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