Abandoned wells are one of the dominant pathways of deep CO leakage, threatening the safety and effectiveness of CO geological storage. Although CO wellbore flow has been discussed in several studies, the analysis of the CO wellbore leakage under evolving recharge conditions based on the transient wellbore-reservoir fully coupled model, which can describe the CO gas-liquid phase change, has yet to be reported. Thus, a transient wellbore-reservoir fully coupled model is established in this study to investigate the interaction between CO injection and wellbore leakage. The results show that the fluid wellbore leakage may cause significant disturbance to the reservoir and injection well, and the fluid leakage process can be divided into different stages according to the leakage and recharge characteristics. Besides, the wellhead temperature of the abandoned well shows a different variation trend compared with previous studies, which is attributed to the evolving reservoir recharge. The parameter analysis indicates that the gap aperture in the plugs of the abandoned well, plug locations, CO injection rate, and reservoir permeability have apparent effects on the fluid leakage rates but have little impact on the leakage pattern. Finally, a dimensionless parameter, the ratio of leakage to injection mass, is proposed to generalize the leakage degree, and the empirical relationship of the ratio of leakage to injection mass with time is established to facilitate quick estimation. This study broadens the understanding of CO wellbore leakage and provides a simple method to predict similar leakage scenarios approximately.

中文翻译：

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考虑 CO2 相变的不断变化的补给条件下瞬态 H2O-CO2 井筒泄漏

废弃井是二氧化碳深层泄漏的主要途径之一，威胁着二氧化碳地质封存的安全性和有效性。尽管一些研究已经讨论了CO井筒流动，但基于瞬态井筒-储层全耦合模型对不断变化的补给条件下CO井筒泄漏的分析尚未见报道，该模型可以描述CO气液相变。因此，本研究建立了瞬态井筒-储层全耦合模型来研究CO注入与井筒泄漏之间的相互作用。结果表明，流体井筒渗漏可能对储层和注入井造成显着扰动，根据渗漏和补给特征，流体渗漏过程可分为不同阶段。此外，废弃井的井口温度与以往的研究相比呈现出不同的变化趋势，这归因于储层补给的演变。参数分析表明，废弃井塞体间隙孔径、塞体位置、CO注入量和储层渗透率对流体渗漏率影响明显，但对渗漏模式影响不大。最后，提出了一个无量纲参数——泄漏与喷射质量之比来概括泄漏程度，并建立了泄漏与喷射质量之比随时间的经验关系，以便于快速估算。这项研究拓宽了对 CO 井筒泄漏的理解，并提供了一种简单的方法来近似预测类似的泄漏情况。