Gas-bearing properties of coal reservoirs in China

Gas-bearing properties constitute important basis for geological selection of target areas for coalbed gas exploration. The South China region is characterized by highest gas contents and methane density of coalbed. Northwest China region is characterized by highest gas intensity. Northeast China region is characterized by highest gas saturability, and the North China region is characterized by balanced and constant values of all four parameters. As far as temporal distribution is concerned, the gas saturability, gas content, and gas qualities are highest in the Late Permian and Late Triassic coal seams and are second highest in the Late Carboniferous and Early Permian coal seams. Gas-bearing intensity is much higher in the Early and Middle Jurassic coals then in other coals, and decreases towards the Late Carboniferous, Early Permian to Early Cretaceous coals in order. Tectonics, coal ranks, coal burial depth, coal petrology, lithology of seals, and hydrogeological conditions provide direct and major controls to gas-bearing properties.