Evaluation of fault reactivation risks during drilling of the horizontal well using results of one-dimensional geomechanical modeling

The article presents main factors affecting the fault stability. Concepts of critically stressed faults and critical pore pressure are discussed. The methodologies for evaluation of stressed-deformed state of rocks in the vicinity of fault zones during reservoir depletion and injection, well drilling are analyzed. 1D geomechanical models of fishbone sidetracks and main borehole of the well N are constructed. The fault stability evaluation is made using Mohr – Coulomb failurecriterion from data of insitustresses and near-wellborestressescalculated from Kirsch wellbore solution. Optimal mud weight ranges are determined for safe drilling of fishbone boreholes accounting fault reactivation risks. Basic recommendations for optimal drilling through the interval of unstable shales are made.