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基于多孔介质连续力学,考虑各向异性页岩的热流固耦合作用,建立了各向异性多孔介质孔隙热弹性力学基本方程和页岩地层井眼稳定分析数学模型,采用MATLAB软件编制了数值求解程序,分析了流固耦合、热固耦合、热流固耦合三种不同耦合模式下井周孔隙压力、地层温度、应力分布和井眼稳定性随时间变化的特征。结果表明:数值解与解析解计算结果吻合较好(误差仅0.028%),实例井井眼扩径率计算结果与实际情况基本吻合,验证了本文模型和方法的正确性;温度和孔隙压力的改变对井周应力分布影响较大,地层温度降低、井内压力增加有利于井眼稳定,孔隙压力升高不利于井眼稳定;页岩地层井眼稳定性具有显著的时变效应,随着钻开地层时间的增加,井眼不稳定区域和井眼扩径率逐级变大。孔隙热弹性力学分析方法可用于分析不同时间的井眼失稳规律,可为解决页岩井眼失稳问题提供更加科学的计算手段和方法。
Based on the continuum mechanics of porous media and considering the thermo-fluid-solid coupling of anisotropic shale, the basic equations of thermal elasticity of porous media in anisotropic porous media and the mathematical model of wellbore stability analysis in shale stratum are established. The numerical solution program The characteristics of wellbore pore pressure, formation temperature, stress distribution and borehole stability with time under different coupling modes of fluid-solid coupling, thermomechanical coupling and thermo-fluid-solid coupling were analyzed. The results show that the calculated results are in good agreement with the analytic solution (the error is only 0.028%). The calculated results of the well diameter expansion of the practical well coincide well with the actual situation, which verifies the correctness of the model and the method. The temperature and pore pressure The change has a great influence on the wellbore stress distribution, the temperature of the formation decreases, and the increase of the pressure in the well is beneficial to the wellbore stability. The increase of the pore pressure is not conducive to the wellbore stability. The wellbore stability of the shale formation has a significant time-varying effect. With the increase of formation time, borehole instability and borehole expansion rate gradually increase. Pore thermo-mechanical analysis method can be used to analyze wellbore instability at different times and provide more scientific calculation methods and methods for solving the instability of shale borehole.