A review of offshore carbon dioxide geological storage from a source-sink perspective

Offshore carbon dioxide (CO2) geological storage is a vital climate mitigation strategy, providing greater capacity and security over terrestrial alternatives. While global efforts are shifting from in-situ demonstration to large-scale deployment, offshore carbon capture, utilization, and storage (CCUS) implementations are constrained by spatial mismatches between carbon sources and storage sinks. This review synthesizes advancements in marine CO2 storage from a source-sink perspective, bridging research and practical solutions to accelerate offshore CCUS development. The review explores the fundamentals of marine CO2 sequestration, covering water column and sub-seabed geological storage, emphasizing gravitational and hydrate trapping mechanisms. This study highlights the research progress in source-sink matching integration, including spatiotemporal optimization models, cluster-hub developments, diversity of storage reservoirs, geological capacity and site assessment, offshore gas reinjection and coastal sources, hybrid maritime transportation and networks, carbon utilization and uncertainty management. A global analysis of offshore CCUS projects across 21 countries summarizes regional source-route-sink innovations and lessons from Europe, the Americas, Oceania, and Asia. Five principal offshore source-sink schemes are identified, spanning direct subsea storage to cross-border and net-zero scenarios, alongside discussions on the evolving international and national regulatory frameworks governing sub-seabed CO2 storage. Bibliometric analysis reveals a research trend shift from theoretical frameworks to interdisciplinary applications. Future research efforts should prioritize advanced modeling, techno-economic-risk assessments, multi-system coordination and international governance to improve scalability, cost-effectiveness, and sustainability of offshore deployment.