Differences for geochemical controlling factors between coal-bed and conventional natural gases

Contrasting the coal-bed thermal evolution and the coal-bed gas geochemical characteristics in the Jincheng area of south Qinshui Basin and in the Huozhou area,western Qinshui Basin,central China,suggests that the geochemical characteristics of coal-bed gas,such as components and carbon isotopic compositions,are controlled by the key geological period,when the coal-bed reached the highest mature rank.Whereas the components and carbon isotopes of the coal-bed gas could reflect the coal-bed thermal evolution.Because the coal-bed gas is very different from conventional natural gas in storage mechanism,the effect on the geochemical characteristics of coal-bed gas by thermal evolution is different from stage and consecution accumulation processes for the conventional natural gas.The storage mechanism difference has obvious effects on the geochemical characteristics of coal-bed gas,which is different from that of the conventional natural gas.