Abstract

This study investigates the impacts of rock anisotropy (mainly transverse isotropy, TI) on the near-wellbore stress distribution and the consequential creation of drilling induced tensile fractures (DITF). First, by utilizing an earlier analytical solution, a theoretical model has been successfully developed and implemented in conducting sensitivity studies. This model is applicable to any specific borehole orientation, rock anisotropy, and in-situ stress conditions. The results indicate that the TI medium can significantly influence the stress concentration around the wellbore, and consequently, affects the onset of borehole failure. Second, a tensile fracture tracing program has been coded based on the stress model coupled with Ong’s wellbore-stability design code. Parametric studies lead to the following findings: i) en echelon tensile fractures appear in asymmetrical pairs, ii) fracture trajectories depend on the formation anisotropy. Finally, this model can help constrain in-situ states of stress incorporating with the DITF observed in image logs.

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