The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive developme...The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive development of micro-and nano-scale pore and throat systems.Characterizing the microscopic properties of these reservoirs using nondestructive,quantitative methods serves as an important means to determine the characteristics of microscopic pores and throats in tight-sand reservoirs and the mechanism behind the influence of these characteristics on reservoir porosity and permeability.In this study,a low-permeability sandstone sample and two tight sandstone samples collected from the Ordos Basin were nondestructively tested using high-resolution nano-CT technology to quantitively characterize their microscopic pore throat structures and model them three-dimensionally(in 3D)based on CT threshold differences and gray models.A thorough analysis and comparison reveal that the three samples exhibit a certain positive correlation between their porosity and permeability but the most important factor affecting both porosity and permeability is the microscopic pore throat structure.Although the number of pores in tight sandstones shows a minor impact on their porosity,large pores(more than 20μm)contribute predominantly to porosity,suggesting that the permeability of tight sandstones is controlled primarily by large pore throats.For these samples,higher permeability corresponds to larger average throat sizes.Therefore,throats with average radii greater than 2μm can significantly improve the permeability of tight sandstones.展开更多
The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and ...The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.展开更多
The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is si...The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is significant to understand the tectonic transformation of the northern margin of the NCC.In this work,the detrital zircon and apatite(U-Th)/He chronological system were analyzed in the northern part of the OB,and have provided new evidence for the regional tectonic evolution.The(U-Th)/He chronological data states the weighted ages of 240‒235 Ma,141 Ma with the peak distribution of 244 Ma,219 Ma,173 Ma,147‒132 Ma.The thermal evolution,geochronological data,and regional unconformities have proved four stages of regional tectonic evolution for the OB and its surroundings in the Mesozoic:(1)The Late Permian-Early Triassic;(2)the Late Triassic-Early Jurassic;(3)the Late Jurassic-Early Cretaceous;(4)the Late Cretaceous-Early Paleogene.It is indicated that the multi-directional convergence from the surrounding tectonic units has controlled the Mesozoic tectonic evolution of the OB.Four-stage tectonic evolution reflected the activation or end of different plate movements and provided new time constraints for the regional tectonic evolution of the NCC in the Mesozoic.展开更多
Clarifying the mechanisms through which coal mining affects groundwater storage(GWS)variations is crucial for water resource conservation and sustainable development.The Ordos Mining Region in China,a key energy base ...Clarifying the mechanisms through which coal mining affects groundwater storage(GWS)variations is crucial for water resource conservation and sustainable development.The Ordos Mining Region in China,a key energy base in China with significant strategic importance,has undergone intensive coal mining activities that have substantially disrupted regional groundwater circulation.This study integrated data from the Gravity Recovery and Climate Experiment Satellite(GRACE)and Famine Early Warning Systems Network(FEWS NET)Land Data Assimilation System(FLDAS)models,combined with weighted downscaling methodology and water balance principles,to reconstruct high-resolution(0.01°)terrestrial water storage(TWS)and GWS changes in the Ordos Mining Region,China from April 2002 to December 2021.The accuracy of GWS variations were validated through pumping test measurements.Subsequently,Geodetector analysis was implemented to quantify the contributions of natural and anthropogenic factors to groundwater storage dynamics.Key findings include:1)TWS in the study area showed a fluctuating but overall decreasing trend,with a total reduction of 8901.11 mm during study period.The most significant annual decrease occurred in 2021,reaching 1696.77 mm.2)GWS exhibited an accelerated decline,with an average annual change rate of 44.35 mm/yr,totaling a decrease of 887.05 mm.The lowest annual groundwater storage level was recorded in 2020,reaching 185.69 mm.3)Precipitation(PRE)contributed the most to GWS variation(q=0.52),followed by coal mining water consumption(MWS)(q=0.41).The interaction between PRE and MWS exhibited a nonlinear enhancement effect on GWS changes(0.54).The synergistic effect of natural hydrological factors has a great influence on the change of GWS,but coal mining water consumption will continue to reduce GWS.These findings provide critical references for the management and regulation of groundwater resource in mining regions.展开更多
On May 16th,the press conference of the 8th China(ORDOS)International Cashmere and Wool Exhibition organized by China Wool Textile Association was held in Inner Mongolia Grand Hotel in Beijing.The 8th China(ORDOS)Inte...On May 16th,the press conference of the 8th China(ORDOS)International Cashmere and Wool Exhibition organized by China Wool Textile Association was held in Inner Mongolia Grand Hotel in Beijing.The 8th China(ORDOS)International Cashmere and Wool Exhibition will be held in the National Fitness Center of Dongsheng District,Ordos City from July 18th to 20th with the theme of“Cashmere Chain Links the World,Intelligence Empowers the Future”.展开更多
Recent studies have highlighted the presence of lithium enrichment in coals within the Ordos Basin,which has garnered significant attention due to the potential economic value.However,most research has concentrated pr...Recent studies have highlighted the presence of lithium enrichment in coals within the Ordos Basin,which has garnered significant attention due to the potential economic value.However,most research has concentrated primarily on the coal seams of the Taiyuan and Shanxi formations,with limited reports on the Benxi Formation.To address this gap,our study focused on elucidating the geochemical characteristics and origins of the lithium enrichment in the No.8 coal of the Benxi Formation through the use of optical microscopy and inductively coupled plasma mass spectrometry(ICP-MS).The results showed that the No.8 coal was a bituminous coal,characterized by medium ash yield,low volatile matter,high total sulfur content and medium vitrinite proportion.The No.8 coal was enriched in Li(average 91.7 ppm,CC=6.55)and Zr(average 191 ppm,CC=5.30),the unusual enrichment of Li being primarily located in the middle of the coal.The minerals in the coal were predominantly clay minerals,along with minor amounts of pyrite,quartz and calcite.The occurrence mode of Li in the No.8 coal was associated with aluminosilicate minerals,presumably kaolinite.Based on geochemical characteristics,the sedimentary source of the No.8 coal was intermediate-felsic volcanic rock from the Yinshan oldland.The enrichment of Li can be attributed to the supply of terrestrial debris from the Yinshan oldland and the depositional environment.Our analysis identifies three distinct stages of lithium enrichment,emphasizing the critical role played by the terrestrial debris,as well as the acidic to partially reducing conditions,in facilitating this process.In conclusion,our study sheds light on the mechanisms underlying lithium enrichment in the No.8 coal of the Benxi Formation,highlighting the significance of geological factors in shaping the distribution and concentration of critical metals in coal.展开更多
This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability ...This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability carbonate,low-permeability sandstone and tight sandstone,as well as the progress in deep coal-rock gas development.The current challenges and future development directions are also discussed.Mature development models have been formed for the three representative types of gas reservoirs in the Ordos Basin:(1)Low-permeability carbonate reservoir development model featuring groove fine-scale characterization and three-dimensional vertical succession between Upper and Lower Paleozoic formations.(2)Low-permeability sandstone reservoir development model emphasizing horizontal well pressure-depletion production and vertical well pressure-controlled production.(3)Tight sandstone gas reservoir development model focusing on single-well productivity enhancement and well placement optimization.In deep coal-rock gas development,significant progress has been achieved in reservoir evaluation,sweet spot prediction,and geosteering of horizontal wells.The three types of reservoirs have entered the mid-to-late stages of the development,when the main challenge lies in accurately characterizing residual gas,evaluating secondary gas-bearing layers,and developing precise potential-tapping strategies.In contrast,for the early-stage development of deep coal-rock gas,continuous technological upgrades and cost reduction are essential to achieving economically viable large-scale development.Four key directions of future research and technological breakthroughs are proposed:(1)Utilizing dual-porosity(fracture-matrix)modeling techniques in low-permeability carbonate reservoirs to delineate the volume and distribution of remaining gas in secondary pay zones,supporting well pattern optimization and production enhancement of existing wells.(2)Integrating well-log and seismic data to characterize reservoir spatial distribution of successive strata,enhancing drilling success rates in low-permeability sandstone reservoirs.(3)Utilizing the advantages of horizontal wells to penetrate effective reservoirs laterally,achieving meter-scale quantification of small-scale single sand bodies in tight gas reservoirs,and applying high-resolution 3D geological models to clarify the distribution of remaining gas and guide well placement optimization.(4)Further strengthening the evaluation of deep coal-rock gas in terms of resource potential,well type and pattern,reservoir stimulation,single-well performance,and economic viability.展开更多
Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals th...Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals the fluid characteristics,gas accumulation control factors and accumulation modes in the Upper Paleozoic coal reservoirs.The study indicates findings in two aspects.First,the 1500-1800 m interval represents the critical transition zone between open fluid system in shallow-medium depths and closed fluid system in deep depths.The reservoirs above 1500 m reflect intense water invasion,with discrete pressure gradient distribution,and the presence of methane mixed with varying degrees of secondary biogenic gas,and they generally exhibit high water saturation and adsorbed gas undersaturation.The reservoirs deeper than 1800 m,with extremely low permeability,are self-sealed,and contains closed fluid systems formed jointly by the hydrodynamic lateral blocking and tight caprock confinement.Within these systems,surface runoff infiltration is weak,the degree of secondary fluid transformation is minimal,and the pressure gradient is relatively uniform.The adsorbed gas saturation exceeds 100%in most seams,and the free gas content primarily ranges from 1 m^(3)/t to 8 m^(3)/t(greater than 10 m^(3)/t in some seams).Second,the gas accumulation in deep coals is primarily controlled by coal quality,reservoir-caprock assemblage,and structural position governed storage,wettability and sealing properties,under the constraints of the underground temperature and pressure conditions.High-rank,low-ash yield coals with limestone and mudstone caprocks show superior gas accumulation potential.Positive structural highs and wide and gentle negative structural lows are favorable sites for gas enrichment,while slope belts of fold limbs exhibit relatively lower gas content.This research enhances understanding of gas accumulation mechanisms in coal reservoirs and provides effective parameter reference for precise zone evaluation and innovation of adaptive stimulation technologies for deep resources.展开更多
Lacustrine shale oil reservoirs of the Upper Triassic Chang 7 Member in the Ordos Basin have demonstrated significant potential for hydrocarbon resources.Natural fractures play a crucial role in hydrocarbon enrichment...Lacustrine shale oil reservoirs of the Upper Triassic Chang 7 Member in the Ordos Basin have demonstrated significant potential for hydrocarbon resources.Natural fractures play a crucial role in hydrocarbon enrichment and production.Outcrops,cores,borehole image logs,thin sections,and FE-SEM images were used to investigate the types and characteristics of natural fractures in the Chang 7 Member.The factors controlling fracture development and the mechanisms of bedding-parallel fracture formation were revealed by integrating TOC analysis,XRD analysis,and rock pyrolysis.Results show that natural fractures in the study area include high-angle tectonic fractures and nearly horizontal bedding-parallel fractures.Brittle minerals and bed thickness control the occurrence and attributes of tectonic fractures.High TOC content and thermal maturity positively affect the development of bedding-parallel fractures,formed through the conversion of organic matter to hydrocarbons or the smectite-to-illite transformation.Additionally,the dominant orientations of tectonic fractures intersect the present-day maximum horizontal principal stress at a small angle,resulting in large apertures and good effectiveness.Bedding-parallel fractures contribute to enhance porosity and provide favorable pathways for lateral hydrocarbon migration.Collectively,this study could provide valuable insights for finding promising exploration areas in lacustrine shale oil reservoirs in the Ordos Basin and worldwide.展开更多
Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater f...Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.展开更多
The formation of Mesozoic natural gas in the Pengyang area of southwestern Ordos Basin is discussed,from the perspective of microbial community characteristics,in order to clarify the relationship between the origin o...The formation of Mesozoic natural gas in the Pengyang area of southwestern Ordos Basin is discussed,from the perspective of microbial community characteristics,in order to clarify the relationship between the origin of natural gas and its associated indigenous microbial community.The types and diversity of indigenous microbial communities associated with the oil reservoir were studied by means of collecting reservoir formation water samples from exploration wells.The indigenous microbial communities in the Chang 8 member of the Yanchang Formation were primarily distributed within Proteobacteria and Firmicutes,including the specific species and genera of Methylobacter,Pseudomonas,Haibacter,Toxobacillus,Acinetobacter and Adura actinomyces.The results of diversity analysis shows that the number of common genes was 5448,while the number of unique genes and information was less.This reflects the fact that the strata in the study area are relatively closed and not invaded by external water sources,which leads to the development of biological community diversity.In conjunction with the analysis of geochemical characteristics of oil and gas reservoirs in this area,this indicates that the study area possesses the necessary geological conditions for microbial degradation.It is the first time that the species and diversity of the indigenous microbial community in the Ordos Basin have been analyzed,showing that microbial degradation is the main cause of natural gas formation here,changes the characteristics of crude oil in this area and provides first-hand information on the impact of indigenous microorganisms on the reservoir.展开更多
The lamina(combination)types,reservoir characteristics and shale oil occurrence states of organic-rich shale in the Triassic Yanchang Formation Chang 73 sub-member in the Ordos Basin were systematically investigated t...The lamina(combination)types,reservoir characteristics and shale oil occurrence states of organic-rich shale in the Triassic Yanchang Formation Chang 73 sub-member in the Ordos Basin were systematically investigated to reveal the main controlling factors of shale oil occurrence under different lamina combinations.The differential enrichment mechanisms and patterns of shale oil were discussed using the shale oil micro-migration characterization and evaluation methods from the perspectives of relay hydrocarbon supply,stepwise migration,and multi-stage differentiation.The results are obtained in five aspects.First,Chang 73 shale mainly develops five types of lamina combination,i.e.non-laminated shale,sandy laminated shale,tuffaceous laminated shale,mixed laminated shale,and organic-rich laminated shale.Second,shales with different lamina combinations are obviously different in the reservoir space.Specifically,shales with sandy laminae and tuffaceous laminae have a large number of intergranular pores,dissolution pores and hydrocarbon generation-induced fractures.The multi-scale pore and fracture system constitutes the main place for liquid hydrocarbon occurrence.Third,the occurrence and distribution of shale oil in shale with different lamina combinations are jointly controlled by organic matter abundance,reservoir property,thermal evolution degree,mineral composition and laminae scale.The micro-nano-scale pore-fracture networks within shales containing rigid laminae,particularly sandy and tuffaceous laminations,primarily contain free-state light hydrocarbon components.In contrast,adsorption-phase heavy hydrocarbon components predominantly occupy surfaces of organic matter assemblages,clay mineral matrices,and framework mineral particulates.Fourth,there is obvious shale oil micro-migration between shales with different lamina combinations in Chang 73.Generally,such micro-migration is stepwise in a sequence of organic-rich laminated shale→tuffaceous laminated shale→mixed laminated shale→sandy lamiated shale→non-laminated shale.Fifth,the relay hydrocarbon supply of organic matter under the control of the spatial superposition of shales with various laminae,the stepwise migration via multi-scale pore and fracture network,and the multi-differentiation in shales with different lamina combinations under the control of organic-inorganic interactions fundamentally decide the differences of shale oil components between shales with different lamina combinations.展开更多
The Majiagou Formation in the Fuxian area of the southeastern Ordos Basin has undergone a complex diagenetic evolution history under the influence of eustacy and the Caledonian karstification,resulting in several comp...The Majiagou Formation in the Fuxian area of the southeastern Ordos Basin has undergone a complex diagenetic evolution history under the influence of eustacy and the Caledonian karstification,resulting in several complex reservoir types.Through analyses of mineralogy,petrology,and reservoir geology,three major types of dolomite reservoirs with different genetic mechanisms,including anhydritic moldicdissolved pore type,dolomitic intercrystalline-pore type,and fractured type were identified,and their formation mechanisms and distribution patterns were examined.The aphanocrystalline to very finecrystalline anhydritic dolomite was resulted from Sabhak dolomitization,and is characterized by small size of crystals and high content of anhydrite.Dolomite reservoirs of anhydritic moldic-dissolved pore type were developed in multi-stage dissolution processes and mainly distributed at higher positions of the paleogeomorphology where the filling was weak.The very fine to fine-crystalline dolomite of shoal facies was formed under seepage-reflux dolomitization,and characterized by larger sizes of crystals and well-developed intercrystalline pores.Dolomite reservoirs of intercrystalline-pore type were mainly developed at the lower positions of the paleogeomorphology where bedding-parallel karst dissolution was strong.The fractured dolomite reservoirs,generated by the anhydrite swelling and karst cave collapse,occur in multiple horizons but within limited areas due to multi-stage fillings.展开更多
The Longshan orogenic belt is located in the southwestern margin of Ordos Basin at the junction zone between the Western Qinling and Northern Qilian orogenic belt.Voluminous Early Paleozoic magmatism in this area is o...The Longshan orogenic belt is located in the southwestern margin of Ordos Basin at the junction zone between the Western Qinling and Northern Qilian orogenic belt.Voluminous Early Paleozoic magmatism in this area is of key significance for determining the Early Paleozoic tectonic evolution and deep crust-mantle structure.Previous studies mainly focused on the Paleozoic granites;the coeval mafic rocks in this area are still poorly understood.A set of Late Silurian intraplate tholeiitic basalts has been discovered in Longshan area,providing key evidence for the mantle source and deep geodynamic background in this area.The Late Silurian Angou basalt has similar geochemical features as intraplate tholeiitic basalt,with high Na_(2)O/K_(2)O ratios(5.22-8.25),enriched in large ion lithophile elements and LREE.In combination with their relatively evolved Sr-Nd isotopic composition[^(87)Sr/^(86)Sr(i)=0.7128-0.7140;ε_(Nd)(t)=-5.55 to-3.40],it is suggested that it originated from decompression melting of metasomatized enriched mantle in extensional setting.These results indicate that the mantle source in the junction zone of the West Qinling-North Qilian orogenic belt evolved from depleted to enriched with the continuation of Proto-Tethys subduction from the Cambrian to the Silurian.These results are of great significance to understanding the genesis of contemporaneous granite and the crust-mantle interaction in the junction zone between the Western Qinling and Northern Qilian orogenic belt.展开更多
Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores s...Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores systematically the boundary,distribution,geological structure,and tectonic attributes of the Ordos prototype basin in the geological historical periods.The results show that the Ordos block is bounded to the west by the Engorwusu Fault Zone,to the east by the Taihangshan Mountain Piedmont Fault Zone,to the north by the Solonker-Xilamuron Suture Zone,and to the south by the Shangnan-Danfeng Suture Zone.The Ordos Basin boundary was the plate tectonic boundary during the Middle Proterozoic to Paleozoic,and the intra-continental deformation boundary in the Meso-Cenozoic.The basin survived as a marine cratonic basin covering the entire Ordos block during the Middle Proterozoic to Ordovician,a marine-continental transitional depression basin enclosed by an island arc uplift belt at the plate margin during the Carboniferous to Permian,a unified intra-continental lacustrine depression basin in the Triassic,and an intra-continental cratonic basin circled by a rift system in the Cenozoic.The basin scope has been decreasing till the present.The large,widespread prototype basin controlled the exploration area far beyond the present-day sedimentary basin boundary,with multiple target plays vertically.The Ordos Basin has the characteristics of a whole petroleum(or deposition)system.The Middle Proterozoic wide-rift system as a typical basin under the overlying Phanerozoic basin and the Cambrian-Ordovician passive margin basin and intra-cratonic depression in the deep-sited basin will be the important successions for oil and gas exploration in the coming years.展开更多
The Chang 7 sandstone is characterized by complex micro-pore structures,strong heterogeneity,and differential fluid distribution.These characteristics result in low oil recovery.In this paper,various techniques,includ...The Chang 7 sandstone is characterized by complex micro-pore structures,strong heterogeneity,and differential fluid distribution.These characteristics result in low oil recovery.In this paper,various techniques,including high-pressure mercury intrusion,nuclear magnetic resonance,scanning electron microscope,thin section,and X-ray diffraction,are employed to quantitatively evaluate the occurrence characteristics and influencing factors of movable fluids in Chang 7 sandstone reservoirs from the Heshui Block with different fractal structures.Results show that the dominant sandstone type is feldspar lithic fragment sandstone.Chang 7 reservoir has been divided into three types(typesⅠ,Ⅱ,andⅢ)based on capillary pressure curves and pore structure parameters.These reservoirs are characterized by various fractal structures and different movable fluids distribution.Multiple possible factors affecting the movable fluid distribution are analyzed,including physical properties,pore structure,pore size distribution,mineral content,and heterogeneity.Movable fluid saturation is positively correlated with physical properties,weighted average pore-throat radius,median pore-throat radius,final residual mercury saturation,and maximum mercury withdrawal saturation.In contrast,it is negatively correlated with displacement pressure and has no obvious correlation with the sorting coefficient.Micron-and submicron-scale pores are beneficial to the movable fluid occurrence,while nano-scale pores are vice versa.The influence of mineral content on movable fluid occurrence varies with mineral types.Quartz is conducive to the movable fluid occurrence in submicron-scale pores,while carbonate cementation inhibits the movable fluid occurrence in submicron-scale pores.The inhibition of clay on the movable fluid occurrence is mainly reflected in submicron-and nano-scale pores and varies with clay mineral types.The influence of heterogeneity on the movable fluid occurrence is mainly reflected in submicron-scale pores.The occurrence models of movable fluid vary with reservoir types.展开更多
In this paper,a standardized analysis method is established for identifying meat quality-related genes in Ordos finewool sheep using transcriptome sequencing data.A meticulously standardized approach is utilized to in...In this paper,a standardized analysis method is established for identifying meat quality-related genes in Ordos finewool sheep using transcriptome sequencing data.A meticulously standardized approach is utilized to investigate the genetic determinants of meat quality in Ordos fine-wool sheep through transcriptome sequencing analysis.Muscle samples from the longissimus dorsi of one-year-old sheep are collected under controlled conditions,and key texture properties—hardness,elasticity,and chewiness—are measured to categorize samples into high-and low-textural-value groups.Genes significantly associated with meat quality traits are identified through standardized RNA extraction,high-throughput sequencing,and differential gene expression analysis.Functional enrichment analysis reveals their involvement in biological processes such as extracellular matrix organization and metabolic pathways.The findings underscore the pivotal role of standardization in meat quality research,laying a solid scientific foundation for future research on meat quality improvement and molecular breeding.展开更多
An enhanced understanding of the history of the western Qinling-Dabie orogen is pivotal in reconstructing geological processes of the east Asian mainland.However,less attention has been paid to its early-stage uplift-...An enhanced understanding of the history of the western Qinling-Dabie orogen is pivotal in reconstructing geological processes of the east Asian mainland.However,less attention has been paid to its early-stage uplift-erosion history after closure of surrounding oceanic basins at the mid-Paleozoic.In this study,we undertook a comprehensive study including paleocurrent reconstruction,sandstone petrology,and detrital zircon U-Pb dating on Late Carboniferous to Early Permian successions in the southern Ordos neighboring the northern Qinling-Dabie.New provenance data reveal a significant provenance shift at the Carboniferous-Permian transition.The older Benxi Formation was sourced southerly from the North Qinling Terrane that provided detritus mostly of Neoproterozoic and Early Paleozoic ages.In contrast,Early Permian samples yield age relation dominated by Neoarchean,Paleoproterozoic,Early Paleozoic,and Late Paleozoic age populations,with a significant gap of ca.1600-550 Ma,implying a sediment derivation from the Inner Mongolia Continental Arc.This shift is further verified by paleocurrent transition from south to north then.We suggest that the North Qinling Terrane experienced a significant uplift history from ca.500 Ma and remained as a highland until end-Carboniferous.From Early Permian,the North Qinling Terrane was submerged,covered by widespread deltaic sedimentation there.Northerly source from the Inner Mongolia Continental Arc began to be accumulated in the northern flank of the North Qinling Terrane,before termination approximately along the southern North Qinling Terrane,where shallow-water carbonate shelf sedimentation sustained from Devonian to Triassic.This new finding indicates that uplift of the North Qinling Terrane lasted about 150 Ma after the Proto-Tethys Ocean closure.展开更多
1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleon...1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleontology and magnetostratigraphy,formers believed it belonged to the Early Cretaceous(Huang YB,2010).However,the lack of intrusions or volcanic rocks for isotopic dating results in an unclear formation age for the Lower Cretaceous succession.Recently,tuffs were firstly discovered in the Luohandong Formation in the Zhenyuan area,Gansu Province,located in the southwestern Ordos Basin,China.The LA-ICP-MS zircon U-Pb dating of tuffs was carried out.The new ages can precisely constrain the depositional age of the Luohandong Formation and also provide significant indications for the study of regional volcanic activities,paleoclimate,basin evolution,and tectonic setting.展开更多
The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion...The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.展开更多
文摘The physical properties of hydrocarbon reservoirs are important factors affecting the percolation ability of the reservoirs.Tight-sand reservoirs exhibit complex pore throat connectivity due to the extensive development of micro-and nano-scale pore and throat systems.Characterizing the microscopic properties of these reservoirs using nondestructive,quantitative methods serves as an important means to determine the characteristics of microscopic pores and throats in tight-sand reservoirs and the mechanism behind the influence of these characteristics on reservoir porosity and permeability.In this study,a low-permeability sandstone sample and two tight sandstone samples collected from the Ordos Basin were nondestructively tested using high-resolution nano-CT technology to quantitively characterize their microscopic pore throat structures and model them three-dimensionally(in 3D)based on CT threshold differences and gray models.A thorough analysis and comparison reveal that the three samples exhibit a certain positive correlation between their porosity and permeability but the most important factor affecting both porosity and permeability is the microscopic pore throat structure.Although the number of pores in tight sandstones shows a minor impact on their porosity,large pores(more than 20μm)contribute predominantly to porosity,suggesting that the permeability of tight sandstones is controlled primarily by large pore throats.For these samples,higher permeability corresponds to larger average throat sizes.Therefore,throats with average radii greater than 2μm can significantly improve the permeability of tight sandstones.
文摘The tight sandstone reservoirs in the first sub-member of Chang 7 member(Chang 71)of Triassic Yanchang Formation in the Jiyuan area,Ordos Basin,show significant variations in microscopic pore-throat structure(PTS)and fluid mobility due to the influences of the northeast and northwest dual provenance systems.This study performed multiple experimental analyses on nine samples from the area to determine the petrological and petrophysical properties,as well as the PTS characteristics of reservoirs in different provenance-controlled regions.On this basis,the pore-throat size distribution(PSD)obtained from high-pressure mercury injection(HPMI)was utilized to convert the NMR movable fluid T2spectrum,allowing for quantitative characterization of the full PSD and the occurrence characteristics of movable fluids.A systematic analysis was conducted on the primary controlling factors affecting fluid mobility in the reservoir.The results indicated that the lithology in the eastern and western regions is lithic arkose.The eastern sandstones,being farther from the provenance,exhibit higher contents of feldspar and lithic fragments,along with the development of more dissolution pores.The reservoir possesses good petrophysical properties,low displacement pressure,and high pore-throat connectivity and homogeneity,indicating strong fluid mobility.In contrast,the western sandstones,being nearer to the provenance,exhibit poor grain sorting,high contents of lithic fragments,strong compaction and cementation effects,resulting in poor petrophysical properties,and strong pore-throat heterogeneity,revealing weak fluid mobility.The range of full PSD in the eastern reservoir is wider than that in the western reservoir,with relatively well-developed macropores.The macropores are the primary space for occurrence of movable fluids,and controls the fluid mobility of the reservoir.The effective porosity of movable fluids(EPMF)quantitatively represents the pore space occupied by movable fluids within the reservoir and correlates well with porosity,permeability,and PTS parameters,making it a valuable parameter for evaluating fluid mobility.Under the multi-provenance system,the eastern and western reservoirs underwent different sedimentation and diagenesis processes,resulting in differential distribution of reservoir mineral components and pore types,which in turn affects the PTS heterogeneity and reservoir quality.The composition and content of reservoir minerals are intrinsic factors influencing fluid mobility,while the microscopic PTS is the primary factor controlling it.Low clay mineral content,welldeveloped macropores,and weak pore-throat heterogeneity all contribute to the storage and seepage of reservoir fluids.
基金This study was jointly supported by the Science&Technology Fundamental Resources Investigation Program(2022FY101800)National Science Foundation(92162212)+1 种基金the project from the Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences,Wuhan)(TPR-2022-22)the International Geoscience Programme(IGCP-675)。
文摘The Ordos Basin(OB)in the western part of the North China Craton(NCC),was located at the jointed area of multi-plates and has recorded the Mesozoic tectonic characteristics.Its tectonic evolution in the Mesozoic is significant to understand the tectonic transformation of the northern margin of the NCC.In this work,the detrital zircon and apatite(U-Th)/He chronological system were analyzed in the northern part of the OB,and have provided new evidence for the regional tectonic evolution.The(U-Th)/He chronological data states the weighted ages of 240‒235 Ma,141 Ma with the peak distribution of 244 Ma,219 Ma,173 Ma,147‒132 Ma.The thermal evolution,geochronological data,and regional unconformities have proved four stages of regional tectonic evolution for the OB and its surroundings in the Mesozoic:(1)The Late Permian-Early Triassic;(2)the Late Triassic-Early Jurassic;(3)the Late Jurassic-Early Cretaceous;(4)the Late Cretaceous-Early Paleogene.It is indicated that the multi-directional convergence from the surrounding tectonic units has controlled the Mesozoic tectonic evolution of the OB.Four-stage tectonic evolution reflected the activation or end of different plate movements and provided new time constraints for the regional tectonic evolution of the NCC in the Mesozoic.
基金Under the National Key R&D Program Key Project(No.2021YFC3201201)National Natural Science Foundation of China(No.52360032)+2 种基金Basic Scientific Research Business Fee Project of Colleges And Universities Directly Under the Inner Mongolia Autonomous Region(No.JBYYWF2022001)Development Plan of Innovation Team of Colleges And Universities in Inner Mongolia Autonomous Region(No.NMGIRT2313)the Innovation Team of‘Grassland Talents’。
文摘Clarifying the mechanisms through which coal mining affects groundwater storage(GWS)variations is crucial for water resource conservation and sustainable development.The Ordos Mining Region in China,a key energy base in China with significant strategic importance,has undergone intensive coal mining activities that have substantially disrupted regional groundwater circulation.This study integrated data from the Gravity Recovery and Climate Experiment Satellite(GRACE)and Famine Early Warning Systems Network(FEWS NET)Land Data Assimilation System(FLDAS)models,combined with weighted downscaling methodology and water balance principles,to reconstruct high-resolution(0.01°)terrestrial water storage(TWS)and GWS changes in the Ordos Mining Region,China from April 2002 to December 2021.The accuracy of GWS variations were validated through pumping test measurements.Subsequently,Geodetector analysis was implemented to quantify the contributions of natural and anthropogenic factors to groundwater storage dynamics.Key findings include:1)TWS in the study area showed a fluctuating but overall decreasing trend,with a total reduction of 8901.11 mm during study period.The most significant annual decrease occurred in 2021,reaching 1696.77 mm.2)GWS exhibited an accelerated decline,with an average annual change rate of 44.35 mm/yr,totaling a decrease of 887.05 mm.The lowest annual groundwater storage level was recorded in 2020,reaching 185.69 mm.3)Precipitation(PRE)contributed the most to GWS variation(q=0.52),followed by coal mining water consumption(MWS)(q=0.41).The interaction between PRE and MWS exhibited a nonlinear enhancement effect on GWS changes(0.54).The synergistic effect of natural hydrological factors has a great influence on the change of GWS,but coal mining water consumption will continue to reduce GWS.These findings provide critical references for the management and regulation of groundwater resource in mining regions.
文摘On May 16th,the press conference of the 8th China(ORDOS)International Cashmere and Wool Exhibition organized by China Wool Textile Association was held in Inner Mongolia Grand Hotel in Beijing.The 8th China(ORDOS)International Cashmere and Wool Exhibition will be held in the National Fitness Center of Dongsheng District,Ordos City from July 18th to 20th with the theme of“Cashmere Chain Links the World,Intelligence Empowers the Future”.
基金funded by a grant from the National Natural Science Foundation of China(Grant No.41772130)the Natural Science Foundation of Jiangsu Province(Grant No.BK20210521)+4 种基金the Fundamental Research Funds for the Central Universities(Grant No.2021QN1061)‘Energy and Environment Youth Talent Training Program’by China’s Energy Society,China’s Environmental Protection Foundation and the Beijing Energy Society(Grant No.RCJH2022081)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX25_2782)the Graduate Innovation Program of China University of Mining and Technology(No.2025WLKXJ003)the Fundamental Research Funds for the Central Universities(No.202500044)。
文摘Recent studies have highlighted the presence of lithium enrichment in coals within the Ordos Basin,which has garnered significant attention due to the potential economic value.However,most research has concentrated primarily on the coal seams of the Taiyuan and Shanxi formations,with limited reports on the Benxi Formation.To address this gap,our study focused on elucidating the geochemical characteristics and origins of the lithium enrichment in the No.8 coal of the Benxi Formation through the use of optical microscopy and inductively coupled plasma mass spectrometry(ICP-MS).The results showed that the No.8 coal was a bituminous coal,characterized by medium ash yield,low volatile matter,high total sulfur content and medium vitrinite proportion.The No.8 coal was enriched in Li(average 91.7 ppm,CC=6.55)and Zr(average 191 ppm,CC=5.30),the unusual enrichment of Li being primarily located in the middle of the coal.The minerals in the coal were predominantly clay minerals,along with minor amounts of pyrite,quartz and calcite.The occurrence mode of Li in the No.8 coal was associated with aluminosilicate minerals,presumably kaolinite.Based on geochemical characteristics,the sedimentary source of the No.8 coal was intermediate-felsic volcanic rock from the Yinshan oldland.The enrichment of Li can be attributed to the supply of terrestrial debris from the Yinshan oldland and the depositional environment.Our analysis identifies three distinct stages of lithium enrichment,emphasizing the critical role played by the terrestrial debris,as well as the acidic to partially reducing conditions,in facilitating this process.In conclusion,our study sheds light on the mechanisms underlying lithium enrichment in the No.8 coal of the Benxi Formation,highlighting the significance of geological factors in shaping the distribution and concentration of critical metals in coal.
文摘This study systematically reviews the development history and key technological breakthroughs of large gas fields in the Ordos Basin,and summarizes the development models of three gas reservoir types,low-permeability carbonate,low-permeability sandstone and tight sandstone,as well as the progress in deep coal-rock gas development.The current challenges and future development directions are also discussed.Mature development models have been formed for the three representative types of gas reservoirs in the Ordos Basin:(1)Low-permeability carbonate reservoir development model featuring groove fine-scale characterization and three-dimensional vertical succession between Upper and Lower Paleozoic formations.(2)Low-permeability sandstone reservoir development model emphasizing horizontal well pressure-depletion production and vertical well pressure-controlled production.(3)Tight sandstone gas reservoir development model focusing on single-well productivity enhancement and well placement optimization.In deep coal-rock gas development,significant progress has been achieved in reservoir evaluation,sweet spot prediction,and geosteering of horizontal wells.The three types of reservoirs have entered the mid-to-late stages of the development,when the main challenge lies in accurately characterizing residual gas,evaluating secondary gas-bearing layers,and developing precise potential-tapping strategies.In contrast,for the early-stage development of deep coal-rock gas,continuous technological upgrades and cost reduction are essential to achieving economically viable large-scale development.Four key directions of future research and technological breakthroughs are proposed:(1)Utilizing dual-porosity(fracture-matrix)modeling techniques in low-permeability carbonate reservoirs to delineate the volume and distribution of remaining gas in secondary pay zones,supporting well pattern optimization and production enhancement of existing wells.(2)Integrating well-log and seismic data to characterize reservoir spatial distribution of successive strata,enhancing drilling success rates in low-permeability sandstone reservoirs.(3)Utilizing the advantages of horizontal wells to penetrate effective reservoirs laterally,achieving meter-scale quantification of small-scale single sand bodies in tight gas reservoirs,and applying high-resolution 3D geological models to clarify the distribution of remaining gas and guide well placement optimization.(4)Further strengthening the evaluation of deep coal-rock gas in terms of resource potential,well type and pattern,reservoir stimulation,single-well performance,and economic viability.
基金Supported by the National Natural Science Foundation of China(42130802,42272200)CNPC Science and Technology Major Project(2023ZZ18)+1 种基金PetroChina Changqing Oilfield Major Science and Technology Project(2023DZZ01)Technology Project of PetroChina Coalbed Methane Company Limited(2023-KJ-18)。
文摘Based on the test and experimental data from exploration well cores of the Upper Paleozoic in the central-eastern Ordos Basin,combined with structural,burial depth and fluid geochemistry analyses,this study reveals the fluid characteristics,gas accumulation control factors and accumulation modes in the Upper Paleozoic coal reservoirs.The study indicates findings in two aspects.First,the 1500-1800 m interval represents the critical transition zone between open fluid system in shallow-medium depths and closed fluid system in deep depths.The reservoirs above 1500 m reflect intense water invasion,with discrete pressure gradient distribution,and the presence of methane mixed with varying degrees of secondary biogenic gas,and they generally exhibit high water saturation and adsorbed gas undersaturation.The reservoirs deeper than 1800 m,with extremely low permeability,are self-sealed,and contains closed fluid systems formed jointly by the hydrodynamic lateral blocking and tight caprock confinement.Within these systems,surface runoff infiltration is weak,the degree of secondary fluid transformation is minimal,and the pressure gradient is relatively uniform.The adsorbed gas saturation exceeds 100%in most seams,and the free gas content primarily ranges from 1 m^(3)/t to 8 m^(3)/t(greater than 10 m^(3)/t in some seams).Second,the gas accumulation in deep coals is primarily controlled by coal quality,reservoir-caprock assemblage,and structural position governed storage,wettability and sealing properties,under the constraints of the underground temperature and pressure conditions.High-rank,low-ash yield coals with limestone and mudstone caprocks show superior gas accumulation potential.Positive structural highs and wide and gentle negative structural lows are favorable sites for gas enrichment,while slope belts of fold limbs exhibit relatively lower gas content.This research enhances understanding of gas accumulation mechanisms in coal reservoirs and provides effective parameter reference for precise zone evaluation and innovation of adaptive stimulation technologies for deep resources.
基金supported by the National Natural Science Foundation of China(42090025,42302148)State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development(33550000-22-ZC0613-0336)CNPC Innovation Found(2023DQ02-0103)。
文摘Lacustrine shale oil reservoirs of the Upper Triassic Chang 7 Member in the Ordos Basin have demonstrated significant potential for hydrocarbon resources.Natural fractures play a crucial role in hydrocarbon enrichment and production.Outcrops,cores,borehole image logs,thin sections,and FE-SEM images were used to investigate the types and characteristics of natural fractures in the Chang 7 Member.The factors controlling fracture development and the mechanisms of bedding-parallel fracture formation were revealed by integrating TOC analysis,XRD analysis,and rock pyrolysis.Results show that natural fractures in the study area include high-angle tectonic fractures and nearly horizontal bedding-parallel fractures.Brittle minerals and bed thickness control the occurrence and attributes of tectonic fractures.High TOC content and thermal maturity positively affect the development of bedding-parallel fractures,formed through the conversion of organic matter to hydrocarbons or the smectite-to-illite transformation.Additionally,the dominant orientations of tectonic fractures intersect the present-day maximum horizontal principal stress at a small angle,resulting in large apertures and good effectiveness.Bedding-parallel fractures contribute to enhance porosity and provide favorable pathways for lateral hydrocarbon migration.Collectively,this study could provide valuable insights for finding promising exploration areas in lacustrine shale oil reservoirs in the Ordos Basin and worldwide.
基金supported by the Natural Science Foundation of Inner Mongolia Autonomous Region(2024QN04014)the Open Research Fund of Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station,China Institute of Water Resources and Hydropower Research(Grant No.YSS202401)+2 种基金Scientific Research Support Program for Introducing Talents at the Inner Mongolia Autonomous Region of China(DC2400002177 and DC2400003177)Major Projects of Erdos Science and Technology(Project No.2022EEDSKJZDZX015)Applied technology research and development project in Jungar Banner of Inner Mongolia Autonomous Region of China(2023YY-13).
文摘Groundwater is essential for maintaining public health,promoting economic development,and ensuring ecosystem stability in arid and semi-arid regions.The northwestern Ordos Basin(China)primarily relies on groundwater from multilayered aquifer systems;however,our knowledge of the hydrochemical characteristics and water quality of groundwater in this region is limited.Here,we employed a newly collected dataset of 94 groundwater samples from different aquifers to constrain the source,controlling processes of fluoride in groundwater,and its potential health risk in the area.Groundwater is characterized by Na-Cl and Na-SO_(4) types with a minor Na-HCO_(3) type,which is primarily controlled by ion exchange,silicate weathering,and the dissolution of carbonate and evaporite minerals.Of the groundwater samples,42%exceeded the fluoride limit of 1.5 mg/L established by the World Health Organization(WHO).This is mainly attributed to geogenic sources,including fluorine-bearing mineral dissolution,cation exchange,evaporation,and competitive adsorption.The water quality index suggests that most samples are unsuitable for drinking.Health risk assessment results based on the Monte Carlo simulation indicate that children face significantly higher non-carcinogenic health risks from fluoride exposure than adults(both males and females).These findings provide new insights into the complex hydrogeochemical evolution of fluoride in groundwater and the groundwater quality status in multi-aquifer systems,contributing to the sustainable development and management of groundwater resources in the Ordos Basin.
基金financially supported by National Science and Technology Major Projects(Grant Nos.2016ZX05050,2017ZX05001002-008)CNPC Major Projects(Grant No.2021DJ2203)The Open Fund by the State Key Laboratory of Continental Dynamics,Northwest University and the Key Laboratory for Digital Land and Resources of Jiangxi Province(Grant No.DLLJ202017)。
文摘The formation of Mesozoic natural gas in the Pengyang area of southwestern Ordos Basin is discussed,from the perspective of microbial community characteristics,in order to clarify the relationship between the origin of natural gas and its associated indigenous microbial community.The types and diversity of indigenous microbial communities associated with the oil reservoir were studied by means of collecting reservoir formation water samples from exploration wells.The indigenous microbial communities in the Chang 8 member of the Yanchang Formation were primarily distributed within Proteobacteria and Firmicutes,including the specific species and genera of Methylobacter,Pseudomonas,Haibacter,Toxobacillus,Acinetobacter and Adura actinomyces.The results of diversity analysis shows that the number of common genes was 5448,while the number of unique genes and information was less.This reflects the fact that the strata in the study area are relatively closed and not invaded by external water sources,which leads to the development of biological community diversity.In conjunction with the analysis of geochemical characteristics of oil and gas reservoirs in this area,this indicates that the study area possesses the necessary geological conditions for microbial degradation.It is the first time that the species and diversity of the indigenous microbial community in the Ordos Basin have been analyzed,showing that microbial degradation is the main cause of natural gas formation here,changes the characteristics of crude oil in this area and provides first-hand information on the impact of indigenous microorganisms on the reservoir.
基金Supported by the National Natural Science Foundation of China(42302184)Innovation Group Project of Basic Research in Gansu Province,China(22JR5RA045)。
文摘The lamina(combination)types,reservoir characteristics and shale oil occurrence states of organic-rich shale in the Triassic Yanchang Formation Chang 73 sub-member in the Ordos Basin were systematically investigated to reveal the main controlling factors of shale oil occurrence under different lamina combinations.The differential enrichment mechanisms and patterns of shale oil were discussed using the shale oil micro-migration characterization and evaluation methods from the perspectives of relay hydrocarbon supply,stepwise migration,and multi-stage differentiation.The results are obtained in five aspects.First,Chang 73 shale mainly develops five types of lamina combination,i.e.non-laminated shale,sandy laminated shale,tuffaceous laminated shale,mixed laminated shale,and organic-rich laminated shale.Second,shales with different lamina combinations are obviously different in the reservoir space.Specifically,shales with sandy laminae and tuffaceous laminae have a large number of intergranular pores,dissolution pores and hydrocarbon generation-induced fractures.The multi-scale pore and fracture system constitutes the main place for liquid hydrocarbon occurrence.Third,the occurrence and distribution of shale oil in shale with different lamina combinations are jointly controlled by organic matter abundance,reservoir property,thermal evolution degree,mineral composition and laminae scale.The micro-nano-scale pore-fracture networks within shales containing rigid laminae,particularly sandy and tuffaceous laminations,primarily contain free-state light hydrocarbon components.In contrast,adsorption-phase heavy hydrocarbon components predominantly occupy surfaces of organic matter assemblages,clay mineral matrices,and framework mineral particulates.Fourth,there is obvious shale oil micro-migration between shales with different lamina combinations in Chang 73.Generally,such micro-migration is stepwise in a sequence of organic-rich laminated shale→tuffaceous laminated shale→mixed laminated shale→sandy lamiated shale→non-laminated shale.Fifth,the relay hydrocarbon supply of organic matter under the control of the spatial superposition of shales with various laminae,the stepwise migration via multi-scale pore and fracture network,and the multi-differentiation in shales with different lamina combinations under the control of organic-inorganic interactions fundamentally decide the differences of shale oil components between shales with different lamina combinations.
基金The research project is funded by the Geological Joint Fund(U2244209).
文摘The Majiagou Formation in the Fuxian area of the southeastern Ordos Basin has undergone a complex diagenetic evolution history under the influence of eustacy and the Caledonian karstification,resulting in several complex reservoir types.Through analyses of mineralogy,petrology,and reservoir geology,three major types of dolomite reservoirs with different genetic mechanisms,including anhydritic moldicdissolved pore type,dolomitic intercrystalline-pore type,and fractured type were identified,and their formation mechanisms and distribution patterns were examined.The aphanocrystalline to very finecrystalline anhydritic dolomite was resulted from Sabhak dolomitization,and is characterized by small size of crystals and high content of anhydrite.Dolomite reservoirs of anhydritic moldic-dissolved pore type were developed in multi-stage dissolution processes and mainly distributed at higher positions of the paleogeomorphology where the filling was weak.The very fine to fine-crystalline dolomite of shoal facies was formed under seepage-reflux dolomitization,and characterized by larger sizes of crystals and well-developed intercrystalline pores.Dolomite reservoirs of intercrystalline-pore type were mainly developed at the lower positions of the paleogeomorphology where bedding-parallel karst dissolution was strong.The fractured dolomite reservoirs,generated by the anhydrite swelling and karst cave collapse,occur in multiple horizons but within limited areas due to multi-stage fillings.
基金supported by the National Natural Science Foundation of China(42172010,42372071,41102037)。
文摘The Longshan orogenic belt is located in the southwestern margin of Ordos Basin at the junction zone between the Western Qinling and Northern Qilian orogenic belt.Voluminous Early Paleozoic magmatism in this area is of key significance for determining the Early Paleozoic tectonic evolution and deep crust-mantle structure.Previous studies mainly focused on the Paleozoic granites;the coeval mafic rocks in this area are still poorly understood.A set of Late Silurian intraplate tholeiitic basalts has been discovered in Longshan area,providing key evidence for the mantle source and deep geodynamic background in this area.The Late Silurian Angou basalt has similar geochemical features as intraplate tholeiitic basalt,with high Na_(2)O/K_(2)O ratios(5.22-8.25),enriched in large ion lithophile elements and LREE.In combination with their relatively evolved Sr-Nd isotopic composition[^(87)Sr/^(86)Sr(i)=0.7128-0.7140;ε_(Nd)(t)=-5.55 to-3.40],it is suggested that it originated from decompression melting of metasomatized enriched mantle in extensional setting.These results indicate that the mantle source in the junction zone of the West Qinling-North Qilian orogenic belt evolved from depleted to enriched with the continuation of Proto-Tethys subduction from the Cambrian to the Silurian.These results are of great significance to understanding the genesis of contemporaneous granite and the crust-mantle interaction in the junction zone between the Western Qinling and Northern Qilian orogenic belt.
基金Supported by the National Natural Science Foundation of China(42330810)Major Science and Technology Project of PetroChina Changqing Oilfield Company(ZDZX2021-01).
文摘Based on the analysis of surface geological survey,exploratory well,gravity-magnetic-electric and seismic data,and through mapping the sedimentary basin and its peripheral orogenic belts together,this paper explores systematically the boundary,distribution,geological structure,and tectonic attributes of the Ordos prototype basin in the geological historical periods.The results show that the Ordos block is bounded to the west by the Engorwusu Fault Zone,to the east by the Taihangshan Mountain Piedmont Fault Zone,to the north by the Solonker-Xilamuron Suture Zone,and to the south by the Shangnan-Danfeng Suture Zone.The Ordos Basin boundary was the plate tectonic boundary during the Middle Proterozoic to Paleozoic,and the intra-continental deformation boundary in the Meso-Cenozoic.The basin survived as a marine cratonic basin covering the entire Ordos block during the Middle Proterozoic to Ordovician,a marine-continental transitional depression basin enclosed by an island arc uplift belt at the plate margin during the Carboniferous to Permian,a unified intra-continental lacustrine depression basin in the Triassic,and an intra-continental cratonic basin circled by a rift system in the Cenozoic.The basin scope has been decreasing till the present.The large,widespread prototype basin controlled the exploration area far beyond the present-day sedimentary basin boundary,with multiple target plays vertically.The Ordos Basin has the characteristics of a whole petroleum(or deposition)system.The Middle Proterozoic wide-rift system as a typical basin under the overlying Phanerozoic basin and the Cambrian-Ordovician passive margin basin and intra-cratonic depression in the deep-sited basin will be the important successions for oil and gas exploration in the coming years.
基金funded by the National Natural Science Foundation of China(41872127)。
文摘The Chang 7 sandstone is characterized by complex micro-pore structures,strong heterogeneity,and differential fluid distribution.These characteristics result in low oil recovery.In this paper,various techniques,including high-pressure mercury intrusion,nuclear magnetic resonance,scanning electron microscope,thin section,and X-ray diffraction,are employed to quantitatively evaluate the occurrence characteristics and influencing factors of movable fluids in Chang 7 sandstone reservoirs from the Heshui Block with different fractal structures.Results show that the dominant sandstone type is feldspar lithic fragment sandstone.Chang 7 reservoir has been divided into three types(typesⅠ,Ⅱ,andⅢ)based on capillary pressure curves and pore structure parameters.These reservoirs are characterized by various fractal structures and different movable fluids distribution.Multiple possible factors affecting the movable fluid distribution are analyzed,including physical properties,pore structure,pore size distribution,mineral content,and heterogeneity.Movable fluid saturation is positively correlated with physical properties,weighted average pore-throat radius,median pore-throat radius,final residual mercury saturation,and maximum mercury withdrawal saturation.In contrast,it is negatively correlated with displacement pressure and has no obvious correlation with the sorting coefficient.Micron-and submicron-scale pores are beneficial to the movable fluid occurrence,while nano-scale pores are vice versa.The influence of mineral content on movable fluid occurrence varies with mineral types.Quartz is conducive to the movable fluid occurrence in submicron-scale pores,while carbonate cementation inhibits the movable fluid occurrence in submicron-scale pores.The inhibition of clay on the movable fluid occurrence is mainly reflected in submicron-and nano-scale pores and varies with clay mineral types.The influence of heterogeneity on the movable fluid occurrence is mainly reflected in submicron-scale pores.The occurrence models of movable fluid vary with reservoir types.
基金funded by the 2023 Inner Mongolia Public Institution High-Level Talent Introduction Scientific Research Support Project,and the Ordos Municipal Science and Technology Major Special Project(Grant No.2022EEDSKJZDZX021).
文摘In this paper,a standardized analysis method is established for identifying meat quality-related genes in Ordos finewool sheep using transcriptome sequencing data.A meticulously standardized approach is utilized to investigate the genetic determinants of meat quality in Ordos fine-wool sheep through transcriptome sequencing analysis.Muscle samples from the longissimus dorsi of one-year-old sheep are collected under controlled conditions,and key texture properties—hardness,elasticity,and chewiness—are measured to categorize samples into high-and low-textural-value groups.Genes significantly associated with meat quality traits are identified through standardized RNA extraction,high-throughput sequencing,and differential gene expression analysis.Functional enrichment analysis reveals their involvement in biological processes such as extracellular matrix organization and metabolic pathways.The findings underscore the pivotal role of standardization in meat quality research,laying a solid scientific foundation for future research on meat quality improvement and molecular breeding.
基金the National Natural Science Foundation of China(Grant Nos:42372253 and 42072260)the Youth Innovation Team of Shaanxi Universitiesthe Science and Technology Project of PetroChina(No.2023ZZ0201).
文摘An enhanced understanding of the history of the western Qinling-Dabie orogen is pivotal in reconstructing geological processes of the east Asian mainland.However,less attention has been paid to its early-stage uplift-erosion history after closure of surrounding oceanic basins at the mid-Paleozoic.In this study,we undertook a comprehensive study including paleocurrent reconstruction,sandstone petrology,and detrital zircon U-Pb dating on Late Carboniferous to Early Permian successions in the southern Ordos neighboring the northern Qinling-Dabie.New provenance data reveal a significant provenance shift at the Carboniferous-Permian transition.The older Benxi Formation was sourced southerly from the North Qinling Terrane that provided detritus mostly of Neoproterozoic and Early Paleozoic ages.In contrast,Early Permian samples yield age relation dominated by Neoarchean,Paleoproterozoic,Early Paleozoic,and Late Paleozoic age populations,with a significant gap of ca.1600-550 Ma,implying a sediment derivation from the Inner Mongolia Continental Arc.This shift is further verified by paleocurrent transition from south to north then.We suggest that the North Qinling Terrane experienced a significant uplift history from ca.500 Ma and remained as a highland until end-Carboniferous.From Early Permian,the North Qinling Terrane was submerged,covered by widespread deltaic sedimentation there.Northerly source from the Inner Mongolia Continental Arc began to be accumulated in the northern flank of the North Qinling Terrane,before termination approximately along the southern North Qinling Terrane,where shallow-water carbonate shelf sedimentation sustained from Devonian to Triassic.This new finding indicates that uplift of the North Qinling Terrane lasted about 150 Ma after the Proto-Tethys Ocean closure.
基金supported by the Science&Technology Fundamental Resources Investigation Program of China(2022FY101800)the National Science Foundation of China(92162212)the International Geoscience Programme(IGCP 675).
文摘1.Objective,The Cretaceous succession is characteristic of the aeolian sedimentary system in the Ordos Basin,which is the major ore-bearing layer for the sandstone-type uranium deposits.Based on the research of paleontology and magnetostratigraphy,formers believed it belonged to the Early Cretaceous(Huang YB,2010).However,the lack of intrusions or volcanic rocks for isotopic dating results in an unclear formation age for the Lower Cretaceous succession.Recently,tuffs were firstly discovered in the Luohandong Formation in the Zhenyuan area,Gansu Province,located in the southwestern Ordos Basin,China.The LA-ICP-MS zircon U-Pb dating of tuffs was carried out.The new ages can precisely constrain the depositional age of the Luohandong Formation and also provide significant indications for the study of regional volcanic activities,paleoclimate,basin evolution,and tectonic setting.
基金supported by the project of the Exploration Department of the Huabei Oilfield Company of Sinopec(No.34550008-20-ZC0609-0031).
文摘The origin of tight reservoirs in the Yanchang Formation of the Ordos Basin and their relationship with hydrocarbon charging remain unclear.Based on petrological observations,physical property analysis,fluid inclusion system analysis and in situ U-Pb dating,the sequence of tight sandstone reservoir densification and oil charging was determined.Through petrological observations,fluid inclusion analysis and physical property analysis,it is concluded that compaction and cementation are the primary causes of reservoir densification.When the content of calcite cement is less than or equal to 7%,compaction dominates densification;otherwise,cementation becomes more significant.However,determining the exact timing of compaction densification proved challenging.Microscopic observations revealed that oil charging likely occurred either before or during the densification of the reservoir.According to in situ U-Pb dating and the porosity evolution curve,cementation densification occurred between 167.0±20.0 Ma and 151.8 Ma.Temperature measurements of the aqueous inclusions indicate that oil charging occurred between 125.0 and 96.0 Ma,suggesting that densification preceded oil charging.This study provides valuable insights for the future exploration of tight oil reservoirs in the Ordos Basin.
