Analysing the effect of bedding plane orientation on the wellbore failure

The paper presents a theory of the “plane of weakness” modelling applied to a deviated borehole that penetrated through laminated shale containing numerous parallel weakness planes. The obtained results show that the strength envelope for anisotropic rock is characterised by a U-shaped reduction in strength for failure along the weakness plane, confining pressure from 20 MPa to 80 MPa whithout any change in the failure mechanism of the shale.