STUDY ON SHALE WELLBORE STABILITY BASED ON THERMO-HYDRO-MECHANICAL COUPLING

摘要

In the whole process of oil drilling, the influence of temperature is always present. Heat conduction between the formation and drilling fluid changes the effective stress and pore pressure in wall rock, and affects wellbore stability. The experiment of shale thermo-hydro-mechanical coupling is too difficult to achieve, so the methods of theoretical analysis and numerical simulation is implemented in this paper. According to the theory of mixtures, the mathematical model of thermo-hydro-mechanical coupling is deduced. Then, the multi-fields coupled analysis program is written by software FORTRAN and calculated by ABAQUS. Using this method, the thermo-hydro-mechanical coupled numerical simulation of wellbore stability in shale is achieved, which obtains the variation of temperature, seepage and stress in wall rock. Based on the simulation results, the influence of temperature on wellbore stability is discussed by define collapse coefficient and fracture coefficient. This paper has some guiding significance for drilling design of ultra-deep high temperature wells.