Abstract: The injection-production alternation of gas reservoir-type gas storage leads to caprock deformation and pore pressure change, which further results in different degrees of dynamic changes in the geostress field of caprock, thus affecting the mechanical integrity and sealing performance of the caprock. Combined with the principle of effective stress and 3D caprock thin bending plate theory, an analytical model of caprock pore pressure and geostress is established, the results of which are compared with the numerical simulation results, thus verifying the rationality of the analytical model. On this basis, the paper investigates the change law of the caprock stress magnitude and geostress mechanism of S gas storage in China in the depletion-injection-production process. Results show that the farther away from the reservoir, the less obvious the disturbance of pore pressure and geostress is in the caprock, and the stress state of the strata suffering from obvious injection-production disturbance will change in the reverse, strike-slip, and normal fault mechanism. Based on caprock stress analyses, it is concluded that the dynamic mechanical integrity of caprock is in a critical state when the upper limit pressure coefficient of S gas storage is 1.5 (about 18 MPa). Finally, the scheme of multi-condition alternating mechanical test suitable for S gas storage is explored and proposed, thus providing a reference for laboratory tests of similar projects.

Key words: gas reservoir-type gas storage, caprock, evolution of stress field, mechanical integrity, sealing capacity, alternating mechanical test

摘要： 气藏型储气库注采交变导致盖层发生变形以及孔隙压力变化，进而使盖层地应力场发生不同程度的动态变化，影响盖层的力学完整性和密封性。结合有效应力原理与盖层三维弯曲薄板理论，建立了储/盖层孔隙压力与地应力解析模型，并与数值模拟结果进行了对比，验证了解析模型的合理性。在此基础上，研究了中国储气库S在衰竭-注采过程中储/盖层应力量值与地应力机制变化规律。研究结果表明，距离储层越远，盖层孔隙压力与地应力扰动越不明显，而受注采扰动明显的地层的应力状态会在逆—走滑—正断层机制间变化。根据盖层应力分析，得到了储气库S在上限压力系数为1.5（约为18 MPa）时，盖层动态力学完整性处于临界状态。最后探讨并给出了适用于储气库S的多工况交变力学试验方案，以期为类似工程室内试验提供参考。

关键词: 气藏型储气库, 盖层, 应力场演化, 力学完整性, 密封性, 交变力学试验