To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and We...To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and Weiyuan areas of the Sichuan Basin were analyzed.Paleoproductivity proxy parameters(Babio,Siex,and Ni/Al),clastic influx proxies(TiO2 and Ti/Al),redox indices(V/Cr,Ni/Co,V/(V+Ni),and U/Th),and hydrothermal indicators(Fe,Mn,and Y concentrations;Fe/Ti ratio and a Ni-Zn-Co diagram)were employed to decipher the paleoenvironment of the Lower Longmaxi Formation shales.TiO2 and Ti/Al indicated low terrigenous detrital influx in all three areas.However,Babio,Siex,and Ni/Al indicated high productivity in the Jiaoshiba area.V/Cr,Ni/Co,and U/Th indicated higher oxygen content with larger fluctuations in the Zhaotong and Weiyuan areas.Fe,Mn,and Y concentrations and the Fe/Ti ratio implied greater active hydrothermal activity in the Weiyuan area.These heterogeneities were considered to be closely related to the paleoenvironment and paleogeography,and the large basement faults that developed during the Chuanzhong paleo-uplift could have provided vents for deep-hydrothermal-fluid upwelling.The redox indices(V/Cr,Ni/Co,and U/Th)and a paleoproductivity proxy(Ni/Al)displayed a significant correlation with the TOC,suggesting that both excellent preservation conditions and high paleoproductivity were the controlling factors for the enrichment of organic matter in the Longmaxi Formation shale.There was no obvious correlation between the clastic influx proxy(Ti/Al)and the TOC due to the extremely low supply of terrigenous debris.The hydrothermal indicator(Fe/Ti)was negatively correlated with the TOC in the Weiyuan area,indicating that hydrothermal activity may have played a negative role in the accumulation of organic matter.This study suggests that the enrichment of organic matter in the Longmaxi Formation marine shale varied according to the paleogeography and sedimentary environment.展开更多
The relationship between marine transgression and the distribution of lacustrine organic matter has restricted shale oil and gas exploration for decades.In this study,the research objective is to analyze the sedimenta...The relationship between marine transgression and the distribution of lacustrine organic matter has restricted shale oil and gas exploration for decades.In this study,the research objective is to analyze the sedimentary environment and evaluate its influence on organic matter in transgressive lacustrine shale.The study uses various analyses including total organic carbon(TOC),Rock-Eval pyrolysis,gas chromatography-mass spectrometry(GC-MS),trace element and isotope analysis.Finally,the study proposes an enrichment model for organic matter.The lacustrine shale of the second member of the Funing Formation(E_(1)f^(2))is divided into three sequences.The results indicate that the depositional environment of the organic matter during this period was an arid and humid,reduced,closed,rift lake basin.In the first sequence,high salinity resulted from increased evaporation,leading to low primary biological productivity.At this time,the lake basin belonged to a salinized closed lake basin.Intermittent transgressions began in the second sequence,with the deep lake area still being dominated by a reducing environment.The third sequence saw the environment evolve into a closed lake basin characterized by a warm and humid freshwater environment with high primary productivity.Marine transgressions introduce a substantial amount of marine plankton,nutrient elements,as well as more CO_(2) and CO_(3)^(2−)into the lake,leading to increased primary productivity.The sedimentary model for transgressive lacustrine source rocks proposed here serves as an example for similar transgressive lake basins.展开更多
The organic-inorganic transformation and interaction act as the critical role in the occurrence of nanopores within the organic-rich shales during thermal maturation.Hydrous pyrolysis experiments were conducted on the...The organic-inorganic transformation and interaction act as the critical role in the occurrence of nanopores within the organic-rich shales during thermal maturation.Hydrous pyrolysis experiments were conducted on the organic-rich mudrock collected from the Upper Cretaceous Nenjiang Formation of the Songliao Basin,China in a closed system.The pore types and pore network,and organic and inorganic compositions of pyrolyzed shales were detected from the early to over mature stages(%Ro=0.61-4.01).The experimental results indicate that geochemical transformation of organic matters and minerals and the interaction control the formation and evolution of nanoporosity.In oil window mineral matrix pores are infilled by the generated oil,K-feldspar dissolution by organic acids promotes clay illitization to form illite,and the catalytic effects of clays(e.g.illite)in the complex of organic matter and clays may promote the in-situ retained oil cracking to generate natural gas,resulting in the early occurrence of organic-matter pores in the complex within oil window.Due to significant primary cracking of solid kerogen to generate extractable liquid oil,pore volume for storing fluids presents a persistent increase and approaches the maximum at the end of oil window.In gas window intensive oil cracking facilitates the hydrocarbon migrating out of the source home and pyrobitumen formation,resulting in the significant occurrence of modified mineral matrix pores and organic-matter pores.Pore volume for hosting hydrocarbons presents a slight decrease at%Ro=1.36-2.47 due to pyrobitumen formation by oil secondary cracking.The organic-inorganic interaction favors clay illitization,quartz dissolution,and pyrite and carbonate decomposition,which facilitate the occurrence of nanoporosity.Pyrobitumen within the complex with illite and organic matters are much more porous than that hosted in modified mineral matrix pores and microfractures.The catalytic effects of clays are supposed to be responsible for this.This study improves our understanding of the formation and evolution pathways of nanoporosity and the underlying controls in organic-rich shales during thermal maturation,and hence should be helpful in evaluating the sweet spots for shale-oil and shale-gas plays in a sedimentary basin.展开更多
The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between a...The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving…展开更多
Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that mainta...Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the rel…展开更多
Using multidiscipline methodologies, the differences in preservation and enrichment mechanisms of organic matter (OM) in muddy sediment and mudstone are investigated. In clay fractions, concentrations of TOC and chlor...Using multidiscipline methodologies, the differences in preservation and enrichment mechanisms of organic matter (OM) in muddy sediment and mudstone are investigated. In clay fractions, concentrations of TOC and chloroform bitumen “A” are significantly higher than those in coarser fractions. This indicates that clay minerals (CM) play an important role in enriching OM. The content of chloroform bitumen “A” increases obviously in the clay fraction, which reveals that dissolvable OM is the main composition of coalesce with clay minerals. Furthermore, TG and DTA data show that OM enrichment mechanisms and preservation forms have multiplicity. Several exothermic peaks in the DTA curves demonstrate that muddy sediment and mudstone contain a number of bioclasts and amorphous OM besides dissolvable OM. Through analyzing with XRD and DTA after mudstone samples were pretreated, the conclusions can be arrived at. Firstly, CM interlayer space of XRD curves and exothermic peaks of DTA curves both change as temperature increases. Secondly, the changes of CM interlayer space and exothermic peaks are concordant and stable around 350°C. All these are the features that OM enters CM interlayers to form stable organo-clay complexes. Therefore, the combination format of OM with CM is not only surface adsorption, partial OM enters CM interlayers to form stable organo-clay complexes. Finally, through the research on OM preservation forms and enrichment mechanisms in muddy sediment and mudstone, the hydrocarbon-generation processes and the global carbon cycle and budget can be explained.展开更多
基金supported by U.S. National Science Foundation (No. 1661733)the National Science and Technology Major Project of China (No. 2017ZX05005002-008)+3 种基金the National Natural Science Foundation of China (No. 41772121)the National Natural Science Foundation of China (No. 41630312)the Open Fund of the Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology and the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development (No. GSYKY-B09-33)Department of Geology, Northwest University, China, for the financial support given to the first author
文摘To investigate the mechanism of the organic-matter enrichment in the Lower Longmaxi Formation shale,the geochemistry and total organic carbon(TOC)of the Longmaxi Formation black shales in the Jiaoshiba,Zhaotong,and Weiyuan areas of the Sichuan Basin were analyzed.Paleoproductivity proxy parameters(Babio,Siex,and Ni/Al),clastic influx proxies(TiO2 and Ti/Al),redox indices(V/Cr,Ni/Co,V/(V+Ni),and U/Th),and hydrothermal indicators(Fe,Mn,and Y concentrations;Fe/Ti ratio and a Ni-Zn-Co diagram)were employed to decipher the paleoenvironment of the Lower Longmaxi Formation shales.TiO2 and Ti/Al indicated low terrigenous detrital influx in all three areas.However,Babio,Siex,and Ni/Al indicated high productivity in the Jiaoshiba area.V/Cr,Ni/Co,and U/Th indicated higher oxygen content with larger fluctuations in the Zhaotong and Weiyuan areas.Fe,Mn,and Y concentrations and the Fe/Ti ratio implied greater active hydrothermal activity in the Weiyuan area.These heterogeneities were considered to be closely related to the paleoenvironment and paleogeography,and the large basement faults that developed during the Chuanzhong paleo-uplift could have provided vents for deep-hydrothermal-fluid upwelling.The redox indices(V/Cr,Ni/Co,and U/Th)and a paleoproductivity proxy(Ni/Al)displayed a significant correlation with the TOC,suggesting that both excellent preservation conditions and high paleoproductivity were the controlling factors for the enrichment of organic matter in the Longmaxi Formation shale.There was no obvious correlation between the clastic influx proxy(Ti/Al)and the TOC due to the extremely low supply of terrigenous debris.The hydrothermal indicator(Fe/Ti)was negatively correlated with the TOC in the Weiyuan area,indicating that hydrothermal activity may have played a negative role in the accumulation of organic matter.This study suggests that the enrichment of organic matter in the Longmaxi Formation marine shale varied according to the paleogeography and sedimentary environment.
基金financially supported by the National Natural Science Foundation of China(Grant No.42072150)and we thank the sponsors of these projects.
文摘The relationship between marine transgression and the distribution of lacustrine organic matter has restricted shale oil and gas exploration for decades.In this study,the research objective is to analyze the sedimentary environment and evaluate its influence on organic matter in transgressive lacustrine shale.The study uses various analyses including total organic carbon(TOC),Rock-Eval pyrolysis,gas chromatography-mass spectrometry(GC-MS),trace element and isotope analysis.Finally,the study proposes an enrichment model for organic matter.The lacustrine shale of the second member of the Funing Formation(E_(1)f^(2))is divided into three sequences.The results indicate that the depositional environment of the organic matter during this period was an arid and humid,reduced,closed,rift lake basin.In the first sequence,high salinity resulted from increased evaporation,leading to low primary biological productivity.At this time,the lake basin belonged to a salinized closed lake basin.Intermittent transgressions began in the second sequence,with the deep lake area still being dominated by a reducing environment.The third sequence saw the environment evolve into a closed lake basin characterized by a warm and humid freshwater environment with high primary productivity.Marine transgressions introduce a substantial amount of marine plankton,nutrient elements,as well as more CO_(2) and CO_(3)^(2−)into the lake,leading to increased primary productivity.The sedimentary model for transgressive lacustrine source rocks proposed here serves as an example for similar transgressive lake basins.
基金National Nature Science Foundation of China(No.42030803,42073066),and the valuable comments and suggestions by three anonymous referees that greatly improved this paper.
文摘The organic-inorganic transformation and interaction act as the critical role in the occurrence of nanopores within the organic-rich shales during thermal maturation.Hydrous pyrolysis experiments were conducted on the organic-rich mudrock collected from the Upper Cretaceous Nenjiang Formation of the Songliao Basin,China in a closed system.The pore types and pore network,and organic and inorganic compositions of pyrolyzed shales were detected from the early to over mature stages(%Ro=0.61-4.01).The experimental results indicate that geochemical transformation of organic matters and minerals and the interaction control the formation and evolution of nanoporosity.In oil window mineral matrix pores are infilled by the generated oil,K-feldspar dissolution by organic acids promotes clay illitization to form illite,and the catalytic effects of clays(e.g.illite)in the complex of organic matter and clays may promote the in-situ retained oil cracking to generate natural gas,resulting in the early occurrence of organic-matter pores in the complex within oil window.Due to significant primary cracking of solid kerogen to generate extractable liquid oil,pore volume for storing fluids presents a persistent increase and approaches the maximum at the end of oil window.In gas window intensive oil cracking facilitates the hydrocarbon migrating out of the source home and pyrobitumen formation,resulting in the significant occurrence of modified mineral matrix pores and organic-matter pores.Pore volume for hosting hydrocarbons presents a slight decrease at%Ro=1.36-2.47 due to pyrobitumen formation by oil secondary cracking.The organic-inorganic interaction favors clay illitization,quartz dissolution,and pyrite and carbonate decomposition,which facilitate the occurrence of nanoporosity.Pyrobitumen within the complex with illite and organic matters are much more porous than that hosted in modified mineral matrix pores and microfractures.The catalytic effects of clays are supposed to be responsible for this.This study improves our understanding of the formation and evolution pathways of nanoporosity and the underlying controls in organic-rich shales during thermal maturation,and hence should be helpful in evaluating the sweet spots for shale-oil and shale-gas plays in a sedimentary basin.
文摘The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving…
文摘Land use changes can greatly influence soil phosphorus (P) dynamics, especially when converting native forests to agricultural land. Soils in Xishuangbanna, which is one of southwest China s tropical areas that maintain fragments of primary forests, were studied to a) evaluate the effect of two common land use changes, conversion of forests to agricultural land or rubber tree plantation, on the dynamics of available P and total P in bulk soils as well as total P in particle size fractions; b) assess the rel…
基金Supported by the National Natural Science Foundation of China (Grant No. 40672085)China Petroleum and Chemical Corporation Project
文摘Using multidiscipline methodologies, the differences in preservation and enrichment mechanisms of organic matter (OM) in muddy sediment and mudstone are investigated. In clay fractions, concentrations of TOC and chloroform bitumen “A” are significantly higher than those in coarser fractions. This indicates that clay minerals (CM) play an important role in enriching OM. The content of chloroform bitumen “A” increases obviously in the clay fraction, which reveals that dissolvable OM is the main composition of coalesce with clay minerals. Furthermore, TG and DTA data show that OM enrichment mechanisms and preservation forms have multiplicity. Several exothermic peaks in the DTA curves demonstrate that muddy sediment and mudstone contain a number of bioclasts and amorphous OM besides dissolvable OM. Through analyzing with XRD and DTA after mudstone samples were pretreated, the conclusions can be arrived at. Firstly, CM interlayer space of XRD curves and exothermic peaks of DTA curves both change as temperature increases. Secondly, the changes of CM interlayer space and exothermic peaks are concordant and stable around 350°C. All these are the features that OM enters CM interlayers to form stable organo-clay complexes. Therefore, the combination format of OM with CM is not only surface adsorption, partial OM enters CM interlayers to form stable organo-clay complexes. Finally, through the research on OM preservation forms and enrichment mechanisms in muddy sediment and mudstone, the hydrocarbon-generation processes and the global carbon cycle and budget can be explained.
