二氧化碳地质封存过程中断层活化光纤监测适用性研究

A Study on the Applicability of Fault Activation Monitoring Using Fiber Optics during Carbon Dioxide Geological Sequestration Process

摘要: 二氧化碳地质封存是一种将工业产生和大气中捕获的二氧化碳气体安全地储存到地下储层中，并防止其泄露进入大气层对气候造成影响的技术。现有研究表明断层活化、盖层破裂及井筒失效等因素会导致二氧化碳地质封存过程中的泄漏，需要借助监测手段进行安全性监测。分布式光纤传感技术因其井下无电源、抗电磁能力强以及可大范围监测等特性，广泛应用于石油、土木等领域，但尚未应用于二氧化碳地质封存泄露监测。本文首先介绍二氧化碳地质封存技术和光纤监测技术的研究现状及意义，整理归纳目前二氧化碳地质封存典型项目。而后，选定阿尔及利亚In salah二氧化碳封存项目的Krechba气田作为研究区域，通过数值模拟研究了二氧化碳地质封存过程中断层活化光纤监测的应用场景，并探究了二氧化碳注入压力对监测效果的影响。结果表明，随着二氧化碳不断注入，当遇到断层时，会优先沿渗透率更高的断层运移，断层内压力骤增，光纤监测点处会产生明显的拉张应变信号，且不同地质和工程参数会对应变信号特征产生显著影响。研究结果对于分布式光纤监测技术在二氧化碳地质封存过程中的实际应用具有重要参考价值，并为进一步优化监测方案和提高封存系统的安全性提供了理论基础。

Abstract: Carbon dioxide geological sequestration is a technology that safely stores industrial and captured CO₂ gas underground in reservoirs, preventing its release into the atmosphere and mitigating its impact on climate. Existing studies have shown that factors such as fault activation, cap rupture and wellbore failure will lead to leakage during the geological storage of carbon dioxide, and safety monitoring needs to be carried out with the help of monitoring methods. Distributed optical fiber sensing technology is widely used in petroleum, civil engineering and other fields due to its characteristics of no underground power supply, strong electromagnetic resistance and large-scale monitoring, but has not yet been applied to carbon dioxide geological storage leakage monitoring. This paper first introduces the research status and significance of carbon dioxide geological storage technology and optical fiber monitoring technology and summarizes the current typical projects of carbon dioxide geological storage. Then, the Krechba gas field of the in salah CO₂ storage project in Algeria was selected as the research area, and the application scenarios of fault layer activation fiber monitoring in the process of CO₂ geological storage were studied through numerical simulation CO₂ injection pressure on the monitoring effect were explored. The results show that with the continuous injection of carbon dioxide, when encountering faults, it will preferentially migrate along faults with higher permeability, the pressure in the faults will increase sharply, obvious tensile strain signals will be generated at the optical fiber monitoring points, and different geological and engineering parameters will have a significant impact on the characteristics of strain signals. The research results have important reference value for the practical application of distributed optical fiber monitoring technology in the process of CO₂ geological storage, and provide a theoretical basis for further optimizing the monitoring scheme and improving the security of the storage system.