The oils in the Rewapu Block of the Halahatang Oilfield in the Tarim Basin(northwestern China) were geochemically analyzed by gas chromatography–mass spectrometry to investigate their origin and possible secondary al...The oils in the Rewapu Block of the Halahatang Oilfield in the Tarim Basin(northwestern China) were geochemically analyzed by gas chromatography–mass spectrometry to investigate their origin and possible secondary alteration. The physical properties and chemical compositions of these Ordovician oils vary greatly, ranging from light to extremely heavy oils. All these oils belong to one single population and were derived from same source kitchen/bed. The differences in their chemical compositions and physical properties mainly result from secondary alteration of oils that were charged during the early phase of trap formation. The thickness of Upper Ordovician and Silurian caprocks of oil reservoirs in the Rewapu Block is higher than that in the north part of the Halahatang region, and therefore, significant biodegradation process is prevented. Compared to heavy oils in the north part, the Rewapu oils are dominated by light oils with no 25-norhopanes and no GC–MS ‘‘hump''(UCM: unresolved complex mixture) on the chromatographic baselines. The heavy oils in Wells RP7 and RP101 C were primarily influenced by water washing since apparent reduction of alkylated dibenzothiophenes was observed. The local geological background favored the water washing alteration. The reservoir geochemical study has practical application in hydrocarbon exploration and predicts the nature of oils in this oilfield.展开更多
The deeply buried Lower Cambrian Longwangmiao Formation and Upper Ediacaran Dengying Formation from the Sichuan Basin,China,have a total natural gas reserve up to 3×10^(12)m^(3).The complex diagenetic evolution a...The deeply buried Lower Cambrian Longwangmiao Formation and Upper Ediacaran Dengying Formation from the Sichuan Basin,China,have a total natural gas reserve up to 3×10^(12)m^(3).The complex diagenetic evolution and their impacts on the present-day reservoir quality have not been systematically elucidated,hampering the current exploration.Crucially,the integration and comparation diagenetic study on these two formations,which may be able to shed new lights on reservoir formation mechanism,are yet to be systemically evaluated.By compiling geochemistry data,including carbonate U-Pb ages and petrophysics data,coupled with new petrology,trace elements,and strontium isotope data,of various types of diagenetic carbonates,this study aims to decipher the potential links between diagenesis and reservoir development of both formations.Intriguingly,similar diagenetic sequence,which contains five distinctive dolomite phases,is established in both formations.The matrix dolomite(D1)and early dolomite cement(D2)were likely formed by reflux dolomitization,as inferred by their nearly syn-depositional U-Pb ages and elevatedδ^(18)O caused by seawater evaporation.The subsequent moderate burial dolomite cement(D3)was most plausibly the product of burial compaction as indicated by its lighterδ^(18)O and slightly younger U-Pb ages compared with D1 and D2.Whereas deep burial dolomite cements(D4 and D5)yield markedly depletedδ^(18)O,elevated ^(87)Sr/^(86)Sr,along with much younger U-Pb ages and higher precipitation temperatures,suggesting that they were likely linked to hydrothermal fluids.Despite the wide occurrence of meteoric and organic acids leaching and thermochemical sulfate reduction,they may have only played a subsidiary role on these reservoirs development.Instead,superior reservoir quality is tightly linked to tectonics as inferred by higher reservoir quality closely related to the well-developed fractures and faults filled with abundant hydrothermal minerals.Notably,good reservoirs in both formations are mainly attributed to high permeability caused by tectonics.Hence,this new contribution emphasizes the crucial role of tectonics on spatially explicit reservoir prediction of deep to ultra-deep(up to>8000 m)carbonates in the Sichuan Basin,as well as other sedimentary basin analogues in China.展开更多
Based on gas chromatography and gas chromatography mass spectrometry techniques, the authors researched biomarker characteristics of the Linxi Formation source rocks in the area of Taohaiyingzi, and analyzed the infor...Based on gas chromatography and gas chromatography mass spectrometry techniques, the authors researched biomarker characteristics of the Linxi Formation source rocks in the area of Taohaiyingzi, and analyzed the information and petroleum geological significance that were indicated by source of organic matter, sedimentary environment, maturity and so on. Gas chromatography peak of saturated hydrocarbons from Linxi Formation source rocks showed ‘‘the former peak'' of the single peak distribution and the C23-dominant main peak. This indicates that the main source of organic matter was mixed organic matter; Pr/Ph ratios ranged from 0.3 to 0.6, indicating a strongly reducing sedimentary environment.Molecular fossil assemblages in Linxi Formation source rocks were abundant in tricyclic terpane with long side chains, had high level of gammacerane, and showed dominant distribution of C27 steranes. Gammacerane ratios range from 0.15 to 0.29, with an average of 0.19, implying that Linxi Formation hydrocarbon source rocks were formed in the environment of micro-saltwater water to half-saltwater water. The hopanes/steranes ratios are mainly between 0.6 and 1.0, with an average of 0.84, implying that bacteria and algae had almost the samecontribution to organic matter. C27 steranes abundance is high and the ratio of C27steranes/C29 steranes is 1.13,showing that algae is the main source of hydrocarbon precursors.展开更多
The Woodford–Mississippian"Commingled Production"is a prolific unconventional hydrocarbon play in Oklahoma,USA.The tight reservoirs feature variations in produced fluid chemistry usually explained by differ...The Woodford–Mississippian"Commingled Production"is a prolific unconventional hydrocarbon play in Oklahoma,USA.The tight reservoirs feature variations in produced fluid chemistry usually explained by different possible source rocks.Such chemical variations are regularly obtained from bulk,molecular,and isotopic characteristics.In this study,we present a new geochemical investigation of gasoline range hydrocarbons,biomarkers,and diamondoids in oils from Mississippian carbonate and Woodford Shale.A set of oil/condensate samples were examined using high-performance gas chromatography and mass spectrometry.The result of the condensates from the Anadarko Basin shows a distinct geochemical fingerprint reflected in light hydrocarbon characterized by heptane star diagrams,convinced by biomarker characteristics and diamantane isomeric distributions.Two possible source rocks were identified,the Woodford Shale and Mississippian mudrocks,with a variable degree of mixing.Thermal maturity based on light hydrocarbon parameters indicates that condensates from the Anadarko Basin are of the highest maturity,followed by"Old"Woodford-sourced oils and central Oklahoma tight oils.These geochemical parameters shed light on petroleum migration within Devonian–Mississippian petroleum systems and mitigate geological risk in exploring and developing petroleum reservoirs.展开更多
Tight gas exploration plays an important part in China’s unconventional energy strategy.The tight gas reservoirs in the Jurassic Shaximiao Formation in the Qiulin and Jinhua Gas Fields of central Sichuan Basin are ch...Tight gas exploration plays an important part in China’s unconventional energy strategy.The tight gas reservoirs in the Jurassic Shaximiao Formation in the Qiulin and Jinhua Gas Fields of central Sichuan Basin are characterized by shallow burial depths and large reserves.The evolution of the fluid phases is a key element in understanding the accumulation of hydrocarbons in tight gas reservoirs.This study investigates the fluid accumulation mechanisms and the indicators of reservoir properties preservation and degradation in a tight gas reservoir.Based on petrographic observations and micro-Raman spectroscopy,pure CH4 inclusions,pure CO2 inclusions,hybrid CH4–CO2 gas inclusions,and N2-rich gas inclusions were studied in quartz grains.The pressure–volume–temperature–composition properties(PVT-x)of the CH4 and CO2 bearing inclusions were determined using quantitative Raman analysis and thermodynamic models,while the density of pure CO2 inclusions was calculated based on the separation of Fermi diad.Two stages of CO2 fluid accumulation were observed:primary CO2 inclusions,characterized by higher densities(0.874–1.020 g/cm3)and higher homogenization temperatures(>210°C)and secondary CO2 inclusions,characterized by lower densities(0.514–0.715 g/cm3)and lower homogenization temperatures:~180–200°C).CO2 inclusions with abnormally high homogenization temperatures are thought to be the result of deep hydrothermal fluid activity.The pore fluid pressure(44.0–58.5 MPa)calculated from the Raman shift of C–H symmetric stretching(v1)band of methane inclusions is key to understanding the development of overpressure.PT entrapment conditions and simulation of burial history can be used to constrain the timing of paleo-fluid emplacement.Methane accumulated in the late Cretaceous(~75–65 Ma),close to the maximum burial depth during the early stages of the Himalayan tectonic event while maximum overpressure occurred at~70 Ma,just before uplift.Later,hydrocarbon gas migrated through the faults and gradually displaced the early emplaced CO2 in the reservoirs accompanied by a continuous decrease in overpressure during and after the Himalayan event,which has led to a decrease in the reservoir sealing capabilities.The continuous release of overpressure to present-day conditions indicates that the tectonic movement after the Himalayan period has led to a decline in reservoir conditions and sealing properties.展开更多
Retraction Note to:Petroleum Science(2020)17:582-597https://doi.org/10.1007/s12182-020-00441-1The authors have retracted their article(Wang et al.2020)because of significant textual overlap with previously published w...Retraction Note to:Petroleum Science(2020)17:582-597https://doi.org/10.1007/s12182-020-00441-1The authors have retracted their article(Wang et al.2020)because of significant textual overlap with previously published works(Atwah et al.2019;Wang and Paul Philp 2019).All authors agree with this retraction.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.41272158)the Foundation of the State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing(PRP/open-1710)
文摘The oils in the Rewapu Block of the Halahatang Oilfield in the Tarim Basin(northwestern China) were geochemically analyzed by gas chromatography–mass spectrometry to investigate their origin and possible secondary alteration. The physical properties and chemical compositions of these Ordovician oils vary greatly, ranging from light to extremely heavy oils. All these oils belong to one single population and were derived from same source kitchen/bed. The differences in their chemical compositions and physical properties mainly result from secondary alteration of oils that were charged during the early phase of trap formation. The thickness of Upper Ordovician and Silurian caprocks of oil reservoirs in the Rewapu Block is higher than that in the north part of the Halahatang region, and therefore, significant biodegradation process is prevented. Compared to heavy oils in the north part, the Rewapu oils are dominated by light oils with no 25-norhopanes and no GC–MS ‘‘hump''(UCM: unresolved complex mixture) on the chromatographic baselines. The heavy oils in Wells RP7 and RP101 C were primarily influenced by water washing since apparent reduction of alkylated dibenzothiophenes was observed. The local geological background favored the water washing alteration. The reservoir geochemical study has practical application in hydrocarbon exploration and predicts the nature of oils in this oilfield.
基金supported by grants from the National Natural Science Foundation of China(41972149,41890843).
文摘The deeply buried Lower Cambrian Longwangmiao Formation and Upper Ediacaran Dengying Formation from the Sichuan Basin,China,have a total natural gas reserve up to 3×10^(12)m^(3).The complex diagenetic evolution and their impacts on the present-day reservoir quality have not been systematically elucidated,hampering the current exploration.Crucially,the integration and comparation diagenetic study on these two formations,which may be able to shed new lights on reservoir formation mechanism,are yet to be systemically evaluated.By compiling geochemistry data,including carbonate U-Pb ages and petrophysics data,coupled with new petrology,trace elements,and strontium isotope data,of various types of diagenetic carbonates,this study aims to decipher the potential links between diagenesis and reservoir development of both formations.Intriguingly,similar diagenetic sequence,which contains five distinctive dolomite phases,is established in both formations.The matrix dolomite(D1)and early dolomite cement(D2)were likely formed by reflux dolomitization,as inferred by their nearly syn-depositional U-Pb ages and elevatedδ^(18)O caused by seawater evaporation.The subsequent moderate burial dolomite cement(D3)was most plausibly the product of burial compaction as indicated by its lighterδ^(18)O and slightly younger U-Pb ages compared with D1 and D2.Whereas deep burial dolomite cements(D4 and D5)yield markedly depletedδ^(18)O,elevated ^(87)Sr/^(86)Sr,along with much younger U-Pb ages and higher precipitation temperatures,suggesting that they were likely linked to hydrothermal fluids.Despite the wide occurrence of meteoric and organic acids leaching and thermochemical sulfate reduction,they may have only played a subsidiary role on these reservoirs development.Instead,superior reservoir quality is tightly linked to tectonics as inferred by higher reservoir quality closely related to the well-developed fractures and faults filled with abundant hydrothermal minerals.Notably,good reservoirs in both formations are mainly attributed to high permeability caused by tectonics.Hence,this new contribution emphasizes the crucial role of tectonics on spatially explicit reservoir prediction of deep to ultra-deep(up to>8000 m)carbonates in the Sichuan Basin,as well as other sedimentary basin analogues in China.
文摘Based on gas chromatography and gas chromatography mass spectrometry techniques, the authors researched biomarker characteristics of the Linxi Formation source rocks in the area of Taohaiyingzi, and analyzed the information and petroleum geological significance that were indicated by source of organic matter, sedimentary environment, maturity and so on. Gas chromatography peak of saturated hydrocarbons from Linxi Formation source rocks showed ‘‘the former peak'' of the single peak distribution and the C23-dominant main peak. This indicates that the main source of organic matter was mixed organic matter; Pr/Ph ratios ranged from 0.3 to 0.6, indicating a strongly reducing sedimentary environment.Molecular fossil assemblages in Linxi Formation source rocks were abundant in tricyclic terpane with long side chains, had high level of gammacerane, and showed dominant distribution of C27 steranes. Gammacerane ratios range from 0.15 to 0.29, with an average of 0.19, implying that Linxi Formation hydrocarbon source rocks were formed in the environment of micro-saltwater water to half-saltwater water. The hopanes/steranes ratios are mainly between 0.6 and 1.0, with an average of 0.84, implying that bacteria and algae had almost the samecontribution to organic matter. C27 steranes abundance is high and the ratio of C27steranes/C29 steranes is 1.13,showing that algae is the main source of hydrocarbon precursors.
基金National Natural Science Foundation of China(No.41802152)Natural Science Foundation of Hubei Province,China(No.2017CFB321)+3 种基金Open Fund of Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education,China(No.K2017-18)Open Foundation of Top Disciplines in Yangtze UniversityOpen Fund of State Key Laboratory of Petroleum Resources and ProspectingChina University of Petroleum,Beijing(No.PRP/open-1605)for providing financial support
文摘The Woodford–Mississippian"Commingled Production"is a prolific unconventional hydrocarbon play in Oklahoma,USA.The tight reservoirs feature variations in produced fluid chemistry usually explained by different possible source rocks.Such chemical variations are regularly obtained from bulk,molecular,and isotopic characteristics.In this study,we present a new geochemical investigation of gasoline range hydrocarbons,biomarkers,and diamondoids in oils from Mississippian carbonate and Woodford Shale.A set of oil/condensate samples were examined using high-performance gas chromatography and mass spectrometry.The result of the condensates from the Anadarko Basin shows a distinct geochemical fingerprint reflected in light hydrocarbon characterized by heptane star diagrams,convinced by biomarker characteristics and diamantane isomeric distributions.Two possible source rocks were identified,the Woodford Shale and Mississippian mudrocks,with a variable degree of mixing.Thermal maturity based on light hydrocarbon parameters indicates that condensates from the Anadarko Basin are of the highest maturity,followed by"Old"Woodford-sourced oils and central Oklahoma tight oils.These geochemical parameters shed light on petroleum migration within Devonian–Mississippian petroleum systems and mitigate geological risk in exploring and developing petroleum reservoirs.
基金We would like to thank the Open Foundation of Top Disciplines in Yangtze University for financial assistance to this research,the National Natural Science Foundation of China(No.41972148)the Open Foundation of Hubei Key Laboratory of Marine Geological Resources(MGR202008)。
文摘Tight gas exploration plays an important part in China’s unconventional energy strategy.The tight gas reservoirs in the Jurassic Shaximiao Formation in the Qiulin and Jinhua Gas Fields of central Sichuan Basin are characterized by shallow burial depths and large reserves.The evolution of the fluid phases is a key element in understanding the accumulation of hydrocarbons in tight gas reservoirs.This study investigates the fluid accumulation mechanisms and the indicators of reservoir properties preservation and degradation in a tight gas reservoir.Based on petrographic observations and micro-Raman spectroscopy,pure CH4 inclusions,pure CO2 inclusions,hybrid CH4–CO2 gas inclusions,and N2-rich gas inclusions were studied in quartz grains.The pressure–volume–temperature–composition properties(PVT-x)of the CH4 and CO2 bearing inclusions were determined using quantitative Raman analysis and thermodynamic models,while the density of pure CO2 inclusions was calculated based on the separation of Fermi diad.Two stages of CO2 fluid accumulation were observed:primary CO2 inclusions,characterized by higher densities(0.874–1.020 g/cm3)and higher homogenization temperatures(>210°C)and secondary CO2 inclusions,characterized by lower densities(0.514–0.715 g/cm3)and lower homogenization temperatures:~180–200°C).CO2 inclusions with abnormally high homogenization temperatures are thought to be the result of deep hydrothermal fluid activity.The pore fluid pressure(44.0–58.5 MPa)calculated from the Raman shift of C–H symmetric stretching(v1)band of methane inclusions is key to understanding the development of overpressure.PT entrapment conditions and simulation of burial history can be used to constrain the timing of paleo-fluid emplacement.Methane accumulated in the late Cretaceous(~75–65 Ma),close to the maximum burial depth during the early stages of the Himalayan tectonic event while maximum overpressure occurred at~70 Ma,just before uplift.Later,hydrocarbon gas migrated through the faults and gradually displaced the early emplaced CO2 in the reservoirs accompanied by a continuous decrease in overpressure during and after the Himalayan event,which has led to a decrease in the reservoir sealing capabilities.The continuous release of overpressure to present-day conditions indicates that the tectonic movement after the Himalayan period has led to a decline in reservoir conditions and sealing properties.
文摘Retraction Note to:Petroleum Science(2020)17:582-597https://doi.org/10.1007/s12182-020-00441-1The authors have retracted their article(Wang et al.2020)because of significant textual overlap with previously published works(Atwah et al.2019;Wang and Paul Philp 2019).All authors agree with this retraction.