The origin and charging directions of Neogene biodegraded oils: A geochemical study of large oil fields in the middle of the Shijiutuo Uplift,Bohai Sea,China |
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| Institution: | 1. School of Geoscience, China University of Petroleum, Changjiang West Road, No.66, Huangdao District, Qingdao, Shandong, 266580, China;2. Key Laboratory of Tectonics and Petroleum Resources, Ministry of Education, China University of Geosciences, Wuhan, 430074, China;3. Tianjin Branch of China National Offshore Oil Company Ltd., Tianjin, 300452, China;4. Department of Earth Sciences, Zhejiang University, Hangzhou, Zhejiang, 310027, China;5. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Fuxue Road No. 18, Changping, Beijing, 102249, China;1. State Key Laboratory of Petroleum Resources and Engineering, Beijing 102249, China;2. Wuxi Research Institute of Petroleum Geology, Sinopec Petroleum Exploration & Production Research Institute, Wuxi 214151, China;3. Unconventional Natural Gas Institute, China University of Petroleum, Beijing 102249, China;4. Geology Scientific Research Institute of Shengli Oilfield Company, Sinopec, Dongying 257015, China;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;2. Unconventional Natural Gas Research Institute, China University of Petroleum, Beijing 102249, China;3. Key Laboratory of Petroleum Resource Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;4. College of Geosciences, China University of Petroleum, Beijing 102249, China;1. Basin and Reservoir Research Center, College of Geosciences, China University of Petroleum, Changping, Beijing, 102249, China;2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Changping, Beijing 102249, China;3. Research Institute of Petroleum Exploration and Development in Dagang Oilfield, Tianjin 300280, China;1. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, 18 Fuxue Road, Beijing 102249, China;2. Department of Geology, University of Regina, 3737 Wascana Parkway, Regina, Saskatchewan S4S 0A2, Canada;3. Exploration & Development Institute, Xinjiang Oil Field Company, 29 Junggar Road, Karamay, Xinjiang 834000, China |
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| Abstract: | Two large oil fields (QHD32-6 and QHD33-1), located in the middle part of the Shijiutuo Uplift, have generally suffered mild biodegradation. Based on multivariate statistical analysis of the biomarker parameters, this study discussed the origin and charging directions for these two oil fields.In contrast to Ed3-derived oil, all available oil samples from these two large oil fields displayed low C19/C23, C24/C26 and high G/H and 4-MSI, which are attributed to the mixtures of oils derived from the Shahejie (Es1 and Es3) source rocks. Oils in QHD32-6, which contain relatively more Es3-derived oil, are called Group I oils, and most oils in QHD33-1, which share relatively more Es1-derived oil, are called Group II oils. Our mixed oil experiments reveal the predominant Es3- and Es1-derived oil contribution for Group I and Group II oil groups, respectively; however, the selection of end member oils warrants further research.Based on comparisons of biomarker parameters, the QHD32-6 oil field was mainly charged in the north by oil generated from Shahejie formation source rocks in the Bozhong depression. However, oils from the north of QHD32-6 field display a remarkable difference to the oils in the south of this field, which may indicate that a charging pathway exists from the QHD33-1 field. Considering the variations in biomarker compositions in the west to -east and northwest to -southeast sections across the QHD33-1 and QHD32-6 oil fields, it can be deduced that Es3-sourced oil migrated westward to the QHD32-6 traps, and then charging by Es1 oil from the Bozhong Sag resulted in the QHD33-1 oil field being characterized by the mixture of Es3- and Es1-sourced oil. Moreover, migration of Es1-derived oil from the Qinnan Sag was not identified, implying that the QHD33-1 oil field is mainly charged from the northeast of the Bozhong Sag. |
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| Keywords: | Bohai Sea Shijiutuo Uplift Origin Charging direction Biomarkers |
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