Geological CO2 sequestration in saline aquifers: Implication on potential solutions of China's power sector

The rapid growth of energy demands in China surpasses the progress of introducing new clean energy sources. China has relied upon fossil fuel for several decades, which caused China to produce the largest CO2 emission and to influence climate change in the world. Thus, China's fossil fuel-dependent power sector needs to reduce CO2 emission. Carbon capture and storage (CCS) is one of the solutions to decrease CO2 emission, and geological CO2 sequestration (GCS) is recommended considering its high potential and effectiveness. In this study, the efforts to implement geological CO2 sequestration in China are reviewed, and current technical issues are addressed. The potential storage candidates including depleted oil and gas reservoirs, unminable coal seams, saline aquifers, and hydrate bearing sediments are introduced with the data collected from the pilot, demonstration, and large-scale projects in China. Among potential sites, saline aquifers have been considered as sites with the highest potential for CO2 storage in China because of their enormous capacity. Main trapping mechanisms including structural-, capillary residual-, solubility- and mineral-trappings support saline aquifers as the most possible CO2 storage site. Also, CO2 injectivity and CO2-brine displacement efficiency in saline aquifers are explored to improve the efficiency of CO2 injection with current techniques including visualizing experimental testing method for two-phase immiscible flow such as microfluidic model and X-ray computed tomography (X-CT) method. Finally, regulatory acts in China are explained as the potential rules for monitoring the safety of the GCS projects in China.