracture initiation pressure and fracture initiation angle.The results show that the degree of anisotropy in material coefficients strongly affects the effective stresses around the borehole and enhances the potential for borehole failure,and that Poisson ratio anisotropy does not affect significantly the fracturing pressure and angle for low anisotropy ratios,but it affects the effect of anisotropy in elastic modulus.

Key words: shale reservoir, horizontal well, well stress, the anisotropic, safety window, bedding