Research progress of multi-source and multi-stage genesis of CO₂-enriched CBM and the enlightenments for its exploration and development

CO₂-enriched coalbed methane(CBM) carries important geological information on CBM genesis and accumulation, and is closely related to the exploration and evaluation of CBM resources. On the basis of the systematic summary of the current research progress of CBM genesis, the current research status of the genetic mechanism of CO₂-enriched CBM reservoirs was scientifically analyzed by dissecting the special geological examples of CO₂-enriched CBM reservoirs in the southern Junggar Basin, and the problems in the research process of CBM genesis were comprehensively pointed out. The study shows that the generation of CBM has multiple sources and multiple stages, and different genesis of CBM significantly varies in geochemical characteristics. As there are limitations in the current CBM genesis identification charts and standards, it is necessary to establish a multi-factor comprehensive identification system of CBM genesis, and along with the regional geological conditions and parent material inheritance differences, the CBM genesis and the associated geological process are comprehensively explained. The gas composition, isotopic composition, and accumulation process of CO₂-enriched CBM reservoirs, are closely related to multiple geochemical and biogeochemical effects, including the generation and accumulation of CO₂ in the early coalification, the differential dissolution and consumption of CO₂ with the participation of groundwater, migration and fractionation, and the later transformation of microorganisms. For the different genesis of CBM reservoirs, the corresponding resource evaluation index system should be established to effectively delineate sweet spots and sweet formations. For CO₂-enriched CBM reservoirs, it is necessary to scientifically establish a standard for defining the depth of the aeolian oxidation zone and carry out the effective evaluation of CBM resources.