The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Pa...The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.展开更多
In the Jimusaer Sag of the Junggar Basin,crude oils from the upper and lower sweet-spot intervals of the Permian Lucaogou Formation display a pronounced“light-heavy reversal”in oil properties that indicates a fundam...In the Jimusaer Sag of the Junggar Basin,crude oils from the upper and lower sweet-spot intervals of the Permian Lucaogou Formation display a pronounced“light-heavy reversal”in oil properties that indicates a fundamental mismatch between oil composition and host rock maturity.To resolve this anomaly,this study integrates geological,geochemical,and petrophysical datasets and systematically evaluates the combined roles of thermal evolution,organofacies,wettability,abnormal overpressure,and migration-related fractionation on shale oil composition.On this basis,a“staged charging-cumulative charging”model is proposed to explain compositional heterogeneity in lacustrine shale oils.The results demonstrate that crude-oil compositions are jointly controlled by the extent of biomarker depletion,the temporal evolution of hydrocarbon charging,and the openness of the source-reservoir system,rather than by thermal maturity or organofacies alone.The upper sweet-spot interval is interpreted to have functioned as a semi-open system during early stages,in which hydrocarbon generation and expulsion were broadly synchronous,leading to preferential loss of early-generated,biomarker-rich heavy components,whereas progressive shale diagenesis at later stages promoted the retention of highly mature,light hydrocarbons.In contrast,the lower sweet-spot interval represents a relatively closed system,where hydrocarbons generated during multiple stages continuously accumulated and were preserved as mixed charges;overprinting by multi-phase fluids progressively weakened sterane isomerization signals,rendering them unreliable indicators of individual charging events or final thermal maturity.This charging behavior provides a reasonable explanation for anomalously low or distorted biomarker parameters observed in intervals of low or similar maturity.Overall,the proposed charging model reconciles the observed reversal in crude-oil properties and,by shifting the interpretive focus from static maturity assessment to charging dynamics,offers a new theoretical basis for understanding lacustrine shale oil accumulation processes,and guiding sweet-spot selection and exploration-development strategies.展开更多
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
Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the mult...Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the multi-stage dolomite cements have been studied by means of core observations,thin section identification,fluid inclusions,and in situ elements and isotopic analyses in order to reaveal the paleofluid evolution processes and their effects on the reservoir quality.The fibrous dolomite cement(FDC)and bladed dolomite cement(BDC)both have similar geochemical properties and homogenization temperature(Th)to the matrix dolostone.Subsequent early silicification occurs(QZ1).However,silt-to fine-sized crystalline dolomite cement(CD2)has higher concentration of Fe and medium rare earth element,more negativeδ^(18)O than for FDC and BDC,and 103.4-150.2℃in Th.The first petroleum charge episode solid bitumen 1(SB1)followed the CD2.The medium to coarse sized crystalline dolomite cement(CD3)is characterized by the higher Mn and lower Sr concentration than CD2,positiveδEu anomaly,negativeδ^(13)C andδ^(18)O,high^(87)Sr/^(86)Sr ratio and 138.9℃-184.3℃in Th.The solid bitumen 2(SB2)occurs after CD3.Subsequently,the saddle dolomite(SD)has higher Fe and Mn concentration and lower Na and Sr than others cement,δEu positive anomaly,negativeδ^(13)C andδ^(18)O,high ^(87)Sr/^(86)Sr ratio and 177.5℃-243.6℃in Th.Eventually massive silicification(QZ2)took place.The FDC,BDC,QZ1 and SB1 formed in the early diagenetic stage and have little negative effect on the reservoir quality.But the CD2 and CD3 dramatically decreased the reservoir quality related to a quantity of hydrothermal fluids entrance in the mesodiagenetic stage along the strike-slip faults and the unconformity surface at top of the Deng-2 Member during the late stage of the Caledonian orogeny.The reservoir spaces were retained and enlarged during the late diagenetic stage when the peak petroleum charge occurred,massive silicification and thermochemical sulfate reduction took place with SB2,SD and QZ2 being formed.The research outcome may update our understanding on the retention mechanism and the insights for further hydrocarbon exploration of Precambrian ultra-deep microbial reservoirs.展开更多
Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evol...Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evolution of aromatic hydrocarbons during late-mature to over-mature stage （R0=1.13%-2.85%） was characterized, and aromatic indicators suitable for recognizing the organic source and sedimentary environment of high maturity source rocks were discussed. The results indicated that the concentrations of low carbon-cycle naphthalene as well phenanthrene series reduce gradually with increasing Ro at the highly mature levels. However, some high-cyclic components such as chrysene, benzofluoranthene, and benzo[e]pyrene are relatively enriched, in companying an enhancement of parent aromatic compounds. The variations are attributed to thermal cracking and polymerization reactions due to continuous dehydrogenation under enhanced burial temperature. As thermal maturity rises, MPI1 （Methylphenanthrene Index） values display a two-modal varying trend, namely, increasing when Ro is below 1.80% and decreasing above 1.8% Ro. The relationships between Ro and MPI1 are Ro=0.98MPI1＋0.37 for R0〈1.80% and R0=-0.90MPI1＋3.02 at R0〉1.8%, being different from the previous research. The amount of dibenzofurans declines sharply at Ro higher than 1.1%, leading to a significant change of relative composition among dibenzothiophenes, dibenzofurans and fluorenes （referred as three-fluorenes series composition）. Thus, this parameter appears to be unsuitable for identifying the sedimentary environment of the highly matured source rocks. 4-/1-MDBT （methyldibenzothiophene） ratio could be served as an effective indicator for organic facies, and can distinguish coals from mudstones at over-maturity in this case. The ratios of 2,6-/2,10-DMP （dimethylphenanthrene） and 1,7-/1,9-DMP and relative abundance of triaromatic steroids in these highly mature rocks could be considered as biological source parameters for relative input of terrigenous versus aquatic organic matter.展开更多
The Devonian Woodford Shale in the Anadarko Basin is a highly organic,hydrocarbon source rock.Accurate values of vitrinite reflectance(R_o)present in the Woodford Shale penetrated by 52 control wells were measured dir...The Devonian Woodford Shale in the Anadarko Basin is a highly organic,hydrocarbon source rock.Accurate values of vitrinite reflectance(R_o)present in the Woodford Shale penetrated by 52 control wells were measured directly.These vitrinite reflectance values,when plotted against borehole resistivity for the middle member of the Woodford Shale in the wells,display a rarely reported finding that deep resistivity readings decrease as R_o increases when R_o is greater than 0.90%.This phenomenon may be attributed to that aromatic and resin compounds containing conjugated pi bonds generated within source rocks are more electrically conductive than aliphatic compounds.And aromatic and resin fractions were generated more than aliphatic fraction when source rock maturity further increases beyond oil peak.The finding of the relationship between deep resistivity and R_o may re-investigate the previously found linear relationship between source rock formation and aid to unconventional play exploration.展开更多
基金supported by the CNPC Science and Technology Major Project of the Fourteenth Five-Year Plan(2021DJ0101)the National Natural Science Foundation of China(U19B600302,41872148)。
文摘The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.
基金Supported by the National Natural Science Foundation of China(42173030,42302161,42473034)State Science and Technology Major Project for New Oil and Gas Exploration and Development,Ministry of Science and Technology(2025ZD1400803)。
文摘In the Jimusaer Sag of the Junggar Basin,crude oils from the upper and lower sweet-spot intervals of the Permian Lucaogou Formation display a pronounced“light-heavy reversal”in oil properties that indicates a fundamental mismatch between oil composition and host rock maturity.To resolve this anomaly,this study integrates geological,geochemical,and petrophysical datasets and systematically evaluates the combined roles of thermal evolution,organofacies,wettability,abnormal overpressure,and migration-related fractionation on shale oil composition.On this basis,a“staged charging-cumulative charging”model is proposed to explain compositional heterogeneity in lacustrine shale oils.The results demonstrate that crude-oil compositions are jointly controlled by the extent of biomarker depletion,the temporal evolution of hydrocarbon charging,and the openness of the source-reservoir system,rather than by thermal maturity or organofacies alone.The upper sweet-spot interval is interpreted to have functioned as a semi-open system during early stages,in which hydrocarbon generation and expulsion were broadly synchronous,leading to preferential loss of early-generated,biomarker-rich heavy components,whereas progressive shale diagenesis at later stages promoted the retention of highly mature,light hydrocarbons.In contrast,the lower sweet-spot interval represents a relatively closed system,where hydrocarbons generated during multiple stages continuously accumulated and were preserved as mixed charges;overprinting by multi-phase fluids progressively weakened sterane isomerization signals,rendering them unreliable indicators of individual charging events or final thermal maturity.This charging behavior provides a reasonable explanation for anomalously low or distorted biomarker parameters observed in intervals of low or similar maturity.Overall,the proposed charging model reconciles the observed reversal in crude-oil properties and,by shifting the interpretive focus from static maturity assessment to charging dynamics,offers a new theoretical basis for understanding lacustrine shale oil accumulation processes,and guiding sweet-spot selection and exploration-development strategies.
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 Natural Science Foundation of China(Nos.41872150,42230310)the Joint Funds of National Natural Science Foundation of China(Grant No.U19B6003)。
文摘Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the multi-stage dolomite cements have been studied by means of core observations,thin section identification,fluid inclusions,and in situ elements and isotopic analyses in order to reaveal the paleofluid evolution processes and their effects on the reservoir quality.The fibrous dolomite cement(FDC)and bladed dolomite cement(BDC)both have similar geochemical properties and homogenization temperature(Th)to the matrix dolostone.Subsequent early silicification occurs(QZ1).However,silt-to fine-sized crystalline dolomite cement(CD2)has higher concentration of Fe and medium rare earth element,more negativeδ^(18)O than for FDC and BDC,and 103.4-150.2℃in Th.The first petroleum charge episode solid bitumen 1(SB1)followed the CD2.The medium to coarse sized crystalline dolomite cement(CD3)is characterized by the higher Mn and lower Sr concentration than CD2,positiveδEu anomaly,negativeδ^(13)C andδ^(18)O,high^(87)Sr/^(86)Sr ratio and 138.9℃-184.3℃in Th.The solid bitumen 2(SB2)occurs after CD3.Subsequently,the saddle dolomite(SD)has higher Fe and Mn concentration and lower Na and Sr than others cement,δEu positive anomaly,negativeδ^(13)C andδ^(18)O,high ^(87)Sr/^(86)Sr ratio and 177.5℃-243.6℃in Th.Eventually massive silicification(QZ2)took place.The FDC,BDC,QZ1 and SB1 formed in the early diagenetic stage and have little negative effect on the reservoir quality.But the CD2 and CD3 dramatically decreased the reservoir quality related to a quantity of hydrothermal fluids entrance in the mesodiagenetic stage along the strike-slip faults and the unconformity surface at top of the Deng-2 Member during the late stage of the Caledonian orogeny.The reservoir spaces were retained and enlarged during the late diagenetic stage when the peak petroleum charge occurred,massive silicification and thermochemical sulfate reduction took place with SB2,SD and QZ2 being formed.The research outcome may update our understanding on the retention mechanism and the insights for further hydrocarbon exploration of Precambrian ultra-deep microbial reservoirs.
基金supported by the Key State Science and Technology Project(Grant No.2011ZX05005-03-009HZ)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20130101110051)
文摘Based on the GC-MS analytical data of aromatic fractions of over forty highly mature coal-bearing source rock samples collected from the Upper Triassic Xujiahe Formation in the northern Sichuan Basin, the thermal evolution of aromatic hydrocarbons during late-mature to over-mature stage （R0=1.13%-2.85%） was characterized, and aromatic indicators suitable for recognizing the organic source and sedimentary environment of high maturity source rocks were discussed. The results indicated that the concentrations of low carbon-cycle naphthalene as well phenanthrene series reduce gradually with increasing Ro at the highly mature levels. However, some high-cyclic components such as chrysene, benzofluoranthene, and benzo[e]pyrene are relatively enriched, in companying an enhancement of parent aromatic compounds. The variations are attributed to thermal cracking and polymerization reactions due to continuous dehydrogenation under enhanced burial temperature. As thermal maturity rises, MPI1 （Methylphenanthrene Index） values display a two-modal varying trend, namely, increasing when Ro is below 1.80% and decreasing above 1.8% Ro. The relationships between Ro and MPI1 are Ro=0.98MPI1＋0.37 for R0〈1.80% and R0=-0.90MPI1＋3.02 at R0〉1.8%, being different from the previous research. The amount of dibenzofurans declines sharply at Ro higher than 1.1%, leading to a significant change of relative composition among dibenzothiophenes, dibenzofurans and fluorenes （referred as three-fluorenes series composition）. Thus, this parameter appears to be unsuitable for identifying the sedimentary environment of the highly matured source rocks. 4-/1-MDBT （methyldibenzothiophene） ratio could be served as an effective indicator for organic facies, and can distinguish coals from mudstones at over-maturity in this case. The ratios of 2,6-/2,10-DMP （dimethylphenanthrene） and 1,7-/1,9-DMP and relative abundance of triaromatic steroids in these highly mature rocks could be considered as biological source parameters for relative input of terrigenous versus aquatic organic matter.
基金funded by the Foundation of State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(No.PRP/open-1605)partly supported by the Open Fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education(No.K2017-18)Tight Oil Enrichment and Key Exploration and Development Technology Project of National Science and Technology Major Project(Nos.2016ZX05046-002 and 2016ZX05047-005)
文摘The Devonian Woodford Shale in the Anadarko Basin is a highly organic,hydrocarbon source rock.Accurate values of vitrinite reflectance(R_o)present in the Woodford Shale penetrated by 52 control wells were measured directly.These vitrinite reflectance values,when plotted against borehole resistivity for the middle member of the Woodford Shale in the wells,display a rarely reported finding that deep resistivity readings decrease as R_o increases when R_o is greater than 0.90%.This phenomenon may be attributed to that aromatic and resin compounds containing conjugated pi bonds generated within source rocks are more electrically conductive than aliphatic compounds.And aromatic and resin fractions were generated more than aliphatic fraction when source rock maturity further increases beyond oil peak.The finding of the relationship between deep resistivity and R_o may re-investigate the previously found linear relationship between source rock formation and aid to unconventional play exploration.
