Geochemistry and charge history of oils from the Yuqi area of Tarim Basin,NW China |
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| Institution: | 1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 10083, China;2. Beijing Research Institute of Uranium Geology, Beijing 100029, China;1. Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Science, Peking University, Beijing 100871, China;2. Institute of Geophysics, Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Xinjiang 830013, China;3. PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China;1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China;2. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China;3. Geological institute of North China Oilfield Erenhot branch company, PetroChina, Renqiu 062550, China;1. School of Geosciences, China University of Petroleum, 66 Changjiang West Road, Huangdao District, Qingdao, Shandong, 266580, China;2. College of Geosciences, China University of Petroleum, 18 Fuxue Road, Changping District, Beijing, 102249, China;3. College of Geological Science and Engineering, Shandong University of Science and Technology, 579 Qianwangang Road, Huangdao District, Qingdao, Shandong, 266510, China;1. State Key Laboratory of Petroleum Resources and Prospecting, College of Geosciences, China University of Petroleum, Beijing 102249, China;2. Research Institute of Petroleum Exploration and Development, Tarim Oilfield Company, PetroChina, Xinjiang, Korla 841000, China;1. Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics, CAS, Beijing 100029, China;2. Key Lab of Exploration Technologies for Oil and Gas Resources of Ministry of Education, Yangtze University, Wuhan 430100, China;3. Institute of Earth Sciences, Hebrew University, Jerusalem 91904, Israel;4. Liverpool University, Department of Earth, Ocean and Ecological Sciences, Liverpool, Merseyside L69 3GP, UK;1. Research Institute of Petroleum Exploration and Development, Tarim Oilfield Company, PetroChina, Xinjiang Korla 841000, China;2. State Key Laboratory of Petroleum Resources and Prospecting, College of Geosciences, China University of Petroleum, Beijing 102249, China |
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| Abstract: | The geochemistry, origin and charge history of oils from the Yuqi area of Tarim Basin have been investigated, through GC, GC-MS and fluid inclusion microthermometry analysis. The Yuqi oils accumulated mainly in three intervals: (1) in the Lower-Middle Ordovician Yingshan Formation (O1-2y) carbonate reservoirs; (2) in the overlying Upper Triassic Halahatang Formation (T3h); and (3) in the Lower Cretaceous Yageliemu Formation (K1y) sandstones. Oils from different reservoirs have distinct physical properties, varying from extra-heavy (O1-2y), heavy (T3h), to light oils (T3h and K1y). However, their geochemical compositions show a high degree of similarity, which indicates that they derive from the same source rock. Abundant tricyclic terpanes, gammacerane, dibenzothiophene and C21 C22steranes, together with a low level of diasteranes, indicate an anoxic marine source rock for oils in the Yuqi area. Oil-oil correlation shows that Yuqi oils derive from the same source bed as Tahe oils. The co-occurrence of intact n-alkanes and 25-norhopanes in all the samples supports the proposition that there is a mixture of an early filled severely biodegraded oil and a late filled fresh oil.In this study, charge history is examined on the basis of integration of fluid inclusion homogenization temperature data with 1D burial-thermal history models. Two episodes of oil charging are identified in the O1-2y reservoir (well YQX1-1) at around 436-420 Ma (Middle-Late Silurian) and 10-3 Ma (Miocene to Pliocene), respectively. For the samples from the T3h and K1y intervals, only one episode of oil charge is indicated by the homogenization temperatures of coexisting aqueous inclusions with an inferred timing around 10-3 Ma. The T3h heavy oil reservoir is assumed to be a secondary hydrocarbon pool, which accumulated by re-migration and re-distribution of hydrocarbons from O1-2y hydrocarbon pools. The few early biodegraded oils in the K1y light oils were probably picked up along the migration pathway during the late fresh oil charging. |
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| Keywords: | Tarim basin Tabei uplift Yuqi area Crude oils Geochemistry Oil charge history |
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