Evaluation of the Suitability of China’s Offshore Basins for CO₂ Geological Storage

Offshore carbon dioxide (CO₂) geological storage is a promising strategy for reducing carbon emissions and supporting sustainable development in coastal regions within a carbon neutrality framework. However, only a few works have focused on offshore basins in China. To address this gap, this study established a dual indicator system that comprises necessary and critical indices and is integrated with the analytic hierarchy process. A coupled analysis was then performed to evaluate the suitability of 10 offshore sedimentary basins in China for CO₂ geological storage. The necessary indicator system focuses on storage potential, geological conditions, and engineering feasibility. Meanwhile, the critical indicator system emphasizes the safety of storage projects and the viability of drilling operations. Evaluation results revealed that China’s offshore basins have undergone two geological evolution stages, namely, the rifting and post-rifting phases, leading to the formation of a dual-layer structure characterized by faulted lower layers and sagged upper layers. These basins have thick and widespread Cenozoic strata, generally low seismic activity, and medium-to-low geothermal gradients. They form five reservoir-caprock systems with favorable geological conditions for CO₂ storage. The Pearl River Mouth, East China Sea Shelf, and Bohai Basins emerged as primary candidates that offer substantial storage potential to support carbon neutrality goals in the Bohai Rim Economic Zone, Yangtze River Delta Economic Zone, and Guangdong-Hong Kong-Macao Greater Bay Area. The Beibu Gulf and South Yellow Sea Basins were identified as secondary candidates, and the Qiongdongnan and Yinggehai Basins were considered potential alternatives.