Reservoir-cap combination optimization and assessment of CO₂ geological storage in East China Sea shelf basin

The East China Sea shelf basin, the largest offshore sedimentary basin in China, is recognized as an exceptional site for geological CO₂ storage due to its substantial storage potential, proximity to carbon sources, and advanced exploration maturity. In this study, we investigated the basin’s structural and sedimentary geological conditions and established assessment criteria for reservoir-caprock layers by integrating drilling and seismic data, thereby optimizing reservoir-caprock combinations and delineating favorable zones. Results demonstrate that the Paleocene strata in the Oujiang Sag and the Oligocene-Miocene strata in the Xihu Sag exhibit favorable geological conditions for CO₂ storage. Vertically, the distribution of reservoir-caprock combinations differs between the eastern and western regions. The eastern basin hosts predominantly in the Oligocene and Miocene sequences, while the western basin in the Paleocene and Eocene sequences. Horizontally, favorable zones in the eastern basin clustered within the Xihu Sag, whereas the western basin focused in the Oujiang Sag. In the southern basin, favorable zones distribute along the western slopes of structural units. This study presents the first targeted assessment of CO₂ storage potential in the East China Sea shelf basin to identify optimal reservoir-caprock zones by combining sedimentary distribution patterns. The findings provide critical geological insights and practical references for implementing offshore CO₂ storage strategies in East China.