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Before the 1960s, it was never imagined that coalbed methane could form large gas fields or significant gas-producing areas. So, is coalbed methane a combustible gas formed from coal? More precisely, coalbed methane refers to a hydrocarbon natural gas whose main component is methane, and which is formed through thermal evolution during the coalification process of coal seams in coal formations (mainly humic coal) as well as humic-type dispersed organic matter. It and coalbed methane both belong to coal-type gases, but their occurrence conditions differ; meanwhile, associated gas and condensate gas from the same oil field are of completely different origins. In 1959, the Groningen gas field was discovered in northern Netherlands, and it was determined to be associated with the coal seams of the Middle Carboniferous period. Following intensive exploration, more than a dozen major gas fields were discovered in the southern part of the North Sea basin in the mid-1960s, with total proven reserves exceeding 4.5 trillion cubic meters, making it the world’s second-largest gas-producing region; the source of this gas remains linked to Carboniferous coal-bearing deposits. Since then, such natural gas stored in coal-bearing basins has attracted tremendous attention from many **. Exploration and development practices, along with theoretical research findings, have finally revealed the true nature of the formation and evolution of such natural gas, naming it coalbed methane. Coalbed methane is produced in coal-bearing and organic-rich shale formations; both coal and dispersed organic matter serve as the primary materials for coal-derived hydrocarbons. Coal is primarily formed from the remains of ancient plants, which can be either higher plants or lower plants such as algae. Based on the different coal-forming substances, the genetic types of coal are classified into humic coal, peat coal, and residual coal. The vast majority of coal seams that formed and are widely distributed across various periods since the Carboniferous era have coal rock components derived from the wood of higher plants; they represent coal seams formed by the accumulation of ancient terrestrial higher plants in normal peat swamp environments, and are commonly referred to as humic coal. A favorable coal-forming environment is a peat swamp area that facilitates plant growth, reproduction, and accumulation. In an oxygen-deficient environment, plant remains first form peat layers; as the sediment thickens and ground temperatures rise, through processes of dehydration, compaction, and an increase in carbon content along with a decrease in oxygen content, they enter the stage of coalification. Coalification is the evolutionary and metamorphic process of different coal ranks, as well as a process in which carbon in coal continues to accumulate while hydrogen, oxygen, and nitrogen decrease. Coalification successively forms different coal ranks such as lignite, bituminous coal, gas coal, subbituminous coal, coking coal, lean coal, weak coal, and anthracite; during this process, methane, heavy hydrocarbons, carbon dioxide, carbon monoxide, and ammonia are generated. At different coal ranks and temperatures, the composition and yield ratio of coalbed methane vary, with the gas generation rate increasing as the coal rank increases. Based on the formation and composition of known coalbed methane reservoirs both domestically and internationally, coalbed methane reservoirs have the following characteristics: their source rock dates mainly to the Carboniferous-Permian period, which was a time of coal formation worldwide ； Its composition is complex, but it is primarily composed of methane, with a concentration of over 90% in most cases ； The content of heavy hydrocarbons is low, rarely exceeding 20% ； It generally contains small amounts of non-hydrocarbon gases, such as nitrogen, ammonia, hydrogen sulfide, carbon dioxide, noble gases, and mercury vapor.