A comprehensive study was conducted on the hydrocarbon generation potential of the deeply buried Permian source rocks with high-over mature in the southwestern part of the Central Depression,Junggar Basin.Using rock-e...A comprehensive study was conducted on the hydrocarbon generation potential of the deeply buried Permian source rocks with high-over mature in the southwestern part of the Central Depression,Junggar Basin.Using rock-eval pyrolysis,carbon-sulfur analysis,kerogen macerals analysis,adamantane quantification,molecular geochemistry,and major and trace element analysis,coupled with organic carbon recovery methods.The evaluation primarily focused on thermal maturation,types,and abundance of organic matter,with an emphasis on summarizing methods for evaluating high-over mature source rocks.The results demonstrate that the Permian source rocks in the Shawan Sag(Well Zhengshen-101)and the Penyijingxi Sag(Well Zhuangshen-1)have reached a high-over mature stage,as evidenced by vitrinite reflectance(Ro),adamantane parameters,methyl phenanthrene indices(MPI),and Laser Raman spectroscopy.Horizontally,for the Fengcheng(P_(1)f)and Lower Wuerhe(P_(2)w)formations,the Well Zhengshen101 in the Shawan Sag is thermally more matured than the Well Zhuangshen-1 in the Penyijingxi Sag,while vertically,both wells show that the P_(1)f is thermally more mature than the P_(2)w.Raman and Fourier transform infrared(FTIR)spectroscopy confirm that Type Ⅱ kerogen is the dominant organic matter type.Through material balance,degradation ratio,and inorganic element methods,obtain the original content of organic carbon(TOC_(0))and hydrocarbon generation potential(S_(1)+S_(2)).After restoration,the P_(1)f samples from Well Zhengshen-101 in the Shawan Sag show moderate to high-quality organic matter abundance,predominantly high-quality;the P_(2)w samples are classified as high-quality source rocks.The Xiazijie Formation(P_(2)x)and the P_(2)w samples from Well Zhuangshen-1 in the Penyijingxi Sag range from poor to high-quality,predominantly good to high-quality.Horizontally,the P_(2)w samples from Well Zhengshen101 in the Shawan Sag exhibit higher organic matter abundance compared to those from Well Zhuangshen-1 in the Penyijingxi Sag.Notably,the P_(2)x source rocks in the Penyijingxi Sag demonstrate superior potential compared to the P_(2)w,highlighting their underexplored significance.Comprehensive analysis of the depositional environment in the study area indicates that the Well Zhengshen-101 in the Shawan Sag may experience a deeper,stable reducing environment with moderate sedimentation rates,stable water stratification,and a more abundant nutrient supply,all of which favor organic matter enrichment.This systematic evaluation advances methodologies for assessing high-over mature source rocks and underscores the exploration potential of high-over mature Permian source rocks in the Junggar Basin.Meanwhile,comparison with the highly mature marine shales of the Sichuan Basin further accentuates the methodological innovation of this study.展开更多
Water-soluble organic acid anions(WSOAA)in subsurface water have been intensively studied during past several decades.They are used as natural gas precursor,tracer for the movement of underground fluid,indicator for p...Water-soluble organic acid anions(WSOAA)in subsurface water have been intensively studied during past several decades.They are used as natural gas precursor,tracer for the movement of underground fluid,indicator for porosity improvement,and detecter of deep subsurface life on the Earth.However,little is known about the distributions and origins of organic acids at deep-ultradeep depth underground.Herein,we collected twenty-nine source rock samples covering a wide maturity range from the Ordos,Qinshui,Junggar,Minhe,and Southern North China basins,as well as six subsurface water samples with depth between 6544 and 8396 m from industrial gas producing wells in the Tarim Basin,China.We carried out pyrolysis experiments at various temperatures(250–450℃)to investigate the role of water on the generation of organic acids.Results show that there are considerable amounts of WSOAA detected in both high-over mature source rocks and deep-ultradeep subsurface water.WSOAA mainly consists of monocarboxylates,predominately formate and acetate.High-TOC oil-generating source rock has low production rate of organic acids due to lack of hydrogen.Different source rocks have distinct ratios of formate to acetate concentration,expressed as c(formate)/c(acetate),which is due to significant differences in both initial molecular structure and metabolite.This indicates that c(formate)/c(acetate)can be used to distinguish types of organic matters(OMs).Concentrations of WSOAA show a“sharp decrease-slight increase-slow decrease”evolution trend with progressive maturity.Moreover,there are higher production rates of organic acids under hydrous pyrolysis experiments at≥400℃.All geochemical signatures indicate that at both deep-ultradeep depth and high-over mature stages,the formation of organic acids is attributed to the thermochemical oxidation of organic components by mainly hydroxyl radicals,challenging the traditional model of organic acid evolution.This work suggests that petroleum exploration can be extended to great depths in sedimentary basins,when formation temperatures are not exceeding 230℃.展开更多
基金sponsored by the National Natural Science Foundation of China under grant nos.42372160 and 42072172Natural Science Foundation of Shandong Province,China(nos.ZR2021QD072 and ZR2020QD040)。
文摘A comprehensive study was conducted on the hydrocarbon generation potential of the deeply buried Permian source rocks with high-over mature in the southwestern part of the Central Depression,Junggar Basin.Using rock-eval pyrolysis,carbon-sulfur analysis,kerogen macerals analysis,adamantane quantification,molecular geochemistry,and major and trace element analysis,coupled with organic carbon recovery methods.The evaluation primarily focused on thermal maturation,types,and abundance of organic matter,with an emphasis on summarizing methods for evaluating high-over mature source rocks.The results demonstrate that the Permian source rocks in the Shawan Sag(Well Zhengshen-101)and the Penyijingxi Sag(Well Zhuangshen-1)have reached a high-over mature stage,as evidenced by vitrinite reflectance(Ro),adamantane parameters,methyl phenanthrene indices(MPI),and Laser Raman spectroscopy.Horizontally,for the Fengcheng(P_(1)f)and Lower Wuerhe(P_(2)w)formations,the Well Zhengshen101 in the Shawan Sag is thermally more matured than the Well Zhuangshen-1 in the Penyijingxi Sag,while vertically,both wells show that the P_(1)f is thermally more mature than the P_(2)w.Raman and Fourier transform infrared(FTIR)spectroscopy confirm that Type Ⅱ kerogen is the dominant organic matter type.Through material balance,degradation ratio,and inorganic element methods,obtain the original content of organic carbon(TOC_(0))and hydrocarbon generation potential(S_(1)+S_(2)).After restoration,the P_(1)f samples from Well Zhengshen-101 in the Shawan Sag show moderate to high-quality organic matter abundance,predominantly high-quality;the P_(2)w samples are classified as high-quality source rocks.The Xiazijie Formation(P_(2)x)and the P_(2)w samples from Well Zhuangshen-1 in the Penyijingxi Sag range from poor to high-quality,predominantly good to high-quality.Horizontally,the P_(2)w samples from Well Zhengshen101 in the Shawan Sag exhibit higher organic matter abundance compared to those from Well Zhuangshen-1 in the Penyijingxi Sag.Notably,the P_(2)x source rocks in the Penyijingxi Sag demonstrate superior potential compared to the P_(2)w,highlighting their underexplored significance.Comprehensive analysis of the depositional environment in the study area indicates that the Well Zhengshen-101 in the Shawan Sag may experience a deeper,stable reducing environment with moderate sedimentation rates,stable water stratification,and a more abundant nutrient supply,all of which favor organic matter enrichment.This systematic evaluation advances methodologies for assessing high-over mature source rocks and underscores the exploration potential of high-over mature Permian source rocks in the Junggar Basin.Meanwhile,comparison with the highly mature marine shales of the Sichuan Basin further accentuates the methodological innovation of this study.
基金supported by the National Nature Science Foundation of China(Nos.42203027,U2244209,41872147)the China Postdoctoral Science Foundation(No.2023M730039).
文摘Water-soluble organic acid anions(WSOAA)in subsurface water have been intensively studied during past several decades.They are used as natural gas precursor,tracer for the movement of underground fluid,indicator for porosity improvement,and detecter of deep subsurface life on the Earth.However,little is known about the distributions and origins of organic acids at deep-ultradeep depth underground.Herein,we collected twenty-nine source rock samples covering a wide maturity range from the Ordos,Qinshui,Junggar,Minhe,and Southern North China basins,as well as six subsurface water samples with depth between 6544 and 8396 m from industrial gas producing wells in the Tarim Basin,China.We carried out pyrolysis experiments at various temperatures(250–450℃)to investigate the role of water on the generation of organic acids.Results show that there are considerable amounts of WSOAA detected in both high-over mature source rocks and deep-ultradeep subsurface water.WSOAA mainly consists of monocarboxylates,predominately formate and acetate.High-TOC oil-generating source rock has low production rate of organic acids due to lack of hydrogen.Different source rocks have distinct ratios of formate to acetate concentration,expressed as c(formate)/c(acetate),which is due to significant differences in both initial molecular structure and metabolite.This indicates that c(formate)/c(acetate)can be used to distinguish types of organic matters(OMs).Concentrations of WSOAA show a“sharp decrease-slight increase-slow decrease”evolution trend with progressive maturity.Moreover,there are higher production rates of organic acids under hydrous pyrolysis experiments at≥400℃.All geochemical signatures indicate that at both deep-ultradeep depth and high-over mature stages,the formation of organic acids is attributed to the thermochemical oxidation of organic components by mainly hydroxyl radicals,challenging the traditional model of organic acid evolution.This work suggests that petroleum exploration can be extended to great depths in sedimentary basins,when formation temperatures are not exceeding 230℃.
