油藏埋存CO_2泄漏机制及故障树分析

利用故障树分析法,结合油田CO_2驱和埋存示范区泄漏及环境监测结果,对油藏埋存CO_2发生泄漏的途径和泄漏机制进行分析,并对CO_2驱和埋存示范区进行环境监测。结果表明:对圈闭性很好的油藏,井的密封性失效(包括套管和井口设施损坏)、固井不完善及水泥环腐蚀是造成CO_2泄漏的主要原因;整体上,埋存于地下的CO_2没有发生大规模的泄漏,但在近井土壤中CO_2含量有增加的趋势,越靠近井口土壤中CO_2含量越大,表明CO_2通过井内套管柱或不完整水泥环发生了微量泄漏。故障树分析结果对CO_2埋存区的泄漏监测和预防具有指导意义。

Mechanisms and fault tree analysis of CO2 leakage during geological storage in oil reservoirs

In this study, the leaking mechanisms and potential pathways of CO₂ during geological storage in oil reservoirs were analyzed based on a fault tree analysis method, in combination with the field monitoring results of a CO₂ enhanced oil recovery (EOR) and storage demonstration project. The analysis results show that the sealing failures of injector and oil production wells, including casing and wellhead facilities damage, and well cementing failure, are the main reasons for the leakage of CO₂, which have been observed in the field monitoring. There has been no reported large-scale leakage of CO₂ occurring, but relatively high and abnormal CO₂ concentration in soil near some wellbores were measured, indicating that there was some leakage of CO₂ through well casing string or incomplete cement ring occurring. The fault tree analysis results can provide guidelines for monitoring and preventing leakage of CO₂ during geological storage.