Source of condensate oil in the middle of southern margin, Junggar Basin, NW China

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• 作者：Jianping CHEN^a ; ^b ; ^c ; ^{chenjp@petrochina.com.cn" class="auth_mail" title="E-mail the corresponding author} ; Chunping DENG^a ; ^b ; ^c ; Xulong WANG^d ; Yunyan NI^a ; ^b ; ^c ; Yongge SUN^e ; Zhe ZHAO^a ; Peirong WANG^c ; Jiande LIAO^d ; Dijia ZHANG^a ; ^b ; ^c ; Digang LIANG^a ; ^b ; ^c
• 关键词：condensate oil ; oil source ; molecular carbon isotope ; biomarker ; Cretaceous ; southern margin of Junggar Basin
• 刊名：Petroleum Exploration and Development
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：43
• 期：5
• 页码：902-913
• 全文大小：1340 K

文摘

Through detailed geochemical analysis of over 40 crude oil, condensate oil and heavy oil samples in the southern margin of Junggar Basin, and based on the hydrocarbon generation condition of five sets of source rocks, with the combination between compositions of carbon isotopes of whole oil, light hydrocarbon, n-alkanes isoprenoids and biomarker composition characteristics, a detailed discussion on the source of the condensate oil in anticlines in the central part of the southern margin was carried out. Condensate oils from the central part of the southern margin have abundant isoprenoids, Pr/Ph<1.0. Carbon isotopes of whole oil are low with δ¹³C value between −27‰ and −28‰. The δ¹³C value of alkanes with carbon number smaller than 9 ranges from −26‰ to −24‰, carbon isotopes of C₉₊ n-alkanes decrease remarkably with increasing carbon number, and the δ¹³C value of C₁₉₊ n-alkanes is lower than −30‰. The δ¹³C value of pristane and phytane is lower than −29‰. The biomarker components contain abundant C₂₇ steranes and C₃₀ methyl steranes, “V” shape distribution of C₂₇, C₂₈ and C₂₉ 20R sterane, abundant tricyclic terpanes with dominance of C₂₁, and relatively high content of gammacerane with two isomers. The 20S/(20S+20R) ratio of C₂₉ steranes is between 0.40 and 0.50, and the maturity calculated by the methylphenanthrene index and distribution fraction (R_c) ranges from 0.70% to 1.1%. These geochemical characteristics of the condensate oils are very similar to those mature crude oils from the typical Cretaceous lacustrine source rocks in the central part of southern margin, but are greatly different from those of typical Jurassic crude oils, implying that these condensate oils are derived from mature Cretaceous lacustrine source rocks instead of highly mature Jurassic coal-measures source rocks.