LAUSR

Abstract One of the most important problems encountered during drilling operation is lost circulation through the natural/induced fractures, which increases the operational time and costs. Wellbore strengthening (WBS) by plugging the fractures using lost control materials (LCM) is an effective strategy to overcome this problem. Various analytical studies have been previously conducted to model this process. Although the formation pore pressure and its temperature variations have been identified as influential factors in wellbore stability evaluations, in the majority of previous models, the effect of temperature and poroelastic properties have not been taken into account. In this paper, a thermo-poroelastic analytical model has been presented based on fracture mechanics to add the stresses resulting from the changes in pore pressure and fluid temperature to the previously analytical elastic equations. According to the obtained results, wellbore cooling due to the circulation of drilling fluid with a temperature less than the formation temperature produces tensile stresses around the wellbore and increases the probability of the growth of pre-existing fractures or initiation of new ones. On the other hand, considering the effect of formation pore pressure can significantly reduce the stress intensity factor (SIF) level at the fracture tip. Comparison of the outputs of the thermo-poroelastic model with those of the elastic ones shows that ignoring the impacts of temperature and pore pressure during modeling can result in parameter underestimation or overestimation. In addition, the results of a comprehensive sensitivity analysis indicate that geomechanical parameters (in situ stress anisotropy, Young's modulus, and Poisson's ratio), geometrical parameters (location of LCM plug and fracture length), and poroelastic parameters (Biot's coefficient) considerably affect the success of WBS approach and the final fracture pressure.