CO2封存后地层岩石微观结构变化机理研究进展

CO_2地质封存不仅被认为是提高原油采收率的有效技术手段,更是降低大气中温室气体含量的重要策略,其长期埋存对地质完整性和安全性的影响是中外学者关注的焦点。地层岩石在围压及地下水作用下的软化、变形甚至破坏是石油工程、化学工程及岩土工程所面临的重要课题。搜集了中外学者在各领域内的相关实验及理论研究资料,从地层岩石的化学反应、岩石细观结构的变化、微裂缝的扩展、HMC(hydro-mechanical-chemical)耦合作用过程等方面综述了CO_2酸性流体对地层岩石影响。阐明了CO_2封存过程中地层岩石的微观溶蚀机理,进而从物理、化学角度着重分析了化学-应力耦合作用对岩石细观损伤结构的影响机制及破坏条件,最后根据目前的研究水平进一步提出需要研究的方向以及相应的建议,以便从初期的选址及后期的埋存安全性角度保证CO_2封存工程的顺利进行。

Research status on change mechanism of formation rock microstructure after CO2 sequestration

Geological sequestration of CO₂ is not only considered as an effective technical means to improve oil recovery, but also an important strategy to reduce the content of greenhouse gas in the atmosphere. The impact of long-term storage on geological integrity and security is the focus of scholars at home and abroad. The softening, deformation and even destruction of formation rocks under confining pressure and underground water reaction are important issues facing petroleum engineering, chemical engineering and geotechnical engineering. Relevant experimental and theoretical research data of scholars at home and abroad in various fields are collected, and the influence of CO₂ fluid on formation rocks is summarized from the aspects of chemical reactions of formation rocks, changes of rock microstructure, extension of micro-fractures, coupling process of HMC (hydro-mechanical-chemical) and so on. The micro corrosion mechanism of formation rock in the process of CO₂ sequestration is illustrated, and the structure of the mesoscopic damage mechanism and failure conditions is analyzed from the perspective of the physical, chemical, chemical - stress coupling effect of rock emphatically. Further research direction and corresponding suggestions is proposed according to the current research level, so that to ensure the smooth progress of CO₂ sequestration project in the early site selection and late storage security respectively.