Geological storage of carbon dioxide (CO)

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 CO 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 CO 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 CO 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.