Numerical modeling and analysis of induced thermal stress for a non-isothermal wellbore strengthening process

Abstract

Wellbore strengthening (WBS) methods are broadly applied in the field to combat lost circulation by plugging drilling induced fractures using wellbore strengthening materials (WSM). While changes in formation temperature during drilling have been identified as an important factor in wellbore stability considerations, the performance of WBS in a non-isothermal setting is unclear and remains as a barrier to successful designs of the types and sizes of WSMs. To understand the problem, a 3D finite element analysis was conducted to investigate the state of stresses in near-wellbore region from the interaction between induced thermal stresses and fractures based on different WBS plugging mechanisms. The model developed in this study coupled fluid and heat flow in fractured thermal-poroelastic rock formations and enabled flow restrictions in the fracture for simulating wellbore strengthening processes. By implementing different WBS mechanisms in the simulations, the induced thermal stresses from fluid leakage into the formations were analyzed, and the effectiveness of different WBS strategies in preventing fracture propagation under thermal effects was evaluated.The results disclosed how stresses redistribute around a fractured wellbore as non-isothermal mud invasion and WSM plugging take places. They show that temperature decreases of formation rock due to mud invasion can significantly facilitate fracture propagation and diminish the effectiveness of WBS. Such information is important to the successful management of lost circulation by taking thermal effects into consideration for better WSM design and WBS implementations.