| 高演化地质样品中三芳甾类标志物及其地球化学意义 |
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| 引用本文： | 包建平,倪春华,朱翠山,蒋兴超,申旭.高演化地质样品中三芳甾类标志物及其地球化学意义[J].沉积学报,2020,38(4):898-911. |
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| 作者姓名： | 包建平 倪春华 朱翠山 蒋兴超 申旭 |
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| 作者单位： | 1.长江大学地球化学系/油气资源与勘探技术教育部重点实验室，武汉 430100 |
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| 基金项目： | 国家自然科学基金项目41772119, 41272169 |
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| 摘 要： | 借助色谱质谱仪，对黔南坳陷和黔北坳陷凯里残余油藏凯棠剖面液态石油、岩孔古油藏中的热裂解焦沥青和研究区发育的震旦系陡山沱组、下寒武统牛蹄塘组、上奥陶统五峰组和下志留统龙马溪组四套高演化烃源岩的饱和烃和芳烃馏分进行了分析研究。尽管已有研究认为凯里残余油藏和岩孔古油藏的油源岩均是下寒武统牛蹄塘组，但它们具有完全不同的三芳甾类分布与组成。如凯里残余油藏凯棠剖面的液态原油中C28三芳甾烷优势明显，其含量相当于C26+C27三芳甾烷之和的一倍，且三芳甲藻甾烷在甲基三芳甾烷中的含量极低，它与其他甲基三芳甾烷的比值介于0.02~0.05；而在岩孔古油藏的焦沥青中，C26-28三芳甾烷的相对含量呈现C27 >C28 >C26的趋势，三芳甲藻甾烷丰富，它与其他甲基三芳甾烷的比值约为0.50，即比前者高一个数量级，这与研究区四套高演化烃源岩中三芳甾类标志物的分布与组成十分相似。值得注意的是与常规甾、萜烷生物标志物一样，三芳甾类标志物的分布与组成在四套高演化烃源岩中也出现了明显的趋同现象，从而失去了其在油源研究中的实用价值。因此，在利用常规甾、萜烷和三芳甾类标志物开展油源研究时，应尽可能在成熟度相近的地质样品之间进行，且样品的成熟度应限制在生油窗范围内。
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| 关 键 词： | 三芳甾类 三芳甲藻甾烷 原油 焦沥青 烃源岩 黔北坳陷 黔南坳陷 |
| 收稿时间： | 2019-04-29 |
Triaromatic Steroids and Their Geochemical Significance in Highly Mature Geological Samples in the North Guizhou Depression |
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| Institution: | 1.Geochemistry Department/Key Laboratory of Exploration Technologies for Oil & Gas Resource, Ministry of Education, Yangtze University, Wuhan 430100, China2.Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China |
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| Abstract: | The saturate and aromatic fractions in crude oils from the Kaitang section of the Kaili paleoreservoir and pyrobitumen from the Yankong paleoreservoir and extracts from four sets of highly mature source rocks (Z2ds, ∈1n, O3w and S1l) in the North Guizhou and South Guizhou Depressions were analyzed by gas chromatography?mass spectrometry (GC?MS). Previous results had indicated that crude oil and pyrobitumen from the Kaili and Yankong paleoreservoirs were derived from the ∈1n source rocks in the study area, but this study has shown that the distribution and composition of triaromatic steroids in the two paleoreservoirs (C26?28 triaromatic steranes, C27?29 methyl triaromatic steranes and triaromatic dinosteranes) are completely different. For example, in crude oils from the Kaitang section of the Kaili paleoreservoir, the predominant component of the C26?28 triaromatic steranes is C28, with a relative content about twice that of C26 + C27; but, the triaromatic dinosterane content is very low, with a ratio of triaromatic dinosteranes to other methyl triaromatic steranes of only about 0.02?0.05. However, in pyrobitumen from the Yankong paleoreservoir, the relative abundance of C26?28 triaromatic steranes is C27 > C28 > C26, and triaromatic dinosteranes are relatively abundant, with a ratio of them to the other methyl triaromatic steranes of about 0.50, which is one order of magnitude greater than in the Kaitang section of the Kaili paleoreservoir. Moreover, in four sets of highly mature source rocks in the study area, the triaromatic steroids were very similar and consistent with those in pyrobitumen from the Yankong paleoreservoir. It is notable that the distributions and compositions of triaromatic steroids in highly mature geological samples become comparable and similar (e.g., common steranes and terpanes), and lose their geochemical significance and practical value for oil?source correlation. Therefore, an oil?source correlation study should be carried out between geological samples of similar maturity within oil windows when various biomarkers like steranes, terpanes and triaromatic steroids are used. |
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