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
Four types of Mg-5Zn porous scaffolds with different pore geometries,including body-centered cubic(bcc),the rhombic dodecahedron(RD),gyroid(G),and primitive(P)types,were designed and fabricated using selective laser m...Four types of Mg-5Zn porous scaffolds with different pore geometries,including body-centered cubic(bcc),the rhombic dodecahedron(RD),gyroid(G),and primitive(P)types,were designed and fabricated using selective laser melting.Their forming quality,compression mechanical properties,and degradation behavior were investigated.Results indicate that the fabricated scaffolds exhibit good dimensional accuracy,and the surface chemical polishing treatment significantly improves the forming quality and reduces porosity error in porous scaffolds.Compared to the ones with rod structures(bcc,RD),the scaffolds with surface structures(G,P)have less powder particle adhesion.The G porous scaffold exhibits the best forming quality for the same design porosity.The predominant failure mode of scaffolds during compression is a 45°shear fracture.At a porosity of 75%,the compression property of all scaffolds meets the compressive property requirements of cancellous bone,while bcc and G structures show relatively better compression property.After immersion in Hank's solution for 168 h,the B-2-75% pore structure scaffold exhibits severe localized corrosion,with fractures in partial pillar connections.In contrast,the G-3-75% pore structure scaffold mainly undergoes uniform corrosion,maintaining structural integrity,and its corrosion rate and loss of compressive properties are less than those of the B-2-75%structure.After comparison,the G-pore structure scaffold is preferred.展开更多
Changes to the microstructure of a hard carbon(HC)and its solid electrolyte interface(SEI)can be effective in improving the electrode kinetics.However,achieving fast charging using a simple and inexpensive strategy wi...Changes to the microstructure of a hard carbon(HC)and its solid electrolyte interface(SEI)can be effective in improving the electrode kinetics.However,achieving fast charging using a simple and inexpensive strategy without sacrificing its initial Coulombic efficiency remains a challenge in sodium ion batteries.A simple liquid-phase coating approach has been used to generate a pitch-derived soft carbon layer on the HC surface,and its effect on the porosity of HC and SEI chemistry has been studied.A variety of structural characterizations show a soft carbon coating can increase the defect and ultra-micropore contents.The increase in ultra-micropore comes from both the soft carbon coatings and the larger pores within the HC that are partially filled by pitch,which provides more Na+storage sites.In-situ FTIR/EIS and ex-situ XPS showed that the soft carbon coating induced the formation of thinner SEI that is richer in NaF from the electrolyte,which stabilized the interface and promoted the charge transfer process.As a result,the anode produced fastcharging(329.8 mAh g^(−1)at 30 mA g^(−1)and 198.6 mAh g^(−1)at 300 mA g^(−1))and had a better cycling performance(a high capacity retention of 81.4%after 100 cycles at 150 mA g^(−1)).This work reveals the critical role of coating layer in changing the pore structure,SEI chemistry and diffusion kinetics of hard carbon,which enables rational design of sodium-ion battery anode with enhanced fast charging capability.展开更多
The development of sustainable electrode materials for energy storage systems has become very important and porous carbons derived from biomass have become an important candidate because of their tunable pore structur...The development of sustainable electrode materials for energy storage systems has become very important and porous carbons derived from biomass have become an important candidate because of their tunable pore structure,environmental friendliness,and cost-effectiveness.Recent advances in controlling the pore structure of these carbons and its relationship between to is energy storage performance are discussed,emphasizing the critical role of a balanced distribution of micropores,mesopores and macropores in determining electrochemical behavior.Particular attention is given to how the intrinsic components of biomass precursors(lignin,cellulose,and hemicellulose)influence pore formation during carbonization.Carbonization and activation strategies to precisely control the pore structure are introduced.Finally,key challenges in the industrial production of these carbons are outlined,and future research directions are proposed.These include the establishment of a database of biomass intrinsic structures and machine learning-assisted pore structure engineering,aimed at providing guidance for the design of high-performance carbon materials for next-generation energy storage devices.展开更多
Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiv...Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiveness,and environ-mental friendliness.The pyrolysis method affects the microstructure of the material,and ultimately its so-dium storage performance.Our previous work has shown that pyrolysis in a sealed graphite vessel im-proved the sodium storage performance of the car-bon,however the changes in its microstructure and the way this influences the sodium storage are still unclear.A series of hard carbon materials derived from corncobs(CCG-T,where T is the pyrolysis temperature)were pyrolyzed in a sealed graphite vessel at different temperatures.As the pyrolysis temperature increased from 1000 to 1400℃ small carbon domains gradually transformed into long and curved domains.At the same time,a greater number of large open pores with uniform apertures,as well as more closed pores,were formed.With the further increase of pyrolysis temperature to 1600℃,the long and curved domains became longer and straighter,and some closed pores gradually became open.CCG-1400,with abundant closed pores,had a superior SIB performance,with an initial reversible ca-pacity of 320.73 mAh g^(-1) at a current density of 30 mA g^(-1),an initial Coulomb efficiency(ICE)of 84.34%,and a capacity re-tention of 96.70%after 100 cycles.This study provides a method for the precise regulation of the microcrystalline and pore structures of hard carbon materials.展开更多
A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580...A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580 to 640℃.X-ray computed tomography was used to visualize pores,and crystal plasticity finite element simulation was adopted for deformation analysis.The microstructure characterizations reveal a hierarchical cell feature composed of α-Mg and eutectic phases.With the increase of injection temperature,large cell content in the material decreases,while the strength of the alloy increases.The underlying mechanism about strength change is that coarse-grained solids experience smaller stress even in hard orientations.The sample fabricated at a moderate temperature of 620℃ exhibits the highest elongation,least quantity and lower local concentration of pores.The detachment and tearing cracks formed at lower injection temperature and defect bands formed at higher injection temperature add additional crack sources and deteriorate the ductility of the materials.展开更多
Existing imaging techniques cannot simultaneously achieve high resolution and a wide field of view,and manual multi-mineral segmentation in shale lacks precision.To address these limitations,we propose a comprehensive...Existing imaging techniques cannot simultaneously achieve high resolution and a wide field of view,and manual multi-mineral segmentation in shale lacks precision.To address these limitations,we propose a comprehensive framework based on generative adversarial network(GAN)for characterizing pore structure properties of shale,which incorporates image augmentation,super-resolution reconstruction,and multi-mineral auto-segmentation.Using real 2D and 3D shale images,the framework was assessed through correlation function,entropy,porosity,pore size distribution,and permeability.The application results show that this framework enables the enhancement of 3D low-resolution digital cores by a scale factor of 8,without paired shale images,effectively reconstructing the unresolved fine-scale pores under a low resolution,rather than merely denoising,deblurring,and edge clarification.The trained GAN-based segmentation model effectively improves manual multi-mineral segmentation results,resulting in a strong resemblance to real samples in terms of pore size distribution and permeability.This framework significantly improves the characterization of complex shale microstructures and can be expanded to other heterogeneous porous media,such as carbonate,coal,and tight sandstone reservoirs.展开更多
The black shale samples from the Niutitang Formation in the Yangtze Block were sequentially treated using organic solvent extraction and wet chemical oxidation.The organic matter(OM)in the shales includes physically m...The black shale samples from the Niutitang Formation in the Yangtze Block were sequentially treated using organic solvent extraction and wet chemical oxidation.The organic matter(OM)in the shales includes physically mobile OM(PmOM),chemically mobile OM(CmOM),and stable OM(StOM).The CmOM has the strongest CH_(4)adsorption capacity because it has the largest volume of micropores and mesopores.In contrast,the PmOM has a very negative effect on the CH_(4)adsorption because it is poreless.The XD shale is a siliceous shale,in which the quartz particles wrap partly OM,preventing extraction and oxidation.The SL shale is an argillaceous shale,in which most of the OM is combined with clay minerals to form organo-clay composites.In both the SL and XD shales,the OM that is extractable via organic solvents is distributed among the mineral particles and is interconnected.The conceptual model of marine black shale in different environments needs to be perfected in the future because quantitative and qualitative methods should be combined to clarify the relationship between the known OM types(e.g.,pyrobitumen,solid bitumen,and solid kerogen)and the OM types identified in this study.展开更多
This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron mi...This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron microscopy,high-pressure mercury intrusion,and petrophysical testing to systematically evaluate reservoir petrographic features and pore structures.Results reveal that Benxi Formation sandstones predominantly comprise quartz sandstones,lithic quartz sandstones,and lithic sandstones,characterized by high quartz content,widespread volcanic lithic fragments,moderately well-sorted grains,and complex cement types.Pore types are dominated by residual intergranular and dissolution pores,with minor intracrystalline pores and fractures;overall porosity ranges from 0.17%to 9.07%(average 4.74%),and permeability from 0.01 to 6.05 mD,classifying them as ultra-low porosity and tight reservoirs.High-pressure mercury intrusion indicates microfine throats as the primary structure,divisible into four distinct types.Diagenetically,compaction and cementation are the main drivers of primary pore loss and reservoir tightening,whereas late-stage dissolution partially ameliorates pore networks.Overall,Benxi Formation sandstone reservoirs exhibit pervasive densification but localized favorable pore assemblages and connectivity,facilitating hydrocarbon migration and accumulation.These findings advance understanding of Upper Paleozoic tight sandstone reservoir characteristics and aid in predicting sweet spots.展开更多
Clarifying the pore structure characteristics of shale reservoirs,which are low porosity,low permeability and high heterogeneity,is an essential prerequisite for the efficient development of shale oil and gas.Fractal ...Clarifying the pore structure characteristics of shale reservoirs,which are low porosity,low permeability and high heterogeneity,is an essential prerequisite for the efficient development of shale oil and gas.Fractal theory is especially suited for characterizing the complex pore structures of shales.This work compares the pore structure characteristics between marine shales from the Longmaxi Formation and continental shales from the Shahejie Formation through low-temperature nitrogen adsorption,nuclear magnetic resonance,and scanning electron microscopy.Different fractal scaling models are adopted to determine the fractal dimensions and lacunarities of shales by low-temperature nitrogen adsorption data and scanning electron microscopy images.In addition,the mineral compositions from X-ray diffraction are analyzed to elucidate the mechanisms by which mineral content influences fractal dimensions.Finally,the correlations between total organic carbon content and microscopic structure are discussed.These results indicate that the pore size of marine shale is smaller than that of continental shale.Additionally,the fractal dimensions of marine shales are greater than that of continental shales,suggesting a more complex pore structure.The more quartz and clay content lead to greater complexity in pore space,resulting in higher fractal dimensions.The illite/smectite mixed layer shows a strong positive correlation with fractal dimensions for marine shales,whereas this correlation is less pronounced for continental shales.The presence of microfractures in organic matter leads to a reduction for the pore surface fractal dimension in continental shales.展开更多
Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon explorati...Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon exploration.By analysing the geochemistry and reservoir characteristics of Jurassic lacustrine shales in Sichuan Basin,this study recovers their paleoenvironments and further discusses paleoenvironmental constraints on pore structure.The results show that the Lower Jurassic lacustrine shales in the Sichuan Basin are in a warm and humid semi-anoxic to anoxic lake environment with high productivity,a strong stagnant environment,and a rapid sedimentation rate,with water depths ranging from about 11.54-55.22 m,and a mixture of type Ⅱ/Ⅲ kerogen is developed.In terms of reservoir characteristics,they are dominated by open-slit pores,and the pores are relatively complex.The percentage of mesopores is the highest,while the percentage of macropores is the lowest.Further analysis shows that paleoclimate controls the overall pore complexity and surface relaxation of shales by influencing the weathering rate of mother rocks.Paleoredox conditions control the proportion and complexity of shale pores by influencing TOC content.The research results will provide theoretical basis for improving the exploration efficiency of lacustrine shale resources and expanding exploration target areas.展开更多
Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located ...Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located in the southern Junggar Basin of northwestern China,has geological conditions with rich CBM resources.The 46 Xishanyao coal samples gathered from the drilling cores and coal mines cover 4 types of macrolithotypes(bright coal 1,semi-bright coal 2,semi-dull coal 3,and dull coal 4)and 2 types of coal structures(primary coal I and cataclastic coal II).Based on a range of pore testing experiments and analytical methods,the dual effects of different macrolithotypes and coal structures on pore structures were intensely studied.The results showed that the specific surface area(SSA)and total pore volume(TPV)of coal samples increased gradually from bright to dull coals.For the same macrolithotypes,the SSA and TPV of the primary coals were lower than those of the cataclastic coals.Generally,the pore structures of bright and semi-bright coals are simpler when compared to semi-dull and dull coals with the same coal structure,whereas cataclastic coals have more complicated pore structure systems than primary coals with the same macrolithotypes.The bright and semi-bright coals have higher vitrinite contents and more endogenous fractures,whereas well-developed structural fractures were identified in cataclastic coals.Therefore,bright and semi-bright coals have better pore connectivity than semi-dull and dull coals with the same coal structure,the pore connectivity of cataclastic coals being slightly better than that of primary coals under the same macrolithotypes.In terms of the CBM adsorption conditions,the eight type samples formed a descending order:Ⅱ-4>I-4>Ⅱ-3>Ⅰ-3>Ⅱ-2>Ⅰ-2>Ⅱ-1>Ⅰ-1,while they ranked as follows when consideration was given to the CBM seepage capacities:II-2>Ⅱ-1>Ⅰ-2>Ⅰ-1>Ⅰ-3>Ⅰ-4>Ⅱ-3>Ⅱ-4.As a result,it could be determined that the bright and semi-bright coals had stronger adsorption capacities,whereas the cataclastic coals had better pore connectivity and seepage capacities.Pore structure characteristics should be analysed under the dual control of different macrolithotypes and coal structures,so that they can provide greater value for guiding CBM exploration and exploitation,as along for preventing underground gas accidents.展开更多
The pore structure of rocks significantly influences the porosity and permeability of reservoirs and the migration ability of oil and gas,and being the key task on the development of volcanic gas reservoirs.Nine volca...The pore structure of rocks significantly influences the porosity and permeability of reservoirs and the migration ability of oil and gas,and being the key task on the development of volcanic gas reservoirs.Nine volcanic rock samples from the Yingcheng Formation and Huoshiling Formation in the Longfengshan area of the Changling Fault Depression in the Songliao Basin were selected for this study.The pore structures of the volcanic rocks in the study area were investigated using high-pressure mercury injection,X-ray diffraction combined with fractal theory.The relationships between the fractal dimension and physical properties characteristics,pore structure parameters,and mineral content were analyzed to provide guidance for the development of volcanic rock gas reservoirs.The results show that the reservoir can be divided into 3 types(I,II,and III)based on the shape of the capillary pressure curve,and the physical properties deteriorate successively.Different types of reservoirs exhibit different fractal characteristics.For typesⅠ,ⅡandⅢ,the average total fractal dimensions were 2.3418,2.6850,and 2.9203,respectively.The larger the fractal dimension,the stronger the heterogeneity of reservoir.A small number of macro-pores primarily contributed to permeability.The fractal dimension was negatively correlated with porosity and permeability.The fractal dimension of the rock was strongly correlated with quartz and feldspar contents,and the mineral composition and content are closely related to the pore evolution of the reservoir,which are the internal factors affecting the fractal dimension of volcanic rock.展开更多
As a typical sedimentary soft rock,mudstone has the characteristics of being easily softened and disintegrated under the effect of wetting and drying(WD).The first cycle of WD plays an important role in the entire WD ...As a typical sedimentary soft rock,mudstone has the characteristics of being easily softened and disintegrated under the effect of wetting and drying(WD).The first cycle of WD plays an important role in the entire WD cycles.X-ray micro-computed tomography(micro-CT)was used as a non-destructive tool to quantitatively analyze microstructural changes of the mudstone due to the first cycle of WD.The test results show that WD leads to an increase of pore volume and pore connectivity in the mudstone.The porosity and fractal dimension of each slice of mudstone not only increase in value,but also in fluctuation amplitude.The pattern of variation in the frequency distribution of the equivalent radii of connected,isolated pores and pore throats in mudstone under WD effect satisfies the Gaussian distribution.Under the effect of WD,pores and pore throats with relatively small sizes increase the most.The sphericity of the pores in mudstones is positively correlated with the pore radius.The WD effect transforms the originally angular and flat pores into round and regular pores.This paper can provide a reference for the study of the deterioration and catastrophic mechanisms of mudstone under wetting and drying cycles.展开更多
Complex physical and chemical reactions during CO_(2)sequestration alter the microscopic pore structure of geological formations,impacting sequestration stability.To investigate CO_(2)sequestration dynamics,comprehens...Complex physical and chemical reactions during CO_(2)sequestration alter the microscopic pore structure of geological formations,impacting sequestration stability.To investigate CO_(2)sequestration dynamics,comprehensive physical simulation experiments were conducted under varied pressures,coupled with assessments of changes in mineral composition,ion concentrations,pore morphology,permeability,and sequestration capacity before and after experimentation.Simultaneously,a method using NMR T2spectra changes to measure pore volume shift and estimate CO_(2)sequestration is introduced.It quantifies CO_(2)needed for mineralization of soluble minerals.However,when CO_(2)dissolves in crude oil,the precipitation of asphaltene compounds impairs both seepage and storage capacities.Notably,the impact of dissolution and precipitation is closely associated with storage pressure,with a particularly pronounced influence on smaller pores.As pressure levels rise,the magnitude of pore alterations progressively increases.At a pressure threshold of 25 MPa,the rate of change in small pores due to dissolution reaches a maximum of 39.14%,while precipitation results in a change rate of-58.05%for small pores.The observed formation of dissolution pores and micro-cracks during dissolution,coupled with asphaltene precipitation,provides crucial insights for establishing CO_(2)sequestration parameters and optimizing strategies in low permeability reservoirs.展开更多
With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The ...With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The pore structure not only plays an essential role in the formation of complex fracture networks after fracturing but also in resource accumulation mechanism analyses. The lacustrine organicrich shale samples were selected to carry out petrophysical experiments. Scanning Electron Microscopy(SEM) and X-ray Diffraction were performed to elucidate the geology characteristics. MICP, 2D NMR, CT,and N2adsorption were conducted to classify the pore structure types. The contribution of pore structure to oil accumulation and hydrocarbon enrichment was explained through the N2adsorption test on the original and extracted state and 2D NMR. The results show that micropores with diameter less than20 nm are well-developed. The pore structure was divided into three types. Type Ⅰ is characterized by high porosity, lower surface area, and good pore throat connectivity, with free oil existing in large pores,especially lamellation fractures. The dominant nano-pores are spongy organic pores and resources hosted in large pores have been expelled during high thermal evolution. The content of nano-pores(micropores) increases and the pore volume decreases in Type Ⅱ pore structure. In addition, more absorbed oil was enriched. The pore size distribution of type Ⅱ is similar to that of type Ⅰ. However, the maturity and hydrocarbon accumulation is quite different. The oil reserved in large pores was not expelled attributed to the relatively low thermal evolution compared with type Ⅰ. Structural vitrinite was observed through SEM indicating kerogen of type Ⅲ developed in this kind of reservoir while the type of kerogen in pore structure Ⅰ is type Ⅱ. Type Ⅲ pore structure is characterized by the largest surface area,lowest porosity, and almost isolated pores with rarely free oil. Type Ⅰ makes the most contribution to hydrocarbon accumulation and immigration, which shows the best prospect. Of all of these experiments,N2adsorption exhibits the best in characterizing pores in shales due to its high resolution for the assessment of nano-scale pores. MICP and NMR have a better advantage in characterizing pore space of sandstone reservoirs, even tight sandstone reservoirs. 2D NMR plays an essential role in fluid recognition and saturation calculation. CT scanning provides a 3D visualization of reservoir space and directly shows the relationship between pores and throats and the characteristics of fractures. This study hopes to guide experiment selection in pore structure characterization in different reservoirs. This research provides insight into hydrocarbon accumulation of shales and guidance in the exploration and development of unconventional resources, for example for geothermal and CCUS reservoirs.展开更多
The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for e...The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.展开更多
By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water pu...By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water purification tests that were conducted.The pore characteristics of the pervious concrete were identified using three-dimensional reconstruction software and the relationship between pore structure and water purification performance was quantified by gray entropy correlation analysis.The results showed that the purification efficiency of zeolite-doped pervious concrete was 17.6%-22.3%higher than that of ordinary pervious concrete.The characteristic parameters of the pore structure of permeable concrete,i.e.planar porosity and tortuosity,were determined using three-dimensional reconstruction software.The correlation between the degree of tortuosity and the removal rate reached more than 0.90,indicating that the internal pore structure of pervious concrete has a good correlation with the water purification performance.展开更多
Liquid nitrogen(LN_(2))and microwave are the alternative methods for reservoir fracturing,which are rarely combined.To investigate the combined effects,sandstone is frozen with LN_(2)before microwave heating(MI),and n...Liquid nitrogen(LN_(2))and microwave are the alternative methods for reservoir fracturing,which are rarely combined.To investigate the combined effects,sandstone is frozen with LN_(2)before microwave heating(MI),and nuclear magnetic resonance(NMR),ultrasonic wave,and infrared thermal imaging(ITI)are used to understand the pore structures,moisture change,and surface temperature of the sandstone samples.With the heating time,the average surface temperature of the combining-treatment samples firstly increases from the room temperature(25℃)to 144.7℃(65 s)fast,and then increases slowly to 176.6℃(95 s).For the individual MI,the temperature increases to 146.7℃at 65 s.As 30 min of LN_(2)freezing,the samples perform well in removing pore water during heating.The NMR results show that after LN_(2)freezing,the seepage pores and total pores increase by 2.93%and 4.11%,respectively,and the pore connectivity enhances.However,the individual MI performs weak in enhancing the pore structures,forming a high vapor pressure(0.428 MPa at 65 s)and causing burst after 65 s.Due to the improved pore connectivity,the vapor pressure(0.378 MPa)and temperature are small at 65 s,and burst can be avoided.After freezing,the wave velocity decreases by 13.48%and the damage variable reaches 0.251.The velocity attenuation rates and damage variable gradually increase with heating time;under the same duration,the two variables of the combining treatments are greater than that of the individual treatments.This can prove a reference for gas production in sandstone reservoirs.展开更多
Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of he...Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.展开更多
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Science and Technology Planning Project of Inner Mongolia Science and Technology Department(2022YFSH0021)Key Research and Development Program of Shaanxi Province(2024SF2-GJHX-14,2021SF-296)。
文摘Four types of Mg-5Zn porous scaffolds with different pore geometries,including body-centered cubic(bcc),the rhombic dodecahedron(RD),gyroid(G),and primitive(P)types,were designed and fabricated using selective laser melting.Their forming quality,compression mechanical properties,and degradation behavior were investigated.Results indicate that the fabricated scaffolds exhibit good dimensional accuracy,and the surface chemical polishing treatment significantly improves the forming quality and reduces porosity error in porous scaffolds.Compared to the ones with rod structures(bcc,RD),the scaffolds with surface structures(G,P)have less powder particle adhesion.The G porous scaffold exhibits the best forming quality for the same design porosity.The predominant failure mode of scaffolds during compression is a 45°shear fracture.At a porosity of 75%,the compression property of all scaffolds meets the compressive property requirements of cancellous bone,while bcc and G structures show relatively better compression property.After immersion in Hank's solution for 168 h,the B-2-75% pore structure scaffold exhibits severe localized corrosion,with fractures in partial pillar connections.In contrast,the G-3-75% pore structure scaffold mainly undergoes uniform corrosion,maintaining structural integrity,and its corrosion rate and loss of compressive properties are less than those of the B-2-75%structure.After comparison,the G-pore structure scaffold is preferred.
基金National Key Research and Development Program of China(2022YFE0206300)National Natural Science Foundation of China(U21A2081,22075074,22209047)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2024A1515011620)Hunan Provincial Natural Science Foundation of China(2024JJ5068)Foundation of Yuelushan Center for Industrial Innovation(2023YCII0119)。
文摘Changes to the microstructure of a hard carbon(HC)and its solid electrolyte interface(SEI)can be effective in improving the electrode kinetics.However,achieving fast charging using a simple and inexpensive strategy without sacrificing its initial Coulombic efficiency remains a challenge in sodium ion batteries.A simple liquid-phase coating approach has been used to generate a pitch-derived soft carbon layer on the HC surface,and its effect on the porosity of HC and SEI chemistry has been studied.A variety of structural characterizations show a soft carbon coating can increase the defect and ultra-micropore contents.The increase in ultra-micropore comes from both the soft carbon coatings and the larger pores within the HC that are partially filled by pitch,which provides more Na+storage sites.In-situ FTIR/EIS and ex-situ XPS showed that the soft carbon coating induced the formation of thinner SEI that is richer in NaF from the electrolyte,which stabilized the interface and promoted the charge transfer process.As a result,the anode produced fastcharging(329.8 mAh g^(−1)at 30 mA g^(−1)and 198.6 mAh g^(−1)at 300 mA g^(−1))and had a better cycling performance(a high capacity retention of 81.4%after 100 cycles at 150 mA g^(−1)).This work reveals the critical role of coating layer in changing the pore structure,SEI chemistry and diffusion kinetics of hard carbon,which enables rational design of sodium-ion battery anode with enhanced fast charging capability.
文摘The development of sustainable electrode materials for energy storage systems has become very important and porous carbons derived from biomass have become an important candidate because of their tunable pore structure,environmental friendliness,and cost-effectiveness.Recent advances in controlling the pore structure of these carbons and its relationship between to is energy storage performance are discussed,emphasizing the critical role of a balanced distribution of micropores,mesopores and macropores in determining electrochemical behavior.Particular attention is given to how the intrinsic components of biomass precursors(lignin,cellulose,and hemicellulose)influence pore formation during carbonization.Carbonization and activation strategies to precisely control the pore structure are introduced.Finally,key challenges in the industrial production of these carbons are outlined,and future research directions are proposed.These include the establishment of a database of biomass intrinsic structures and machine learning-assisted pore structure engineering,aimed at providing guidance for the design of high-performance carbon materials for next-generation energy storage devices.
文摘Biomass-derived hard carbons,usually prepared by pyrolysis,are widely considered the most promising anode materials for sodium-ion bat-teries(SIBs)due to their high capacity,low poten-tial,sustainability,cost-effectiveness,and environ-mental friendliness.The pyrolysis method affects the microstructure of the material,and ultimately its so-dium storage performance.Our previous work has shown that pyrolysis in a sealed graphite vessel im-proved the sodium storage performance of the car-bon,however the changes in its microstructure and the way this influences the sodium storage are still unclear.A series of hard carbon materials derived from corncobs(CCG-T,where T is the pyrolysis temperature)were pyrolyzed in a sealed graphite vessel at different temperatures.As the pyrolysis temperature increased from 1000 to 1400℃ small carbon domains gradually transformed into long and curved domains.At the same time,a greater number of large open pores with uniform apertures,as well as more closed pores,were formed.With the further increase of pyrolysis temperature to 1600℃,the long and curved domains became longer and straighter,and some closed pores gradually became open.CCG-1400,with abundant closed pores,had a superior SIB performance,with an initial reversible ca-pacity of 320.73 mAh g^(-1) at a current density of 30 mA g^(-1),an initial Coulomb efficiency(ICE)of 84.34%,and a capacity re-tention of 96.70%after 100 cycles.This study provides a method for the precise regulation of the microcrystalline and pore structures of hard carbon materials.
基金supported by the National Natural Science Foundation of China(Nos.51825101,52001202)the National Key Research and Development Program of China(No.2021YFA1600900)。
文摘A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580 to 640℃.X-ray computed tomography was used to visualize pores,and crystal plasticity finite element simulation was adopted for deformation analysis.The microstructure characterizations reveal a hierarchical cell feature composed of α-Mg and eutectic phases.With the increase of injection temperature,large cell content in the material decreases,while the strength of the alloy increases.The underlying mechanism about strength change is that coarse-grained solids experience smaller stress even in hard orientations.The sample fabricated at a moderate temperature of 620℃ exhibits the highest elongation,least quantity and lower local concentration of pores.The detachment and tearing cracks formed at lower injection temperature and defect bands formed at higher injection temperature add additional crack sources and deteriorate the ductility of the materials.
基金Supported by the National Natural Science Foundation of China(U23A20595,52034010,52288101)National Key Research and Development Program of China(2022YFE0203400)+1 种基金Shandong Provincial Natural Science Foundation(ZR2024ZD17)Fundamental Research Funds for the Central Universities(23CX10004A).
文摘Existing imaging techniques cannot simultaneously achieve high resolution and a wide field of view,and manual multi-mineral segmentation in shale lacks precision.To address these limitations,we propose a comprehensive framework based on generative adversarial network(GAN)for characterizing pore structure properties of shale,which incorporates image augmentation,super-resolution reconstruction,and multi-mineral auto-segmentation.Using real 2D and 3D shale images,the framework was assessed through correlation function,entropy,porosity,pore size distribution,and permeability.The application results show that this framework enables the enhancement of 3D low-resolution digital cores by a scale factor of 8,without paired shale images,effectively reconstructing the unresolved fine-scale pores under a low resolution,rather than merely denoising,deblurring,and edge clarification.The trained GAN-based segmentation model effectively improves manual multi-mineral segmentation results,resulting in a strong resemblance to real samples in terms of pore size distribution and permeability.This framework significantly improves the characterization of complex shale microstructures and can be expanded to other heterogeneous porous media,such as carbonate,coal,and tight sandstone reservoirs.
基金financially supported by the National Natural Science Fund of China(Nos.42002166,41690134,42162016)the Guizhou Provincial Fund Project(Nos.[2020]1Y161,ZK[2021]199,ZK[2022]106)。
文摘The black shale samples from the Niutitang Formation in the Yangtze Block were sequentially treated using organic solvent extraction and wet chemical oxidation.The organic matter(OM)in the shales includes physically mobile OM(PmOM),chemically mobile OM(CmOM),and stable OM(StOM).The CmOM has the strongest CH_(4)adsorption capacity because it has the largest volume of micropores and mesopores.In contrast,the PmOM has a very negative effect on the CH_(4)adsorption because it is poreless.The XD shale is a siliceous shale,in which the quartz particles wrap partly OM,preventing extraction and oxidation.The SL shale is an argillaceous shale,in which most of the OM is combined with clay minerals to form organo-clay composites.In both the SL and XD shales,the OM that is extractable via organic solvents is distributed among the mineral particles and is interconnected.The conceptual model of marine black shale in different environments needs to be perfected in the future because quantitative and qualitative methods should be combined to clarify the relationship between the known OM types(e.g.,pyrobitumen,solid bitumen,and solid kerogen)and the OM types identified in this study.
文摘This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron microscopy,high-pressure mercury intrusion,and petrophysical testing to systematically evaluate reservoir petrographic features and pore structures.Results reveal that Benxi Formation sandstones predominantly comprise quartz sandstones,lithic quartz sandstones,and lithic sandstones,characterized by high quartz content,widespread volcanic lithic fragments,moderately well-sorted grains,and complex cement types.Pore types are dominated by residual intergranular and dissolution pores,with minor intracrystalline pores and fractures;overall porosity ranges from 0.17%to 9.07%(average 4.74%),and permeability from 0.01 to 6.05 mD,classifying them as ultra-low porosity and tight reservoirs.High-pressure mercury intrusion indicates microfine throats as the primary structure,divisible into four distinct types.Diagenetically,compaction and cementation are the main drivers of primary pore loss and reservoir tightening,whereas late-stage dissolution partially ameliorates pore networks.Overall,Benxi Formation sandstone reservoirs exhibit pervasive densification but localized favorable pore assemblages and connectivity,facilitating hydrocarbon migration and accumulation.These findings advance understanding of Upper Paleozoic tight sandstone reservoir characteristics and aid in predicting sweet spots.
基金supported by the National Natural Science Foundation of China(Grant Nos.42172159,42302143,and 52404048).
文摘Clarifying the pore structure characteristics of shale reservoirs,which are low porosity,low permeability and high heterogeneity,is an essential prerequisite for the efficient development of shale oil and gas.Fractal theory is especially suited for characterizing the complex pore structures of shales.This work compares the pore structure characteristics between marine shales from the Longmaxi Formation and continental shales from the Shahejie Formation through low-temperature nitrogen adsorption,nuclear magnetic resonance,and scanning electron microscopy.Different fractal scaling models are adopted to determine the fractal dimensions and lacunarities of shales by low-temperature nitrogen adsorption data and scanning electron microscopy images.In addition,the mineral compositions from X-ray diffraction are analyzed to elucidate the mechanisms by which mineral content influences fractal dimensions.Finally,the correlations between total organic carbon content and microscopic structure are discussed.These results indicate that the pore size of marine shale is smaller than that of continental shale.Additionally,the fractal dimensions of marine shales are greater than that of continental shales,suggesting a more complex pore structure.The more quartz and clay content lead to greater complexity in pore space,resulting in higher fractal dimensions.The illite/smectite mixed layer shows a strong positive correlation with fractal dimensions for marine shales,whereas this correlation is less pronounced for continental shales.The presence of microfractures in organic matter leads to a reduction for the pore surface fractal dimension in continental shales.
基金supported from the Opening fund of State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development(33550000-22-ZC0613-0297)National Natural Science Foundation of China(42102196)the Natural Science Basis Research Plan in Shaanxi Province of China(2022JM-147).
文摘Pore structure directly affects the occurrence and migration of shale hydrocarbon,and the lack of research on the mechanism of the pore structure is an important reason for the hindrance of shale hydrocarbon exploration.By analysing the geochemistry and reservoir characteristics of Jurassic lacustrine shales in Sichuan Basin,this study recovers their paleoenvironments and further discusses paleoenvironmental constraints on pore structure.The results show that the Lower Jurassic lacustrine shales in the Sichuan Basin are in a warm and humid semi-anoxic to anoxic lake environment with high productivity,a strong stagnant environment,and a rapid sedimentation rate,with water depths ranging from about 11.54-55.22 m,and a mixture of type Ⅱ/Ⅲ kerogen is developed.In terms of reservoir characteristics,they are dominated by open-slit pores,and the pores are relatively complex.The percentage of mesopores is the highest,while the percentage of macropores is the lowest.Further analysis shows that paleoclimate controls the overall pore complexity and surface relaxation of shales by influencing the weathering rate of mother rocks.Paleoredox conditions control the proportion and complexity of shale pores by influencing TOC content.The research results will provide theoretical basis for improving the exploration efficiency of lacustrine shale resources and expanding exploration target areas.
基金supported by the National Natural Science Foundation of China(Grant No.42102223)the Chinese Postdoctoral Science Foundation(Grant Nos.2021M693844,2022T150284)+1 种基金the Chinese Geological Survey Project(Grant No.DD20160204-3)the discipline innovation team of Liaoning Technical University(Grant Nos.LNTU20TD-14,LNTU20TD-30)。
文摘Coal pore parameters are closely related to macrolithotypes and coal structures,having a large influence over the gas potential and productivity of coalbed methane(CBM).The Middle Jurassic Xishanyao Formation,located in the southern Junggar Basin of northwestern China,has geological conditions with rich CBM resources.The 46 Xishanyao coal samples gathered from the drilling cores and coal mines cover 4 types of macrolithotypes(bright coal 1,semi-bright coal 2,semi-dull coal 3,and dull coal 4)and 2 types of coal structures(primary coal I and cataclastic coal II).Based on a range of pore testing experiments and analytical methods,the dual effects of different macrolithotypes and coal structures on pore structures were intensely studied.The results showed that the specific surface area(SSA)and total pore volume(TPV)of coal samples increased gradually from bright to dull coals.For the same macrolithotypes,the SSA and TPV of the primary coals were lower than those of the cataclastic coals.Generally,the pore structures of bright and semi-bright coals are simpler when compared to semi-dull and dull coals with the same coal structure,whereas cataclastic coals have more complicated pore structure systems than primary coals with the same macrolithotypes.The bright and semi-bright coals have higher vitrinite contents and more endogenous fractures,whereas well-developed structural fractures were identified in cataclastic coals.Therefore,bright and semi-bright coals have better pore connectivity than semi-dull and dull coals with the same coal structure,the pore connectivity of cataclastic coals being slightly better than that of primary coals under the same macrolithotypes.In terms of the CBM adsorption conditions,the eight type samples formed a descending order:Ⅱ-4>I-4>Ⅱ-3>Ⅰ-3>Ⅱ-2>Ⅰ-2>Ⅱ-1>Ⅰ-1,while they ranked as follows when consideration was given to the CBM seepage capacities:II-2>Ⅱ-1>Ⅰ-2>Ⅰ-1>Ⅰ-3>Ⅰ-4>Ⅱ-3>Ⅱ-4.As a result,it could be determined that the bright and semi-bright coals had stronger adsorption capacities,whereas the cataclastic coals had better pore connectivity and seepage capacities.Pore structure characteristics should be analysed under the dual control of different macrolithotypes and coal structures,so that they can provide greater value for guiding CBM exploration and exploitation,as along for preventing underground gas accidents.
基金Supported by Key Scientific and Technological Projects of Sinopec(No.P21104-2).
文摘The pore structure of rocks significantly influences the porosity and permeability of reservoirs and the migration ability of oil and gas,and being the key task on the development of volcanic gas reservoirs.Nine volcanic rock samples from the Yingcheng Formation and Huoshiling Formation in the Longfengshan area of the Changling Fault Depression in the Songliao Basin were selected for this study.The pore structures of the volcanic rocks in the study area were investigated using high-pressure mercury injection,X-ray diffraction combined with fractal theory.The relationships between the fractal dimension and physical properties characteristics,pore structure parameters,and mineral content were analyzed to provide guidance for the development of volcanic rock gas reservoirs.The results show that the reservoir can be divided into 3 types(I,II,and III)based on the shape of the capillary pressure curve,and the physical properties deteriorate successively.Different types of reservoirs exhibit different fractal characteristics.For typesⅠ,ⅡandⅢ,the average total fractal dimensions were 2.3418,2.6850,and 2.9203,respectively.The larger the fractal dimension,the stronger the heterogeneity of reservoir.A small number of macro-pores primarily contributed to permeability.The fractal dimension was negatively correlated with porosity and permeability.The fractal dimension of the rock was strongly correlated with quartz and feldspar contents,and the mineral composition and content are closely related to the pore evolution of the reservoir,which are the internal factors affecting the fractal dimension of volcanic rock.
基金Project(41877240)supported by the National Natural Science Foundation of China。
文摘As a typical sedimentary soft rock,mudstone has the characteristics of being easily softened and disintegrated under the effect of wetting and drying(WD).The first cycle of WD plays an important role in the entire WD cycles.X-ray micro-computed tomography(micro-CT)was used as a non-destructive tool to quantitatively analyze microstructural changes of the mudstone due to the first cycle of WD.The test results show that WD leads to an increase of pore volume and pore connectivity in the mudstone.The porosity and fractal dimension of each slice of mudstone not only increase in value,but also in fluctuation amplitude.The pattern of variation in the frequency distribution of the equivalent radii of connected,isolated pores and pore throats in mudstone under WD effect satisfies the Gaussian distribution.Under the effect of WD,pores and pore throats with relatively small sizes increase the most.The sphericity of the pores in mudstones is positively correlated with the pore radius.The WD effect transforms the originally angular and flat pores into round and regular pores.This paper can provide a reference for the study of the deterioration and catastrophic mechanisms of mudstone under wetting and drying cycles.
基金support of the National Natural Science Foundation of China(Grant Nos.52174030,52474042 and 52374041)the Postgraduate Innovation Fund Project of Xi'an Shiyou University(No.YCX2411001)the Natural Science Basic Research Program of Shaanxi(Program Nos.2024JCYBMS-256 and 2022JQ-528)。
文摘Complex physical and chemical reactions during CO_(2)sequestration alter the microscopic pore structure of geological formations,impacting sequestration stability.To investigate CO_(2)sequestration dynamics,comprehensive physical simulation experiments were conducted under varied pressures,coupled with assessments of changes in mineral composition,ion concentrations,pore morphology,permeability,and sequestration capacity before and after experimentation.Simultaneously,a method using NMR T2spectra changes to measure pore volume shift and estimate CO_(2)sequestration is introduced.It quantifies CO_(2)needed for mineralization of soluble minerals.However,when CO_(2)dissolves in crude oil,the precipitation of asphaltene compounds impairs both seepage and storage capacities.Notably,the impact of dissolution and precipitation is closely associated with storage pressure,with a particularly pronounced influence on smaller pores.As pressure levels rise,the magnitude of pore alterations progressively increases.At a pressure threshold of 25 MPa,the rate of change in small pores due to dissolution reaches a maximum of 39.14%,while precipitation results in a change rate of-58.05%for small pores.The observed formation of dissolution pores and micro-cracks during dissolution,coupled with asphaltene precipitation,provides crucial insights for establishing CO_(2)sequestration parameters and optimizing strategies in low permeability reservoirs.
基金financially supported by the National Natural Science Foundation of China (Grant No. 42002133)Science Foundation of China University of Petroleum,Beijing No.2462024XKBH009+1 种基金the 2022 AAPG Foundation Grants-in-Aid ProgramChina National Postdoctoral Science Foundation(BX20240425 and 2024M753611)
文摘With the development of unconventional hydrocarbon, how to improve the shale oil and gas recovery become urgent. Therefore hydraulic fracturing becomes the key due to the complicated properties of the reservoirs. The pore structure not only plays an essential role in the formation of complex fracture networks after fracturing but also in resource accumulation mechanism analyses. The lacustrine organicrich shale samples were selected to carry out petrophysical experiments. Scanning Electron Microscopy(SEM) and X-ray Diffraction were performed to elucidate the geology characteristics. MICP, 2D NMR, CT,and N2adsorption were conducted to classify the pore structure types. The contribution of pore structure to oil accumulation and hydrocarbon enrichment was explained through the N2adsorption test on the original and extracted state and 2D NMR. The results show that micropores with diameter less than20 nm are well-developed. The pore structure was divided into three types. Type Ⅰ is characterized by high porosity, lower surface area, and good pore throat connectivity, with free oil existing in large pores,especially lamellation fractures. The dominant nano-pores are spongy organic pores and resources hosted in large pores have been expelled during high thermal evolution. The content of nano-pores(micropores) increases and the pore volume decreases in Type Ⅱ pore structure. In addition, more absorbed oil was enriched. The pore size distribution of type Ⅱ is similar to that of type Ⅰ. However, the maturity and hydrocarbon accumulation is quite different. The oil reserved in large pores was not expelled attributed to the relatively low thermal evolution compared with type Ⅰ. Structural vitrinite was observed through SEM indicating kerogen of type Ⅲ developed in this kind of reservoir while the type of kerogen in pore structure Ⅰ is type Ⅱ. Type Ⅲ pore structure is characterized by the largest surface area,lowest porosity, and almost isolated pores with rarely free oil. Type Ⅰ makes the most contribution to hydrocarbon accumulation and immigration, which shows the best prospect. Of all of these experiments,N2adsorption exhibits the best in characterizing pores in shales due to its high resolution for the assessment of nano-scale pores. MICP and NMR have a better advantage in characterizing pore space of sandstone reservoirs, even tight sandstone reservoirs. 2D NMR plays an essential role in fluid recognition and saturation calculation. CT scanning provides a 3D visualization of reservoir space and directly shows the relationship between pores and throats and the characteristics of fractures. This study hopes to guide experiment selection in pore structure characterization in different reservoirs. This research provides insight into hydrocarbon accumulation of shales and guidance in the exploration and development of unconventional resources, for example for geothermal and CCUS reservoirs.
基金Projects(52204226,52104204,52474276)supported by the National Natural Science Foundation of ChinaProject(tsqnz20221140)supported by the Taishan Scholars Project of China+1 种基金Projects(ZR2022QE243,ZR2024ME097)supported by the Natural Science Foundation of Shandong Province of ChinaProject(252300421010)supported by the Excellent Youth Foundation of Henan Scientific Committee,China。
文摘The geological structure of coal seams in China is remarkably varied and complex,with coalbed methane reservoirs marked by significant heterogeneity and low permeability,creating substantial technical challenges for efficient extraction.This study systematically investigates the impact of liquid nitrogen immersion(LNI)on the coal’s pore structure and its mechanism of enhancing permeability with a combination of quantitative nuclear magnetic resonance(NMR)analysis,nitrogen adsorption experiments,and fractal dimension calculations.The results demonstrate that LNI can damage the coal’s pore structure and promote fracture expansion through thermal stress induction and moisture phase transformation,thereby enhancing the permeability of coal seams.The T_(2)peak area in the NMR experiments on coal samples subjected to LNI treatment shows a significant increase,the Brunauer-Emmett-Teller(BET)specific surface area decreases to 6.02 m^(2)/g,and the Barrett-Joyner-Halenda(BJH)total pore volume increases to 14.99 mm^(3)/g.Furthermore,changes in fractal dimensions(D_(1)rising from 2.804 to 2.837,and D_(2)falling from 2.757 to 2.594)indicate a notable enhancement in the complexity of the pore structure.With increasing LNI cycles,the adsorption capacity of the coal samples diminishes,suggesting a significant optimization of the pore structure.This optimization is particularly evident in the reconstruction of the micropore structure,which in turn greatly enhances the complexity and connectivity of the sample’s pore network.In summary,the study concludes that LNI technology can effectively improve the permeability of coal seams and the extraction efficiency of coalbed methane by optimizing the micropore structure and enhancing pore connectivity,which offers a potential method for enhancing the permeability of gas-bearing coal seams and facilitating the development and utilization of coalbed methane.
基金Hunan Provincial Department of Water Resources:Research on Formula Optimization and Performance Evaluation System of Ecological Concrete for River Water Quality Purification Based on the Dual Carbon Goal(Project No.:XSKJ2024064-44)。
文摘By adding zeolite aggregate with good adsorption properties,different mix ratios of added zeolite pervious concrete(ZPC)were designed to compare the water purification effect of ordinary pervious concrete and water purification tests that were conducted.The pore characteristics of the pervious concrete were identified using three-dimensional reconstruction software and the relationship between pore structure and water purification performance was quantified by gray entropy correlation analysis.The results showed that the purification efficiency of zeolite-doped pervious concrete was 17.6%-22.3%higher than that of ordinary pervious concrete.The characteristic parameters of the pore structure of permeable concrete,i.e.planar porosity and tortuosity,were determined using three-dimensional reconstruction software.The correlation between the degree of tortuosity and the removal rate reached more than 0.90,indicating that the internal pore structure of pervious concrete has a good correlation with the water purification performance.
基金supported by National Natural Science Foundation of China(Grant No.52364004)the Guizhou Provincial Science and Technology Foundation(Grant No.GCC[2022]005-1).
文摘Liquid nitrogen(LN_(2))and microwave are the alternative methods for reservoir fracturing,which are rarely combined.To investigate the combined effects,sandstone is frozen with LN_(2)before microwave heating(MI),and nuclear magnetic resonance(NMR),ultrasonic wave,and infrared thermal imaging(ITI)are used to understand the pore structures,moisture change,and surface temperature of the sandstone samples.With the heating time,the average surface temperature of the combining-treatment samples firstly increases from the room temperature(25℃)to 144.7℃(65 s)fast,and then increases slowly to 176.6℃(95 s).For the individual MI,the temperature increases to 146.7℃at 65 s.As 30 min of LN_(2)freezing,the samples perform well in removing pore water during heating.The NMR results show that after LN_(2)freezing,the seepage pores and total pores increase by 2.93%and 4.11%,respectively,and the pore connectivity enhances.However,the individual MI performs weak in enhancing the pore structures,forming a high vapor pressure(0.428 MPa at 65 s)and causing burst after 65 s.Due to the improved pore connectivity,the vapor pressure(0.378 MPa)and temperature are small at 65 s,and burst can be avoided.After freezing,the wave velocity decreases by 13.48%and the damage variable reaches 0.251.The velocity attenuation rates and damage variable gradually increase with heating time;under the same duration,the two variables of the combining treatments are greater than that of the individual treatments.This can prove a reference for gas production in sandstone reservoirs.
基金supported by the National Natural Science Foundation of China (Grant No. 42002139)the Basic Prospective Project of SINOPEC (Grant No. P23240-3)。
文摘Tight oil is the most viable target for unconventional oil and gas exploration, but the complexity of micro-/nanopore throat systems significantly affects the oil content of reservoirs. To investigate the causes of heterogeneity in oil-bearing reservoirs, a high-pressure mercury injection experiment combined with fractal theory was conducted to analyze the micro pore throat structure characteristics of the tight sandstone of Chang 7 Member reservoirs in the Ordos Basin. The factors controlling the variations in oil content among tight sandstone samples were identified based on mineral composition characteristics. The results indicate that the pore throat radius distribution is mainly unimodal an bimodal. In oil-bearing samples, the pore throat distributions align well with the corresponding permeability contribution curves, while in oil-free samples, there is a clear deviation from these curves. Mesopore throats exert the greatest influence on seepage capacity. Differences in fractal characteristics are primarily reflected in D1 values, with oil-free samples exhibiting D1 values close to 3, indicating an extremely nonuniform pore throat structure at this scale. The content of quartz, plagioclase, and chlorite is significantly higher in oil-bearing samples than in oil-free samples, whereas calcite content is lower in oil-bearing samples. There is a positive correlation between the contents of quartz, plagioclase, and chlorite with D1;their increased presence contributes to a more favorable pore throat structure.Conversely, the calcite contents show an inverse relationship with D1. Cementation increases the complexity of pore throat structures, while multiple diagenetic processes simultaneously control these characteristics, leading to variations in oil content.
