收稿日期: 2009-03-02
修回日期: 2009-06-16
网络出版日期: 2009-10-10
基金资助
国家重点基础研究发展规划项目(编号:2007CB209500)资助.
Geochemical Characteristics of Organic Matter in Low-mature Source Rocks with Microorganisms
Received date: 2009-03-02
Revised date: 2009-06-16
Online published: 2009-10-10
对采自柴达木盆地涩北1井的2块钙质泥岩样品的饱和烃、芳烃和非烃馏分进行了系统的分析。检测出微生物特征生标MPI和角鲨烷化合物,在非烃馏分中检测出不饱和脂肪酸、异构脂肪酸和反异构脂肪酸。样品所处的地温为30℃左右,古环境细菌发育。同时检测出的8,14\|断藿烷和烷基酮系列是微生物对沉积有机质改造的产物。在微生物作用下,低熟源岩有机质发生大分子向小分子转化,强烈的去甲基过程,藿烷C31/32αβ22S/(22S+22R)值和甾烷C29ββ/(ββ+αα)值等参数出现异常。微生物对低熟源岩的生物降解作用,有利于烃源岩生成气态烃,且对其降解具有饱和烃>芳烃>非烃的特征。
王国仓,张晓宝,孟仟祥,房嬛,胡慧瑜,孙敏卓,徐茵 . 低熟烃源岩有机质在微生物作用下的地球化学特征[J]. 天然气地球科学, 2009 , 20(5) : 768 -773 . DOI: 10.11764/j.issn.1672-1926.2009.05.768
Based on two pieces of calcilutite from the Sebei Well 1 in Qaidam basin, a systematic analysis of saturation hydrocarbon and aromatic hydrocarbon and nonhydrocarbon is employed to study the complex hydrocarbon charging histories. By GC/MSD, we found the aqualane and MPI (2,6,10,15,19 pentanethyl-eicosane) of the microbial characteristic biomarkers and the unsaturated fatty acid and isofatty acid and trans-iso-fatty acid. In addition, the ground temperature of samples is about 30℃, which is good for microorganisms thriving. Hence there were some microorganisms in the palaeosedimentary environment of the samples. Microorganisms transformed sedimentary organic matters, so they produced the 8,14-secohopane and alkaneones by the degradation of bacterium-germs. With the participation of microbes, the low mature source rocks would change greatly and the macro molecules were partly transformed to the micro molecules and the demethylation was strong and the ratio of C31/32αβ22S/(22S+22R)of hopanes and C29ββ/(ββ+αα) of steranes occurred abnormally. The result shows that the microbial degradation was helpful to generating gaseous hydrocarbon. And the sequences of degradation of low mature source rocks is saturation hydrocarbon>aromatic hydrocarbon> nonhydrocarbon.
Key words: Qaidam basin; Low\; mature source rock; Biodegradation
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