Basic characteristics and accumulation rules of shale gas in coal measures

shale gas in coal measures is one of the important types of shale gas. This paper studies the hydrocarbon generation and expulsion capacity and preservation conditions of shale gas in coal measures, discusses the development features and distribution rules of shale in China's coal measures. The research indicates that the main characteristics of coal shale are as follow:humus type (type III) of kerogen is predominant, H/C is lower and TOC is higher than that of the usual shale; the low efficiency of oil generation which gives priority to long-term gas generation, difficult and hysteretic gaseous hydrocarbon expulsion, low efficiency of expulsion hydrocarbon and large volume of residual hydrocarbon because of the nature of organic matter; coal seam is not only good source rock, but also is cap-rock with good sealing ability for underlying layers. Therefore shale in coal measures holds favorable ability of gas accumulation and enrichment potential.