藏北南羌塘盆地扎仁地区油苗地球化学特征及意义
Geochemistry and Significance of Oil Seepages in the Zaring Area of the Southern Qiangtang Depression, Northern Tibet
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摘要: 扎仁地区地处南羌塘盆地南缘，属油气研究的“空白区”，结合羌塘盆地扎仁区块1∶〖KG-*2〗5万石油地质构造详查，重点研究了位于该区的地表油苗的生物标志化合物和分子碳同位素特征，并且进行了油源对比。研究资料揭示了原油有机质母质为菌藻类和高等植物，特别是藻类为原油的形成作出了贡献；原油形成于还原—弱还原的咸水环境，显示成熟原油的特征。原油的生物标志物特征和中侏罗统夏里组烃源岩具有亲缘关系，反映了原油主要来源于夏里组烃源岩，但其单体碳同位素特征又与夏里组烃源岩存在一定的差异，反映了混合来源的特征。Abstract: Located on the southern margin of the southern Qaingtang depression, the Zaring area is a “gap area” for hydrocarbon investigation. Detailed reconnaissance of 1∶〖KG-*2〗50,000 petroleum geological structures was carried out in the Zaring block of the Qaingtang Basin, and according to the reconnaissance results the authors analyze biomarkers and molecular carbon isotopic composition of oil seepages in this area, and the oil/source correlation was also discussed in this paper. The data indicate that the oilforming matrixes are algae and higher plants, especially with an important contribution of algae to the formation. The crude oils were formed under weak reductionreduction and salt water environment. The crude oils are mature. The biomarkers of crude oils are closely correlated to those of the Xiali Formation hydrocarbon source rocks, reflecting that crude oils were mainly originated from the Xiali Formation. However, compound specific Cisotope composition exists some differences between crude oils and Xiali Formation hydrocarbon source rocks, indicating a mixture of sources.
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