The origin of the unusually high dibenzothiophene （DBT） concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin was studied by Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR...The origin of the unusually high dibenzothiophene （DBT） concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin was studied by Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）.The most abundant sulfur compounds in the oils are S 1 species with doublebond equivalent （DBE） values of 1-19 and 11-48 carbon atoms.The range of the number of carbon atoms in the sulfur compounds detected by the FT-ICR MS （S 1 species with DBE=9） is about ten times larger than that for sulfur compounds detected by GC/MS （DBTs）.This suggests that FT-ICR MS is a much better approach than GC/MS for characterization of DBTs in crude oils.The abundance of S 1 species with DBE=1-8 decreased with increasing thermal maturity,while the abundance of S 1 species with DBE=9 （primarily DBTs） increased.Therefore,thermal maturity is an important factor in the formation of oils with high DBT concentrations.Unusually high abundances of S 1 species with low DBE values （1-8）,which include sulfide,thiophene and benzothiophene,were observed in several oils,especially the TZ83 （O 1） oil with high or very high thermal maturity.Thermochemical sulfate reduction （TSR） was thought to be the reason for the high abundance of these low DBE compounds in deep reservoirs,and thermochemical sulfate reduction could affect the distribution and composition of DBTs in the oils.According to the results of FT-ICR MS analysis,there are no signs that TSR is occurring or has occurred recently for most of the Lower Ordovician oils.展开更多
The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and...The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and paleo heat flow,geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins.The average heat flow of the Tarim and Sichuan basins are 42.5±7.6 mW/m^(2)and 53.8±7.6 mW/m^(2),respectively,reflecting the characteristics of’cold’and’warm’basins.The geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Tarim Basin are 21.6±2.9℃/km,20.5±2.8℃/km and 19.6±2.8℃/km,respectively,while the geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Sichuan Basin are 21.9±2.3℃/km,22.1±2.5℃/km and23.3±2.4℃/km respectively.The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate.The formation temperatures at depths of 6,000 m,7,000 m,8,000 m,9,000 m and 10,000 m in the Tarim Basin are 80℃-190℃,90℃-220℃,100℃-230℃,110℃-240℃and 120℃-250℃,respectively,while the formation temperatures at depths of 6,000 m,7,000 m,8,000 m and 9,000 m in the Sichuan Basin are 120℃-200℃,140℃-210℃,160℃-260℃and 180℃-280℃,respectively.The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief,fault activity and hydrothermal upwelling.The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak,while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian,rapidly rising at the end of the early Permian and declining since the late Permian.The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin,which results in differential oil and gas generation and conservation in the ultra-deep ancient strata.This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields,but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.展开更多
Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Z...Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Zhongqiu structural belt and the reservoir formation process in Zhongqiu 1 trap remain unclear, so study on these issues may provide important basis for the next step of oil and gas exploration and deployment in Qiulitage structural belt. In this study, a systematic correlation of oil and gas source in Well Zhongqiu 1 has been carried out. The oil in Well Zhongqiu 1 is derived from Triassic lacustrine mudstone, while the gas is a typical coal-derived gas and mainly from Jurassic coal measures. The oil charging in Well Zhongqiu 1 mainly took place during the sedimentary period from Jidike Formation to Kangcun Formation in Neogene, and the oil was mainly contributed by Triassic source rock;large-scale natural gas charging occurred in the sedimentary period of Kuqa Formation in Neogene, and the coal-derived gas generated in the late Jurassic caused large-scale gas invasion to the early Triassic crude oil reservoirs. The Zhongqiu 1 trap was formed earlier than or at the same period as the hydrocarbon generation and expulsion period of Triassic-Jurassic source rocks. Active faults provided paths for hydrocarbon migration. The source rocks-faults-traps matched well in time and space. Traps in the footwall of the Zhongqiu structural fault have similar reservoir-forming conditions with the Zhongqiu 1 trap, so they are favorable targets in the next step of exploration.展开更多
基金funded by the Natural Science FundingCouncil of China(Grant No.#40973031)the Foundationof State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(No.PRPJC2008-02)Natural Science Research Council of China(China 973 National Key Research and Development Program 2011CB201102)
文摘The origin of the unusually high dibenzothiophene （DBT） concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin was studied by Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）.The most abundant sulfur compounds in the oils are S 1 species with doublebond equivalent （DBE） values of 1-19 and 11-48 carbon atoms.The range of the number of carbon atoms in the sulfur compounds detected by the FT-ICR MS （S 1 species with DBE=9） is about ten times larger than that for sulfur compounds detected by GC/MS （DBTs）.This suggests that FT-ICR MS is a much better approach than GC/MS for characterization of DBTs in crude oils.The abundance of S 1 species with DBE=1-8 decreased with increasing thermal maturity,while the abundance of S 1 species with DBE=9 （primarily DBTs） increased.Therefore,thermal maturity is an important factor in the formation of oils with high DBT concentrations.Unusually high abundances of S 1 species with low DBE values （1-8）,which include sulfide,thiophene and benzothiophene,were observed in several oils,especially the TZ83 （O 1） oil with high or very high thermal maturity.Thermochemical sulfate reduction （TSR） was thought to be the reason for the high abundance of these low DBE compounds in deep reservoirs,and thermochemical sulfate reduction could affect the distribution and composition of DBTs in the oils.According to the results of FT-ICR MS analysis,there are no signs that TSR is occurring or has occurred recently for most of the Lower Ordovician oils.
基金supported by the National Key Researchand Development Program of China(No.2017YFC0603102)the National Natural ScienceFoundation of China(No.U19B6003 and 41972125)。
文摘The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins,China,is unfavorable for further hydrocarbon exploration.This study summarizes and contrasts the present-day and paleo heat flow,geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins.The average heat flow of the Tarim and Sichuan basins are 42.5±7.6 mW/m^(2)and 53.8±7.6 mW/m^(2),respectively,reflecting the characteristics of’cold’and’warm’basins.The geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Tarim Basin are 21.6±2.9℃/km,20.5±2.8℃/km and 19.6±2.8℃/km,respectively,while the geothermal gradient with unified depths of 0-5,000 m,0-6,000 m and 0-7,000 m in the Sichuan Basin are 21.9±2.3℃/km,22.1±2.5℃/km and23.3±2.4℃/km respectively.The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate.The formation temperatures at depths of 6,000 m,7,000 m,8,000 m,9,000 m and 10,000 m in the Tarim Basin are 80℃-190℃,90℃-220℃,100℃-230℃,110℃-240℃and 120℃-250℃,respectively,while the formation temperatures at depths of 6,000 m,7,000 m,8,000 m and 9,000 m in the Sichuan Basin are 120℃-200℃,140℃-210℃,160℃-260℃and 180℃-280℃,respectively.The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief,fault activity and hydrothermal upwelling.The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak,while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian,rapidly rising at the end of the early Permian and declining since the late Permian.The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin,which results in differential oil and gas generation and conservation in the ultra-deep ancient strata.This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields,but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.
基金Supported by the China National Science and Technology Major Project(2016ZX05007-003)the National Natural Science Foundation of China(41802138)
文摘Well Zhongqiu 1 obtained highly productive oil-gas stream in the footwall of Zhongqiu structure, marking the strategic breakthrough of Qiulitag structural belt in the Tarim Basin. However, the oil and gas sources in Zhongqiu structural belt and the reservoir formation process in Zhongqiu 1 trap remain unclear, so study on these issues may provide important basis for the next step of oil and gas exploration and deployment in Qiulitage structural belt. In this study, a systematic correlation of oil and gas source in Well Zhongqiu 1 has been carried out. The oil in Well Zhongqiu 1 is derived from Triassic lacustrine mudstone, while the gas is a typical coal-derived gas and mainly from Jurassic coal measures. The oil charging in Well Zhongqiu 1 mainly took place during the sedimentary period from Jidike Formation to Kangcun Formation in Neogene, and the oil was mainly contributed by Triassic source rock;large-scale natural gas charging occurred in the sedimentary period of Kuqa Formation in Neogene, and the coal-derived gas generated in the late Jurassic caused large-scale gas invasion to the early Triassic crude oil reservoirs. The Zhongqiu 1 trap was formed earlier than or at the same period as the hydrocarbon generation and expulsion period of Triassic-Jurassic source rocks. Active faults provided paths for hydrocarbon migration. The source rocks-faults-traps matched well in time and space. Traps in the footwall of the Zhongqiu structural fault have similar reservoir-forming conditions with the Zhongqiu 1 trap, so they are favorable targets in the next step of exploration.
