Abstract Geomechanical analysis and integrity assessment of hydrocarbon reservoirs upon depletion and injection are crucial to ensure that CO2 storage projects can be safely implemented. The Bredasdorp basin in South Africa has a great potential for CO2 storage given its hugely available exploration data. However, there has not been any geomechanical characterization carried out on this basin to determine its integrity issues. The aim of this study is to provide a guideline as to how geomechanical analysis of depleted fields can be done for a safe CO2 sequestration practice. The results obtained from the geomechanical model constructed for the depth of 2570 m indicated that the magnitude of the principal vertical, minimum and maximum horizontal stresses in the field are respectively 57 MPa, 41 MPa and 42–46 MPa, indicating the presence of a normal faulting regime in the caprock and the reservoir. However, according to the pore pressure-stress coupling assessment, this normal faulting is much severe in compartment C3 of the reservoir. Fault reactivation and fracture stability were also investigated after depletion and it was found that faults in the compartments C1 and C2 are stable after depletion. However, normal faults (FNS8 and FNS9) in compartment C3 dipping SW were critically stressed and may be reactivated without a proper injection planning. Fractures in compartment C3 were also critically stressed, highlighting a great potential of leakage from this compartment upon injection. It was also revealed that the sustainable maximum fluid pressure of 25 MPa would not induce any fractures in the reservoir during CO2 storage.

中文翻译：

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CO2 封存场的地质力学特征：南非 Bredasdorp 盆地近乎枯竭气田的案例研究

摘要 油气藏开采和注入时的地质力学分析和完整性评估对于确保二氧化碳封存项目的安全实施至关重要。鉴于其大量可用的勘探数据，南非的 Bredasdorp 盆地具有巨大的二氧化碳封存潜力。然而，尚未对该盆地进行任何地质力学表征以确定其完整性问题。本研究的目的是为如何对枯竭油田进行地质力学分析以实现安全的 CO2 封存实践提供指导。2 570 m深度构造的地质力学模型结果表明，现场主垂直应力、最小水平应力和最大水平应力分别为57 MPa、41 MPa和42-46 MPa，表明在盖层和储层中存在正常断层状态。然而，根据孔隙压力-应力耦合评估，这种正断层在储层 C3 隔间中非常严重。还研究了耗竭后的断层再活化和断裂稳定性，发现 C1 和 C2 层间的断层在耗竭后是稳定的。然而，舱室 C3 倾角 SW 中的正常断层（FNS8 和 FNS9）受到严重压力，可能在没有适当注入计划的情况下重新激活。隔室 C3 中的骨折也受到严重压力，突出了注射时从该隔室泄漏的巨大潜力。还表明，在 CO2 储存期间，25 MPa 的可持续最大流体压力不会在储层中引起任何裂缝。