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Coal-measure gas is the natural gas generated by coal, carbonaceous shale, and dark shale in coal-measure strata. It includes resources of continuous-type coalbed methane (CBM), shale gas and tight gas reservoirs, and trap-type coal-bearing gas reservoirs. Huge in resources, it is an important gas source in the natural gas industry. The formation and distribution characteristics of coal-measure gas in San Juan, Surat, West Siberia and Ordos basins are introduced in this paper. By reviewing the progress of exploration and development of coal-measure gas around the world, the coal-measure gas is confirmed as an important strategic option for gas supply. This understanding is mainly manifested in three aspects. First, globally, the Eurasian east-west coal-accumulation belt and North American north-south coal-accumulation belt are two major coal-accumulation areas in the world, and the Late Carboniferous–Permian, Jurassic and end of Late Cretaceous–Neogene are 3 main coal-accumulation periods. Second, continuous-type and trap-type are two main accumulation modes of coal-measure gas; it is proposed that the area with gas generation intensity of greater than 10×108 m3/km2 is essential for the formation of large coal-measure gas field, and the CBM generated by medium- to high-rank coal is usually enriched in syncline, while CBM generated by low-rank coal is likely to accumulate when the source rock and caprock are in good configuration. Third, it is predicted that coal-measure gas around the world has huge remaining resources, coal-measure gas outside source is concentrated in Central Asia-Russia, the United States, Canada and other countries/regions, while CBM inside source is largely concentrated in 12 countries. The production of coal-measure gas in China is expected to exceed 1000×108 m3 by 2030, including (500–550)×108 m3 conventional coal-measure gas, (400–450)×108 m3 coal-measure tight gas, and (150–200)×108 m3 CBM. Key words: coal-measure gas (CMG), coalbed methane (CBM), tight gas, continuous-type, trap-type, gas generation intensity, resource potential, coal-accumulation period, coal-accumulation area

Based on the controlling of diagenesis and diagenetic facies on reservoir development, this article discusses the formation, classification, and evaluation of diagenetic facies and its application and significance in petroleum exploration. For constructive diagenetic facies such as clastic rock, carbonate rock, and igneous rock, eight kinds of genetic mechanisms are developed, including dissolution of organic acid, dolomitization, and so on. Nine constructive diagenetic facies and seven destructive diagenetic facies are classified. A naming scheme for diagenetic facies is proposed reflecting lithology, diagenesis, porosity, and permeability, that is, “porosity and permeability level + rock type + diagenesis type”. Diagenetic facies are evaluated synthetically and quantitatively on the basis of sedimentary facies, log facies, seismic facies, rock cores, and thin sections, and “four steps” and “superposition of three charts” are put forward as the methods of evaluation and mapping. Favored reservoirs, “sweet spots”, and lithostratigraphic traps can be predicted according to the distribution of different types of diagenetic facies. The development of the study on diagenetic facies is also discussed in the article. Key words: diagenetic facies, formation mechanism, classification and naming, evaluation method, petroleum exploration, diagenetic study