Abstract The oil origin and secondary migration pathways were investigated in the Bonan sag using basin modeling and petroleum geochemical data including biomarker assemblages of saturated hydrocarbons and pyrrolic nitrogen compounds. The modeling of secondary oil migration pathway was performed based on the reconstruction of burial, thermal maturity and oil generation histories. Modeling results are calibrated by the distribution of oil wells and oil fields as well as traced secondary oil migration pathways inferred from pyrrolic nitrogen compounds. Carbazole parameters were selected to trace the secondary oil migration pathway based on the investigation of oil origin. Three groups of oils sourced from source rocks of the third and fourth members of Shahejie Formation (Es3 and Es4) have been identified in this study. Group Ⅰ oils from Es3 source rocks mainly occurred in the center of sag, group Ⅱ oils from Es4 source rocks occurred in the margin regions. Group Ⅲ oils were interpreted to be the mixed sources from Es3 and Es4 source rocks. Three oil migration pathways can be traced by pyrrolic nitrogen compounds based on varied carbazole parameters. The major stages of oil generation of Es3 and Es4 source rocks occurred at about 30–20 Ma and 5-0 Ma, which coincided with oil charge periods. Secondary oil migration pathways have been predicted successfully by the oil migration modeling in the Bonan sag based on the calibration with oil wells, oil fields and the traced oil migration pathways by pyrrolic nitrogen compounds. Favorable zones located on the primary secondary oil migration pathways at the periods of oil charge may be the prospective regions for oil exploration in the Bonan sag.

中文翻译：

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渤海湾盆地渤南凹陷石油成因及次生运移途径

摘要 利用盆地建模和石油地球化学数据，包括饱和烃和吡咯氮化合物的生物标志物组合，研究了渤南凹陷的石油成因和次生运移途径。在重建埋藏、热成熟和生油历史的基础上进行次生石油运移路径建模。建模结果通过油井和油田的分布以及从吡咯氮化合物推断出的追踪次生石油运移途径进行校准。在石油来源调查的基础上，选择咔唑参数来追踪石油次生运移途径。本次研究确定了三组来源于沙三、四段烃源岩（沙三、沙四）的油类。沙三烃源岩Ⅰ组油主要赋存于凹陷中心，沙四烃源岩Ⅱ组油主要赋存于边缘地区。Ⅲ类油被解释为沙三和沙四烃源岩的混合源。基于不同咔唑参数的吡咯氮化合物可以追踪三种石油运移途径。沙三、沙四烃源岩的主要生油期发生在 30～20 Ma 和 5～0 Ma 左右，与石油充注期相吻合。在油井、油田标定和吡咯氮化合物示踪油运移路径的基础上，通过渤南凹陷油运移模型成功预测了次生油运移路径。