Geochemical significance of 17α(H)-diahopane and its application in oil-source correlation of Yanchang formation in Longdong area, Ordos basin, China
Geochemical significance of 17α(H)-diahopane and its application in oil-source correlation of Yanchang formation in Longdong area, Ordos basin, China
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DOI：
10.1016/j.marpetgeo.2015.10.016
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发表时间：
2016-03
影响因子：
4.2
通讯作者：
Weiwei Yang;Guangdi Liu;Yuan Feng
中科院分区：
文献类型：
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作者：
Weiwei Yang;Guangdi Liu;Yuan Feng
鄂尔多斯盆地西南部陇东地区延长组部分原油和岩石抽提物中检测到较高丰度的17α(H)-C30重排藿烷。延长组油页岩、粉质泥岩和碳质泥岩抽提物中C30重排石烷丰度较低，而暗色泥岩抽提物中C30重排石烷丰度较高。对有机质来源、热成熟度和沉积有机相进行了地球化学参数分析。结果表明，沉积-氧化还原环境和岩性可能是决定石墨烯重排的关键因素，这与Peters和Moldowan(1993)的观点一致。根据Diaopane的相对丰度，可将其划分为三个油类。低丰度的1类油来自长7段油页岩，而中高丰度的3类油来自延长组长4+5~长9段暗色泥岩。在151个来自不同地层段的分析和提取的石油样品中，105个样品属于来自油页岩的1类油，46个样品属于来自泥岩的2类和3类油。因此，长7段油页岩是陇东地区的主要有效生油岩，长4段+长5段至长9段暗色泥岩也是重要的生油岩。
Relatively high abundance of 17α(H)–C30rearranged hopane has been detected in some oils and rock extracts from Yanchang Formation of Longdong area, southwestern Ordos basin. Oil shale, silty mudstone and carbonaceous mudstone extracts from Yanchang Formation all have low abundance of C30rearranged hopane, while high concentrations of C30rearranged hopane were observed in the dark mudstone extracts. Analysis on the geochemical parameters of the organic matter origin, thermal maturity, and sedimentary organic facies were carried out. The result showed that the depositional-redox environment and lithology may be the critical factors for the rearrangement of hopanes which usually occurred in suboxic condition with clay-catalyzed reactions, as is consistent with the viewpoint of Peters and Moldowan (1993). According to the relative abundance of diahopane, three oil classes can be identified. Class 1 oil with low abundance of diahopanes was originated from oil shale of Chang 7 member, while Class 2 oil and Class 3 oil with middle to high abundance of diahopanes were derived from dark mudstones of Chang 4 + 5 to Chang 9 members of Yanchang Formation. Of the 151 analyzed oil and extracts samples from different stratigraphic intervals, 105 samples belong to Class 1 oil coming from oil shale, while 46 samples belong to Class 2 and Class 3 oil derived from mudstones. So oil shale of Chang 7 member is the main effective source rock of Longdong area, and dark mudstones of Chang 4 + 5 to Chang 9 member are also important source rocks.