Geochemical characteristics of biogenic gases in China

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• 作者：Yunyan Ni ; ^{niyy@petrochina.com.cn} ; Jinxing Dai ; Caineng Zou ; Fengrong Liao ; Yanhua Shuai ; Ying Zhang
• 关键词：Biogenic gas ; Carbon isotope ; Hydrogen isotope ; Gas origin ; Methanogenic pathway ; China
• 刊名：International Journal of Coal Geology
• 出版年：2013
• 出版时间：1 July, 2013
• 年：2013
• 卷：113
• 期：Complete
• 页码：76-87
• 全文大小：1586 K

文摘

A number of contributions have demonstrated that the stable carbon and hydrogen isotopic compositions together with molecular compositions have a great significance on determination for gas origin and gas generation pathways of biogenic gases. Together with some data from published work, a total of 143 gas samples were compiled from different biogenic gas producing locations in China, to investigate the gas origin and gas generation pathways by the molecular composition, stable carbon and hydrogen isotopes. The results demonstrate that biogenic gases in China are dominated by methane with low level of C_2 + 3 (generally less than 0.5 % ) and low ¦Ä¹³C_CH4 values (generally ¡Ü 55¡ë). The relatively high level of C_2 + 3 (up to 11.79 % ) in the biogenic gases from the Baise and Songliao basins indicates the possible mixture of low-mature thermogenic gases. Biogenic gases from the Jiangzhe coastal area (including Shanghai, Zhejiang, and Jiangsu provinces) and Yingqiong basin have ¦ÄD_CH4 values greater than ? 190¡ë, indicating marine salt water depositional environments. However, all other gases have ¦ÄD_CH4 values less than ? 190¡ë, possibly indicating a terrestrial freshwater or freshwater to slightly saline water depositional environment. The methanogenic pathway of biogenic gases in China is dominated by biogenic carbonate reduction, though a number of these biogenic gases were generated in a terrestrial freshwater or freshwater to slightly saline water depositional environments. Compared to the bacterial carbonate reduction methanognic pathway in the Luliang basin, gas formation mechanism in the Baoshan basin was more toward bacterial methyl-type fermentation, likely due to the relatively higher geothermal gradient in the Baoshan basin.