板桥凹陷原油芳烃组成特征及地球化学意义
Composition Characteristics and Geochemical Significance of Aromatic Hydrocarbons of Crude Oils from the Banqiao Depression
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摘要: 板桥凹陷原油以低密度、低粘度、低含硫和高凝固点、高含蜡量为特征的中—高蜡凝析油—轻质油为主。芳烃色谱—质谱分析结果显示，常规多环芳烃含量高达66.33%～80.81%；其次是三芴系列，在15%～30%之间；芳香甾烷系列含量仅有5.55%。常规多环芳烃又以二环的萘系列和三环的菲系列为主。用甲基菲指数（MPI1）折算的RC反映板桥凹陷原油处于成熟—高成熟阶段，其中，板深35原油（Es3，4 731 m）折算的RC值达到1.60%。三芳甾烷含量和低碳数三芳甾烷比值与甲基菲指数（MPI3）、甲基二苯并噻吩指数（MDR）均有良好的相关性。三芴系列组成特征反映了原油成因环境为偏沼泽相的弱氧化—还原环境。Abstract: Most of crude oils from the Banqiao Depression are condensate or light oils with lower density, lower viscosity, lower sulfur content and higher solidifying point as well as higher wax. The result of aromatic hydrocarbon fraction in oils by GCMS indicate that the content of regular polycyclic aromatic hydrocarbon series vary from 66.33% to 80.81%, the content of dibenzothiophene (SF), dibenzofuran (OF) and fluorene (F) series is 15% to 30%, and the content of fragrant sterane series is merely 5.55%. The naphthalene series and phenanthrene series are main components of regular polycyclic aromatic series. The maturity RC calculated from methylphenanthrene index (MPI1) showa that the crude oils from the Banqiao Depression are mature to higher mature, and the RC of Banshen 35 (Es3，4731m) reaches highly 1.60%. The correlation between the content of low carbon triaromatic sterane in all triaromatic sterane and MDR shows well, and the correlation of fragrant sterane content in aromatic hydrocarbon fraction and methylphenanthrene index (MPI3) or methyldibenzothiophene ratio (MDR) are also good. The distributed characteristics of SF, OF, and F series show that the primary depositional environments of the oils are pooroxidation and deoxidation environments with secondary paludal facies.
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Key words:
- aromatic hydrocarbon /
- maturity /
- depositional environment /
- Banqiao Depression
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