The origin mechanism of coalbed methane in the eastern edge of Ordos Basin

• Published in: Science China. Earth sciences Vol. 56; no. 10; pp. 1701 - 1706
• Main Authors: Li, GuiHong, Zhang, Hong
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.10.2013; Springer Nature B.V
• Subjects: Bacteria; Basins; Carbon dioxide; Carbon isotopes; China; Coal; Coalbed methane; Earth and Environmental Science; Earth science; Earth Sciences; Fluid flow; Fluid mechanics; Hydrodynamics; Low temperature; Meteoric water; Methane; Organic compounds; Origins; Research Paper; Surface water; Water depth; 东缘; 二氧化碳; 成因机制; 次生生物成因; 流体力学; 热气体; 煤层气; 鄂尔多斯盆地; China, People's Rep., Ordos Basin; China, People's Rep; coalbed methane; the eastern edge of the Ordos Basin; origin mechanism
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/s11430-013-4616-3

In the eastern edge of the Ordos Basin, the coalbed methane （CBM） development has not made substantial progress in the past 20 years, and the origin of gas can be used to guide the CBM block-selecting and development. Based on the 37 sets of carbon isotope data, the origin of the gas was determined and the origin mechanism was studied in this work. The δ13CpDB of methane ranges from -70.5‰ to -36.19‰ in the eastern edge in the Ordos Basin and the value becomes heavier from the north to the south. The secondary biogenic gas and the thermogenic gas are mixed in the shallow area and the thermogenic gas occurs in the medium and deep levels. The phenomenon is controlled mainly by the distribution of coal rank and hydrodynamics. Firstly, based on the relationship between China coal rank and methane δ13CpDB, the medium rank coal is dominant in the eastern edge of the Ordos Basin, and the mixture of the secondary biogenic gas and the thermogenic gas is formed in the coal of vitrinite re- flectant ratio （Rmax） between 0.5% and 2.0% if there is appropriate hydrodynamics; at the same time, because of the shallow burial depth, and the well-developed coal outcrop, meteoric water and other surface water carrying bacteria recharge the coal reservoir, metabolize the organic compounds at a relatively low temperature, and generate methane and carbon dioxide. Wherever the trapping mechanisms occur in the coal, such as Liulin and Hancheng, modern gas content should be high.