Evaluation of carbon dioxide geological sequestration potential in coal mining area

Coal bases are the concentration areas of coal exploitation and use in China in which the carbon emission sources are concentrated, and carbon emission reduction is challenging. However, the carbon emission sources and geological sequestration sinks typically correlate well with coal bases, providing favorable conditions for clus-tering carbon capture, utilization, and storage (CCUS). CCUS is the only way for coal bases to achieve near-zero carbon emissions in the future. This study established the constitutive equations of CO2 sequestration capacity for unexploited deep coal seams, residual coal in producing and abandoned mines, and mined-out areas based on their CO2 sequestration form, geological background, and coal mining status. Then, the geological sequestration potential of one of the most important coal bases in east China was discussed according to the constitutive equations of CO2 sequestration capacity by considering matching relationships between sequestration sources (coal-fired power plants) and sinks. The results showed that the coal base has excellent CO2 geological sequestration potential. The total CO2 sequestration capacity in coal seams in the coal base is approximately 0.85 billion tons, including 0.76 billion tons in unexploited deep coal seams, 5.17 million tons in residual coal in producing and abandoned mines, and 82.45 million tons in mined-out areas. The source-sink matching re-lationships of CO2 geological sequestration in the coal base provide favorable conditions for CCUS, and the average distance between the CO2 sequestration sources and target sequestration sinks is only 10 km. The un-exploited deep coal seams with buried depths of 1000-1500 m are primary reservoirs for CO2 geological sequestration in the coal base. In the next 30 years, CO2-enhanced coal bed methane recovery (ECBM) in un-exploited deep coal seams and CO2 sequestration in mined-out areas should become a special CCUS technology in the coal base due to their great CO2 geological sequestration potential. CO2-ECBM and CO2 sequestration in mined-out areas are also significant for other coal bases in China.