Abstract: Geological storage of carbon dioxide (CO₂), a core component of carbon capture, utilization, and storage (CCUS), is a key strategy to mitigate greenhouse gas emissions. However, the continuous expansion of storage capacity increases the risk of CO₂ leakage, posing significant challenges to the safety and effectiveness of storage projects. Firstly, this study provides a comprehensive review of leakage issues and research progress in large-scale CO₂ geological storage. We examine the primary leakage pathways and their underlying physical, chemical, and geological mechanisms, emphasizing wellbores, faults/fractures, and caprocks as critical conduits. We summarize the cascading effects of CO₂ leakage, highlighting its potential impacts on groundwater, soil microorganisms, vegetation, and climate change. Then, we discuss recent advances in leakage monitoring and risk assessment, underscoring the roles of multi-source sensing, intelligent data analysis, and multi-scale coupled models. Furthermore, we review the progress of leakage control and remediation technologies, including cement-based materials, polymer gels, biomineralization, foam injection, and nanotechnology, while identifying limitations regarding long-term stability and large-scale applicability. Finally, we propose future research directions that focus on identifying leakage mechanisms, multi-source monitoring, intelligent early-warning systems, and rapid-response remediation strategies tailored to complex geological conditions, aiming to establish an integrated full-cycle leakage prevention and management framework.

Key words: CO₂ geological storage, leakage mechanism, environmental impact, monitoring means, risk control, repair technology