CHARACTERISTICS AND IMPLICATION OF BIOMARKER COMPOUNDS IN SOURCE ROCKS FROM BEIPIAO FORMATION IN JINYANG BASIN, WESTERN LIAONING PROVINCE
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摘要: 采用气相色谱、气相色谱-质谱技术，研究了辽西金羊盆地北票组烃源岩的生物标志化合物特征，剖析其蕴含的有机质生源、沉积环境、有机质热演化程度等信息.金羊盆地北票组烃源岩样品的正构烷烃的正构烷烃分布图（m/z 85）峰型以"前峰型"的单峰态分布为主，表现出成熟源岩的分布特征；甾烷C29-αββ/（ααα+αββ）值介于0.35~0.58之间，平均为0.50，表明金羊盆地北票组绝大多数烃源岩处于成熟阶段，部分已达生油高峰或高成熟阶段.Pr/Ph值主要介于1.0~3.0之间，表现出弱的姥鲛烷优势；Pr/nC17-Ph/nC18交汇图判识北票组烃源岩以Ⅲ型为主，三环萜烷呈C20为主峰的正态分布，整体表现C24四环二萜含量很高，C24四环二萜/C26三环萜烷比值基本都大于1，SZK01、SZK03井烃源岩的三环萜烷/藿烷比值都低于0.4，烃源岩伽马蜡烷指数分布在0.02~0.30之间，平均值为0.12，说明金羊盆地北票组烃源岩形成于偏氧化性的微咸水-淡水的浅水沉积环境，为典型高等植物输入的沉积相带.Abstract: The gas chromatography and gas chromatography-mass spectrometry are combined to study the characteristics of biomarker compounds in source rocks from Beipiao Formation in Jinyang Basin, western Liaoning Province, by analysis of such information as the sources, sedimentary environment and thermal evolution degree of organic matter in rocks. The mass spectrometry of normal-alkanes for source rock samples shows characteristics of mature source rocks dominated by front peak-typed unimodal distribution. The ratios of C29-αββ/(ααα+αββ), varying between 0.35 and 0.58 with mean value of 0.5, indicate that most source rocks are in mature stage, while some have reached the peak or high mature stage. The Pr/Ph ratio (1.0-3.0) shows a weak pristane advantage. According to the cross plot of Pr/nC17-Ph/nC18, the source rocks are dominated by Ⅲ-type. The tricyclic terpane is normally distributed with C20 as the main peak. The content of C24 tetracyclic diterpane is generally high. The ratios of C24 tetracyclic diterpane and C26 tricyclic terpane are basically greater than 1, while the ratios of tricyclic terpane/hopane of source rocks from SZK01 and SZK03 wells less than 0.4. The gammacerane indexes range from 0.02 to 0.30 with average of 0.12. From the above, the source rocks from Beipiao Formation were formed in the brackish water-freshwater shallow water sedimentary environment with partial oxidation, belonging to typical sedimentary facies zones with advanced plant immigration.
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Key words:
- Jinyang Basin /
- Beipiao Formation /
- source rock /
- biomarker compound /
- Liaoning Province
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