Porothermoelastic Response of a Borehole in Fluid-Saturated Medium Subjected to Thermal Osmosis Effect

Abstract

With the thermo-hydro-mechanical coupling process considered, this paper derives a set of analytical porothermoelastic solutions to field variables including the stress, displacement, and pore pressure fields to evaluate the wellbore stability around a vertical borehole drilled through an isotropic porous rock. The thermal effect on the wellbore stability of the low-permeability saturated rock also introduces the thermal osmosis term. The wellbore problem is decomposed into axisymmetric and deviatoric loading cases considering the borehole subjected to a nonhydrostatic stress field. It obtains the time-dependent distributions of field variables by performing the inversion technique for Laplace transforms to the porothermoelastic solutions in the Laplace domain. The results suggest that the thermal osmosis effect should not be neglected on the premise that a lower permeability porous rock is characterized by the substantially large thermal osmotic coefficient and the small thermal diffusivity values. The case that the thermal osmosis effect reduces the undrained loading effect leads to the decrease of the mean shear stress that is determined by the effective maximum and minimum stress around a borehole, since, and accordingly contributes to the wellbore stability to resist the shear failure.