The effectsof annealing process on the hardness, microstructure, Si diffusion, and the sagging resistance of cold-rolled 4343/3003/4343 Al alloy clad sheets and their 3003 Al alloy core sheets were experimentally inve...The effectsof annealing process on the hardness, microstructure, Si diffusion, and the sagging resistance of cold-rolled 4343/3003/4343 Al alloy clad sheets and their 3003 Al alloy core sheets were experimentally investigated through hardness tests, EBSD observations, EDS analysis, and sagging test.The results showedthat with the increase of annealing temperature, the hardness of both clad sheet and core sheet decreased, while thesaggingresistancesof both clad and core sheets achieved maximum values after annealing at 380℃ for 1h. After annealing at 380℃, the clad layer contained fine and equiaxedrecrystallized grains; the core layer was composed of fully recrystallized coarse grains elongated along the rolling direction. The Si diffusion from the clad layer to the core zone was limited. After annealing at a higher temperature of 440℃ or 550℃, thesaggingresistance of clad sheets worsened precipitously. The grains in the clad layer grew up, obscuring the interface between the clad and core layer; the recrystallized grains in the core layer became finer. Significant amount of Si penetrated into the core layer through the accelerated diffusion. Compared with the microstructure refinement, Si diffusion is the main factor influencing thesaggingresistance.展开更多
Studied in this paper is free vibration of a long span pipeline with nonlinearities taken into account. The pipeline sags under gravity and takes the shape of a plane curve. Vibration in the plane and out of the plane...Studied in this paper is free vibration of a long span pipeline with nonlinearities taken into account. The pipeline sags under gravity and takes the shape of a plane curve. Vibration in the plane and out of the plane is regarded as small motions about the large static deflection. Manifestations of nonlinearities such as amplitude-dependent frequencies and internal resonance are investigated.展开更多
This study examines a 1.32 m thick sediment sequence from the Cunge sag pond in the Litang Basin,eastern Tibetan Plateau,to assess the seismicity of the Litang fault during the Holocene.High-resolution geochemical,gra...This study examines a 1.32 m thick sediment sequence from the Cunge sag pond in the Litang Basin,eastern Tibetan Plateau,to assess the seismicity of the Litang fault during the Holocene.High-resolution geochemical,grain size,magnetic susceptibility,and total organic carbon indicators are employed to obtain a continuous record of changes in elemental,physical,and biological properties within the profile to identify seismic events.The seismic event layer generally comprises two sedimentary rhythms:a lower coarse sand layer and an upper fine silt-clay layer.These layers represent rapid deposition associated with fault activity(Earthquake A)and slower deposition during calm periods or earthquake recurrence intervals(Seismic interval A).Through six^(14)C dating,five seismic events have been identified in the Cunge sag pond section:E1(before 3955 a B.P.),E2(3713-3703 a B.P.),E3(3492-3392 a B.P.),E4(2031-1894 a B.P.),and E5(1384-1321 a B.P.).E1-E4 had shown a good consistency with the paleo-earthquake recorded by the trench,and whereas E5 is a newly identified seismic event,further improving the continuous earthquake sequence of the Litang fault.Based on existing trench data and the seismic event record from the Cunge sag pond,a total of 11 paleo-earthquakes are identified along the Litang fault since the Holocene.The paleo-earthquake activity of the Litang fault exhibits a clustered pattern,with recurrence intervals of both long periods(1000 a)and short periods(500 a).Since 5000 a,the interval between strong earthquake recurrences gradually decreases,indicating an increasing risk of strong earthquakes along the Litang fault.This study presents a continuous record of paleo-earthquakes along the Litang fault,eastern Tibetan Plateau,and can enhance the understanding of regional seismic activity.展开更多
Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the ...Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.展开更多
Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin...Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin,NE China.Focusing on 30 core samples obtained from the first shale oil parameter well,named SYY3 in the study area,we systematically analyzed the composition and stratigraphic distribution of the K_(2)qn~1 heteroatomic compounds using electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),to assess their geological relevance to shale oil.The findings indicate that in the negative ion mode,the heteroatomic compounds predominantly consist of N_(1),N_(1)O_(1)-N_(1)O_(8),O_(1)-O_(8),O_(1)S_(1)-O_(6)S_(1);contrastingly,in the positive ion mode,they are primarily composed of N_(1)-N_(2),N_(1)O_(1)-N_(1)O_(4),N_(2)O_(1),O_(1)-O_(4),O_(1)S_(1)-O_(2)S_(1).Heteroatomic compound distributions vary significantly with depth in the negative ion mode,with minor variations in the positive ion mode.These distributions are categorized into three types based on the negative ion ratio((N_(1)+N_(1)O_(x))/O_(x)):TypeⅠ(>1.5),TypeⅡ(0.8-1.5),and TypeⅢ(<0.8);typesⅠandⅡgenerally exhibit a broader range of carbon numbers compared to TypeⅢ.The distribution of double bond equivalent(DBE)values across various sample types exhibits minimal variance,whereas that of carbon numbers shows substantial differences.Variations in heteroatomic compound compositions among the samples might have resulted from vertical sedimentary heterogeneity and differing biotic contributions.TypeⅢsamples show a decrease in total organic carbon(TOC)and free oil content(S_(1))compared to typesⅠandⅡ,but an increased oil saturation index(OSI),indicating a lower content of free oil but a higher proportion of movable oil.The reduced content of N-containing compounds implies lower paleolake productivity during deposition,leading to a reduction in TOC and S_(1).A lower TOC can enhance oil movability due to reduced oil adsorption,and the decreased presence of polar nitrogenous macromolecules with fewer highC-number heteroatomic compounds further promote shale oil movability.Additionally,the negative ion ratios of N1/N1O1and O2/O1 exhibit positive and negative correlations with the values of TOC,S_(1),and extractable organic matter(EOM),respectively,indicating that the salinity and redox conditions of the depositional water body are the primary controlling factors for both organic matter enrichment and shale oil accumulation.展开更多
Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions...Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.展开更多
Alkaline lacustrine shale is highly heterogeneous,and the complex relationship between the organicinorganic porosity network and hydrocarbon occurrence restricts the effectiveness of shale oil exploration and developm...Alkaline lacustrine shale is highly heterogeneous,and the complex relationship between the organicinorganic porosity network and hydrocarbon occurrence restricts the effectiveness of shale oil exploration and development.Herein,we investigated the Fengcheng Formation(P_(1)f)in Mahu Sag.This study integrated geochemistry,Soxhlet extraction,scanning electron microscopy,gas adsorption,and nuclear magnetic resonance T_(1)-T_(2)spectroscopy to elucidate the microscopic oil occurrence mechanisms in shales.Results indicate the presence of felsic shale,dolomitic shale,lime shale,and mixed shale within the P_(1)f.Matrix pores and microfractures associated with inorganic minerals are the predominant pore types in P_(1)f.Adsorbed oil primarily resides on the surfaces of organic matter and clay minerals,while free oil predominantly occupies inorganic pores and microfractures with larger pore sizes.Variations exist in the quantity and distribution of shale oil accumulation across different scales,where free oil and adsorbed oil are governed by dominant pores with diameters exceeding 10 nm and ineffective pores with diameters below 10 nm,respectively.Shale oil occurrence characteristics are influenced by organic matter,pore structure,and mineral composition.Felsic shale exhibits a high abundance of dominant pores,possesses the highest oil content,predominantly harbors free oil within these dominant pores,and demonstrates good mobility.Fluid occurrence in dolomitic shale and lime shale is intricate,with low oil content and a free oil to adsorbed oil ratio of 1:1.Mixed shale exhibits elevated clay mineral content and a scarcity of dominant pores.Moreover,ineffective pores contain increased bound water,resulting in medium oil content and limited mobility predominantly due to adsorption.Presently,shale oil mainly occurs in the dominant pores with a diameter larger than 10 nm in a free state.During the exploration and development of alkaline lacustrine shale oil resources,emphasis should be placed on identifying sweet spots within the felsic shale characterized by dominant pores.展开更多
Improving salt tolerance and mitigating senescence in the presence of high salinity are crucial for sustaining agricultural productivity.Previous research has demonstrated that hydrogen peroxide(H_(2)O_(2)),specifical...Improving salt tolerance and mitigating senescence in the presence of high salinity are crucial for sustaining agricultural productivity.Previous research has demonstrated that hydrogen peroxide(H_(2)O_(2)),specifically H_(2)O_(2)derived from roots and mediated by the respiratory burst oxidase homolog(NADPH),plays a significant role in regulating ion and plant hormone homeostasis in glycophytic plants,such as Arabidopsis.However,the extent to which root-derived H_(2)O_(2)fulfils similar functions in halophytic plants remains uncertain.Therefore,our study aimed to explore the potential contribution of root-sourced H_(2)O_(2)in delaying leaf senescence induced by high salinity,utilizing seashore paspalum as a model halophytic plant.The application of the NADPH-oxidase inhibitor DPI,coupled with a series of leaf senescence analyses,we revealed that root-derived H_(2)O_(2)significantly retards salt-induced leaf senescence.Furthermore,through the application of hormone analysis,lipidomics,ionomics,Non-invasive Micro-test Technology(NMT),and transcriptomics,we established that NADPH-dependent H_(2)O_(2)induced by salt stress in the roots was indispensable for maintaining the balance of the aging hormone,jasmonic acid(JA),and sodium ion homeostasis within this halophytic plant.Finally,by utilizing AtrbohD Arabidopsis mutants and virus-induced gene silencing(VIGs)in Paspalum vaginatum,we demonstrated the pivotal role played by root-sourced H_(2)O_(2)in upholding JA homeostasis and regulating JA-triggered leaf senescence in P.vaginatum.This study offers novel insights into the mechanisms that govern plant leaf senescence and its response to salinity-induced stress.展开更多
Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are...Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are presented here.Using these geochemical data,the organic matter source and depositional environment of the source rocks,and the correspondence between aliphatic and aromatic palaeovegetation indicators is evaluated.This allows for a reconstruction of the palaeovegetation and palaeoclimate,and reveals the influence of the organic matter source on thermal maturity proxies.Abnormally abundant aliphatic and aromatic diterpenoids from gymnosperms and trace amounts of oleanane-,ursane-and lupane-type triterpenoids from angiosperms were detected.Various source-related proxies,abundant diterpenoids,and non-hopanoid triterpenoids,indicate that the predominant organic matter source was higher land plants.Detection of microbe-derived biomarkers suggest that abundant microbial activity resulted in an additional source of organic matter input.Palaeovegetation proxies,based on aromatic terpenoids from higher plants,are in agreement with those based on aliphatic terpenoid biomarkers.Collectively,they indicate that gymnosperms,rather than angiosperms,contributed the majority of the organic matter.Palaeovegetation composition indicates that during late Eocene,the region surrounding the Xihu Sag was characterized by a relatively cool climate.Elevated Pr/Ph ratios,along with other biomarker indices,further indicate that the source rocks were deposited in a relatively oxic and sulphate-poor,fluvio-deltaic environment.A comprehensive evaluation of maturity indices demonstrates that samples are relatively immature and remain in the early-oil generation window.Despite this,some alkylnaphthalene-and alkylphenanthrene-based thermal maturity parameters were affected by the generation of 1,2,5-trimethylnaphthalene,1,2,5,6-tetramethylnaphthalene and 1-methylphenanthrene,and organic facies that are related to resins.Additionally,the methyldibenzothiophene ratio could be not applied to assess maturity for low mature samples.These indicate that caution must be exercised when viewing alkylnaphthalene-,alkylphenanthrene-and alkyldibenzothiophene-based thermal maturity parameters.Biomarker distributions suggest the Pinghu Formation could be the source of light oils discovered in the Xihu Sag.展开更多
For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter inte...For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter intelligent optimization technique for shale oil reservoirs and verifies it by field application.A self-governing database capable of automatic capture,storage,calls and analysis is established.With this database,22 geological and engineering variables are selected for correlation analysis.A separated fracturing effect prediction model is proposed,with the fracturing learning curve decomposed into two parts:(1)overall trend,which is predicted by the algorithm combining the convolutional neural network with the characteristics of local connection and parameter sharing and the gated recurrent unit that can solve the gradient disappearance;and(2)local fluctuation,which is predicted by integrating the adaptive boosting algorithm to dynamically adjust the random forest weight.A policy gradient-genetic-particle swarm algorithm is designed,which can adaptively adjust the inertia weights and learning factors in the iterative process,significantly improving the optimization ability of the optimization strategy.The fracturing effect prediction and optimization strategy are combined to realize the intelligent optimization of fracturing parameters.The field application verifies that the proposed technique significantly improves the fracturing effects of oil wells,and it has good practicability.展开更多
This study examines the effect of fault sealing on hydrocarbon accumulation in the Xihu Sag where NEand NNE-striking faults within the sag prevent the escape of trapped oil and gas.Analyses like the shale gouge ratio(...This study examines the effect of fault sealing on hydrocarbon accumulation in the Xihu Sag where NEand NNE-striking faults within the sag prevent the escape of trapped oil and gas.Analyses like the shale gouge ratio(SGR),shale smear factor(SSF),and fault lateral sealing coefficient(Fh)are used for a quantitative evaluation of the lateral sealing capacity of faults in the Yuquan area of the Xihu Sag.Paleostructural sections reconstructed using cross-section balancing techniques are used to analyze the evolutionary characteristics of fault sealing.The results indicate that the lateral sealing capacity of faults is mainly controlled by fault throw,clay content,and sand-shale distribution characteristics;in the Yuquan area,fault segments exhibit good lateral sealing when the SGR exceeds 0.5,the SSF is less than2.5,and the Fh is greater than 10.5.The methodology for evaluating fault sealing evolution,established using structural reconstructions during key geological periods,shows that fault sealing capacity increased gradually over time;in the Xihu Sag,effective sealing of the main hydrocarbon-bearing intervals began during the Liulang period.Evaluating fault sealing capacity is also crucial for estimating the rate of hydrocarbon accumulation,and typically shows a positive correlation with gas(oil)column height.In the Yuquan area,the volume of hydrocarbons sealed by the faults increased progressively over time,with a relatively high overall fault sealing capacity during the second hydrocarbon accumulation period.This study provides valuable insights into the evaluation of fault sealing capacity as well as an investigation of the relationship between faults and hydrocarbon migration-accumulation in the Xihu Sag and analogous geological settings.展开更多
In the Pearl River Mouth Basin of the northern South China Sea,extensive commercial shallow gas reservoirs have recently been discovered.However,their formation mechanisms remain poorly constrained.This study employs ...In the Pearl River Mouth Basin of the northern South China Sea,extensive commercial shallow gas reservoirs have recently been discovered.However,their formation mechanisms remain poorly constrained.This study employs integrated petroleum geological and geochemical datasets to elucidate shallow gas systems' genesis and geochemical signatures.Key findings demonstrate that shallow gas reservoirs exhibit distinct geochemical differentiation from deep thermogenic counterparts,characterized by elevated dryness coefficients(>0.9),depleted methane δ^(13)C values(-52‰ to-34.4‰),and^(13)C-enriched ethane and propane isotopes resulting from migration fractionation.The anaerobic environment minimizes microbial alteration,while the complex marine geology challenges conventional interpretations of isotopic source indicators.Light hydrocarbon analysis identifies type Ⅱ_(2)-Ⅲ kerogen as the primary thermogenic gas source,with southern reservoirs showing sapropelic organic matter signatures consistent with oil-cracking origins.Notably,mixed-source reservoirs display an inverse δ^(13)C relationship between carbon dioxide and methane,contrasting with positive correlations typically observed in biogenic gas from carbon dioxide reduction.Quantitative end-member modeling constrains biogenic contributions to ≤30%,confirming thermogenic dominance despite active methanogenesis.Shallow gas accumulation is a dynamic process involving simultaneous charge and diffusion.Synthesizing these insights with prior research,we propose a genetic model for shallow gas reservoirs,highlighting significant differences in source rock maturity,kerogen types,enrichment layers,migration channels,and water depths relative to deep-water counterparts.展开更多
Addressing the critical challenges of viscosity loss and barite sag in synthetic-based drilling fluids(SBDFs)under high-temperature,high-pressure(HTHP)conditions,this study innovatively developed a hyperbranched amide...Addressing the critical challenges of viscosity loss and barite sag in synthetic-based drilling fluids(SBDFs)under high-temperature,high-pressure(HTHP)conditions,this study innovatively developed a hyperbranched amide polymer(SS-1)through a unique stepwise polycondensation strategy.By integrating dynamic ionic crosslinking for temperature-responsive rheology and rigid aromatic moieties ensuring thermal stability beyond 260℃,SS-1 achieves a molecular-level breakthrough.Performance evaluations demonstrate that adding merely 2.0 wt% SS-1 significantly enhances key properties of 210℃-aged SBDFs:plastic viscosity rises to 45 mPa⋅s,electrical stability(emulsion voltage)reaches 1426 V,and the sag factor declines to 0.509,outperforming conventional sulfonated polyacrylamide(S-PAM,0.531)by 4.3%.Mechanistic investigations reveal a trifunctional synergistic anti-sag mechanism involving electrostatic adsorption onto barite surfaces,hyperbranched steric hindrance,and colloid-stabilizing network formation.SS-1 exhibits exceptional HTHP stabilization efficacy,substantially surpassing S-PAM,thereby providing an innovative molecular design strategy and scalable solution for next-generation high-performance drilling fluid stabilizers.展开更多
The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercia...The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercial accumulations have been discovered.An integrated approach combining geochemical analysis,fluid inclusion thermometry,apatite fission-track(AFT)thermochronology,and basin modeling was employed to unravel the paleo-geothermal regime and hydrocarbon generation history of E_(2)s_(3) source rocks.AFT data from the Shahejie Formation’s second member(E_(2)s_(2))reveal a tectonothermal event at 25 Ma that accelerated E_(2)s_(3) maturation.Outside three sub-sag depocenters,current E_(2)s_(2) reservoir temperatures remain below the 25 Ma paleo-geothermal maxima despite subsequent Neogene burial.Hydrocarbon-bearing brine inclusions in E_(2)s_(2) reservoirs exhibit peak homogenization temperatures(Th)at 25 Ma,with minimal high-temperature signals,indicating that E_(2)s_(3) hydrocarbon generation peaked during the Paleogene thermal event,with limited late-stage accumulation.The regional effects of the Dongying Movement necessitate thick Neogene sedimentation to compensate for the 25 Ma paleo-geothermal anomaly.Our findings emphasize targeting Neogene depocenters in petroleum exploration to mitigate the inhibitory effects of high paleo-heat flow on late hydrocarbon generation,thereby enhancing current accumulation potential.展开更多
The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-developme...The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-development stage.Based on the current drilling data,seismic data,and fault development characteristics,this study investigates the connectivity,geometric morphology,planar distribution,and vertical evolution of composite sand bodies(multi-stage superimposed channel sand bodies)within the fault block using seismic forward and inversion modeling.The El3I oil layer group in the third member of the Liushagang Formation is developed in the fan delta-front sub-facies,which mainly consists of subaqueous distributary channels.The thickness of single-stage subaqueous distributary channel sand bodies ranges from 2 to 6 m,and the width of composite channel sand bodies varies from 50 to 100 m.Under the long-term transgression background,the subaqueous distributary channels in the El3I oil layer group are relatively narrow,forming superimposed and continuous composite channel sand bodies through lateral migration and vertical stacking.The long-term base-level cycles control the width of subaqueous distributary channels,while the mid-term base-level cycles control the thickness of these channels.The subaqueous distributary channels developed during the late stage of mid-term base-level fall are thicker than those formed during the early stage.Accordingly,quantitative relationships between channel thickness and width are established for the early and late stages of mid-term base-level fall,to finely depict the evolution patterns of channel sand body geometry and stacking styles across different stages.These findings provide important guidance for accurately predicting the planar distribution and channel width of composite subaqueous distributary channels at different stages of the mid-term baselevel cycles.展开更多
The microscopic occurrence characteristics primarily constrain the enrichment and mobility of shale oil.This study collected the lacustrine shales from the Palaeogene Funing Formation in the Gaoyou Sag, Subei Basin. C...The microscopic occurrence characteristics primarily constrain the enrichment and mobility of shale oil.This study collected the lacustrine shales from the Palaeogene Funing Formation in the Gaoyou Sag, Subei Basin. Conventional and multistage Rock-Eval, scanning electron microscopy, and nuclear magnetic resonance(NMR) T1-T2were performed to analyze the contents and occurrence characteristics of shale oil. Low-temperature nitrogen adsorption-desorption(LTNA/D) experiments were conducted on the shales before and after extraction. The relationships between shale oil occurrence with organic matter and pore structures were then discussed. Predominantly, the shale oil in the Funing Formation is found within fractures, with secondary occurrences in interparticle pores linked to brittle minerals and sizeable intraparticle pores associated with clay minerals. The selected shales can be categorized into two types based on the nitrogen isotherms. Type A shales are characterized by high contents of felsic and calcareous minerals but low clay minerals, with larger TOC and shale oil values. Conversely, Type B shales are marked by abundant clay minerals but diminished TOC and shale oil contents. The lower BET specific surface area(SSA), larger average pore diameter, and simpler pore surfaces and pore structures lead to the Type A shales being more conducive to shale oil enrichment and mobility. Shale oil content is predominantly governed by the abundance of organic matter, while an overabundance of organic matter typically equates to a reduced ratio of free oil and diminished fluidity. The BET SSA, volumes of pores less than 25 and 100 nm at extracted state all correlate negatively with total and adsorbed oil contents but display no correlation with free oil, while they have positive relationships with capillary-bound water.Consequently, pore water is mainly saturated in micropores(<25 nm) and minipores(25-100 nm), as well as adsorbed oil, while free oil, i.e., bound and movable oil, primarily exists in mesopores(100-1000 nm) and macropores(>1000 nm). These findings may enhance the understanding of the microscopic occurrence characteristics of shale oil and will contribute to guide resource estimation and shale oil sweet spot exploitation in the Gaoyou Sag, Subei Basin.展开更多
The ability of faults to transport oil and gas is affected by multiple geological factors,and the effects of various factors on oil and gas migration and accumulation are complex.In this study,based on the drilling an...The ability of faults to transport oil and gas is affected by multiple geological factors,and the effects of various factors on oil and gas migration and accumulation are complex.In this study,based on the drilling and three-dimensional seismic data in the No.4 structural zone of the Nanpu Sag and by considering the effects of fault throw,caprock thickness,shale content,fluid pressure,stress normal to the fault plane,and brittleness,we employed fault transport index(FTI)to quantitatively characterize the vertical transport ability of regional faults.Through statistical analysis,fault transport probability(N_p)was used to characterize the relationship between FTI and the vertical hydrocarbon content in the formations,The results show that the faults with FTI less than 0.75 cannot transport oil and gas,while those with FTI greater than 2.5 are able to transport oil and gas.Specifically,when FTI is between 0.75and 2.5,there is a functional relationship between the probability of faults transporting hydrocarbons and FTI.The current oil and water distribution and paleo oil reservoir test results indicate that there are oil layers or paleo oil reservoirs in horizons with large N_(p).Therefore,FTI can be used as an effective coefficient to indicate the vertical migration paths and accumulation spots of hydrocarbons moving along faults,providing an essential reference for further oil and gas exploration and development.展开更多
Based on drilling,mud logging,core,seismic and imaging logging data,this paper studies the identification and evolution process of negative inversion structures in the Carboniferous buried hills in the No.1 and No.2 f...Based on drilling,mud logging,core,seismic and imaging logging data,this paper studies the identification and evolution process of negative inversion structures in the Carboniferous buried hills in the No.1 and No.2 fault zones of Weixinan Sag,Beibu Gulf Basin,China,and reveals the controls of these structures on high-quality reservoirs.The No.2 fault zone develops significant negative inversion structures in the Carboniferous buried hills,as a result of multi-stage transformations of compressive-tensile stress fields in the period from the Late Hercynian to the Himalayan.The Hercynian carbonates laid the material basis for the formation of high-quality reservoirs.The negative inversion structures mainly control the development of high-quality reservoirs in buried hills through:(1)creating large-scale fractures to increase reservoir space and improve oil-gas flow pathways;(2)regulating stratigraphic differential denudation to highlight dominant lithology for later reservoir transformation;(3)shaping the paleogeomorphological highlands to provide favorable conditions for superficial karstification.The negative inversion structures form a high-quality,composite reservoir space with the synergistic existence of superficial dissolution fractures/cavities and burial-enhanced karst systems through the coupling of fracture network creation,formation denudation screening and multi-stage karst transformation.The research results have guided the breakthrough of the first exploratory well with a daily oil production over 1000 m^(3)in carbonate buried-hill reservoir in the Beibu Gulf Basin,and provide referential geological basis for finding more reserves and achieving higher production in the Carboniferous buried hills in the Weixinan Sag.展开更多
基金Project(U1360104)supported by the National Natural Science Foundation and Bao Steel of ChinaProject(A type,12QH1401200)supported by the Shanghai Rising-Star Program,China
文摘The effectsof annealing process on the hardness, microstructure, Si diffusion, and the sagging resistance of cold-rolled 4343/3003/4343 Al alloy clad sheets and their 3003 Al alloy core sheets were experimentally investigated through hardness tests, EBSD observations, EDS analysis, and sagging test.The results showedthat with the increase of annealing temperature, the hardness of both clad sheet and core sheet decreased, while thesaggingresistancesof both clad and core sheets achieved maximum values after annealing at 380℃ for 1h. After annealing at 380℃, the clad layer contained fine and equiaxedrecrystallized grains; the core layer was composed of fully recrystallized coarse grains elongated along the rolling direction. The Si diffusion from the clad layer to the core zone was limited. After annealing at a higher temperature of 440℃ or 550℃, thesaggingresistance of clad sheets worsened precipitously. The grains in the clad layer grew up, obscuring the interface between the clad and core layer; the recrystallized grains in the core layer became finer. Significant amount of Si penetrated into the core layer through the accelerated diffusion. Compared with the microstructure refinement, Si diffusion is the main factor influencing thesaggingresistance.
文摘Studied in this paper is free vibration of a long span pipeline with nonlinearities taken into account. The pipeline sags under gravity and takes the shape of a plane curve. Vibration in the plane and out of the plane is regarded as small motions about the large static deflection. Manifestations of nonlinearities such as amplitude-dependent frequencies and internal resonance are investigated.
基金supported by the National Natural Science Foundation of China(42202131 and 42177184).
文摘This study examines a 1.32 m thick sediment sequence from the Cunge sag pond in the Litang Basin,eastern Tibetan Plateau,to assess the seismicity of the Litang fault during the Holocene.High-resolution geochemical,grain size,magnetic susceptibility,and total organic carbon indicators are employed to obtain a continuous record of changes in elemental,physical,and biological properties within the profile to identify seismic events.The seismic event layer generally comprises two sedimentary rhythms:a lower coarse sand layer and an upper fine silt-clay layer.These layers represent rapid deposition associated with fault activity(Earthquake A)and slower deposition during calm periods or earthquake recurrence intervals(Seismic interval A).Through six^(14)C dating,five seismic events have been identified in the Cunge sag pond section:E1(before 3955 a B.P.),E2(3713-3703 a B.P.),E3(3492-3392 a B.P.),E4(2031-1894 a B.P.),and E5(1384-1321 a B.P.).E1-E4 had shown a good consistency with the paleo-earthquake recorded by the trench,and whereas E5 is a newly identified seismic event,further improving the continuous earthquake sequence of the Litang fault.Based on existing trench data and the seismic event record from the Cunge sag pond,a total of 11 paleo-earthquakes are identified along the Litang fault since the Holocene.The paleo-earthquake activity of the Litang fault exhibits a clustered pattern,with recurrence intervals of both long periods(1000 a)and short periods(500 a).Since 5000 a,the interval between strong earthquake recurrences gradually decreases,indicating an increasing risk of strong earthquakes along the Litang fault.This study presents a continuous record of paleo-earthquakes along the Litang fault,eastern Tibetan Plateau,and can enhance the understanding of regional seismic activity.
基金Supported by Leading Talent Program of Autonomous Region(2022TSYCLJ0070)PetroChina Prospective and Basic Technological Project(2021DJ0108)Natural Science Foundation for Outstanding Young People in Shandong Province(ZR2022YQ30).
文摘Based on the experimental results of casting thin section,low temperature nitrogen adsorption,high pressure mercury injection,nuclear magnetic resonance T2 spectrum,contact angle and oil-water interfacial tension,the relationship between pore throat structure and crude oil mobility characteristics of full particle sequence reservoirs in the Lower Permian Fengcheng Formation of Mahu Sag,Junggar Basin,are revealed.(1)With the decrease of reservoir particle size,the volume of pores connected by large throats and the volume of large pores show a decreasing trend,and the distribution and peak ranges of throat and pore radius shift to smaller size in an orderly manner.The upper limits of throat radius,porosity and permeability of unconventional reservoirs in Fengcheng Formation are approximately 0.7μm,8%and 0.1×10^(−3)μm^(2),respectively.(2)As the reservoir particle size decreases,the distribution and peak ranges of pores hosting retained oil and movable oil are shifted to a smaller size in an orderly manner.With the increase of driving pressure,the amount of retained and movable oil of the larger particle reservoir samples shows a more obvious trend of decreasing and increasing,respectively.(3)With the increase of throat radius,the driving pressure of reservoir with different particle levels presents three stages,namely rapid decrease,slow decrease and stabilization.The oil driving pressures of various reservoirs and the differences of them decrease with the increase of temperature and obviously decrease with the increase of throat radius.According to the above experimental analysis,it is concluded that the deep shale oil of Fengcheng Formation in Mahu Sag has great potential for production under geological conditions.
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.42072178 and U2244207)the funding project of Northeast Geological S&T Innovation Center of China Geological Survey(Grant No.QCJJ2022-37)Geological Survey Project of China Geological Survey(Grant Nos.DD20190114,DD20230022,and DD20240045)。
文摘Organic-rich mudstones and shales,which hold significant potential for shale oil resources,characterize the first member of the Upper Cretaceous Qingshankou Formation(K_(2)qn~1)in the Sanzhao sag of the Songliao Basin,NE China.Focusing on 30 core samples obtained from the first shale oil parameter well,named SYY3 in the study area,we systematically analyzed the composition and stratigraphic distribution of the K_(2)qn~1 heteroatomic compounds using electrospray ionization Fourier transform-ion cyclotron resonance mass spectrometry(ESI FT-ICR MS),to assess their geological relevance to shale oil.The findings indicate that in the negative ion mode,the heteroatomic compounds predominantly consist of N_(1),N_(1)O_(1)-N_(1)O_(8),O_(1)-O_(8),O_(1)S_(1)-O_(6)S_(1);contrastingly,in the positive ion mode,they are primarily composed of N_(1)-N_(2),N_(1)O_(1)-N_(1)O_(4),N_(2)O_(1),O_(1)-O_(4),O_(1)S_(1)-O_(2)S_(1).Heteroatomic compound distributions vary significantly with depth in the negative ion mode,with minor variations in the positive ion mode.These distributions are categorized into three types based on the negative ion ratio((N_(1)+N_(1)O_(x))/O_(x)):TypeⅠ(>1.5),TypeⅡ(0.8-1.5),and TypeⅢ(<0.8);typesⅠandⅡgenerally exhibit a broader range of carbon numbers compared to TypeⅢ.The distribution of double bond equivalent(DBE)values across various sample types exhibits minimal variance,whereas that of carbon numbers shows substantial differences.Variations in heteroatomic compound compositions among the samples might have resulted from vertical sedimentary heterogeneity and differing biotic contributions.TypeⅢsamples show a decrease in total organic carbon(TOC)and free oil content(S_(1))compared to typesⅠandⅡ,but an increased oil saturation index(OSI),indicating a lower content of free oil but a higher proportion of movable oil.The reduced content of N-containing compounds implies lower paleolake productivity during deposition,leading to a reduction in TOC and S_(1).A lower TOC can enhance oil movability due to reduced oil adsorption,and the decreased presence of polar nitrogenous macromolecules with fewer highC-number heteroatomic compounds further promote shale oil movability.Additionally,the negative ion ratios of N1/N1O1and O2/O1 exhibit positive and negative correlations with the values of TOC,S_(1),and extractable organic matter(EOM),respectively,indicating that the salinity and redox conditions of the depositional water body are the primary controlling factors for both organic matter enrichment and shale oil accumulation.
基金Supported by the Research Project of China National Offshore Oil Corporation(SCKY-2023-HN-3)。
文摘Based on the comprehensive analysis of data from petrology and mineralogy,well logging,seismic surveys,paleontology,and geochemistry,a detailed research was conducted on paleoenvironmental and paleoclimatic conditions,and modeling of the source rocks in the second member of the Eocene Wenchang Formation(Wen 2 Member)in the Northern Shunde Subsag at the southwestern margin of the Pearl River Mouth Basin.The Wen 2 Member hosts excellent,thick lacustrine source rocks with strong longitudinal heterogeneity and an average total organic carbon(TOC)content of over 4.9%.The Wen 2 Member can be divided into three units(I,II,III)from bottom to top.Unit I features excellent source rocks with Type I organic matters(average TOC of 5.9%)primarily sourced from lake organisms;Unit II hosts source rocks dominated by Type II2 organic matters(average TOC of 2.2%),which are originated from mixed sources dominated by terrestrial input.Unit III contains good to excellent source rocks dominated by Type II1 organic matters(average TOC of 4.9%),which are mainly contributed by lake organisms and partially by terrestrial input.Under the background of rapid subsidence and limited source supply during intense rifting period in the Eocene,excellent source rocks were developed in Wen 2 Member in the Northern Shunde Subsag under the coordinated control of warm and humid climate,volcanic activity,and deep-water reducing conditions.During the deposition of Unit I,the warm and humid climate and volcanic activity promoted the proliferation of lake algaes,primarily Granodiscus,resulting in high initial productivity,and deep-water reducing conditions enabled satisfactory preservation of organic matters.These factors jointly controlled the development and occurrence of excellent source rocks.During the deposition of Unit II,a transition from warm to cool and semi-arid paleoclimatic conditions led to a decrease in lake algaes and initial productivity.Additionally,enhanced terrestrial input and shallow-water,weakly oxidizing water conditions caused a significant dilution and decomposition of organic matters,degrading the quality of source rocks.During the deposition of Unit III,when the paleoclimatic conditions are cool and humid,Pediastrum and Botryococcus began to thrive,leading to an increase in productivity.Meanwhile,the reducing environment of semi-deep water facilitated the preservation of excellent source rocks,albeit slightly inferior to those in Unit I.The study results clarify the differential origins and development models of various source rocks in the Shunde Sag,offering valuable guidance for evaluating source rocks and selecting petroleum exploration targets in similar marginal sags.
基金financially supported by the State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development(33550000-22-ZC0613-0006)National Natural Science Foundation of China(42202133)+2 种基金CNPC Innovation Fund(2022DQ02-0106)Strategic Cooperation Technology Projects of the CNPC and CUPB(ZLZX2020-01-05)Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences),Ministry of Education,China(TPR-2023-05)。
文摘Alkaline lacustrine shale is highly heterogeneous,and the complex relationship between the organicinorganic porosity network and hydrocarbon occurrence restricts the effectiveness of shale oil exploration and development.Herein,we investigated the Fengcheng Formation(P_(1)f)in Mahu Sag.This study integrated geochemistry,Soxhlet extraction,scanning electron microscopy,gas adsorption,and nuclear magnetic resonance T_(1)-T_(2)spectroscopy to elucidate the microscopic oil occurrence mechanisms in shales.Results indicate the presence of felsic shale,dolomitic shale,lime shale,and mixed shale within the P_(1)f.Matrix pores and microfractures associated with inorganic minerals are the predominant pore types in P_(1)f.Adsorbed oil primarily resides on the surfaces of organic matter and clay minerals,while free oil predominantly occupies inorganic pores and microfractures with larger pore sizes.Variations exist in the quantity and distribution of shale oil accumulation across different scales,where free oil and adsorbed oil are governed by dominant pores with diameters exceeding 10 nm and ineffective pores with diameters below 10 nm,respectively.Shale oil occurrence characteristics are influenced by organic matter,pore structure,and mineral composition.Felsic shale exhibits a high abundance of dominant pores,possesses the highest oil content,predominantly harbors free oil within these dominant pores,and demonstrates good mobility.Fluid occurrence in dolomitic shale and lime shale is intricate,with low oil content and a free oil to adsorbed oil ratio of 1:1.Mixed shale exhibits elevated clay mineral content and a scarcity of dominant pores.Moreover,ineffective pores contain increased bound water,resulting in medium oil content and limited mobility predominantly due to adsorption.Presently,shale oil mainly occurs in the dominant pores with a diameter larger than 10 nm in a free state.During the exploration and development of alkaline lacustrine shale oil resources,emphasis should be placed on identifying sweet spots within the felsic shale characterized by dominant pores.
基金supported by the Project funded by the Natural Science Foundation of Hainan Province(Grant No.322QN248)the National Natural Science Foundation of China(Grant Nos.32401488,32060409,32371782 and 32460358)+3 种基金the Innovational Fund for Scientific and Technological Personnel of Hainan Province(Grant No.KJRC 2023C21)the Hainan High-level Talents Project(Grant No.321RC475)Collaborative Innovation Center Project of Nanfan and High-Efficiency Tropical Agriculture in Hainan University(XTCX2022NYB08)Collaborative Innovation Center Project of Ecological Civilization in Hainan University(XTCX2022STC10).
文摘Improving salt tolerance and mitigating senescence in the presence of high salinity are crucial for sustaining agricultural productivity.Previous research has demonstrated that hydrogen peroxide(H_(2)O_(2)),specifically H_(2)O_(2)derived from roots and mediated by the respiratory burst oxidase homolog(NADPH),plays a significant role in regulating ion and plant hormone homeostasis in glycophytic plants,such as Arabidopsis.However,the extent to which root-derived H_(2)O_(2)fulfils similar functions in halophytic plants remains uncertain.Therefore,our study aimed to explore the potential contribution of root-sourced H_(2)O_(2)in delaying leaf senescence induced by high salinity,utilizing seashore paspalum as a model halophytic plant.The application of the NADPH-oxidase inhibitor DPI,coupled with a series of leaf senescence analyses,we revealed that root-derived H_(2)O_(2)significantly retards salt-induced leaf senescence.Furthermore,through the application of hormone analysis,lipidomics,ionomics,Non-invasive Micro-test Technology(NMT),and transcriptomics,we established that NADPH-dependent H_(2)O_(2)induced by salt stress in the roots was indispensable for maintaining the balance of the aging hormone,jasmonic acid(JA),and sodium ion homeostasis within this halophytic plant.Finally,by utilizing AtrbohD Arabidopsis mutants and virus-induced gene silencing(VIGs)in Paspalum vaginatum,we demonstrated the pivotal role played by root-sourced H_(2)O_(2)in upholding JA homeostasis and regulating JA-triggered leaf senescence in P.vaginatum.This study offers novel insights into the mechanisms that govern plant leaf senescence and its response to salinity-induced stress.
基金The National Natural Science Foundation of China under contract No.42302189the National Natural Science Foundationof China Joint Fund for Enterprise Innovation and Devel-opment under contract No.U24B6002.
文摘Aliphatic and aromatic biomarkers derived from higher land plants,conventional biomarkers,as well as the carbon stable isotope ratios of kerogens in late Eocene source rocks from the western margin of the Xihu Sag are presented here.Using these geochemical data,the organic matter source and depositional environment of the source rocks,and the correspondence between aliphatic and aromatic palaeovegetation indicators is evaluated.This allows for a reconstruction of the palaeovegetation and palaeoclimate,and reveals the influence of the organic matter source on thermal maturity proxies.Abnormally abundant aliphatic and aromatic diterpenoids from gymnosperms and trace amounts of oleanane-,ursane-and lupane-type triterpenoids from angiosperms were detected.Various source-related proxies,abundant diterpenoids,and non-hopanoid triterpenoids,indicate that the predominant organic matter source was higher land plants.Detection of microbe-derived biomarkers suggest that abundant microbial activity resulted in an additional source of organic matter input.Palaeovegetation proxies,based on aromatic terpenoids from higher plants,are in agreement with those based on aliphatic terpenoid biomarkers.Collectively,they indicate that gymnosperms,rather than angiosperms,contributed the majority of the organic matter.Palaeovegetation composition indicates that during late Eocene,the region surrounding the Xihu Sag was characterized by a relatively cool climate.Elevated Pr/Ph ratios,along with other biomarker indices,further indicate that the source rocks were deposited in a relatively oxic and sulphate-poor,fluvio-deltaic environment.A comprehensive evaluation of maturity indices demonstrates that samples are relatively immature and remain in the early-oil generation window.Despite this,some alkylnaphthalene-and alkylphenanthrene-based thermal maturity parameters were affected by the generation of 1,2,5-trimethylnaphthalene,1,2,5,6-tetramethylnaphthalene and 1-methylphenanthrene,and organic facies that are related to resins.Additionally,the methyldibenzothiophene ratio could be not applied to assess maturity for low mature samples.These indicate that caution must be exercised when viewing alkylnaphthalene-,alkylphenanthrene-and alkyldibenzothiophene-based thermal maturity parameters.Biomarker distributions suggest the Pinghu Formation could be the source of light oils discovered in the Xihu Sag.
基金Supported by the National Science and Technology Major Project(2017ZX05009-005-003)National Natural Science Grant Fund for Surface Project(52174045)+1 种基金Chinese Academy of Engineering Strategic Consulting Project(2018-XZ-09)China National Petroleum Corporation(CNPC)-China University of Petroleum(Beijing)Special Project for Strategic Cooperation in Science and Technology(ZLZX2020-01)。
文摘For shale oil reservoirs in the Jimsar Sag of Junggar Basin,the fracturing treatments are challenged by poor prediction accuracy and difficulty in parameter optimization.This paper presents a fracturing parameter intelligent optimization technique for shale oil reservoirs and verifies it by field application.A self-governing database capable of automatic capture,storage,calls and analysis is established.With this database,22 geological and engineering variables are selected for correlation analysis.A separated fracturing effect prediction model is proposed,with the fracturing learning curve decomposed into two parts:(1)overall trend,which is predicted by the algorithm combining the convolutional neural network with the characteristics of local connection and parameter sharing and the gated recurrent unit that can solve the gradient disappearance;and(2)local fluctuation,which is predicted by integrating the adaptive boosting algorithm to dynamically adjust the random forest weight.A policy gradient-genetic-particle swarm algorithm is designed,which can adaptively adjust the inertia weights and learning factors in the iterative process,significantly improving the optimization ability of the optimization strategy.The fracturing effect prediction and optimization strategy are combined to realize the intelligent optimization of fracturing parameters.The field application verifies that the proposed technique significantly improves the fracturing effects of oil wells,and it has good practicability.
基金financially supported by the National Natural Science Foundation of China(42272151)。
文摘This study examines the effect of fault sealing on hydrocarbon accumulation in the Xihu Sag where NEand NNE-striking faults within the sag prevent the escape of trapped oil and gas.Analyses like the shale gouge ratio(SGR),shale smear factor(SSF),and fault lateral sealing coefficient(Fh)are used for a quantitative evaluation of the lateral sealing capacity of faults in the Yuquan area of the Xihu Sag.Paleostructural sections reconstructed using cross-section balancing techniques are used to analyze the evolutionary characteristics of fault sealing.The results indicate that the lateral sealing capacity of faults is mainly controlled by fault throw,clay content,and sand-shale distribution characteristics;in the Yuquan area,fault segments exhibit good lateral sealing when the SGR exceeds 0.5,the SSF is less than2.5,and the Fh is greater than 10.5.The methodology for evaluating fault sealing evolution,established using structural reconstructions during key geological periods,shows that fault sealing capacity increased gradually over time;in the Xihu Sag,effective sealing of the main hydrocarbon-bearing intervals began during the Liulang period.Evaluating fault sealing capacity is also crucial for estimating the rate of hydrocarbon accumulation,and typically shows a positive correlation with gas(oil)column height.In the Yuquan area,the volume of hydrocarbons sealed by the faults increased progressively over time,with a relatively high overall fault sealing capacity during the second hydrocarbon accumulation period.This study provides valuable insights into the evaluation of fault sealing capacity as well as an investigation of the relationship between faults and hydrocarbon migration-accumulation in the Xihu Sag and analogous geological settings.
基金supported by CNOOC(China) Ltd.'s productive scientific research project"Shallow gas enrichment mechanism and favorable exploration direction in the Baiyun Sag"(Grant No.2022SKPS0082)。
文摘In the Pearl River Mouth Basin of the northern South China Sea,extensive commercial shallow gas reservoirs have recently been discovered.However,their formation mechanisms remain poorly constrained.This study employs integrated petroleum geological and geochemical datasets to elucidate shallow gas systems' genesis and geochemical signatures.Key findings demonstrate that shallow gas reservoirs exhibit distinct geochemical differentiation from deep thermogenic counterparts,characterized by elevated dryness coefficients(>0.9),depleted methane δ^(13)C values(-52‰ to-34.4‰),and^(13)C-enriched ethane and propane isotopes resulting from migration fractionation.The anaerobic environment minimizes microbial alteration,while the complex marine geology challenges conventional interpretations of isotopic source indicators.Light hydrocarbon analysis identifies type Ⅱ_(2)-Ⅲ kerogen as the primary thermogenic gas source,with southern reservoirs showing sapropelic organic matter signatures consistent with oil-cracking origins.Notably,mixed-source reservoirs display an inverse δ^(13)C relationship between carbon dioxide and methane,contrasting with positive correlations typically observed in biogenic gas from carbon dioxide reduction.Quantitative end-member modeling constrains biogenic contributions to ≤30%,confirming thermogenic dominance despite active methanogenesis.Shallow gas accumulation is a dynamic process involving simultaneous charge and diffusion.Synthesizing these insights with prior research,we propose a genetic model for shallow gas reservoirs,highlighting significant differences in source rock maturity,kerogen types,enrichment layers,migration channels,and water depths relative to deep-water counterparts.
基金the National Natural Science Foundation(41802169)Key Laboratory of Polar Geology and Marine Mineral Resources Foudation(HNPY-202506)for supporting this study.
文摘The Shanan sag in the central-western Bohai Bay Basin hosts high-quality Paleogene source rocks within the Shahejie Formation’s third member(E_(2)s_(3)).Despite hydrocarbon indications in Cenozoic strata,no commercial accumulations have been discovered.An integrated approach combining geochemical analysis,fluid inclusion thermometry,apatite fission-track(AFT)thermochronology,and basin modeling was employed to unravel the paleo-geothermal regime and hydrocarbon generation history of E_(2)s_(3) source rocks.AFT data from the Shahejie Formation’s second member(E_(2)s_(2))reveal a tectonothermal event at 25 Ma that accelerated E_(2)s_(3) maturation.Outside three sub-sag depocenters,current E_(2)s_(2) reservoir temperatures remain below the 25 Ma paleo-geothermal maxima despite subsequent Neogene burial.Hydrocarbon-bearing brine inclusions in E_(2)s_(2) reservoirs exhibit peak homogenization temperatures(Th)at 25 Ma,with minimal high-temperature signals,indicating that E_(2)s_(3) hydrocarbon generation peaked during the Paleogene thermal event,with limited late-stage accumulation.The regional effects of the Dongying Movement necessitate thick Neogene sedimentation to compensate for the 25 Ma paleo-geothermal anomaly.Our findings emphasize targeting Neogene depocenters in petroleum exploration to mitigate the inhibitory effects of high paleo-heat flow on late hydrocarbon generation,thereby enhancing current accumulation potential.
文摘The study on sand body connectivity and distribution patterns is of great significance for well emplacement and injection-production pattern analysis in the A oilfield of the Weixi?nan Sag currently at a pre-development stage.Based on the current drilling data,seismic data,and fault development characteristics,this study investigates the connectivity,geometric morphology,planar distribution,and vertical evolution of composite sand bodies(multi-stage superimposed channel sand bodies)within the fault block using seismic forward and inversion modeling.The El3I oil layer group in the third member of the Liushagang Formation is developed in the fan delta-front sub-facies,which mainly consists of subaqueous distributary channels.The thickness of single-stage subaqueous distributary channel sand bodies ranges from 2 to 6 m,and the width of composite channel sand bodies varies from 50 to 100 m.Under the long-term transgression background,the subaqueous distributary channels in the El3I oil layer group are relatively narrow,forming superimposed and continuous composite channel sand bodies through lateral migration and vertical stacking.The long-term base-level cycles control the width of subaqueous distributary channels,while the mid-term base-level cycles control the thickness of these channels.The subaqueous distributary channels developed during the late stage of mid-term base-level fall are thicker than those formed during the early stage.Accordingly,quantitative relationships between channel thickness and width are established for the early and late stages of mid-term base-level fall,to finely depict the evolution patterns of channel sand body geometry and stacking styles across different stages.These findings provide important guidance for accurately predicting the planar distribution and channel width of composite subaqueous distributary channels at different stages of the mid-term baselevel cycles.
基金supported by the National Natural Science Foundation of China(42302160)the Sanya City Science and Technology Innovation Project(2022KJCX51)the Support Plan for Outstanding Youth Innovation Team in Shandong Higher Education Institutions(2022KJ060).
文摘The microscopic occurrence characteristics primarily constrain the enrichment and mobility of shale oil.This study collected the lacustrine shales from the Palaeogene Funing Formation in the Gaoyou Sag, Subei Basin. Conventional and multistage Rock-Eval, scanning electron microscopy, and nuclear magnetic resonance(NMR) T1-T2were performed to analyze the contents and occurrence characteristics of shale oil. Low-temperature nitrogen adsorption-desorption(LTNA/D) experiments were conducted on the shales before and after extraction. The relationships between shale oil occurrence with organic matter and pore structures were then discussed. Predominantly, the shale oil in the Funing Formation is found within fractures, with secondary occurrences in interparticle pores linked to brittle minerals and sizeable intraparticle pores associated with clay minerals. The selected shales can be categorized into two types based on the nitrogen isotherms. Type A shales are characterized by high contents of felsic and calcareous minerals but low clay minerals, with larger TOC and shale oil values. Conversely, Type B shales are marked by abundant clay minerals but diminished TOC and shale oil contents. The lower BET specific surface area(SSA), larger average pore diameter, and simpler pore surfaces and pore structures lead to the Type A shales being more conducive to shale oil enrichment and mobility. Shale oil content is predominantly governed by the abundance of organic matter, while an overabundance of organic matter typically equates to a reduced ratio of free oil and diminished fluidity. The BET SSA, volumes of pores less than 25 and 100 nm at extracted state all correlate negatively with total and adsorbed oil contents but display no correlation with free oil, while they have positive relationships with capillary-bound water.Consequently, pore water is mainly saturated in micropores(<25 nm) and minipores(25-100 nm), as well as adsorbed oil, while free oil, i.e., bound and movable oil, primarily exists in mesopores(100-1000 nm) and macropores(>1000 nm). These findings may enhance the understanding of the microscopic occurrence characteristics of shale oil and will contribute to guide resource estimation and shale oil sweet spot exploitation in the Gaoyou Sag, Subei Basin.
基金supported by the National Natural Science Foundation of China(Grant Nos.42302150 and U20A2093)National Science and Technology Major Project(Grant No.2024ZD1400104)。
文摘The ability of faults to transport oil and gas is affected by multiple geological factors,and the effects of various factors on oil and gas migration and accumulation are complex.In this study,based on the drilling and three-dimensional seismic data in the No.4 structural zone of the Nanpu Sag and by considering the effects of fault throw,caprock thickness,shale content,fluid pressure,stress normal to the fault plane,and brittleness,we employed fault transport index(FTI)to quantitatively characterize the vertical transport ability of regional faults.Through statistical analysis,fault transport probability(N_p)was used to characterize the relationship between FTI and the vertical hydrocarbon content in the formations,The results show that the faults with FTI less than 0.75 cannot transport oil and gas,while those with FTI greater than 2.5 are able to transport oil and gas.Specifically,when FTI is between 0.75and 2.5,there is a functional relationship between the probability of faults transporting hydrocarbons and FTI.The current oil and water distribution and paleo oil reservoir test results indicate that there are oil layers or paleo oil reservoirs in horizons with large N_(p).Therefore,FTI can be used as an effective coefficient to indicate the vertical migration paths and accumulation spots of hydrocarbons moving along faults,providing an essential reference for further oil and gas exploration and development.
基金Supported by the Hainan Provincial Science and Technology Special Project(ZDYF2025GXJS013)CNOOC Zhanjiang Branch Project(CCL2023ZJFN0540).
文摘Based on drilling,mud logging,core,seismic and imaging logging data,this paper studies the identification and evolution process of negative inversion structures in the Carboniferous buried hills in the No.1 and No.2 fault zones of Weixinan Sag,Beibu Gulf Basin,China,and reveals the controls of these structures on high-quality reservoirs.The No.2 fault zone develops significant negative inversion structures in the Carboniferous buried hills,as a result of multi-stage transformations of compressive-tensile stress fields in the period from the Late Hercynian to the Himalayan.The Hercynian carbonates laid the material basis for the formation of high-quality reservoirs.The negative inversion structures mainly control the development of high-quality reservoirs in buried hills through:(1)creating large-scale fractures to increase reservoir space and improve oil-gas flow pathways;(2)regulating stratigraphic differential denudation to highlight dominant lithology for later reservoir transformation;(3)shaping the paleogeomorphological highlands to provide favorable conditions for superficial karstification.The negative inversion structures form a high-quality,composite reservoir space with the synergistic existence of superficial dissolution fractures/cavities and burial-enhanced karst systems through the coupling of fracture network creation,formation denudation screening and multi-stage karst transformation.The research results have guided the breakthrough of the first exploratory well with a daily oil production over 1000 m^(3)in carbonate buried-hill reservoir in the Beibu Gulf Basin,and provide referential geological basis for finding more reserves and achieving higher production in the Carboniferous buried hills in the Weixinan Sag.
