我国煤系地层含气性的初步研究

一、概论我国是发现煤层中有天然气很早的国家.宋代鲁应龙记载:“嘉禾志:顾亭林庵中,有忠烈公祠,近岁忽地裂数尺,中有风涛声,以物探之,应手火起,至今尚然,嘉禾可能是湖南嘉禾县,是出煤的地方,王嘉阴教授指出它可能是煤里放出的一些天然气.

PRELIMINARY RESEARCH ON NATURAL GAS IN COAL SERIES IN CHINA

The results of our analyses of the composition of gases from some coal beds in China show that.(1) hydrocarbon gas predominates the components of gases from the coal beds,while methane claims absolute predominance in hydrocarbon gases;and (2) different types of coal have different content of heavy hydrocarbons,as low as 1.4-2.6% for anthracite and as high as 5-18% for gas coal,gas rich coal,rich coal,coking coal and lean coal,together with a small amount of oil.Many of the characteristics of off and gas shows discovered in the coal series in China are quite similar to those of the abovementioned hydrocarbon components.In the Upper Triassic and Permian systems in the Sichuan and Shan-Gan-Ning basins,gas pools formed by coalification have been discovered.Wet-gas pools are found in the Xiangxi coal series in the central and northwestern parts of Sichuan,producing gas coal and rich gas coal with 8-15% heavy hydrocarbon content.There are three stages in the formation of hydrocarbons during coalification,(1)the early dry gas stage-with lignite(consolidated brown coal and unconsolidated brown coal) and peat,forming primarily methane;(2) the wet gas stage-with sub-bituminous coal,jet coal,gas coal,rich coal,coking coal and lean coal,forming methane,5-20% of heavy hydrocarbons and a small amount of oil;and(3) the late dry gas stage-with lean coal and anthracite,forming large amount of methane and some heavy hydrocarbons(generally 2-3%).The geologic conditions for gas accumulation in coal series are,(1) prolong subsidence of coal basins;(2) cap rock of regional extent;and(3) uplift of long development.