原油和生油岩中完整短链甾类系列化合物(C20-C26的发现及其意义 |
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引用本文: | 潘志清 林壬子. 原油和生油岩中完整短链甾类系列化合物(C20-C26的发现及其意义[J]. 沉积学报, 1991, 9(2): 106-113 |
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作者姓名: | 潘志清 林壬子 |
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作者单位: | 1.北京石油勘探开发研究院; |
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摘 要: | 笔者首次在华北晋县高硫原油和含硫膏泥岩的饱和烃馏份中检测出丰富的短链甾类化合物(C20-C26),它们包括甾烷、甾烯、4-甲基甾烷和4,4-二甲基甾烷。同时,样品中还检测出C23-C25类异戊二烯烷烃。这此化合物是盐湖相沉积环境中细菌输入和降解作用的产物。
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关 键 词: | 短链甾类 类异戊二烯烷烃 γ -蜡烷 盐湖相 细菌输入和降解 |
收稿时间: | 1989-01-24 |
Identification of a Complete Series of Short Side Chain Steroids (C20C26) in Crude Oil and Souree Rock and Its Geochemical Significance |
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Affiliation: | 1.Institute of Petroleum Exploration and Development, Beijing;2.Jianghan Institute of Petroleum |
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Abstract: | A complete series of short side chain steroids (C20-C26) have first been identified in the crude oil and source rock of saline lake facies from Jinxian Sag of North China by GC / MS and the biological origin and geochemical significance of these compounds are dicussed. The short side chain steroid compounds identified include: (a) steranes, which have m/ z 217 or m/z218 base peak in its mass spectrum but the length of their side chain at C-20 position are different (fig.2). (b) 4-methyl and 4, 4-dimethyl pregnanes and homopregnanes (Fig.3). (c) sterenes, whichs molecular weight are 2 units less than the carbons number corresponding steranes and have m / z 281 base peak or characteristic peak on their mass spectrum.lt can be inferred that the position of double bond is on the D ring (Fig.4). There are some geochemical phenomena accompaning the occurrence of short side chain steroids. The content of n?alkanes is lower and the content of lower carbon number is much more than the higher (∑C21-/ ∑C22+= 3.66), and the major peak is C16, there is a higher concentration of C23, C24and C25isoprenoid hydrocarbons (peak K, L and M in Fig.5) Besides higher concentration of pristane and phytane. It is proposed that the high concentrations of isoprenoid hydrocarbons and low carbon number n-alkanes are the result of bacterial input. It is intresting that in our samples the content of short side chain steroids (c20-C26) is much higher than the C27-C29 steranes. the occurrence of a series of short side chain steroids is considered to be the products of some halophilic bacterial activities and, the high concentration of γ- cerane provides another evidence. Furthermore, it has been noticed that the common C21-pregnanes and C22-homopregnanes are dominated in the short side chain steriods.They should be the derivatives from some microorganisms especially from pregnant sterone and pregnant sterol in the halophilic bacteria. As for the origin of all short side chain steroids, however, bacteria (fat discomposition bacteria) degradation leading to side chain rupture of normal steranes could not be excluded. There is nearly not the long side chain hopanes above C30but a high content of C30hopane.It shows that bacterial degradation may result a vanishing of long side chain hopanes and relative richment of C30opane, and indicates shows the existence of the bacterial degradation. In short, the input of organic matter are mainly derived from bacteria and algal, and the original organic matter had experienced a bacterial reconstruction.Therefore, the existence of short side chain steroids and some accompaning marker compounds reflects a hypersaline and component reducing depositional envi- ronment and bacterial biodegradation of some biological precursor molecules. |
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