Publication Date:
2009-02-01
Description:
The Penglai 19-3 (PL19-3) oil field, the largest offshore oil field in China, was found in shallow reservoirs (700–1700 m, 2297–5577 ft) within the most active fault zone in east China. The PL19-3 anticline was not finally formed until about 2.0 Ma and is cut by densely distributed faults. Source rock and crude oil samples from the PL19-3 field were analyzed to determine the origin and formation mechanisms of this large oil field. Three organic-rich, oil-prone source rock intervals exist in the Bozhong subbasin, each of which has a distinct biomarker assemblage. Oil samples from different wells have different biomarker associations, and three source-related oil classes were identified within the PL19-3 field based on biomarker compositions and multivariate analysis of the data. The PL19-3 field displays considerable compositional heterogeneity. The compositional heterogeneity within the field and comparison between oil samples from the PL19-3 field and those from nearby structures suggest three field-filling directions, which is consistent with the results of migration pathway modeling. The PL19-3 field was charged in the north by oil generated from Dongying Formation source rocks in the eastern Bozhong depression and Bodong depression, in the southeast by oil generated from Shahejie Formation source rocks in the Miaoxi depression, and in the northwest by oil generated from Shahejie Formation source rocks in the central Bozhong depression. Oil charge from multiple source rock intervals and multiple generative kitchens and focusing of oil originating from a large area of the Bozhong depression into the same trap resulted in rapid oil accumulation in the PL19-3 structure and the formation of this large oil field in a very young trap within an active fault zone. Fang Hao received his Ph.D. from the China University of Geosciences in 1995. He is now a professor of geology at China University of Petroleum and the director of the State Key Laboratory of Petroleum Resources and Prospecting. He has conducted petroleum geology and geochemistry studies in several Chinese basins. His interest includes petroleum generation, migration, and accumulation in the Bohai Bay Basin. Xinhuai Zhou has a Ph.D. in geology from the China University of Geosciences. He is now the chief geologist of the Technology Department of the Tianjin branch of CNOOC Ltd. He has conducted petroleum geology studies in the Bohai Bay Basin for more than 10 years. His publications include studies of petroleum generation, migration, and accumulation in the offshore area of the Bohai Bay Basin. Yangming Zhu received his Ph.D. from the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (CAS) in 1993. He is now a professor of geochemistry at Zhejiang University. He has conducted petroleum geochemistry studies in several Chinese basins. His interest is now in the study of deposition and evolution of lacustrine source rocks. Xiaohuan Bao received his Ph.D. from the China University of Geosciences in 2008. He is now a research scientist at the university. His interest is in basin modeling and chemometric analysis of geological and geochemical data. Yuanyuan Yang graduated in 2007 with a degree in geochemistry from the Yangtze University and is now a graduate student at China University of Petroleum. Her interest is in the study of biomarker compositions of lacustrine source rocks and crude oils in the Bohai Bay Basin.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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