Carbon capture,utilization and storage(CCUS)is a critical technology to achieve large-scale car-bon emission reduction,and the leakage risk after CO2 injection is one of its concerns.Although no deep-stored CO2 leakage accident has occurred in the CCUS project,there are many natural CO2 leakage events worldwide,and the study of the analogous natural CO2 leakage process will provide a valuable reference for the leakage risk assessment of the CCUS project.In this study,taking a typical CO2 wellbore leakage site in the southern Xining Basin,Well ZK10,as the study object,we established a numerical model on the basis of the measured data to investigate the kinetic mechanism and the accompanying chemical characteristics dur-ing the periodic eruption.The study results show that many factors,including CO2 exsolution,gas-lift effect,and the dynamic recharge of groundwater from the reservoir,control the periodic eruption of Well ZK10.Synchronously,under the control of CO2 exsolution and fluid mixing,the pH value of groundwater within the wellbore above the flash point increases with the decrease of depth,and changes periodically with the eruption.During the periodic eruption of ZK10,calcite and quartz are precipitated within the well-bore,and their precipitation characteristics are different due to their disparate solubilities in the groundwa-ter.These results can provide a reference for the investigation of leakage mechanism and chemical charac-teristics of CO2 leakage along wellbores in similar natural scenes or CCUS projects,and then provide a basis for relevant departments to develop monitoring and prevention measures.
关键词
天然二氧化碳/井筒泄漏/间歇喷发/化学反应/CCUS技术/数值模拟
Key words
natural CO2/wellbore leakage/periodic eruption/chemical reaction/carbon capture,utilization and storage(CCUS)technology/numerical simulation
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