Geochemical Characteristics of Tertiary Source Rocks in the South Area of Western Qaidam Basin
Online published: 2008-04-20
Based on analyses of source rocks in the Tertiary system in the south area of the western Qaidam basin, the low limit value of TOC is fixed on 0.4%. On this basis, the upper part of Xiagancaigou Formation(E2 3) and the lower part of Xiagancaigou Formation(E1 3) in the Hongshi sag, Zhahaquan sag and Shizigou zone are considered as effective source rocks. By the biomarkers analyses of 24 effective source rocks, we examined the sediment characteristics of the saline lacustrine environment to investigate the Geochemical characteristics. The results show: the Tertiary source rocks in the area are characterized by even over odd preference of n\|Alkanes, Pr/Ph<0.6 and high abundance of gammaceranes and C35 homohopanes, but these characteristics are different in all sags or zones. Different values of Pr/Ph, C35 homohopane/C34 homohopane and gammacerane /C30 hopane reveal that the sediment environment of Tertiary source rocks in the Hongshi sag, Yuejing zone and Shizigou zone is a high saline lacustrine and strong reduction environment and that of Shizigou zone is relatively inferior, while that of Zhahaquan sag is a low\|saline lacustrine and low reduction environment. The two types of oils in the south area of the western Qaidam basin, further, two independent hydrocarbon systems may be indicated by the two patterns of Tertiary source rocks in the same area.
Key words： Qaidam basin; Tertiary; Source rocks; Geochemistry
LI Hong-Bei, ZHANG Min, ZHANG Chun-Meng, BANG De-Hua . Geochemical Characteristics of Tertiary Source Rocks in the South Area of Western Qaidam Basin[J]. Natural Gas Geoscience, 2008 , 19(4) : 519 -523 . DOI: 10.11764/j.issn.1672-1926.2008.04.519
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