Oil origin and secondary migration pathway in the Bonan sag, Bohai Bay Basin, China. (December 2020)

• Record Type: Journal Article
• Authors: Han, Jinhu; Guo, Xiaowen; Dong, Tian; He, Sheng; Wang, Yongshi; Wang, Xuejun; Hua, Yanqi; Zhao, Wen; Chen, Jiaxu
• Is Part Of: Marine and petroleum geology. Volume 122(2020)
• Publication Date: 2020-12
• Subjects: Secondary oil migration pathway -- Oil-source correlation -- Basin modeling -- Pyrrolic nitrogen compounds -- Bonan sag; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2020.104702
• Languages: English
• ISSNs: 0264-8172

Abstract

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. Highlights: 1. The origin of oils was investigated in an extremely oil-rich sag. 2. The secondary oil migration pathways of Es3 and Es4 intervals were determined at the periods of oil charging by basin modeling. 3. By integrated analysis of basin modeling and pyrrolic nitrogen compounds, the secondary oil migration pathways were traced. 4. Favorable oil accumulation regions were predicted in the Es3 and Es4 intervals.