Geological Storage Conditions and Potential Assessment of CO₂ in Deep Saline Aquifers, Qingjiang Basin

The geological storage of CO₂ in deep saline aquifers of sedimentary basins is the main way of CO₂ storage and an important means to achieve carbon reduction goals on a large scale in the short term. The Qingjiang Basin has developed high quality deep saline reservoirs and cap rocks, which have the potential for CO₂ geological storage. However, there has been no systematic study on its storage geological conditions and potential in the past. By the date collection, field investigation, and testing analysis works, a comprehensive study was conducted on the geological conditions of CO₂ storage in the Qingjiang Basin. Embedded analysis was carried out on the characteristics of reservoir-cap conditions, fault development, hydrogeology, geothermal geology, etc. Using the storage potential calculation formula recommended by the Carbon Storage Leaders Forum, the CO₂ geological storage capacity in the Qingjiang Basin was evaluated. The results show that there are two sets of reservoir-cap combinations suitable for CO₂ storage developed in the deep part of the Qingjiang Basin: in Cretaceous, the glutenite of Hekou Formation is the reservoir, and the argillaceous rocks of Tangbian Formation is the cap rock; the glutenite of Lianhe Formation in Cretaceous and the first member of the Xinyu Formation in Paleogene is the reservoir, and the gypsum and argillaceous rocks of the second, third, fourth member of the Xinyu Formation is the cap rock. Well rock character and mineral composition conditions has been developed in the reservoir, with high porosity and permeability; the advantages in the cap rock has been developed with dense lithology, low porosity and permeability, and high breakthrough pressure. The main control fault of the basin has little impact on the strata deformation of the basin after its formation, and the development scale and fault displacement of secondary faults are not significant. The saline aquifers has hydraulic sealing effect and has no hydraulic connection with surface water sources. After preliminary assessment, the effective CO₂ storage capacity of the deep saline reservoir in the Qingjiang Basin is 3.93×10⁸ t, which is of large storage potential, and can be used as a geological disposal space for CO₂ in the Poyang Lake Economic Circle in northern Jiangxi.