Origins of Oil Seepages in the Southern Guizhou Depression, SW China: Evidence from Carbon Isotopes, Sulfur Isotopes and Biomarkers
详细信息
- 责任者：He Xunyun (Key Laboratory of Petroleum Resources Research ; Institute of Geology and Geophysics ; Chinese Academy of Sciences ; Beijing 100029 ; China) ; Cai Chunfang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(3)
- 关键词：生物标志化合物 ; biomarkers ; 碳同位素 ; carbon isotopes ; 硫同位素 ; sulfur isotopes ; 贵州 ; Guizhou Province
- 页码：p.1059-1072
- 图表：illus., 3 tables, 42 refs.
- 分类号：1003
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
An oil-source rock correlation method based on carbon isotopes,sulfur isotopes and biomarkers is described for potential source rocks and oil seepages in the southern Guizhou Depression to elucidate the origins of oil seepages.The results show that the oil seepages have bulk δ13C values from-33.04‰ to-31.63‰,average-32.26‰(n=18),and have δ34S values from +16.06‰ to +23.06‰,average +18.99‰(n=4);the oil seepages are biodegraded with a varying degree,there are many differences in distribution of steranes and terpanes,but they are all relatively rich in tricyclic terpanes,gammacerane,triaromatic steroids,aryl isoprenoids,retene and dibenzothiophene;C25 tricyclic terpane to C24 tetracyclic terpane and the cross plot of dibenzothiophene to phenanthrene and pristane to phytane indicate that the oil seepages are marine origin petroleum;Ts/(Ts+Tm),C29sterane20S/(20S+20R) and methylphenanthrene index all demonstrate that the oil seepages are mature to highly mature.The source rocks from the Lower Cambrian Niutitang Formation in the study area have bulk δ13Ckerogen values from-35.79‰ to-29.88‰,average-32.85‰(n=35),and have δ34Skerogen values from +14.78‰ to +17.60‰,average +16.32‰(n=4),they are well-correlated with those of oil seepages.However the source rocks from the Devonian,Carboniferous and Permian all show bulk δ13Ckerogen values of more than-29.00‰,which are significantly heavier than those of oil seepages.The source rocks from the Lower Devonian,Middle Devonian and Permian show δ34Skerogen values from-9.10‰ to-6.78‰,+0.63‰ to +7.93‰,and-7.40‰ to +4.00‰,respectively,which are significantly lighter than those of oil seepages.Moreover,the source rocks from the Lower Cambrian are relatively rich in gammacerane,triaromatic steroids,aryl isoprenoids,retene and dibenzothiophene,whereas the other source rocks are absent or poor of triaromatic steroids and retene,and show lower abundance of gammacerane and dibenzothiophene.Thus it is demonstrated comprehensively that the oil seepages from the southern Guizhou Depression have the same origin,and are genetically linked to the source rocks of the Lower Cambrian.
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