4. Wellbore Strengthening Models

This chapter presents theoretical models for the evaluation of wellbore strengthening based on plugging/bridging lost circulation fractures using LCMs. An analytical model and a finite-element numerical model are presented. The analytical model is developed based on linear elastic fracture mechanics. It can be used for a fast prediction of fracture pressure enhancement due to fracture bridging, considering near-wellbore stress concentration, in situ stress anisotropy, and different LCM bridge locations. It can also be used to perform quantitative parameter sensitivity analyses to illustrate the undying mechanisms of wellbore strengthening. However, the analytical model cannot provide detailed stress and displacement information local to the wellbore and fracture in wellbore strengthening treatments and it does not consider the porous nature of the formation. To this end, a poroelastic finite-element numerical model is also developed in this chapter. The finite-element model can be used to quantify near-wellbore stress and fracture geometry, before and after bridging fractures. Effects of various parameters are investigated through a comprehensive parametric study using the numerical model. Several useful implications for field applications are obtained based on the parametric study.