Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbon...Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.展开更多
Particle settling in narrow rough fractures is a common but poorly understood phenomenon during hydraulic fracturing.This study first constructs a large slot with two rough surfaces to simulate rock fractures and empl...Particle settling in narrow rough fractures is a common but poorly understood phenomenon during hydraulic fracturing.This study first constructs a large slot with two rough surfaces to simulate rock fractures and employs the particle image velocimetry to measure particle settling.Results show that particle settling in the rough slot is more complex than in the smooth slot.Rough pathways significantly change particle settling characteristics.The rough-walled slot alters the classic settling process by creating preferential pathways,localized trapping,and vortex-driven redistribution.Particles settle along preferential pathways,increasing settling velocity.The wall retardation effect becomes more prominent for large particles,reducing the settling velocity.Particle settling induces vortices throughout the rough surface,affecting particle behavior.Higher particle volume fractions increase settling nonuniformity,leading to unstable fluid flow within fractures,characterized by high vorticity and upward flow.The frequent interplay between particles and particle-walls,and fluid resistance complicates particle trajectories and settling behavior.Fluid viscosity significantly changes settling patterns and promotes particle clusters,forming chain-like and curtain-like clusters in rough fractures.An innovative model is proposed to predict settling velocity in rough fractures.展开更多
Xining,a river valley city in China’s arid region,serves as an important industrial hub with a fragile ecological environment.While groundwater heavy metal pollution in this area has drawn increasing concern,the sour...Xining,a river valley city in China’s arid region,serves as an important industrial hub with a fragile ecological environment.While groundwater heavy metal pollution in this area has drawn increasing concern,the sources and associated human health risks remain inadequately understood.This study analyzed 144 shallow groundwater samples from urban Xining for 14 heavy metals(Fe,Al,B,Mn,Ba,Zn,Pb,Cr^(6+),Ni,Cu,Co,Sb,Cd,and As)using the Nemerow comprehensive pollution index,correlation analysis,and the USEPA health risk assessment model.Results identified Fe,Al,B,Mn,Ba,Pb,Cd,and As as the primary pollutants,especially concentrated in river valley plains.These contaminants primarily originate from natural sedimentary conditions and human activities such as industrial and agricultural development.The pollution indices for Al,Pb,Mn,and Fe exceeded clean water thresholds,indicating serious contamination and the need for enhanced regulation.Health risk assessments revealed that children face greater exposure risks than adults,with arsenic and nickel being the main contributors to carcinogenic risk.Sensitivity analysis further showed that As,Fe,and Cd posed the greatest non-carcinogenic and carcinogenic risks,particularly in human-impacted areas such as the Nanchuan and Beichuan valleys and Ganhegou.These findings provide essential insights for groundwater safety management in plateau river valley cities and similar vulnerable regions.展开更多
Many mature onshore oilfields have entered a high-water-cut stage,with reservoir recovery approaching economic limits.Converting these depleted or nearly depleted reservoirs into underground gas storage(UGS)facilities...Many mature onshore oilfields have entered a high-water-cut stage,with reservoir recovery approaching economic limits.Converting these depleted or nearly depleted reservoirs into underground gas storage(UGS)facilities offers an efficient way to leverage their substantial storage potential.During cyclic gas injection and withdrawal,however,the reservoir experiences complex three-phase flow and repeated stress fluctuations,which can induce rock fatigue,inelastic deformation,and ultimately sand production.This study uses controlled physical experiments to simulate sand production in reservoir rocks subjected to alternating gas injection and production under three-phase conditions.After preparing oil-water-saturated cores through waterflooding,gas is introduced to perform repeated displacement cycles.Polynomial models relating core mass loss to water-oil ratio and cycle number are developed using the Newton interpolation method,enabling prediction of sand production under various operating conditions.Results show that,within the critical pressure-difference range for sand onset,permeability increases with water-oil ratio.When the water-oil ratio lies between 0.3 and 1,sand production decreases progressively;beyond a ratio of 1,sand production increases with further increases in water-oil ratio.The number of displacement cycles exerts a dominant influence:sand production remains relatively stable between 25 and 55 cycles but rises sharply thereafter.Average sand production during cycles 55–100 is 5.27 times higher than during cycles 5–55.These findings indicate that cumulative structural damage to the rock framework intensifies significantly with repeated cycling,making cycle number a critical factor governing sand production in UGS operations.展开更多
The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately...The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately,forming rhythmic units.At present,detailed analyses of these rhythms of rock salt are still limited,which directly affects the achievement of comprehensive and in-depth understanding of the developmental laws pertaining to this kind of saline lake.Therefore,we selected the typical rhythmic'bamboo-like'rock salts of the Shizhai Depression in Jiangsu Province as the research subject.Through careful observation of rock salts in hand samples and detailed petrographic and mineralogical analyses,we analyzed the hydrogen and oxygen isotopic compositions,homogenization temperatures and chemical compositions of individual fluid inclusions in halite crystals.Early-stage rhythmic deposition was a product of continental saline lake evolution in winter or spring,late-stage rhythmic deposition being the product of evolution in the summer.The seasonal evolution of the halite sequences was determined and two brine enrichment events were identified.In addition,the quiet saline lake environment with concentrated brine represented by rock salt was more likely to precipitate potassium.This study provides a new reference for the evolution of both Paleogene climate and saline lakes in eastern China.展开更多
Geogas survey is an unconventional geochemical prospecting method that has proven particularly effective in exploring concealed ore deposits.However,its application in covered areas has been questioned due to the lack...Geogas survey is an unconventional geochemical prospecting method that has proven particularly effective in exploring concealed ore deposits.However,its application in covered areas has been questioned due to the lack of a confirmed geogas formation mechanism.Investigating the sources of geogas anomalies can help clarify this mechanism.This study focuses on the Bairendaba silver-polymetallic deposit,located in a grassland-covered area.Tracer research was conducted on lead isotope compositions in the mining area by analyzing various solid media(soil,rocks,ores)and geogas samples.The results revealed considerable differences in lead isotope compositions between background geogas samples and solid media.Furthermore,the lead isotope compositions of anomalous geogas samples differed markedly from those of background samples.These anomalous samples are located closer to the ore body,suggesting that ore-derived lead is incorporated into the geogas.The anomalous lead in geogas is inferred to originate from deep,concealed ore bodies.This study provides a theoretical basis for applying geogas surveys in mineral exploration within covered terrains.展开更多
The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicat...The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.展开更多
In this paper,a model named fictitious soil pile was introduced to solve the boundary coupled problem at the pile tip.In the model,the soil column between pile tip and bedrock was treated as a fictitious pile,which ha...In this paper,a model named fictitious soil pile was introduced to solve the boundary coupled problem at the pile tip.In the model,the soil column between pile tip and bedrock was treated as a fictitious pile,which has the same properties as the local soil.The tip of the fictitious soil pile was assumed to rest on a rigid rock and no tip movement was allowed.In combination with the plane strain theory,the analytical solutions of vertical vibration response of piles in a frequency domain and the corresponding semi-analytical solutions in a time domain were obtained using the Laplace transforms and inverse Fourier transforms.A parametric study of pile response at the pile tip and head showed that the thickness and layering of the stratum between pile tip and bedrock have a significant influence on the complex impedances.Finally,two applications of the analytical model were presented.One is to identify the defects of the pile shaft,in which the proposed model was proved to be accurate to identify the location as well as the length of pile defects.Another application of the model is to identify the sediment thickness under the pile tip.The results showed that the sediment can lead to the decrease of the pile stiffness and increase of the damping,especially when the pile is under a low frequency load.展开更多
Shale fractures are an important factor controlling shale gas enrichment and high-productivity zones in the Longmaxi Formation,Jiaoshiba area in eastern Sichuan.Drilling results have,however,shown that the shale fract...Shale fractures are an important factor controlling shale gas enrichment and high-productivity zones in the Longmaxi Formation,Jiaoshiba area in eastern Sichuan.Drilling results have,however,shown that the shale fracture density does not have a straightforward correlation with shale gas productivity.Based on logging data,drilling and seismic data,the relationship between shale fracture and shale gas accumulation is investigated by integrating the results of experiments and geophysical methods.The following conclusions have been drawn:(1)Tracer diffusion tests indicate that zones of fracture act as favorable channels for shale gas migration and high-angle fractures promote gas accumulation.(2)Based on the result of azimuthal anisotropy prediction,a fracture system with anisotropy strength values between 1 and 1.15 represents a moderate development of high-angle fractures,which is considered to be favorable for shale gas accumulation and high productivity,while fracture systems with anisotropy strength values larger than 1.15 indicate over-development of shale fracture,which may result in the destruction of the shale reservoir preservation conditions.展开更多
The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region,western Tianshan,China.We present the geology,geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabat...The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region,western Tianshan,China.We present the geology,geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabate district with the intent to constrain their tectonic setting and petrogenesis.Porphyries in the Dabate district include granite porphyry I(gray white color with large phenocrysts),granite porphyry II(pink color with small phenocrysts)and quartz porphyry.Granite porphyry II is the Cu and Mo ore-bearing granitoid in the Dabate deposit.LA-ICPMS zircon U-Pb analyses indicate that granite porphyry II was emplaced at 284.2±1.8 Ma.Granite porphyry I and II have similar geochemical features and are both highly fractionated granites:(1)They have high SiO2 content(70.93–80.18 wt%and 72.14–72.64 wt%,respectively),total alkali(7.58–8.95 wt%and 9.35–9.68 wt%,respectively),mafic index(0.95–0.98 and 0.93–0.94,respectively)and felsic index(0.79–0.94 and 0.89–0.91,respectively);(2)They are characterized by pronounced negative Eu anomaly,"seagullstyle"chondrite-normalized REE patterns and"tetrad effect"of REE;(3)They are rich in Rb,K,Th,Ta,Zr,Hf,Y and REE,but depleted in Sr,P,Ti and Nb.The magma of granite porphyries in Dabate can be interpreted to have been generated by partial melting of the upper crust due to mantle-derived magma underplating in a post-collisional extensional setting.展开更多
Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to ...Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 μm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.展开更多
Detecting the timing and amount of deformation is critical for understanding the physical causes and eventually warning of possible landslide hazards. Monitoring of deformation of structures and ground surface displac...Detecting the timing and amount of deformation is critical for understanding the physical causes and eventually warning of possible landslide hazards. Monitoring of deformation of structures and ground surface displacements during landslides can be accomplished by using different types of systems and techniques. Besides geotechnical or physical techniques, remote sensing techniques can be classified as satellite techniques, photo-grammetric techniques, geodetic techniques, ground based techniques, and so on. To study and govern growing geological disasters in China, especially in the Three Gorges area, Three Gorges Research Center for Geo-hazard （TGRG） is establishing an infra structure to ef-fectively and comprehensively analyze the mechanism of landslide deformation, focused on the Huangtupo landslide, using of various ad-vanced monitoring systems and techniques. In this article, the framework and latest advances of integration of multi remote sensing techniques in the infrastructure are presented. Different remote sensing techniques, data processing and integrating methods, and the latest results are discussed in detail. At last, reviews on current work and suggestions for further work are put forward.展开更多
Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibe...Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibet,the Gudui geothermal field belongs to the Sangri-Cuona rift belt,also known as the Sangri-Cuona geothermal belt,and is representative of the non-volcanic geothermal systems in the Himalayas.In this study,oxygen-18 and deuterium isotope compositions as well as 87Sr/86Sr ratios of water samples collected from the Gudui geothermal field were characterized to understand the origin and mixing processes of the geothermal fluids at Gudui.Hydrogen and oxygen isotope plots show both,deep and shallow reservoirs in the Gudui geothermal field.Deep geothermal fluids are the mixing product of magmatic and infiltrating snow-melt water.Calculations show that the magma fluid component of the deep geothermal fluids account for about 21.10%-24.04%;magma fluids lay also be a contributing source of lithium.The linear relationship of the 87Sr/86Sr isotopic ratio versus the 1/Sr plot indicates that shallow geothermal fluids form from the mixing of deep geothermal fluids with cold groundwater.Using a binary mixing model with deep geothermal fluid and cold groundwater as two end-members,the nixing ratios of the latter in most surface hot springs samples were calculated to be between 5% and 10%.Combined with basic geological characteristics,hydrogen and oxygen isotope characteristics,strontium concentration,87Sr/(86)Sr ratios,and the binary mixing model,we infer the 6 th-Class Reservoirs Evolution Conceptual Model(6-CRECM) for the Gudui geothermal system.This model represents an idealized summary of the characteristics of the Gudui geothermal field based on our comprehensive understanding of the origin and mixing processes of the geothermal fluid in Gudui.This study may aid in identifying the geothermal and geochemical origin of the Gudui high-temperature hydrothermal systems in remote Tibet of China,whose potential for geothermal development and utilization is enormous and untapped.展开更多
The northeastern Tibetan Plateau is located at the convergence of the Asian winter and summer monsoons and westerlies; thus, this area has witnessed historic climate changes.The Xunhua basin is an intermontane basin o...The northeastern Tibetan Plateau is located at the convergence of the Asian winter and summer monsoons and westerlies; thus, this area has witnessed historic climate changes.The Xunhua basin is an intermontane basin on the northeastern margin of the Tibetan Plateau.The basin contains more than 2000 m of Cenozoic fluvial–lacustrine sediments, recording a long history of climate and environmental changes.We collected the mid-Miocene sediments from the Xunhua basin and used palynological methods to discuss the relationship between aridification in the interior of Asia, global cooling, and uplift of the Tibetan Plateau.Based on the palynological analysis of the Xigou section, Xunhua basin, the palynological diagram is subdivided into three pollen zones and past vegetation and climate are reconstructed.Zone I, Ephedripites–Nitraridites–Chenopodipollis–Quercoidites（14.0–12.5 Ma）, represents mixed shrub–steppe vegetation with a dry and cold climate.In zone II, Pinaceae–Betulaepollenites–Ephedripites–Chenopodipollis–Graminidites（12.5–8.0 Ma）, the vegetation and climate conditions improved, even though the vegetation was still dominated by shrub–steppe taxa.Zone III, Ephedripites–Nitrariadites–Chenopodipollis（8.0–5.0 Ma）, represents desert steppe vegetation with drier and colder climate.The palynological records suggest that shrub–steppe dominated the whole Xigou section and the content gradually increased, implying a protracted aridification process, although there was an obvious climate improvement during 12.5–8.0 Ma.The aridification in the Xunhua basin and surrounding mountains during 14.0–12.5 Ma was probably related to global cooling induced by the rapid expansion of the East Antarctic ice-sheets and the relatively higher evaporation rate.During the 12.5–8.0 Ma period, although topographic changes（uplift of Jishi Shan） decreased precipitation and strengthened aridification in the Xunhua basin on leeward slopes, the improved vegetation and climate conditions were probably controlled by the decrease in evaporation rates as a result of continuous cooling.From 8.0 to 5.0 Ma, the rapid development of the desert steppe can be attributed to global cooling and uplift of the Tibetan Plateau.展开更多
Geothermal resources are increasingly gaining attention as a competitive,clean energy source to address the energy crisis and mitigate climate change.The Wugongshan area,situated in the southeast coast geothermal belt...Geothermal resources are increasingly gaining attention as a competitive,clean energy source to address the energy crisis and mitigate climate change.The Wugongshan area,situated in the southeast coast geothermal belt of China,is a typical geothermal anomaly and contains abundant medium-and low-temperature geothermal resources.This study employed hydrogeochemical and isotopic techniques to explore the cyclic evolution of geothermal water in the western Wugongshan region,encompassing the recharge origin,water-rock interaction mechanisms,and residence time.The results show that the geothermal water in the western region of Wugongshan is weakly alkaline,with low enthalpy and mineralization levels.The hydrochemistry of geothermal waters is dominated by Na-HCO_(3)and Na-SO_(4),while the hydrochemistry types of cold springs are all Na-HCO_(3).The hydrochemistry types of surface waters and rain waters are NaHCO_(3)or Ca-HCO_(3).The δD and δ^(18)O values reveal that the geothermal waters are recharged by atmospheric precipitation at an altitude between 550.0 and 1218.6 m.Molar ratios of maj or solutes and isotopic compositions of^(87)Sr/^(86)Sr underscore the significant role of silicate weathering,dissolution,and cation exchange in controlling geothermal water chemistry.Additionally,geothermal waters experienced varying degrees of mixing with cold water during their ascent.Theδ^(13)C values suggest that the primary sources of carbon in the geothermal waters were biogenic and organic.Theδ^(34)S value suggests that the sulfates in geothermal water originate from sulfide minerals in the surrounding rock.Age dating using 3H and^(14)C isotopes suggests that geothermal waters have a residence time exceeding 1 kaBP and undergo a long-distance cycling process.展开更多
We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results...We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.展开更多
Reconstruction of the desert paleoclimate is important to understand the mechanisms that triggered and/or enhanced climate change.Through optically stimulated luminescence(OSL)dating,grain size,magnetic susceptibility...Reconstruction of the desert paleoclimate is important to understand the mechanisms that triggered and/or enhanced climate change.Through optically stimulated luminescence(OSL)dating,grain size,magnetic susceptibility,X-ray powder diffraction(XRD)and geochemical indicators,we provide a welldated record of a sedimentary outcrop on the southeast margin of the Bardain Jaran Desert,Northwest China,during the last glacial period.Four Qz-OSL ages are obtained,41.0±3.4 ka,54.7±4.4 ka,59.5±5.0 ka and 66.8±5.8 ka,corresponding to the depths of 35 cm,70 cm,150 cm and 200 cm respectively.Indicators like grain size,clay content,magnetic susceptibility,XRD and geochemical index(e.g.Sr,Ba,Sr/Ca)jointly indicate abrupt climate changes at the depth of 35 cm(age,ca.41.0 ka)and200 cm(age,ca.67 ka).Namely,the 280 cm sedimentary outcrop perfectly records a warm wet climate stage,corresponding to the late Marine Isotope Stages(MIS)4 to the early MIS 3.Besides,there is a trend of grain size increase after around 40ka BP,which is most likely a signal of wind strength change.Our research supports that enhancing Siberian High pressure system during the late MIS 3played a key role in NW East Asia climate evolution.展开更多
This thesis focuses Arsenic(As) distribution and occurrence in groundwater of Yangtze River Delta economic region, East China. 2019 groundwater samples were collected to analyze 26 chemical compositions, including As....This thesis focuses Arsenic(As) distribution and occurrence in groundwater of Yangtze River Delta economic region, East China. 2019 groundwater samples were collected to analyze 26 chemical compositions, including As. The Principal Component Analysis(PCA) was used to find out As source in groundwater. The results show that average As concentration in groundwater of this study is 9.33 μg/l, and maximum As concentration is up to 510 μg/l. The variation coefficient is 314.34%. High arsenic phreatic water(>10 μg/l) distributes along the Yangtze River and its estuary. Weak hydrodynamic conditions, wide p H value variation range and deteriorating environment are dominating factors, especially in Yangtze River Delta. The PCA suggests that arsenic in phreatic water is mainly of natural origin. Part of arsenic may directly originate from sediment organics and be related to organics decomposition.展开更多
The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crysta...The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone(SSZ). However,economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone(MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr~# values(100 Cr/(Cr+Al))(47.7-55.1 and 46.5-51.7, respectively) than those in the high-Cr chromitites(78.2-80.4), harzburgites(72.6-77.9) and mantle dunites(79.4-84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements(PGE).The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10-0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.展开更多
The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation ...The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation of reasonable development plans.This work established a new reservoir pressure prediction model based on the material balance equation(MBE)of coal reservoir,which considers the self-regulating effects of coal reservoirs and the dynamic change of equivalent drainage area(EDA).According to the proposed model,the reservoir pressure can be predicted based on reservoir condition data and the actual production data of a single well.Compared with traditional reservoir pressure prediction models which regard EDA as a fixed value,the proposed model can better predict the average pressure of reservoirs.Moreover,orthogonal experiments were designed to evaluate the sensitivity of reservoir parameters on the reservoir pressure prediction results of this proposed model.The results show that the saturation of irreducible water is the most sensitive parameter,followed by Langmuir volume and reservoir porosity,and Langmuir pressure is the least sensitive parameter.In addition,the pressure drop of reservoirs is negatively correlated with the saturation of irreducible water and the Langmuir volume,while it is positively correlated with porosity.This work analyzed the reservoir pressure drop characteristics of the CBM wells in the Shizhuangnan Block of the Qinshui Basin,and the results show that the CBM reservoir depressurization can be divided into three types,i.e.,rapidly drop type,medium-term stability type,and slowly drop type.The drainage features of wells were reasonably interpreted based on the comprehensive analysis of the reservoir depressurization type;the latter was coupled to the corresponding permeability dynamic change characteristics,eventually proving the applicability of the proposed model.展开更多
基金This study was supported by the project ofthe Science and Technology Innovation Fund of Command Center of Natural Resources Intergrated Survey entitled“Temporal and spatial distribution of paleochannel and origin of organic carbon burial in the Western Bohai Sea since 2.28Ma”(KC20220011)the project entitled“Characterization of Carboniferous-Early Permian heterogeneous porous carbonate reservoirs and hydrocarbon potential analysis in the central uplift of the South Yellow Sea Basin”(KLSG2304)+3 种基金by the Key laboratory of Submarine Science,Ministry of Natural Resources,the project entitled“1∶50000 Marine regional Geological survey in Caofeidian Sea Area,Bohai Sea”(ZD20220602)“1∶250000 Marine regional Geological survey in Weihai Sea Area,North Yellow Sea”(DD20230412)“Geological survey on tectonic and sedimentary conditions of Laoshan uplift”(DD2016015)by the China Geological Survey,and the project entitled“Study on Hydrocarbon Accumulation Failure and Fluid Evolution Reduction of the Permian Reservoir in the Laoshan Uplift,South Yellow Sea”(42076220)organized by the National Natural Science Foundation of China.
文摘Mesozoic-Palaeozoic marine carbonate rocks are crucial hydrocarbon reservoirs in the Central Uplift area of the South Yellow Sea Basin(SYSB).Due to the scarcity of boreholes and the significant heterogeneity of carbonate reservoirs,the distribution of porous carbonate reservoirs and their related key controlling factors remain unclear.In this study,factors affecting the distribution of porous Carboniferous-Early Permian carbonate reservoirs in the SYSB were investigated through seismic inversion and isotope analysis.The log-seismic characteristics of porous carbonate reservoirs,sensitive lithology parameters,and physical property parameters were extracted and analyzed.The pre-stack simultaneous inversion technique was applied to predict the lithology and physical properties of porous carbonate reservoirs.Moreover,the sedimentary of carbonate was analyzed using isotopes of carbon,oxygen,and strontium.The results show that porous carbonate reservoirs are mainly developed in the open platform sediments with porosities of 3%-5%and are mainly distributed in the paleo-highland(Huanglong Formation and Chuanshan Formation)and the slope of paleo-highland(Hezhou Formation).The porous carbonate reservoirs of the Qixia Formation are only locally developed.In addition,the negativeδ13C excursions indicate a warm and humid tropical climate with three sea-level fluctuations in the study area from the Carboniferous to Early Permian.The favorable conditions for developing porous carbonate rocks include the sedimentary environment and diagenetic process.The primary pore tends to form in high-energy environments of the paleo-highland,and the secondary pore is increased by dissolution during the syngenetic or quasi-syngenetic period.According to the hydrocarbon potential analysis,the Late Ordovician Wufeng Formation and Lower Silurian Gaojiabian Formation are the source rocks in the high-maturity-over-maturity stage,the Carboniferous-Lower Permian carbonate is the good reservoirs,and the Late Permian Longtan-Dalong Formation is the stable seal,ensuring a huge hydrocarbon accumulation potential in SYSB.The methods proposed in this study can be applied to other carbonate-dominated strata worldwide.
基金supported by the National Natural Science Foundation of China(Grant No.52274035)。
文摘Particle settling in narrow rough fractures is a common but poorly understood phenomenon during hydraulic fracturing.This study first constructs a large slot with two rough surfaces to simulate rock fractures and employs the particle image velocimetry to measure particle settling.Results show that particle settling in the rough slot is more complex than in the smooth slot.Rough pathways significantly change particle settling characteristics.The rough-walled slot alters the classic settling process by creating preferential pathways,localized trapping,and vortex-driven redistribution.Particles settle along preferential pathways,increasing settling velocity.The wall retardation effect becomes more prominent for large particles,reducing the settling velocity.Particle settling induces vortices throughout the rough surface,affecting particle behavior.Higher particle volume fractions increase settling nonuniformity,leading to unstable fluid flow within fractures,characterized by high vorticity and upward flow.The frequent interplay between particles and particle-walls,and fluid resistance complicates particle trajectories and settling behavior.Fluid viscosity significantly changes settling patterns and promotes particle clusters,forming chain-like and curtain-like clusters in rough fractures.An innovative model is proposed to predict settling velocity in rough fractures.
基金supported by the projects of the Geological Survey(DD20240501104,DD20230422).
文摘Xining,a river valley city in China’s arid region,serves as an important industrial hub with a fragile ecological environment.While groundwater heavy metal pollution in this area has drawn increasing concern,the sources and associated human health risks remain inadequately understood.This study analyzed 144 shallow groundwater samples from urban Xining for 14 heavy metals(Fe,Al,B,Mn,Ba,Zn,Pb,Cr^(6+),Ni,Cu,Co,Sb,Cd,and As)using the Nemerow comprehensive pollution index,correlation analysis,and the USEPA health risk assessment model.Results identified Fe,Al,B,Mn,Ba,Pb,Cd,and As as the primary pollutants,especially concentrated in river valley plains.These contaminants primarily originate from natural sedimentary conditions and human activities such as industrial and agricultural development.The pollution indices for Al,Pb,Mn,and Fe exceeded clean water thresholds,indicating serious contamination and the need for enhanced regulation.Health risk assessments revealed that children face greater exposure risks than adults,with arsenic and nickel being the main contributors to carcinogenic risk.Sensitivity analysis further showed that As,Fe,and Cd posed the greatest non-carcinogenic and carcinogenic risks,particularly in human-impacted areas such as the Nanchuan and Beichuan valleys and Ganhegou.These findings provide essential insights for groundwater safety management in plateau river valley cities and similar vulnerable regions.
基金National Science and Technology Major Project(2025ZD1406805)“Key Technology for Efficient Construction of New Underground Gas Storage”Research Project of CNPC(2023DJ8308)“Research on Wellbore Treatment and Rapid Construction Method of Oil and Gas Reservoir and Thin Salt Layer Storage”National Key Research and Development Program of China(Grant No.2025ZD1406805 and Grant No.2025ZD1011105).
文摘Many mature onshore oilfields have entered a high-water-cut stage,with reservoir recovery approaching economic limits.Converting these depleted or nearly depleted reservoirs into underground gas storage(UGS)facilities offers an efficient way to leverage their substantial storage potential.During cyclic gas injection and withdrawal,however,the reservoir experiences complex three-phase flow and repeated stress fluctuations,which can induce rock fatigue,inelastic deformation,and ultimately sand production.This study uses controlled physical experiments to simulate sand production in reservoir rocks subjected to alternating gas injection and production under three-phase conditions.After preparing oil-water-saturated cores through waterflooding,gas is introduced to perform repeated displacement cycles.Polynomial models relating core mass loss to water-oil ratio and cycle number are developed using the Newton interpolation method,enabling prediction of sand production under various operating conditions.Results show that,within the critical pressure-difference range for sand onset,permeability increases with water-oil ratio.When the water-oil ratio lies between 0.3 and 1,sand production decreases progressively;beyond a ratio of 1,sand production increases with further increases in water-oil ratio.The number of displacement cycles exerts a dominant influence:sand production remains relatively stable between 25 and 55 cycles but rises sharply thereafter.Average sand production during cycles 55–100 is 5.27 times higher than during cycles 5–55.These findings indicate that cumulative structural damage to the rock framework intensifies significantly with repeated cycling,making cycle number a critical factor governing sand production in UGS operations.
基金supported by the Natural Science Foundation of Jiangxi Province,China(Grant No.20242BAB20130)the Basic Research Funds Program of the Chinese Academy of Geological Sciences(Grant No.YYWF201607)the National Natural Science Foundation of China(Grant No.41902064)。
文摘The phenomenon of'bamboo-like'thin interlayers developed in rock salt is one of the most prominent features of Paleogene salt-bearing strata in eastern China,where centimeter-thick rock salts appear separately,forming rhythmic units.At present,detailed analyses of these rhythms of rock salt are still limited,which directly affects the achievement of comprehensive and in-depth understanding of the developmental laws pertaining to this kind of saline lake.Therefore,we selected the typical rhythmic'bamboo-like'rock salts of the Shizhai Depression in Jiangsu Province as the research subject.Through careful observation of rock salts in hand samples and detailed petrographic and mineralogical analyses,we analyzed the hydrogen and oxygen isotopic compositions,homogenization temperatures and chemical compositions of individual fluid inclusions in halite crystals.Early-stage rhythmic deposition was a product of continental saline lake evolution in winter or spring,late-stage rhythmic deposition being the product of evolution in the summer.The seasonal evolution of the halite sequences was determined and two brine enrichment events were identified.In addition,the quiet saline lake environment with concentrated brine represented by rock salt was more likely to precipitate potassium.This study provides a new reference for the evolution of both Paleogene climate and saline lakes in eastern China.
基金supported by Key Laboratory of Ionic Rare Earth Resources and Environment,Ministry of Natural Resources(No.2023IRERE102)National Nonprofit Institute Research Grant of Institute of Geophysical and Geochemical Exploration(AS2022P03)。
文摘Geogas survey is an unconventional geochemical prospecting method that has proven particularly effective in exploring concealed ore deposits.However,its application in covered areas has been questioned due to the lack of a confirmed geogas formation mechanism.Investigating the sources of geogas anomalies can help clarify this mechanism.This study focuses on the Bairendaba silver-polymetallic deposit,located in a grassland-covered area.Tracer research was conducted on lead isotope compositions in the mining area by analyzing various solid media(soil,rocks,ores)and geogas samples.The results revealed considerable differences in lead isotope compositions between background geogas samples and solid media.Furthermore,the lead isotope compositions of anomalous geogas samples differed markedly from those of background samples.These anomalous samples are located closer to the ore body,suggesting that ore-derived lead is incorporated into the geogas.The anomalous lead in geogas is inferred to originate from deep,concealed ore bodies.This study provides a theoretical basis for applying geogas surveys in mineral exploration within covered terrains.
基金jointly sponsored by the Public Science and Technology Research Funds Projects,Ministry of Land Resources of the People’s Republic of China(project No.201511017 and 201511022-02)the Basic Research Fund of the Chinese Academy of Geological Sciences(Grant No.YYWF201608)+3 种基金the National Natural Science Foundation of China(Grant No.41402178)Geological Survey Project of the China Geological Survey(project 1212011405040)Golden Dragon Mining Co.Ltd.(project XZJL-2013-JS03)China Scholarship Council
文摘The Tiegelongnan deposit is a newly discovered super-large porphyry-epithermal Cu-（Au） deposit in the western part of the Bangong Co-Nujiang metallogenic belt, Tibet（China）. Field geology and geochronology indicate that the porphyry mineralization was closely related to the Early Cretaceous intermediate-felsic intrusions（ca. 123–120 Ma）. Various epithermal ore and gangue mineral types were discovered in the middle-shallow part of the orebody, indicating the presence of epithermal mineralization at Tiegelongnan. Potassic, propylitic, phyllic and advanced argillic alteration zones were identified. 40Ar/39Ar dating of hydrothermal biotite（potassic zone）, sericite（phyllic zone）, and alunite（advanced argillic zone） in/around the ore-bearing granodiorite porphyry yielded 121.1±0.6 Ma（1σ）, 120.8±0.7 Ma（1σ） and 117.9±1.6 Ma（1σ）, respectively. Five hydrothermal mineralization stages were identified, of which the Stage IV pyrite was Rb-Sr dated to be 117.5±1.8 Ma（2σ）, representing the end of epithermal mineralization. Field geology and geochronology suggest that both the epithermal and porphyry mineralization belong to the same magmatic-hydrothermal system. The Tiegelongnan super-large Cu-（Au） deposit may have undergone a prolonged magmatichydrothermal evolution, with the major mineralization event occurring at ca.120–117Ma.
基金Project (No. 50879077) supported by the National Natural Science Foundation of China
文摘In this paper,a model named fictitious soil pile was introduced to solve the boundary coupled problem at the pile tip.In the model,the soil column between pile tip and bedrock was treated as a fictitious pile,which has the same properties as the local soil.The tip of the fictitious soil pile was assumed to rest on a rigid rock and no tip movement was allowed.In combination with the plane strain theory,the analytical solutions of vertical vibration response of piles in a frequency domain and the corresponding semi-analytical solutions in a time domain were obtained using the Laplace transforms and inverse Fourier transforms.A parametric study of pile response at the pile tip and head showed that the thickness and layering of the stratum between pile tip and bedrock have a significant influence on the complex impedances.Finally,two applications of the analytical model were presented.One is to identify the defects of the pile shaft,in which the proposed model was proved to be accurate to identify the location as well as the length of pile defects.Another application of the model is to identify the sediment thickness under the pile tip.The results showed that the sediment can lead to the decrease of the pile stiffness and increase of the damping,especially when the pile is under a low frequency load.
基金supported by the National Key Basic Research Program of China(973 Program,No.2014CB239104)National Science and Technology Major Project(No.2017ZX05049002-005)+1 种基金Sinopec Basic Prospect Project(No.G5800-16-ZS-KJB043)NSFC-Sinopec Joint Key Project(No.U1663207)
文摘Shale fractures are an important factor controlling shale gas enrichment and high-productivity zones in the Longmaxi Formation,Jiaoshiba area in eastern Sichuan.Drilling results have,however,shown that the shale fracture density does not have a straightforward correlation with shale gas productivity.Based on logging data,drilling and seismic data,the relationship between shale fracture and shale gas accumulation is investigated by integrating the results of experiments and geophysical methods.The following conclusions have been drawn:(1)Tracer diffusion tests indicate that zones of fracture act as favorable channels for shale gas migration and high-angle fractures promote gas accumulation.(2)Based on the result of azimuthal anisotropy prediction,a fracture system with anisotropy strength values between 1 and 1.15 represents a moderate development of high-angle fractures,which is considered to be favorable for shale gas accumulation and high productivity,while fracture systems with anisotropy strength values larger than 1.15 indicate over-development of shale fracture,which may result in the destruction of the shale reservoir preservation conditions.
基金financially supported by NSFC project 41203035the National Basic Research Program(2012CB416803)the Chinese Geological Survey Program(DD20160124)
文摘The Dabate Mo-Cu deposit is a medium-sized porphyry-type deposit in the Sailimu Lake region,western Tianshan,China.We present the geology,geochemistry and zircon U-Pb geochronology of granite porphyries from the Dabate district with the intent to constrain their tectonic setting and petrogenesis.Porphyries in the Dabate district include granite porphyry I(gray white color with large phenocrysts),granite porphyry II(pink color with small phenocrysts)and quartz porphyry.Granite porphyry II is the Cu and Mo ore-bearing granitoid in the Dabate deposit.LA-ICPMS zircon U-Pb analyses indicate that granite porphyry II was emplaced at 284.2±1.8 Ma.Granite porphyry I and II have similar geochemical features and are both highly fractionated granites:(1)They have high SiO2 content(70.93–80.18 wt%and 72.14–72.64 wt%,respectively),total alkali(7.58–8.95 wt%and 9.35–9.68 wt%,respectively),mafic index(0.95–0.98 and 0.93–0.94,respectively)and felsic index(0.79–0.94 and 0.89–0.91,respectively);(2)They are characterized by pronounced negative Eu anomaly,"seagullstyle"chondrite-normalized REE patterns and"tetrad effect"of REE;(3)They are rich in Rb,K,Th,Ta,Zr,Hf,Y and REE,but depleted in Sr,P,Ti and Nb.The magma of granite porphyries in Dabate can be interpreted to have been generated by partial melting of the upper crust due to mantle-derived magma underplating in a post-collisional extensional setting.
基金funded by grants from the NSF China(Nos.41502062,41672046,41541017,41641015)the China Geological Survey(Nos.DD20160023-01,201511022)+2 种基金National Key Research and Development Project of China(2016YFC0600310)from the Institute of Geology,Chinese Academy of Geological Sciences(J1526)IGCP–649
文摘Various combinations of diamond, moissanite, zircon, corundum, rutile and titanitehave been recovered from the Bulqiza chromitites. More than 10 grains of diamond have been recovered, most of which are pale yellow to reddish–orange to colorless. The grains are all 100–300 μm in size and mostly anhedral, but with a range of morphologies including elongated, octahedral and subhedral varieties. Their identification was confirmed by a characteristic shift in the Raman spectra between 1325 cm-1 and 1333 cm-1, mostly at 1331.51 cm-1 or 1326.96 cm-1. This investigation extends the occurrence of diamond and moissanite to the Bulqiza chromitites in the Eastern Mirdita Ophiolite. Integration of the mineralogical, petrological and geochemical data of the Bulqiza chromitites suggests their multi–stage formation. Magnesiochromite grains and perhaps small bodies of chromitite formed at various depths in the upper mantle, and encapsulated the ultra–high pressure, highly reduced and crustal minerals. Some oceanic crustal slabs containing the magnesiochromite and their inclusion were later trapped in suprasubduction zones, where they were modified by tholeiitic and boninitic arc magmas, thus changing the magnesiochromite compositions and depositing chromitite ores in melt channels.
基金supported by the National Basic Research Program of China (No. 2011CB707001)the National Natural Science Foundation of China (Nos. 41102209, 41102210, 41071291, 40802045 and 40821061)+5 种基金the Postdoctoral Science Foundation of China (No. 20110491232)the Natural Science Foundation of Hubei Province (No. 2010CDB04105)the Key Technology R & D Program of Wuhan (No. 201110821237)the Young Scientist Program of Wuhan (No. 201150431074)the Fundamental Research Funds for the Central Universities (Nos. CUG100705 and CUG100313)Additional support was provided by Ministry of Education of China (No. B07039)
文摘Detecting the timing and amount of deformation is critical for understanding the physical causes and eventually warning of possible landslide hazards. Monitoring of deformation of structures and ground surface displacements during landslides can be accomplished by using different types of systems and techniques. Besides geotechnical or physical techniques, remote sensing techniques can be classified as satellite techniques, photo-grammetric techniques, geodetic techniques, ground based techniques, and so on. To study and govern growing geological disasters in China, especially in the Three Gorges area, Three Gorges Research Center for Geo-hazard （TGRG） is establishing an infra structure to ef-fectively and comprehensively analyze the mechanism of landslide deformation, focused on the Huangtupo landslide, using of various ad-vanced monitoring systems and techniques. In this article, the framework and latest advances of integration of multi remote sensing techniques in the infrastructure are presented. Different remote sensing techniques, data processing and integrating methods, and the latest results are discussed in detail. At last, reviews on current work and suggestions for further work are put forward.
基金This work was financially supported by the China Geological Survey(Grant No.DD20160054)the National Natural Science Foundation of China(Grant No.U1407207)the National Key Research and Development Program of China(Grant No.2017YFC0602802).
文摘Tho Gudui geothermal field records the highest temperature at equivalent borehole depths among the lainland hydrothermal systems in China's Mainland.Located about 150 km southeast of Lhasa City,the capital of Tibet,the Gudui geothermal field belongs to the Sangri-Cuona rift belt,also known as the Sangri-Cuona geothermal belt,and is representative of the non-volcanic geothermal systems in the Himalayas.In this study,oxygen-18 and deuterium isotope compositions as well as 87Sr/86Sr ratios of water samples collected from the Gudui geothermal field were characterized to understand the origin and mixing processes of the geothermal fluids at Gudui.Hydrogen and oxygen isotope plots show both,deep and shallow reservoirs in the Gudui geothermal field.Deep geothermal fluids are the mixing product of magmatic and infiltrating snow-melt water.Calculations show that the magma fluid component of the deep geothermal fluids account for about 21.10%-24.04%;magma fluids lay also be a contributing source of lithium.The linear relationship of the 87Sr/86Sr isotopic ratio versus the 1/Sr plot indicates that shallow geothermal fluids form from the mixing of deep geothermal fluids with cold groundwater.Using a binary mixing model with deep geothermal fluid and cold groundwater as two end-members,the nixing ratios of the latter in most surface hot springs samples were calculated to be between 5% and 10%.Combined with basic geological characteristics,hydrogen and oxygen isotope characteristics,strontium concentration,87Sr/(86)Sr ratios,and the binary mixing model,we infer the 6 th-Class Reservoirs Evolution Conceptual Model(6-CRECM) for the Gudui geothermal system.This model represents an idealized summary of the characteristics of the Gudui geothermal field based on our comprehensive understanding of the origin and mixing processes of the geothermal fluid in Gudui.This study may aid in identifying the geothermal and geochemical origin of the Gudui high-temperature hydrothermal systems in remote Tibet of China,whose potential for geothermal development and utilization is enormous and untapped.
基金supported by Foundation of Geological Survey of China (no.1212011121261)the National Natural Science Foundation (no.40902049)the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (no.GBL11307)
文摘The northeastern Tibetan Plateau is located at the convergence of the Asian winter and summer monsoons and westerlies; thus, this area has witnessed historic climate changes.The Xunhua basin is an intermontane basin on the northeastern margin of the Tibetan Plateau.The basin contains more than 2000 m of Cenozoic fluvial–lacustrine sediments, recording a long history of climate and environmental changes.We collected the mid-Miocene sediments from the Xunhua basin and used palynological methods to discuss the relationship between aridification in the interior of Asia, global cooling, and uplift of the Tibetan Plateau.Based on the palynological analysis of the Xigou section, Xunhua basin, the palynological diagram is subdivided into three pollen zones and past vegetation and climate are reconstructed.Zone I, Ephedripites–Nitraridites–Chenopodipollis–Quercoidites（14.0–12.5 Ma）, represents mixed shrub–steppe vegetation with a dry and cold climate.In zone II, Pinaceae–Betulaepollenites–Ephedripites–Chenopodipollis–Graminidites（12.5–8.0 Ma）, the vegetation and climate conditions improved, even though the vegetation was still dominated by shrub–steppe taxa.Zone III, Ephedripites–Nitrariadites–Chenopodipollis（8.0–5.0 Ma）, represents desert steppe vegetation with drier and colder climate.The palynological records suggest that shrub–steppe dominated the whole Xigou section and the content gradually increased, implying a protracted aridification process, although there was an obvious climate improvement during 12.5–8.0 Ma.The aridification in the Xunhua basin and surrounding mountains during 14.0–12.5 Ma was probably related to global cooling induced by the rapid expansion of the East Antarctic ice-sheets and the relatively higher evaporation rate.During the 12.5–8.0 Ma period, although topographic changes（uplift of Jishi Shan） decreased precipitation and strengthened aridification in the Xunhua basin on leeward slopes, the improved vegetation and climate conditions were probably controlled by the decrease in evaporation rates as a result of continuous cooling.From 8.0 to 5.0 Ma, the rapid development of the desert steppe can be attributed to global cooling and uplift of the Tibetan Plateau.
基金funded by the project of China Geological Survey(Grant No.DD20221677-2)the Central Public-Interest Scientific Institution Basal Research Fund(Grant No.JKYQN202307)。
文摘Geothermal resources are increasingly gaining attention as a competitive,clean energy source to address the energy crisis and mitigate climate change.The Wugongshan area,situated in the southeast coast geothermal belt of China,is a typical geothermal anomaly and contains abundant medium-and low-temperature geothermal resources.This study employed hydrogeochemical and isotopic techniques to explore the cyclic evolution of geothermal water in the western Wugongshan region,encompassing the recharge origin,water-rock interaction mechanisms,and residence time.The results show that the geothermal water in the western region of Wugongshan is weakly alkaline,with low enthalpy and mineralization levels.The hydrochemistry of geothermal waters is dominated by Na-HCO_(3)and Na-SO_(4),while the hydrochemistry types of cold springs are all Na-HCO_(3).The hydrochemistry types of surface waters and rain waters are NaHCO_(3)or Ca-HCO_(3).The δD and δ^(18)O values reveal that the geothermal waters are recharged by atmospheric precipitation at an altitude between 550.0 and 1218.6 m.Molar ratios of maj or solutes and isotopic compositions of^(87)Sr/^(86)Sr underscore the significant role of silicate weathering,dissolution,and cation exchange in controlling geothermal water chemistry.Additionally,geothermal waters experienced varying degrees of mixing with cold water during their ascent.Theδ^(13)C values suggest that the primary sources of carbon in the geothermal waters were biogenic and organic.Theδ^(34)S value suggests that the sulfates in geothermal water originate from sulfide minerals in the surrounding rock.Age dating using 3H and^(14)C isotopes suggests that geothermal waters have a residence time exceeding 1 kaBP and undergo a long-distance cycling process.
基金supported by the Important National Science Technology Specific Projects of China(No.2016ZX05010-001-003).
文摘We present lithofacies classifications for a tight gas sandstone reservoir by analyzing hierarchies of heterogeneities.We use principal component analysis(PCA)to overcome the two level of heterogeneities,which results in a better lithofacies classification than the traditional cutoff method.The classical volumetric method is used for estimating oil/gas in-place resources in the petroleum industry since its inception is not accurate because it ignores the heterogeneities of and correlation between the petrophysical properties.We present the importance and methods of accounting for the heterogeneities of and correlation between petrophysical properties for more accurate hydrocarbon volumetric estimations.We also demonstrate the impacts of modeling the heterogeneities and correlation in porosity and hydrocarbon saturation for hydrocarbon volumetric estimations with a tight sandstone gas reservoir.Furthermore,geoscientists have traditionally considered that small-scale heterogeneities only impact subsurface fluid flow,but not impact the hydrocarbon resource volumetric estimation.We show the importance of modeling small-scale heterogeneities using fine cell size in reservoir modeling of unconventional resources for accurate resource assessment.
基金financial support from China University of Geosciences, Beijingsupported by the Project of National Nature Science Foundation of China (Grant No. 41572094)+2 种基金the Ph. D Research Start-up Fund of Fuyang Normal University (Grant No. 2016kyqd0004)the Scientific Research Project of Fuyang Normal University (Grant No. 2018FSKJ08ZD)the Key Project of Youth Science Funds of Fuyang Normal University (Gran No. rcxm201907)
文摘Reconstruction of the desert paleoclimate is important to understand the mechanisms that triggered and/or enhanced climate change.Through optically stimulated luminescence(OSL)dating,grain size,magnetic susceptibility,X-ray powder diffraction(XRD)and geochemical indicators,we provide a welldated record of a sedimentary outcrop on the southeast margin of the Bardain Jaran Desert,Northwest China,during the last glacial period.Four Qz-OSL ages are obtained,41.0±3.4 ka,54.7±4.4 ka,59.5±5.0 ka and 66.8±5.8 ka,corresponding to the depths of 35 cm,70 cm,150 cm and 200 cm respectively.Indicators like grain size,clay content,magnetic susceptibility,XRD and geochemical index(e.g.Sr,Ba,Sr/Ca)jointly indicate abrupt climate changes at the depth of 35 cm(age,ca.41.0 ka)and200 cm(age,ca.67 ka).Namely,the 280 cm sedimentary outcrop perfectly records a warm wet climate stage,corresponding to the late Marine Isotope Stages(MIS)4 to the early MIS 3.Besides,there is a trend of grain size increase after around 40ka BP,which is most likely a signal of wind strength change.Our research supports that enhancing Siberian High pressure system during the late MIS 3played a key role in NW East Asia climate evolution.
基金supported by the National Natural Science Foundation of China (Grant No. 41302209)the National groundwater investigation project (Grant No.1212011121169)
文摘This thesis focuses Arsenic(As) distribution and occurrence in groundwater of Yangtze River Delta economic region, East China. 2019 groundwater samples were collected to analyze 26 chemical compositions, including As. The Principal Component Analysis(PCA) was used to find out As source in groundwater. The results show that average As concentration in groundwater of this study is 9.33 μg/l, and maximum As concentration is up to 510 μg/l. The variation coefficient is 314.34%. High arsenic phreatic water(>10 μg/l) distributes along the Yangtze River and its estuary. Weak hydrodynamic conditions, wide p H value variation range and deteriorating environment are dominating factors, especially in Yangtze River Delta. The PCA suggests that arsenic in phreatic water is mainly of natural origin. Part of arsenic may directly originate from sediment organics and be related to organics decomposition.
基金financially supported by the National Natural Science Foundation of China(grants No.41541017,41641015,41720104009)the China Geological Survey(grants No.DD20160023-01,201511022)the Research funding from the Chinese Academy of Geological Sciences(grant No.YYWF201702)
文摘The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone(SSZ). However,economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone(MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr~# values(100 Cr/(Cr+Al))(47.7-55.1 and 46.5-51.7, respectively) than those in the high-Cr chromitites(78.2-80.4), harzburgites(72.6-77.9) and mantle dunites(79.4-84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements(PGE).The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10-0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.
基金financially supported by the National Natural Science Foundation of China (grants No. 41772159/D0208, No. 41872178)the National Science and Technology Major Project of China (grant No. 2017ZX05064003)
文摘The main methods of coalbed methane(CBM)development are drainage and depressurization,and a precise prediction of coal reservoir pressure is thus crucial for the evaluation of reservoir potentials and the formulation of reasonable development plans.This work established a new reservoir pressure prediction model based on the material balance equation(MBE)of coal reservoir,which considers the self-regulating effects of coal reservoirs and the dynamic change of equivalent drainage area(EDA).According to the proposed model,the reservoir pressure can be predicted based on reservoir condition data and the actual production data of a single well.Compared with traditional reservoir pressure prediction models which regard EDA as a fixed value,the proposed model can better predict the average pressure of reservoirs.Moreover,orthogonal experiments were designed to evaluate the sensitivity of reservoir parameters on the reservoir pressure prediction results of this proposed model.The results show that the saturation of irreducible water is the most sensitive parameter,followed by Langmuir volume and reservoir porosity,and Langmuir pressure is the least sensitive parameter.In addition,the pressure drop of reservoirs is negatively correlated with the saturation of irreducible water and the Langmuir volume,while it is positively correlated with porosity.This work analyzed the reservoir pressure drop characteristics of the CBM wells in the Shizhuangnan Block of the Qinshui Basin,and the results show that the CBM reservoir depressurization can be divided into three types,i.e.,rapidly drop type,medium-term stability type,and slowly drop type.The drainage features of wells were reasonably interpreted based on the comprehensive analysis of the reservoir depressurization type;the latter was coupled to the corresponding permeability dynamic change characteristics,eventually proving the applicability of the proposed model.
