Thermoporoelastic Effect on Shale Stability

摘要

This paper presents the consistency of thermal effects, i.e., the thermal-induced pore pressure and rock stresses, between two available models for inclined boreholes. Thermal effects for both a permeable and an impermeable boundary are studied. The solutions of pore pressure and stresses are provided and the singularity is removed in the solutions for the condition of hydraulic diffusivity being equal to thermal diffusivity. The analytical solutions in Laplace domain and in the real-time domain are verified using the finite-difference solutions. The collapse failure index and critical mud weights, as well as thermally-induced pore pressure, are presented and analyzed under the circumstance of heating and cooling the wellbore. Results show that heating the wellbore can destabilize the near-wellbore region by raising both the collapse and the fracturing mud weight. The model presented in this paper can be applicable to deep-water drilling where a narrow mud weight window often occurs.