南堡凹陷潜山原油特征与成因探讨
摘要: 南堡凹陷滩海区深部古生界已相继发现数口高产工业油气流井，其性质不同于上伏第三系原油。采用地质地球化学方法相结合途径，对油气特征与成因进行了剖析。已发现潜山原油主要为高蜡油、其次为凝析油。GC、GC/MS分析表明，潜山原油中链烷烃组分含量较高、甾萜类生标含量较低且异构化程度较高；富含重排甾烷、重排藿烷与18a（H）-新降藿烷（Ts）与C29Ts；部分生标如升藿烷系列有明显热裂解现象，指示潜山原油较高的成熟度。油—油、油—岩对比表明，潜山原油与沙二+三段烃源岩有成因联系。供烃方式主要包含近距离—烃源岩直接披覆于潜山及源—储通过断层对接供烃、远距离—断层和风化壳运移输导两种。南堡凹陷潜山高蜡油的形成主要与烃源岩主要为Ⅱ2-Ⅲ型有机质类型有利于提供蜡质烃以及深部奥陶系油气藏极可能遭受气洗有关。气洗迹象包括低分子量链烷烃被切割、萘系列相对丰度低于菲系列，出现“倒转”等反常现象。南堡凹陷潜山油气特征与成因研究有助于揭示该区深部油气藏的形成机制及开展深部油气资源评价。
Characteristics and Formation Mechanism of Deep Oils from Nanpu Depression, Bohai Bay Basin
Abstract: Industrial petroleum was discovered from Palaeozoic deep horizons in the Nanpu depression, Bohai Bay Basin, which is different from the overlying Tertiary oils from view of physical and chemical properties. Conventional geochemical methods were used to delineate the oils combined with geological analysis. There are two types of the deep buried hill oils were discovered, one is high waxy oil in the Ordovician and another is condensate oils in the Cambrian. It was observed by GC, GC-MS that, the buried hill oils contain high contents of alkyl alkanes while low concentrations of biomarkers such as steranes and hopanes. The distinguishing characteristics of the oils are high to super-high concentrations of diasteranes, diahopane, 18α(H) -22, 27, 29-trinorhopane and (Ts) and C29Ts detected in the oils with obvious thermal cracking of homohopanes, suggesting high thermal maturity of the oils. Oil-oil and oil-source rock correlations show that the oils have close genetic affinity with the Es2+3 source rocks. Hydrocarbons can be charged into the burial hill from the Es2+3 rocks directly overlying on the buried hill and/or contacted with the buried hill reservoir through faults displacement, characterized by short migration distance. Meanwhile, hydrocarbons derived from source rocks can also migrate through deeply cutting faults and Palaeozoic weathered crust into the buried hill reservoir with relatively long migration distance. It was suggested that both the kerogen type (Ⅱ2-Ⅲ) of the source rocks and gas invasion in geological history should be responsible for the formation of the high waxy oils. The former is liable to generate waxy hydrocarbons, and the latter can be inferred from the fact that the n-alkanes with carbon number less than C19 in the oils were commonly depleted and the relative concentration of naphthalenes are a little less than that of the phenanthrenes. These phenomena are obviously abnormal compared with that of the shallow oils overlying. This study is helpful for unraveling hydrocarbons accumulation mechanisms and deep petroleum resources evaluation in the area.
南堡凹陷潜山原油特征与成因探讨[J]. 沉积学报, 2014, 32(2): 376-384.
| 引用本文: |
南堡凹陷潜山原油特征与成因探讨[J]. 沉积学报, 2014, 32(2): 376-384.
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Characteristics and Formation Mechanism of Deep Oils from Nanpu Depression, Bohai Bay Basin[J]. Acta Sedimentologica Sinica, 2014, 32(2): 376-384.
| Citation: |
Characteristics and Formation Mechanism of Deep Oils from Nanpu Depression, Bohai Bay Basin[J]. Acta Sedimentologica Sinica, 2014, 32(2): 376-384.
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