This paper presents a wellbore stability design code that can be used to optimally drill, complete and stimulate inclined wells. The design code was developed for the most general case where the borehole, in-situ stress, and rock property coordinate frames are totally independent of each other. It essentially consists of a three-dimensional linear elastic stress analysis in anisotropic formations. Although this particular paper is only limited to tensile failure, based on the minimum normal stress theory, the numerical model is also able to consider shear failure by involving a generalized three-dimensional anisotropic yield criterion. The design code enables the selection of the most optimum borehole orientation and wellbore fluid gradient to avoid fracture initiation. It is also useful in conducting sensitivity studies, particularly when the data is scanty. A remarkable finding by exercising such code was that fracture initiation is strongly dependent on the formation anisotropy; a contradiction to the current industry thinking.

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