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
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
WANG Guo-cang，ZHANG Xiao-bao，MENG Qian-xiang，FANG Xuan，HU Hui-yu，SUN Min-zhuo . Geochemical Characteristics of Organic Matter in Low-mature Source Rocks with Microorganisms[J]. Natural Gas Geoscience, 2009 , 20(5) : 768 -773 . DOI: 10.11764/j.issn.1672-1926.2009.05.768
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