Low-field NMR application in the characterization of CO2 geological storage and utilization related to shale gas reservoirs: a brief review

CO2 geological storage and utilization (CGSU) is considered a far-reaching technique to meet the demand of increasing energy supply and decreasing CO2 emissions. For CGSUs related to shale gas reservoirs, experimental investigations have attracted variable methodologies, among which low-field NMR (LF-NMR) is a promising method and is playing an increasingly key role in reservoir characterization. Herein, the application of this nondestructive, sensitive, and quick LF-NMR technique in characterizing CGSU behavior in shale gas reservoirs is reviewed. First, the basic principle of LF-NMR for H-1-fluid detection is introduced, which is the theoretical foundation of the reviewed achievements in this paper. Then, the reviewed works are related to the LF-NMR-based measurements of CH4 adsorption capacity and the CO2-CH4 interaction in shale, as well as the performance on CO2 sequestration and simultaneous enhanced gas recovery from shale. Basically, the reviewed achievements have exhibited a large potential for LF-NMR application in CGSUs related to shale gas reservoirs, although some limitations and deficiencies still need to be improved. Accordingly, some suggestions are proposed for a more responsible development of the LF-NMR technique. Hopefully, this review is helpful in promoting the expanding application of the LF-NMR technique in CGSU implementation in shale gas reservoirs.