Numerical Simulation of CO2 Storage in Subseabed Sediments in the Shenhu Area, South China Sea: The Effect of Reservoir Permeability Anisotropy

CCUS has been an important technological approach to mitigate global warming, and CO2 storage plays a key role in this process. The ocean is a huge potential carbon sink; therein, CO2 injected into subseabed sediments will form relatively stable CO2 hydrate under the appropriate conditions, which is expected to achieve long-term CO2 storage. Of special interest is that marine sediments are generally anisotropic in permeability; this would significantly affect the resulting storage behavior of CO2. In this study, by constructing a large-scale numerical model of CO2 storage in the South China Sea, we investigated the effect of permeability anisotropy on CO2 transport and transformation. The results show that the mass of CO2 stored in the free phase is higher than that in the hydrate phase during the CO2 storage process; the CO2 hydrate storage efficiency is larger in reservoirs with large permeability anisotropy values; the increase in Rhv expands the horizontal extent of the hydrate cap but restricts the hydrate volume in the vertical zone. In addition, the study proposed a double-layer CO2 injection method assisted by increasing the vertical pressure to improve the hydrate storage efficiency. These findings provide a scientific basis for CO2 storage in subseabed reservoirs with permeability anisotropy.