| 我国生物气藏碳、氢同位素特征、形成途径及意义 |
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| 引用本文： | 沈平,王晓锋,徐茵,史宝光,徐永昌.我国生物气藏碳、氢同位素特征、形成途径及意义[J].沉积学报,2010,28(1):183-187. |
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| 作者姓名： | 沈平 王晓锋 徐茵 史宝光 徐永昌 |
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| 作者单位： | 中国科学院油气资源研究重点实验室,兰州,730000;中国科学院油气资源研究重点实验室,兰州,730000;中国科学院油气资源研究重点实验室,兰州,730000;中国科学院油气资源研究重点实验室,兰州,730000;中国科学院油气资源研究重点实验室,兰州,730000 |
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| 摘 要： | 生物气碳、氢同位素组成是探讨其形成途径和成藏特征的基本手段，研究基于我国10个生物气气藏31个气样的碳、氢同位素组成资料探讨了这些气藏的形成途径和成藏特征。研究表明:这些气藏的氢同位素组成可以分为三个区间，即δDCH4>-200‰；δDCH4值在-250‰～-200‰之间和δDCH4<-250‰。前人认为在陆相淡水条件下生物气的形成途径主要是乙酸发酵作用，我国10个气藏31个气样碳、氢同位素研究表明，海相及盐湖相条件下生物气形成途径为典型的CO2还原途径，具有重的氢同位素组成，其δDCH4>-200‰，而陆相条件下成藏的生物气也主要为CO2还原途径，但氢同位素组成较典型海相成因生物气轻，其δDCH4值在-250‰～-200‰之间。其值可能与古湖泊水介质的咸化程度有关。从柴达木的资料来看，随水介质咸度增大，生物甲烷氢同位素组成也具有相应增大趋势。陆相条件下有处于CO2还原和乙酸发酵两种作用过渡区形成的生物气气藏，其形成可能与古水介质无咸化过程和地温梯度较高有关，如保山盆地。该区形成的生物气具有轻的氢同位素组成，δDCH4<-250‰，碳同位素组成则相对较重，其碳、氢同位素组成之间具有较好的负相关。生物气碳、氢同位素组成的成气机理及途径有可能成为判识自然界采集的生物气气样是否具有工业意义，一般而言，乙酸发酵途径形成的生物气不利于成藏。
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| 关 键 词： | 生物气 同位素 形成途径 |
| 收稿时间： | 1900-01-01 |
Carbon and Hydrogen Isotopic Compositions: generation pathway of bacterial gas in China |
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| SHEN Ping,WANG Xiao-feng,XU Yin,SHI Bao-guang,XU Yong-chang.Carbon and Hydrogen Isotopic Compositions: generation pathway of bacterial gas in China[J].Acta Sedimentologica Sinica,2010,28(1):183-187. |
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| Authors: | SHEN Ping WANG Xiao-feng XU Yin SHI Bao-guang XU Yong-chang |
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| Institution: | Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000 |
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| Abstract: | The carbon and hydrogen isotopic composition of biogenic gas could indicate its forming mechanism and pool-forming characteristics. In this paper, the forming ways and pool-forming characteristics of the biogenic gas are researched according to the carbon and hydrogen isotopic composition of thirty-one samples from ten biogenic gas res-ervoirs. The studies show that the hydrogen isotopic composition of these biogenic gas reservoirs can be divided into three zones, i.e. δD_(CH_4)-200‰, -200‰ ) δD_(CH_4) < 250‰, and δD_(CH_4) <-250‰. The research results of forerunner showed that the main way of biogenic gas forming under the condition of continental fresh water facies is acetate fer-mentation. Our research results show that the typical way of biogenic gas forming under marine and saline lake facies is CO_2 reduction, and the biogenic gas have heavy hydrogen isotopic composition, such as the values of δD_(CH_4) are greater than -200‰; however, the main way of biogenic gas forming under the condition of land facies is the same way too, but they have light hydrogen isotopic composition which may relate to salty degree of ancient lakes as water medi-um, such as the values of δD_(CH_4) are between -200‰ and -250‰. As compared with the relational data of Qaidam Ba-sin, it is showed that the hydrogen isotope composition of the biogenic methane has the same trend as salty degree of water medium increases. The biogenic gas reservoir formed in continental transition region, in which CO_2 reduction generated CH_(4) in company with fermentation together, may relate to constant salinity of ancient water medium and rel-atively high geothermal gradient, such as Baoshan basin. It has light hydrogen isotope, such as the value of δD_(CH_4) less than -250‰, and heavy carbon isotope, which result in a negative correlation between its carbon and hydrogen iso-tope. The carbon and hydrogen isotope composition of biogenic gas controlled by the formation mechanism and ways can be used to identify whether it has industrial utilization value. In general, the biogenic gas from acetate fermenta-tion is not favorable for the formation of gas reservoir. |
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| Keywords: | bacterial gas isotopic composition generation pathway |
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