| Formation of Natural Bitumen and its Implication for Oil/gas Prospect in Dabashan Foreland |
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| 作者姓名： | LI Rongxi DONG Shuwen ZHANG Xue and ZHU Ruijing |
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| 作者单位： | 1 Key Laboratory of West Mineral Resource and Geology Engineering, Education Ministry of China, Chang’an University, Xi’an 710054, China;2 School of Earth Science and Resource, Chang’an University, Xi’an 710054, China;3 Chinese Academy of Geological Sciences, Beijing 100037, China |
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| 基金项目： | Thanks are given to Prof. Hu Jianmin and Dr. Shi Wei from the Chinese Academy of Geological Sciences for their help in the field work. This research was funded by CNSF (No.41173055) and marine department, Sinopec. |
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| 摘 要： | Natural bitumen is the evolutionary residue of hydrocarbon of sedimentary organic matter. Several kinds of bitumen with different occurrences, including bitumen in source rock, migration bitumen filled in fault, oil-bed bitumen and paleo-reservoir bitumen, are distributed widely in the Dabashan foreland. These kinds of bitumen represent the process of oil/gas formation, migration and accumulation in the region. Bitumen in source rock filled in fractures and stylolite and experienced deformation simultaneously together with source rock themselves. It indicated that oil/gas generation and expelling from source rock occurred under normal buried thermal conditions during prototype basin evolution stages prior to orogeny. Occurrences of bitumen in source rock indicated that paleo-reservoir formation conditions existed in the Dabashan foreland. Migration bitumen being widespread in the fault revealed that the fault was the main channel for oil/gas migration, which occurred synchronously with Jurassic foreland deformation. Oil-bed bitumen was the kind of pyrolysis bitumen that distributed in solution pores of reservoir rock in the Dabashan foreland depression, the northeastern Sichuan Basin. Geochemistry of oil-bed bitumen indicated that natural gas that accumulated in the Dabashan foreland depression formed from liquid hydrocarbon by pyrolysis process. However, paleo-reservior bitumen in the Dabashan forleland was the kind of degradation bitumen that formed from liquid hydrocarbon within the paleo-reservior by oxidation, alteration and other secondary changes due to paleo-reservior damage during tectonics in the Dabashan foreland. In combination with the tectonic evolution of the Dabashan foreland, it is proposed that the oil/gas generated, migrated and accumulated to form the paleo-reservoir during the Triassic Indosinian tectonic movement. Jurassic collision orogeny, the Yanshan tectonic movement, led to intracontinental orogeny of the Dabashan area accompanied by geofluid expelling and paleo-reservoir damage in the Dabashan foreland. The present work proposed that there is liquid hydrocarbon exploration potential in the Dabashan foreland, while there are prospects for the existence of natural gas in the Dabashan foreland depression.
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| 关 键 词： | bitumen paleo-reservoir oil/gas formation migration Dabashan foreland |
| 收稿时间： | 2/2/2010 12:00:00 AM |
| 修稿时间： | 2011/8/23 0:00:00 |
Formation of Natural Bitumen and its Implication for Oil/gas Prospect in Dabashan Foreland |
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| Authors: | LI Rongxi DONG Shuwen ZHANG Xue ZHU Ruijing |
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| Institution: | 1. Key Laboratory of West Mineral Resource and Geology Engineering, Education Ministry of China, Chang'an University, Xi'an 710054, China;2. School of Earth Science and Resource, Chang'an University, Xi'an 710054, China;3. Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | Natural bitumen is the evolutionary residue of hydrocarbon of sedimentary organic matter. Several kinds of bitumen with different occurrences, including bitumen in source rock, migration bitumen filled in fault, oil‐bed bitumen and paleo‐reservoir bitumen, are distributed widely in the Dabashan foreland. These kinds of bitumen represent the process of oil/gas formation, migration and accumulation in the region. Bitumen in source rock filled in fractures and stylolite and experienced deformation simultaneously together with source rock themselves. It indicated that oil/gas generation and expelling from source rock occurred under normal buried thermal conditions during prototype basin evolution stages prior to orogeny. Occurrences of bitumen in source rock indicated that paleoreservoir formation conditions existed in the Dabashan foreland. Migration bitumen being widespread in the fault revealed that the fault was the main channel for oil/gas migration, which occurred synchronously with Jurassic foreland deformation. Oil‐bed bitumen was the kind of pyrolysis bitumen that distributed in solution pores of reservoir rock in the Dabashan foreland depression, the northeastern Sichuan Basin. Geochemistry of oil‐bed bitumen indicated that natural gas that accumulated in the Dabashan foreland depression formed from liquid hydrocarbon by pyrolysis process. However, paleo‐reservior bitumen in the Dabashan forleland was the kind of degradation bitumen that formed from liquid hydrocarbon within the paleo‐reservior by oxidation, alteration and other secondary changes due to paleo‐reservior damage during tectonics in the Dabashan foreland. In combination with the tectonic evolution of the Dabashan foreland, it is proposed that the oil/gas generated, migrated and accumulated to form the paleo‐reservoir during the Triassic Indosinian tectonic movement. Jurassic collision orogeny, the Yanshan tectonic movement, led to intracontinental orogeny of the Dabashan area accompanied by geofluid expelling and paleo‐reservoir damage in the Dabashan foreland. The present work proposed that there is liquid hydrocarbon exploration potential in the Dabashan foreland, while there are prospects for the existence of natural gas in the Dabashan foreland depression. |
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| Keywords: | bitumen paleo‐reservoir oil/gas formation migration Dabashan foreland |
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