Abstract The success rate of wellbore strengthening is relatively low in shales. Thus, a multi-field coupling wellbore strengthening model was developed by introducing the fully coupled thermo-chemo-poroelastic theory into wellbore strengthening physical model and the fracture element was added to study the closure process of isolated fracture in shales. The thermal and chemical effects were researched by observing the change of hoop stress and fracture aperture. Results show that thermal factor is crucial to wellbore strengthening. The preliminary treatment of wellbore strengthening is mainly controlled by adjusting thermal gradient, combined with a reasonable chemical gradient to inhibit hydration and swelling of clay. The anisotropic Young's modulus and Poisson's ratio are sensitive to hoop stress, the solute diffusion coefficient and permeability anisotropy have a minor effect on wellbore strengthening in low permeability formation. Compared with short fracture, the relatively longer fracture is beneficial for wellbore strengthening with bridging location near the fracture mouth.

中文翻译：

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页岩地层井筒强化处理的热化学效应

摘要 页岩井筒加固成功率较低。为此，将热-化学-孔弹性全耦合理论引入井筒加固物理模型，建立多场耦合井筒加固模型，并加入裂缝单元研究页岩孤立裂缝闭合过程。通过观察环向应力和断裂孔径的变化研究了热效应和化学效应。结果表明，热因素对井筒加固至关重要。井筒加固的前期处理主要通过调节热梯度来控制，并结合合理的化学梯度来抑制粘土的水化和膨胀。各向异性杨氏模量和泊松比对环向应力敏感，溶质扩散系数和渗透率各向异性对低渗透地层的井筒强化影响较小。与短裂缝相比，相对较长的裂缝有利于井筒加固，桥接位置靠近裂缝口。