Based on stratigraphic variations of petrology,geochemistry(major,trace elements),and pyrite framboids,we study the sedimentary environment of siliceous rocks of the Wufeng Formation in Wuxi,Northeastern Chongqing,Chi...Based on stratigraphic variations of petrology,geochemistry(major,trace elements),and pyrite framboids,we study the sedimentary environment of siliceous rocks of the Wufeng Formation in Wuxi,Northeastern Chongqing,China.Coupled Al2O3/(Al2O3þFe2O3),SiO2/Al2O3,with AleFeeMn values indicate that Wufeng Formation are deposited in a continental margin and influenced by detrital input.UEF-MoEF and V/CreU/Th cross-plots suggest that the siliceous shale was formed in dysoxic to anoxic conditions.Redox proxies imply that the lower,the middle to upper,and the top part of the Wufeng sediments were deposited in an anoxic,dysoxic and oxic environment,respectively.Accordingly,the average size of pyrite framboids are gradually increased from bottom to top,showing that increased oxidisability.A complete vibratory third-order cycle of sea level fluctuations during the Wufeng deposition can be identified.During Wufeng to Longmaxi transition,the sedimentary environment exhibits a short-scale oscillatory pattern and was probably transformed from an outer shelf to inner shelf.Coupled multi-proxies are considered more reliable proxies for deciphering redox conditions in fine-grained sediment.展开更多
A breakthrough has been recently made in the hydrocarbon exploration of the Permian pyroclastic rocks in the Jianyang Area,western Sichuan Basin,China.With an aim to decipher the impacts of the eruption environment,th...A breakthrough has been recently made in the hydrocarbon exploration of the Permian pyroclastic rocks in the Jianyang Area,western Sichuan Basin,China.With an aim to decipher the impacts of the eruption environment,the temperature of hydrothermal fluids,and the paleo-salinity on the formation of authigenic mineral assemblage and pores,this study implements comprehensive petrographic and geochemical studies through the integrated core and thin section analyses.The data presented demonstrate that the Permian volcanic intervals are intensively affected by an event of Emei taphrogeny.During basaltic magma upward migration,fractional crystallization of anorthose results in slightlyalkaline magma.The specific pyroclastic rocks are formed by the eruption of slightly-alkaline magma in the sea or a salt lake and subsequent hydrothermal alteration.During deposition and diagenesis,the authigenic mineral association is constrained jointly by the sodium-rich and high salinity water environment,and mid-high temperature,high-salinity hydrothermal fluid.Specifically,the sodium-rich hydrothermal fluid,which may sustain till the late diagenesis stage,caused pervasive albitization of pyroclastic rocks,then leading to mineral transformation and formation of a series of mineral associations.Therefore,zeolitization of volcanic glass and vesicle-infillings of zeolite is an essential condition for later mineral transformation and dissolution.Albitization of analcite,recrystallization induced by deep hydrothermal fluids,and both meteoric and deep burial dissolution expanding the micro-pore space ultimately formed porous pyroclastic reservoirs.展开更多
The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin.Its reservoirs were well developed.And many kinds of fillings wh...The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin.Its reservoirs were well developed.And many kinds of fillings which lead to the decrease of pores can be seen in reservoir pores and caves.In this paper,the pore fillings of the Dengying Formation reservoir in Sichuan basin are the object of study.The types and characteristics of the fillings are studied in detail by means of rock slices analysis,cathode luminescence,trace elements and inclusion temperature measurement.The study shows that the fillings include dolomite fillings and siliceous quartz fillings and bitumen fillings.Among them,dolomite fillings can be divided into botryoidal dolomite fillings,foliated dolomite fillings,finely-medium crystalline dolomite fillings and coarse crystalline dolomite fillings.50%–80%of the pores are filled by the dolomite fillings with botryoidal structure,and the pores can be partially full filled;0%–20%of pores are filled by foliated dolomite fillings;20–80%of the pores are filled by finely-medium dolomite fillings;20–80%of the pores are filled by coarse crystalline dolomite fillings.1%–5%of secondary pores are often filled by siliceous quartzs,and the pores can be partially full filled.Bitumen fillings often occur after the above-mentioned fillings,and the residual pores are often semi-filled by bitumens,which makes the original pores and throat smaller and reduces the effective porosity and permeability of the reservoir.So,it is a destructive diagenesis.The pore fillings make the secondary porosity in the reservoir significantly lower,which is not conducive to the formation and preservation of the Dengying Formation reservoir.展开更多
基金This research was funded by the National Major projects of Science and Technology(Grant No.2017ZX05001001-002)the Project of Sichuan Key Laboratory of Natural Gas Geology of China(Grant No.2015trqdz01)
文摘Based on stratigraphic variations of petrology,geochemistry(major,trace elements),and pyrite framboids,we study the sedimentary environment of siliceous rocks of the Wufeng Formation in Wuxi,Northeastern Chongqing,China.Coupled Al2O3/(Al2O3þFe2O3),SiO2/Al2O3,with AleFeeMn values indicate that Wufeng Formation are deposited in a continental margin and influenced by detrital input.UEF-MoEF and V/CreU/Th cross-plots suggest that the siliceous shale was formed in dysoxic to anoxic conditions.Redox proxies imply that the lower,the middle to upper,and the top part of the Wufeng sediments were deposited in an anoxic,dysoxic and oxic environment,respectively.Accordingly,the average size of pyrite framboids are gradually increased from bottom to top,showing that increased oxidisability.A complete vibratory third-order cycle of sea level fluctuations during the Wufeng deposition can be identified.During Wufeng to Longmaxi transition,the sedimentary environment exhibits a short-scale oscillatory pattern and was probably transformed from an outer shelf to inner shelf.Coupled multi-proxies are considered more reliable proxies for deciphering redox conditions in fine-grained sediment.
基金This work was granted by the National Natural Science Foundation of China(Grant No.41202109)the National Major Science and Technology Projects of China(Grant No.2016ZX05007004001)+1 种基金the Innovation Foundation of PetroChina Carbonate Key laboratory(RIPED-HZDZY-2019-JS-695)the China Scholarship Council.Thanks are expressed to our colleagues involved in igneous rocks researching in the Sichuan Basin,as well as to several anonymous reviewers from which this article has benefited.
文摘A breakthrough has been recently made in the hydrocarbon exploration of the Permian pyroclastic rocks in the Jianyang Area,western Sichuan Basin,China.With an aim to decipher the impacts of the eruption environment,the temperature of hydrothermal fluids,and the paleo-salinity on the formation of authigenic mineral assemblage and pores,this study implements comprehensive petrographic and geochemical studies through the integrated core and thin section analyses.The data presented demonstrate that the Permian volcanic intervals are intensively affected by an event of Emei taphrogeny.During basaltic magma upward migration,fractional crystallization of anorthose results in slightlyalkaline magma.The specific pyroclastic rocks are formed by the eruption of slightly-alkaline magma in the sea or a salt lake and subsequent hydrothermal alteration.During deposition and diagenesis,the authigenic mineral association is constrained jointly by the sodium-rich and high salinity water environment,and mid-high temperature,high-salinity hydrothermal fluid.Specifically,the sodium-rich hydrothermal fluid,which may sustain till the late diagenesis stage,caused pervasive albitization of pyroclastic rocks,then leading to mineral transformation and formation of a series of mineral associations.Therefore,zeolitization of volcanic glass and vesicle-infillings of zeolite is an essential condition for later mineral transformation and dissolution.Albitization of analcite,recrystallization induced by deep hydrothermal fluids,and both meteoric and deep burial dissolution expanding the micro-pore space ultimately formed porous pyroclastic reservoirs.
基金This research was supported by National Science and technology major project(2017ZX05001001-002)PetroChina Innovation Foundation(2018D-5007-0105)+2 种基金Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Chengdu University of Technology)(PLC20180304)open fund of Shandong Provincial key laboratory of Depositional mineralization(No.DMsMzO1TO35)scientific research starting project of SWPU(No.2017QHZ005).
文摘The Sinian Dengying Formation in the Sichuan basin is an important potential reservoir for oil and gas exploration in the periphery of the Sichuan basin.Its reservoirs were well developed.And many kinds of fillings which lead to the decrease of pores can be seen in reservoir pores and caves.In this paper,the pore fillings of the Dengying Formation reservoir in Sichuan basin are the object of study.The types and characteristics of the fillings are studied in detail by means of rock slices analysis,cathode luminescence,trace elements and inclusion temperature measurement.The study shows that the fillings include dolomite fillings and siliceous quartz fillings and bitumen fillings.Among them,dolomite fillings can be divided into botryoidal dolomite fillings,foliated dolomite fillings,finely-medium crystalline dolomite fillings and coarse crystalline dolomite fillings.50%–80%of the pores are filled by the dolomite fillings with botryoidal structure,and the pores can be partially full filled;0%–20%of pores are filled by foliated dolomite fillings;20–80%of the pores are filled by finely-medium dolomite fillings;20–80%of the pores are filled by coarse crystalline dolomite fillings.1%–5%of secondary pores are often filled by siliceous quartzs,and the pores can be partially full filled.Bitumen fillings often occur after the above-mentioned fillings,and the residual pores are often semi-filled by bitumens,which makes the original pores and throat smaller and reduces the effective porosity and permeability of the reservoir.So,it is a destructive diagenesis.The pore fillings make the secondary porosity in the reservoir significantly lower,which is not conducive to the formation and preservation of the Dengying Formation reservoir.
