Progress and expectation of CO2 sequestration safety in coal seams

The technology of negative carbon emission represented by CO2 geological sequestration is an important way to meet the strategic goal of carbon peak and carbon neutrality in China. Coal seam CO2 sequestration has low cost and can achieve efficient coalbed methane recovery, especially in line with China’s green development concept. It is a strategic requirement to arrange CO2 sequestration safety research in coal seams as soon as possible to achieve the goal of carbon peak and carbon neutrality in China. In this work, the status quo and safety problems of CO2 sequestration technology in coal seams were sorted out and analyzed. At present, CO2 sequestration in coal seams is still in the demonstration stage, and the large-scale application has not been realized yet. The safety of CO2 sequestration in coal seams is mainly affected by the sequestration geological structure, geological disaster, engineering disturbance, and other factors. However, the existing safety monitoring methods mostly focus on monitoring CO2 or some environmental effects caused by CO2 leakage, and lack of attention to the safety of sequestration geologic body itself. There are many gaps in the research on coal seam carbon sequestration mechanism and whole live circle safety, which is the key factors restricting the development of CO2 sequestration technology in coal seams in China. In view of the existing problems, we raised four key technologies, i.e., mechanism and main control factors of coal seam carbon sequestration security, risk detection and safety evaluation method of coal seam carbon sequestration, the whole life cycle safety monitoring and early warning technology of coal seam carbon sequestration and the coal seam carbon sequestration risk response and emergency disposal regulations. Through the above four aspects of research, it is expected to build the whole process theory and technology method system of coal seam carbon sequestration including scientific site selection, safety monitoring and early warning, as well as standardized emergency, which lays the theoretical and technical foundation for the commercialization and large-scale of coal seam carbon sequestration in China.