Geological storage of CO₂ technologies has become an important and effective way to reduce the greenhouse gas emissions, especially when it is combined with CO₂ enhanced oil recovery (EOR), which can not only trap CO₂ but also enhance oil recovery. However, the risk of CO₂ leakage has always been a prominent issue. In this paper, the mechanisms and pathways of CO₂ leakage during geological storage in oil reservoirs were analyzed using fault tree analysis (FTR). Besides, monitoring technologies were discussed and deployed in a CO₂ EOR demonstration project. The analysis results showed that the sealing failures of oil producer and CO₂ injector wells, like well cement failure and casing failure, are the main reasons for the CO₂ leakage, which has been observed in the oil field monitoring project. The monitoring results indicated that there is no large‐scale CO₂ leakage, while relatively high and abnormal CO₂ concentration in soil gas near some wellbores are observed, which indicates there is some leakage of CO₂ through incomplete cement ring and well casing string. FTR results provide guidelines for monitoring and preventing of CO₂ leakage during geological storage in oil reservoirs. The near‐surface monitoring methods, especially the soil gas monitoring technologies, can effectively detect the leakage of CO₂, and are a proper method for CO₂ leakage monitoring. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

中文翻译：

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利用故障树分析识别油藏潜在的CO2泄漏途径和机理

CO ₂技术的地质存储已成为减少温室气体排放的重要而有效的方法，特别是与CO ₂增强采油量（EOR）结合使用时，EOR不仅可以捕集CO _2，而且可以提高采油量。然而，CO ₂泄漏的风险一直是一个突出的问题。本文运用故障树分析法（FTR）分析了油藏地质储藏过程中CO ₂泄漏的机理和途径。此外，在CO ₂ EOR示范项目中讨论并部署了监控技术。分析结果表明，采油厂与CO ₂的密封失效注入井，如水泥固井和套管失灵，是导致CO ₂泄漏的主要原因，这已在油田监测项目中观察到。监测结果表明，没有大规模的CO ₂泄漏，但在一些井眼附近的土壤气体中观察到了相对较高和异常的CO ₂浓度，这表明有一些CO ₂通过不完整的水泥环和井套管柱泄漏。FTR结果提供了在储油层地质存储过程中监测和防止CO ₂泄漏的指南。近地表监测方法，特别是土壤气体监测技术，可以有效地检测CO ₂泄漏，并且是监测CO ₂泄漏的合适方法。©2020年化学工业协会和John Wiley＆Sons，Ltd.