Carbon capture and storage (CCS) in deep geological aquifers has shown to be the most viable option for mitigating the greenhouse gas effect of carbon dioxide (CO2) at a large scale. However, the underground formations often possess discontinuities in the caprocks, leaking the stored CO2. Potential leakage paths, such as abandoned wells, have been growing due to excessively unplugged oil and gas exploration wells. The leakage of CO2 from these wells is a major concern, considering their negative impact on the environment and compromising CO2 storage efficiency. Recently, microbially induced calcite precipitation (MICP) technology has proven to be an effective and sustainable method for reducing the permeability of geomaterials. Nevertheless, the MICP process involves intricate interactions among bio-chemo-hydraulics (BCH) domains to comprehend the reactive transport of biochemicals. The complex nature of the MICP process poses difficulties in setting the biochemical injection durations for a particular target distance at the given injection rate. Given this, the present study developed a coupled numerical model and employed it as a workable tool for optimising MICP injections to plug the abandoned well connecting two deep geological aquifers. Following that, the study evaluated the leakage of CO2 using flow migration rates in the untreated and MICP-treated leaky aquifer. The study proposed a novel optimisation strategy for biochemical injections under near and far-field leakage conditions. The sensitivity of biochemical injection durations on the attached bacterial amount and permeability in the leak was also determined. The observations from the present study indicated a complete reduction in the CO2 migration rates from the abandoned well due to a reduced permeability after MICP, thereby indicating the efficacy of the proposed optimisation methodology. Further, a cost analysis of the MICP treatment indicated a rational application cost with the target distance compared to the detrimental effects of CO2 leakage.

中文翻译：

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用于密封含水层泄漏路径以用于 CO2 地质封存应用的微生物诱导方解石沉淀 （MICP） 注入策略的数值优化


深部地质含水层中的碳捕集与封存 （CCS） 已被证明是大规模减轻二氧化碳 （CO2） 温室气体影响的最可行选择。然而，地下地层的盖层通常具有不连续性，导致储存的 CO2 泄漏。由于石油和天然气勘探井的过度堵塞，潜在的泄漏路径（例如废弃的井）一直在增加。考虑到这些井的 CO2 泄漏对环境的负面影响并损害 CO2 封存效率，它们是一个主要问题。最近，微生物诱导方解石沉淀 （MICP） 技术已被证明是降低土工材料渗透性的有效且可持续的方法。然而，MICP 过程涉及生物化学液压 （BCH） 领域之间错综复杂的相互作用，以理解生化物质的反应性运输。MICP 过程的复杂性使得在给定注射速率下为特定目标距离设置生化注射持续时间变得困难。有鉴于此，本研究开发了一个耦合数值模型，并将其用作优化 MICP 注入的可行工具，以堵塞连接两个深地质含水层的废弃井。之后，该研究使用未经处理和 MICP 处理的泄漏含水层中的流动迁移速率评估了 CO2 的泄漏。该研究提出了一种在近场和远场泄漏条件下进行生化注入的新型优化策略。还确定了生化注射持续时间对泄漏中附着细菌量和通透性的敏感性。 本研究的观察结果表明，由于 MICP 后渗透率降低，废弃井的 CO2 迁移速率完全降低，从而表明了所提出的优化方法的有效性。此外，MICP 处理的成本分析表明，与 CO2 泄漏的不利影响相比，目标距离的应用成本是合理的。