Publication Date:
2011-05-01
Description:
The offshore Bohai Bay Basin, located in the central Bohai Bay Basin, north China, one of the most petroliferous basins in China. In this article, based on formation-testing temperature, drill-stem tests, and bottom-hole temperature data, 80 thermal gradient values at the depth interval of 0 to approximately 3000 m (~9843 ft) in the offshore Bohai Bay Basin were obtained. The basinwide average thermal gradient is 31.8 ± 4.6°C/km. Based on the above thermal gradient data and the corresponding average weighted thermal conductivity data, 80 measured terrestrial heat flow values were obtained. These values range from 33.5 to 84.0 mW/m2, with an average value of 60.8 ± 8.7 mW/m2. The heat flow and thermal gradient distribution in this region generally show higher values in the uplifts and lower ones in the sags. A thermal history, derived from vitrinite reflectance and apatite fission-track) data, indicates that Paleogene cooling occurred after a period of much higher paleogeothermal gradient (38∼54°C/km). Tectonic subsidence analysis reveals that the area experienced initial synrift subsidence during the Paleogene followed by subsequent thermal subsidence since the Neogene. Thermal and tectonic subsidence histories of this area are of great significance to petroleum exploration and hydrocarbon resource assessment because they bear directly on issues of petroleum source rock maturation. The maturation and hydrocarbon expulsion histories of the Paleogene Shahejie 3 Formation (E2 s 3), which is the most important source rock in the offshore Bohai Bay Basin, are modeled. Results show that the Shahejie 3 Formation is in a high mature stage at the present day, and the Bozhong and Qikou sags are the most important kitchens. The Huanghekou sag became the third most important hydrocarbon kitchen in the early Neogene. Based on this hydrocarbon kitchen evolution, oil and gas mainly accumulated after 12 Ma. The evolution of kitchen areas may provide new insights for the understanding of the oil and gas exploration potential of the offshore Bohai Bay Basin. Yinhui Zuo received his master's degree in mineral survey and exploration from Chengdu University of Technology in 2008 and is now a candidate for a Ph.D. from the China University of Petroleum, Beijing. His current interests include tectonothermal evolution of sedimentary basin and hydrocarbon accumulation history analysis. Nansheng Qiu received his Ph.D. in structural geology from the Institute of Geology, Chinese Academy of Sciences in 1994. He is now a professor of geology at the China University of Petroleum, Beijing. He has conducted tectonothermal history and hydrocarbon generation history in several Chinese basins. His current research interests include tectonothermal evolution of sedimentary basin and hydrocarbon accumulation history analysis. Yuan Zhang received her master's degree in structural geology from the China University of Petroleum, Beijing, in 2008. She is now an employee at Monitor Center for Energy-saving and Emission, China National Offshore Oil Corporation (CNOOC). Her current interest is in energy management. Cuicui Li is a graduate student at the China University of Petroleum, Beijing. Her current interests include tectonothermal evolution of sedimentary basins and hydrocarbon accumulation history analysis. Jianping Li received his master's degree in geochemistry from the China University of Geosciences, Beijing, in 1989. He is now a senior engineer at the Tianjin branch of the China National Offshore Oil Company Ltd. His current research interests include oil and gas exploration geology and oil and gas geochemistry in the Bohai Bay Basin. Yonghua Guo received his master's degree in petroleum geology from the China University of Geosciences, Wuhan, in 1989. He is now a senior geologist at the Tianjin branch of the China National Offshore Oil Company Ltd. His current research interests include petroleum geochemistry and hydrocarbon accumulation history in Bohai Bay Basin. Xiongqi Pang received his Ph.D. in petroleum geology from the China University of Geosciences, Beijing, in 1991. He is now a professor of geology and vice president at the China University of Petroleum, Beijing. He has conducted basin analysis, oil and gas resource assessment, and oil and gas accumulation mechanisms in several Chinese basins. His current research interests include basin analysis, oil and gas resource assessment, and oil and gas accumulation mechanisms.
Print ISSN:
0149-1423
Electronic ISSN:
1943-2674
Topics:
Geosciences
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