Abstract:

CO₂ geological storage is one of the most important means to mitigate the greenhouse effect.The safety of CO₂ securely stored in underground reservoirs largely depends on the mechanical integrity of the caprock.This paper establishes a coupled fluid-solid model for CO₂ geological storage to study the changes in pore pressure,vertical displacement,and effective stress in the caprock during the CO₂ injection process.It analyzes the effects of CO₂ injection rate,caprock elastic parameters,and geostress factors on the occurrence of tensile and shear failures in the caprock.The results indicate that,at the initial stage of CO₂ injection, changes in pore pressure,vertical displacement,and effective stress at the bottom of the cap near the injection well are significant but gradually stabilize thereafter.The area near the injection well is considered the most critical part of the caprock,where the risk of mechanical failure is greatest.During the CO₂ injection process,the injection rate and geostress factors have the most significant impact on the occurrence of mechanical failures in the caprock.The findings of this study provide a theoretical basis for assessing the long-term stability and safety of CO₂ geological storage systems.

Key words: CO₂ geological storage, Caprock, Tensile failure, Shear failure, Numerical simulation

摘要：

CO₂地质封存是缓解温室效应的重要手段之一。CO₂能否安全地储存在地下储层中，在很大程度上取决于盖层的力学完整性。通过建立CO₂地质封存流固耦合模型，研究了CO₂注入过程中盖层的孔隙压力、垂直位移和有效应力的变化规律，分析了CO₂注入速率、盖层弹性参数以及地应力因数对盖层发生拉伸破坏和剪切破坏的影响。结果表明，在CO₂注入初期，注入井附近盖层底部孔隙压力、垂直位移和有效应力的变化较大，随后趋于平缓；注入井附近的盖层被认为是封存系统最关键的部分，该位置发生力学破坏的风险最大；在CO₂注入过程中，注入速率和地应力因数对盖层发生力学破坏的影响最为显著。研究结果可为评估CO₂地质封存系统的长期稳定性和安全性提供理论依据。

关键词: CO₂地质封存, 盖层, 拉伸破坏, 剪切破坏, 数值模拟