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
Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH ...Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH solution using electrochemical methods and immersion test. Effect of porous structures on the corrosion behavior of the porous Ni3Al intermetallics was studied. The results indicate that the porous Ni3Al intermetallics with higher porosities suffer more serious corrosion than the ones with lower porosities because the complicated interconnected porous structures and the large true surface areas exist in the samples with a higher porosity. But the corrosion rates of the porous Ni3Al intermetallics are not proportional to the true surface areas. The reason is that the pore size, pore size distribution and pore shape of the porous Ni3Al intermetallics change with the increasing porosity. All the porous Ni3Al intermetallics with different porosities exhibit excellent corrosion resistance in a strong alkali solution.展开更多
We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective mediu...We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models.By analyzing the measured data from carbonate samples in the TL area,a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed,which is a prerequisite in the analysis of carbonate reservoirs.A workflow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model.We performed numerical experiments and compared the theoretical prediction and measured data.The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs.The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.展开更多
Hydrophilic characteristics of rocks are affected by their microscopic pore structures,which clearly change after water absorption.Water absorption tests and scanning electron microscopic（SEM） experiments on rock sa...Hydrophilic characteristics of rocks are affected by their microscopic pore structures,which clearly change after water absorption.Water absorption tests and scanning electron microscopic（SEM） experiments on rock samples,located at a site in Tibet,China,were carried out Changes of rock pore structures before and after water absorption were studied with the distribution of pore sizes and fractal characteristics of pores.The results show that surface porosities,fractal dimensions of pores and the complexity of pore structures increased because the number of new small pores produced increased or the original macropore flow channels were expanded after rocks absorbed water.There were points of inflection on their water absorption curves.After water absorption of other rocks,surface porosities and fractal dimensions of pores and complexity of pore structures decreased as the original pore flow channels became filled.Water absorption curves did not change.Surface porosity and the pore fractal dimensions of rocks have good linear relationships before and after water absorption.展开更多
Co–Mo catalysts applied on the hydrodesulfurization（HDS） for FCC gasoline were prepared with Zn–Al layered double hydroxides（LDHs） to improve their performances,and the effects of pore structures and acidity on ...Co–Mo catalysts applied on the hydrodesulfurization（HDS） for FCC gasoline were prepared with Zn–Al layered double hydroxides（LDHs） to improve their performances,and the effects of pore structures and acidity on HDS performances were studied in detail. A series of Zn–Al/LDHs samples with different pore structures and acidities are synthesized on the bases of co-precipitation of OH-,CO2-,Al3＋,and Zn2＋. The neutralization p H is a main factor to affect the pore structures and acidity of Zn–Al/LDHs,and a series of Zn–Al/LDHs with different pore structures and acidities are obtained. Based on the representative samples with different specific surface areas（SBET） and acidities,three Co Mo/LDHs catalysts were prepared,and their HDS performances were compared with traditional Co Mo/Al2O3 catalysts. The results indicated that catalysts prepared with high SBETpossessed high HDS activity,and Br？nsted acid sites could reduce the thiol content in the product to some extent. All the three catalysts prepared with LDHs displayed little lower HDS activity but higher selectivity than Co Mo/Al2O3,and could restrain the reactions of re-combination between olefin and H2 S which could be due to the existence of Br？nsted acid sites.展开更多
Three cement samples were prepared, includi ng OPC consisted of 100wt% portland cement, PFA consisted of 70wt% portland cemen t and 30wt% fly-ash, and CA consisted of 70wt% portland cement and 30wt% modifi ed fly ash...Three cement samples were prepared, includi ng OPC consisted of 100wt% portland cement, PFA consisted of 70wt% portland cemen t and 30wt% fly-ash, and CA consisted of 70wt% portland cement and 30wt% modifi ed fly ash. The strength of hardened cement paste of these samples was tested an d their pore structures were determined by a mercury intrusion porosimeter. More over,the data of the pore structures of three samples were comprehensively analy zed. The relations between the pore structures and the compressive strength of t he three samples were studied. The experimental results show that the relations between the porosity determined by the mercury intrusion porosimeter and the com pressive strength are not notable, and the total pore surface area, the average pore diameter and the median pore diameter could be used to explain the differen ce of the strength of the tested samples.展开更多
Based on the experiments of nitrogen gas adsorption(N_2 GA) and nuclear magnetic resonance(NMR),the multifractal characteristics of pore structures in shale and tight s andstone from the Chang 7 member of Trias sic Ya...Based on the experiments of nitrogen gas adsorption(N_2 GA) and nuclear magnetic resonance(NMR),the multifractal characteristics of pore structures in shale and tight s andstone from the Chang 7 member of Trias sic Yanchang Formation in Ordos Basin,NW China,are investigated.The multifractal spectra obtained from N2 GA and NMR are analyzed with pore throat structure parameters.The results show that the pore size distributions obtained from N2 GA and NMR are different,and the obtained multifractal characteristics vary from each other.The specific surface and total pore volume obtained by N2 GA experiment have correlations with multifractal characteristics.For the core samples with the similar specific surface,the value of the deviation of multifractal spectra Rd increases with the increase in the proportion of large pores.When the proportion of macropores is small,the Rd value will increase with the increase in specific surface.The multifractal characteristics of pore structures are influenced by specific surface area,average pore size and adsorption volume measured from N2 GA experiment.The multifractal characteristic parameters of tight sandstone measured from NMR spectra are larger than those of shale,which may be caused by the differences in pore size distribution and porosity of shale and tight sandstone.展开更多
The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations...The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation(LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.展开更多
Microcosmic details of pore structure are the essential factors affecting the elastic properties of tight sandstone reservoirs,while the relationships in between are still incompletely clear due to the fact that quant...Microcosmic details of pore structure are the essential factors affecting the elastic properties of tight sandstone reservoirs,while the relationships in between are still incompletely clear due to the fact that quantitative or semi-quantitative experiments are hard to achieve.Here,three sets of tight sandstone samples from the Junggar Basin are selected elaborately based on casting thin sections,XRD detection,and petro-physical measurement,and each set is characterized by a single varied microcosmic factor(pore connectedness,pore type,and grain size)of the pore structure.An ultrasonic pulse transmission technique is conducted to study the response of elastic properties to the varied microcosmic details of pore structure in the situation of different pore fluid(gas,brine,and oil)saturation and confining pressure.Observations show samples with less connectedness,inter-granular dominant pores,and smaller grain size showed greater velocities in normal conditions.Vpis more sensitive to the variations of pore type,while Vsis more sensitive to the variations of grain size.Samples with better connectedness at fluid saturation(oil or brine)show greater sensitivity to the confining pressure than those with gas saturation with a growth rate of 6.9%-11.9%,and the sensitivity is more likely controlled by connectedness.The pore types(inter-granular or intra-granular)can be distinguished by the sensitivity of velocities to the variation of pore fluid at high confining pressure(>60 MPa).The samples with small grain sizes tend to be more sensitive to the variations of confining pressure.With this knowledge,we can semi-quantitatively distinguish the complex pore structures with different fluids by the variation of elastic properties,which can help improve the precision of seismic reservoir prediction for tight sandstone reservoirs.展开更多
The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation ...The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.展开更多
A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 c...A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.展开更多
Open-celled porous （TiB2-Al2O3）/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis （SHS）. Effects of 10Al-3B2O3-3TiO2 conten...Open-celled porous （TiB2-Al2O3）/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis （SHS）. Effects of 10Al-3B2O3-3TiO2 contents （0-20 wt%） on the pore structures and the quasi-static compressive behaviors of the resultant materials were investigated. The porous （TiBE-Al2O3）/NiAl composites exhibit composite pore structure consisting of homogeneously distributed and interconnected millimeter pores and micropores. The millimeter pores virtually inherit the shape and size of carbamide particles, while the pore size of micropores increases with increasing the 10Al-3BEO3-3TiO2 content. Depending on the volume fraction of the carbamide, the porosity of the porous materials can be easily controlled in a range of 55%-85%. When the porosity is about 72%, the compressive strengths of porous NiAl and porous （TiBE-Al203）/NiAl composite with 15% 10Al-3B2O3-3TiO2 in green compact are 19 and 32 MPa, and the corresponding strains are 2.9% and 5.7%, respectively. Furthermore, the quasi-static compressive behavior of porous （TiB2-AlEO3）/NiAl composites can be estimated by Gibson-Ashby model.展开更多
Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we syst...Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we systematically study the microscopic pore structures of shales by using Argon-ion polishing Scanning Electron Microscope(SEM),high-pressure mercury injection and low-temperature nitrogen adsorption and desorption experiments.The study results show that:the Longmaxi Shale in this area are dominated by nano-scale pores which can be classified into organic pores,inorganic pores(intergranular pores,intragranular pores,inter-crystalline pores and dissolution pores),microfractures(intragranular structure fractures,interlayer sliding fractures,diagenetic shrinkage joints and abnormal-pressure fractures from organic evolution),among which organic pores and clay mineral pores are predominant and organic pores are the most common;a TOC value shows an obvious positive correlation with the content of organic pores,which account for up to 50%in the lower-quality shales with a TOC of over 2%where they are most developed;microscopic pore structures are very complex and open,with pores being mainly in cylinder shape with two ends open,or in parallel tabular shape with four sides open and 2–30 nm in diameter,being mostly medium pores.On this basis,factors affecting the micropore structures of shales in this area are studied.It is concluded that organic matter abundance and thermal maturity are the major factors controlling the microscopic pore structures of shales,while the effects of clay mineral content are relatively insignificant.展开更多
High-temperature infrared-regulating ceramics are essentialfoerxtreme-environmentapplicationsrequiring broadband infrared reflection(1-6μm),such as spacecraft thermal protection,military stealth systems,and related f...High-temperature infrared-regulating ceramics are essentialfoerxtreme-environmentapplicationsrequiring broadband infrared reflection(1-6μm),such as spacecraft thermal protection,military stealth systems,and related fields.Precise control of pore structures is crucial for enhancing ceramic infrared reflectance,as pores directly influence the scattering intensity and scattering path of radiation.However,achieving broadband reflectance above 0.9 remains challenging because of unclear pore-radiation interaction mechanisms and insufficient structural control.This study employs optical simulations to systematically analyze how pore parameters enhance infrared reflectance.The results demonstrate that pore sizes matching the infrared wavelength,highaspect ratios,and aligned orientations synergistically enhance reflection.Guided by simulations,directional pore-structured yttria-stabilized zirconia(YSZ)ceramics were fabricated via a rolling extrusion method using graphite flakes as sacrificial templates.The optimized ceramics exhibited tailored pore parameters(size:0.2-6μm,aspect ratio:3.2-3.9,orientation angle:<30°),achieving exceptional infrared reflectance(>0.9).This study clarifies pore-radiation interactions and presents a scalable strategy to produce advanced thermal shielding materials.展开更多
To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with g...To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with graphene oxide(GO).The micro-pore structure of GOPM is characterized using LF-NMR and SEM.Fractal theory is applied to calculate the fractal dimension of pore volume,and the deterioration patterns are analyzed based on the evolution characteristics of capillary pores.The experimental results indicate that,after 25 salt-freeze-thaw cycles(SFTc),SO2-4 ions penetrate the matrix,generating corrosion products that fill existing pores and enhance the compactness of the specimen.As the number of cycles increases,the ongoing formation and expansion of corrosion products within the matrix,combined with persistent freezing forces,and result in the degradation of the pore structure.Therefore,the mass loss rate(MLR)of the specimens shows a trend of first decreasing and then increasing,while the relative dynamic elastic modulus(RDEM)initially increases and then decreases.Compared to the PC group specimens,the G3PM group specimens show a 28.71% reduction in MLR and a 31.42% increase in RDEM after 150 SFTc.The fractal dimensions of the transition pores,capillary pores,and macropores in the G3PM specimens first increase and then decrease as the number of SFTc increases.Among them,the capillary pores show the highest correlation with MLR and RDEM,with correlation coefficients of 0.97438 and 0.98555,respectively.展开更多
Reactive melt infiltration(RMI)is an effective method for fabrication of highly dense carbon fiber reinforced ultra-high temperature ceramic matrix composites(Cf/UHTCs).In this work,C_(f)/SiC-ZrC-ZrB_(2)composites wer...Reactive melt infiltration(RMI)is an effective method for fabrication of highly dense carbon fiber reinforced ultra-high temperature ceramic matrix composites(Cf/UHTCs).In this work,C_(f)/SiC-ZrC-ZrB_(2)composites were fabricated by infiltrating ZrSi_(2)melt into porous C_(f)/B_(4)C-C preforms,where the physical and chemical reactions involved during the RMI process were identified and analyzed.Inhomogeneous infiltration between the inter-and intra-bundle pores was revealed,and was found to be strongly related to the pore structures of the C_(f)/B_(4)C-C preform.It is indicated that the inhomogeneous infiltration can be mitigated remarkably with increasing porosity and pore size of the preform.The effect of pore size on the RMI process was also investigated by a quantitative model,which agrees very well with the experiment results.It further indicates that the inhomogeneous infiltration can also be relieved at elevated RMI temperature.However,excessive infiltration at elevated temperature or more porous preform may cause serious erosion on interphase and fibers,leading to mechanical properties deterioration of the final composites.展开更多
CO_(2)sequestration/storage shows considerable impacts on the pore structures and compressive strength of concrete.This paper presents a study in which coral aggregates were presoaked in Ca(OH)_(2) slurries with diffe...CO_(2)sequestration/storage shows considerable impacts on the pore structures and compressive strength of concrete.This paper presents a study in which coral aggregates were presoaked in Ca(OH)_(2) slurries with different solid-to-liquid ratios(i.e.0.2,0.4,and 0.6 g/mL)followed by accelerated carbonation.The effects of CO_(2)sequestration on the particle size distribution,cylinder compressive strength,water absorption,and apparent density of coral aggregate were investigated.The evolution of pore structures in coral aggregate concrete after CO_(2)sequestration was also studied.Additionally,the effect of CO_(2)sequestration on the development of compressive strength of coral aggregate concrete was explored.The results showed that CO_(2)sequestration affected the properties of coral aggregate.Moreover,the porosity of CaCO_(3) formed by CO_(2)sequestration was the highest in the concrete.With the increase of solidto-liquid ratio,the porosity of cement pastes and the CaCO_(3) increased,and more big pores existed in the cement pastes and CaCO_(3).Furthermore,the compressive strength of coral aggregate concrete when the solid-to-liquid ratio was 0.2 g/mL increased compared with that before CO_(2)sequestration,but the compressive strength reduced when the ratio increased to 0.6 g/mL.展开更多
1 Introduction Immobilization of homogeneous catalysts onto polymer supports through covalent attachment has received wide attention because these materials offer advantage features of heterogeneous catalysis to homog...1 Introduction Immobilization of homogeneous catalysts onto polymer supports through covalent attachment has received wide attention because these materials offer advantage features of heterogeneous catalysis to homogeneous systems.The polymer-supported catalysts enhance their thermal stability,selectivity,recyclability and easy separation from reaction products leading to the operationally flexible[1-2].Such behaviour prompted us to know the effect of pore structures of polymer supporters on catalytic ...展开更多
Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling....Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.展开更多
The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and signi...The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and significantly variable gas contents of the drilled shales.Excitingly,the first major breakthrough in deep and ultra-deep Lower Cambrian shale gas was made recently in the well Z201 in the southern Sichuan Basin,with a gas yield exceeding 73×10^(4)m^(3)/d.The success of well Z201 provides a favorable geological case to reveal the distinct enrichment mechanism of deep and ultra-deep Lower Cambrian shale gas.In this study,at drilling site of well Z201,fresh shale core samples with different gasin-place contents were collected,and their geochemical,pore development and water-bearing characteristics were analyzed systematically.The results showed that the Z201 organic-rich shales reached an overmature stage,with an average Raman maturity of 3.70%.The Z201 shales with high gas-in-place contents are mainly located in the Qiongzhusi 12section and the upper Qiongzhusi 11section,with an average gas-in-place content of 10.08 cm^(3)/g.Compared to the shales with low gas-in-place contents,the shales with high gas-in-place contents exhibit higher total organic carbon contents,greater porosities,and lower water saturations,providing more effective pore spaces for shale gas enrichment.The effective pore structures of the deep and ultra-deep Lower Cambrian shales are the primary factors affecting their gas-in-place contents.Similar to the shales with high gas-in-place contents of well Z201,the deep and ultra-deep Lower Cambrian shales in the Mianyang-Changning intracratonic sag,especially in the Ziyang area,generally developed in deep-water shelf facies with high total organic carbon contents and thick sedimentary thickness,providing favorable conditions for the development and preservation of effective pores.Therefore,they are the most promising targets for Lower Cambrian shale gas exploration.展开更多
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Project(2009CB623406)supported by the National Basic Research Program of ChinaProject(12JJ4044)supported by the Natural Science Foundation of Hunan Province,ChinaProject(13C902)supported by the Scientific Research Fund of Hunan Provincial Education Department,China
文摘Porous Ni3Al intermetallics were fabricated by elemental powder reactive synthesis method, using carbamide powders as space holders. Corrosion behavior of porous Ni3Al intermetallics was investigated in a 6 mol/L KOH solution using electrochemical methods and immersion test. Effect of porous structures on the corrosion behavior of the porous Ni3Al intermetallics was studied. The results indicate that the porous Ni3Al intermetallics with higher porosities suffer more serious corrosion than the ones with lower porosities because the complicated interconnected porous structures and the large true surface areas exist in the samples with a higher porosity. But the corrosion rates of the porous Ni3Al intermetallics are not proportional to the true surface areas. The reason is that the pore size, pore size distribution and pore shape of the porous Ni3Al intermetallics change with the increasing porosity. All the porous Ni3Al intermetallics with different porosities exhibit excellent corrosion resistance in a strong alkali solution.
基金supported by the National Natural Science Foundation of China(No.41274136)
文摘We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models.By analyzing the measured data from carbonate samples in the TL area,a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed,which is a prerequisite in the analysis of carbonate reservoirs.A workflow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model.We performed numerical experiments and compared the theoretical prediction and measured data.The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs.The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.
基金Financial support for this work,provided by the Key Basic Research Program of China(Nos.2010CB226800 and 2007CB202200)National Natural Science Foundation of China(No. 50490270)the Innovation Team Development Program of the Ministry of Education of China(No.IRT0656)
文摘Hydrophilic characteristics of rocks are affected by their microscopic pore structures,which clearly change after water absorption.Water absorption tests and scanning electron microscopic（SEM） experiments on rock samples,located at a site in Tibet,China,were carried out Changes of rock pore structures before and after water absorption were studied with the distribution of pore sizes and fractal characteristics of pores.The results show that surface porosities,fractal dimensions of pores and the complexity of pore structures increased because the number of new small pores produced increased or the original macropore flow channels were expanded after rocks absorbed water.There were points of inflection on their water absorption curves.After water absorption of other rocks,surface porosities and fractal dimensions of pores and complexity of pore structures decreased as the original pore flow channels became filled.Water absorption curves did not change.Surface porosity and the pore fractal dimensions of rocks have good linear relationships before and after water absorption.
文摘Co–Mo catalysts applied on the hydrodesulfurization（HDS） for FCC gasoline were prepared with Zn–Al layered double hydroxides（LDHs） to improve their performances,and the effects of pore structures and acidity on HDS performances were studied in detail. A series of Zn–Al/LDHs samples with different pore structures and acidities are synthesized on the bases of co-precipitation of OH-,CO2-,Al3＋,and Zn2＋. The neutralization p H is a main factor to affect the pore structures and acidity of Zn–Al/LDHs,and a series of Zn–Al/LDHs with different pore structures and acidities are obtained. Based on the representative samples with different specific surface areas（SBET） and acidities,three Co Mo/LDHs catalysts were prepared,and their HDS performances were compared with traditional Co Mo/Al2O3 catalysts. The results indicated that catalysts prepared with high SBETpossessed high HDS activity,and Br？nsted acid sites could reduce the thiol content in the product to some extent. All the three catalysts prepared with LDHs displayed little lower HDS activity but higher selectivity than Co Mo/Al2O3,and could restrain the reactions of re-combination between olefin and H2 S which could be due to the existence of Br？nsted acid sites.
基金Funded by the National Key Fundamental Research and Develop ment Program of China(2001CB610703)
文摘Three cement samples were prepared, includi ng OPC consisted of 100wt% portland cement, PFA consisted of 70wt% portland cemen t and 30wt% fly-ash, and CA consisted of 70wt% portland cement and 30wt% modifi ed fly ash. The strength of hardened cement paste of these samples was tested an d their pore structures were determined by a mercury intrusion porosimeter. More over,the data of the pore structures of three samples were comprehensively analy zed. The relations between the pore structures and the compressive strength of t he three samples were studied. The experimental results show that the relations between the porosity determined by the mercury intrusion porosimeter and the com pressive strength are not notable, and the total pore surface area, the average pore diameter and the median pore diameter could be used to explain the differen ce of the strength of the tested samples.
基金supported by the National Natural Science Foundation of China(No.51874320)Scientific Research Foundation of China University of Petroleum,Beijing(No.2462017BJB11)。
文摘Based on the experiments of nitrogen gas adsorption(N_2 GA) and nuclear magnetic resonance(NMR),the multifractal characteristics of pore structures in shale and tight s andstone from the Chang 7 member of Trias sic Yanchang Formation in Ordos Basin,NW China,are investigated.The multifractal spectra obtained from N2 GA and NMR are analyzed with pore throat structure parameters.The results show that the pore size distributions obtained from N2 GA and NMR are different,and the obtained multifractal characteristics vary from each other.The specific surface and total pore volume obtained by N2 GA experiment have correlations with multifractal characteristics.For the core samples with the similar specific surface,the value of the deviation of multifractal spectra Rd increases with the increase in the proportion of large pores.When the proportion of macropores is small,the Rd value will increase with the increase in specific surface.The multifractal characteristics of pore structures are influenced by specific surface area,average pore size and adsorption volume measured from N2 GA experiment.The multifractal characteristic parameters of tight sandstone measured from NMR spectra are larger than those of shale,which may be caused by the differences in pore size distribution and porosity of shale and tight sandstone.
基金supported by the State Key Basic Research Program of China(No.2011CB201202)
文摘The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation(LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.
基金supported by the Open Fund(PLC2020002,PLC20190507)of the State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Chengdu University of Technology)National Natural Science Foundation of China(42004112,42274175,42030812,41974160)+1 种基金sponsored by Special projects of local science and technology development guided by the central government in Sichuan(2021ZYD0030)Natural Science Foundation of Sichuan Province(23NSFSC5311)
文摘Microcosmic details of pore structure are the essential factors affecting the elastic properties of tight sandstone reservoirs,while the relationships in between are still incompletely clear due to the fact that quantitative or semi-quantitative experiments are hard to achieve.Here,three sets of tight sandstone samples from the Junggar Basin are selected elaborately based on casting thin sections,XRD detection,and petro-physical measurement,and each set is characterized by a single varied microcosmic factor(pore connectedness,pore type,and grain size)of the pore structure.An ultrasonic pulse transmission technique is conducted to study the response of elastic properties to the varied microcosmic details of pore structure in the situation of different pore fluid(gas,brine,and oil)saturation and confining pressure.Observations show samples with less connectedness,inter-granular dominant pores,and smaller grain size showed greater velocities in normal conditions.Vpis more sensitive to the variations of pore type,while Vsis more sensitive to the variations of grain size.Samples with better connectedness at fluid saturation(oil or brine)show greater sensitivity to the confining pressure than those with gas saturation with a growth rate of 6.9%-11.9%,and the sensitivity is more likely controlled by connectedness.The pore types(inter-granular or intra-granular)can be distinguished by the sensitivity of velocities to the variation of pore fluid at high confining pressure(>60 MPa).The samples with small grain sizes tend to be more sensitive to the variations of confining pressure.With this knowledge,we can semi-quantitatively distinguish the complex pore structures with different fluids by the variation of elastic properties,which can help improve the precision of seismic reservoir prediction for tight sandstone reservoirs.
基金supported by the National Natural Science Foundation of China(Grant no.41704109)the Jiangsu Province Outstanding Youth Fund Project(Grant no.BK20200021).
文摘The wave-induced local fluid flow mechanism is relevant to the complex heterogeneity of pore structures in rocks.The analysis of the local fluid flow mechanism is useful for accurately describing the wave propagation characteristics in reservoir rocks.In the exploration and production of hydrocarbon reservoirs,the real stratum may be partially saturated with a multi-phase fluid mixture in general.Therefore,it is of great significance to investigate the wave velocity dispersion and attenuation features in relation to pore structures and fluids.In this work,the characteristics of fabric microstructures are obtained on the basis of pressure dependency of dry rock moduli using the effective medium theory.A novel anelasticity theoretical model for the wave propagation in a partially-saturated medium is presented by combining the extended Gurevich squirt-flow model and White patchysaturation theory.Numerical simulations are used to analyze wave propagation characteristics that depend on water saturation,external patchy diameter,and viscosity.We consider a tight sandstone from the Qingyang area of the Ordos Basin in west China and perform ultrasonic measurements under partial saturation states and different confining pressures,where the basic properties of the rock are obtained at the full gas saturation.The comparison of experimental data and theoretical modeling results shows a fairly good agreement,indicating that the new theory is effective.
基金Jiangsu Innovation and Entrepreneurship ProgramJiangsu Provincial Special Program of Medical Science (BL2012004)+3 种基金Jiangsu R&D Innovation Program (BY2014059-07)the Priority Academic Program Development of Jiangsu High Education Institutionsthe National Natural Science Foundation of China (No. 51472279)the Jiangsu Six Peak of Talents Program (2013-WSW-056) for financial supports
文摘A green biocompatible foaming method utilizing natural coconut oil and cornstarch was developed to fabricate highly porous functional ceramics with controllable strengths and pore structures. The poros- ity of A1203 ceramics prepared via this method reached 79.6%-86.9% while these ceramics maintained high compressive strengths of 2.2-5.5 MPa. More importantly, porous A1203 ceramic with a pore size gra- dient was also readily fabricated by casting serial layers of foams that were set for different time periods. The potential applications of porous Al2O3 and HA ceramics fabricated by this green foaming method in- cluding scaffolds for oil cleaning and cell culture, respectively, were also demonstrated.
基金financially supported by the Natural Science Foundation of Shandong Province (No.ZR2014EMM009)the Public School Visiting Fund of Shandong University of Science and Technology
文摘Open-celled porous （TiB2-Al2O3）/NiAl composites were successfully fabricated by using spherical carbamide as space holders via self-propagating high-temperature synthesis （SHS）. Effects of 10Al-3B2O3-3TiO2 contents （0-20 wt%） on the pore structures and the quasi-static compressive behaviors of the resultant materials were investigated. The porous （TiBE-Al2O3）/NiAl composites exhibit composite pore structure consisting of homogeneously distributed and interconnected millimeter pores and micropores. The millimeter pores virtually inherit the shape and size of carbamide particles, while the pore size of micropores increases with increasing the 10Al-3BEO3-3TiO2 content. Depending on the volume fraction of the carbamide, the porosity of the porous materials can be easily controlled in a range of 55%-85%. When the porosity is about 72%, the compressive strengths of porous NiAl and porous （TiBE-Al203）/NiAl composite with 15% 10Al-3B2O3-3TiO2 in green compact are 19 and 32 MPa, and the corresponding strains are 2.9% and 5.7%, respectively. Furthermore, the quasi-static compressive behavior of porous （TiB2-AlEO3）/NiAl composites can be estimated by Gibson-Ashby model.
文摘Pore structures in shales are a main factor affecting the storage capacity and production performance of shale gas reservoirs.Taking Longmaxi Shales in the Jiaoshiba area of the Sichuan Basin as a study object,we systematically study the microscopic pore structures of shales by using Argon-ion polishing Scanning Electron Microscope(SEM),high-pressure mercury injection and low-temperature nitrogen adsorption and desorption experiments.The study results show that:the Longmaxi Shale in this area are dominated by nano-scale pores which can be classified into organic pores,inorganic pores(intergranular pores,intragranular pores,inter-crystalline pores and dissolution pores),microfractures(intragranular structure fractures,interlayer sliding fractures,diagenetic shrinkage joints and abnormal-pressure fractures from organic evolution),among which organic pores and clay mineral pores are predominant and organic pores are the most common;a TOC value shows an obvious positive correlation with the content of organic pores,which account for up to 50%in the lower-quality shales with a TOC of over 2%where they are most developed;microscopic pore structures are very complex and open,with pores being mainly in cylinder shape with two ends open,or in parallel tabular shape with four sides open and 2–30 nm in diameter,being mostly medium pores.On this basis,factors affecting the micropore structures of shales in this area are studied.It is concluded that organic matter abundance and thermal maturity are the major factors controlling the microscopic pore structures of shales,while the effects of clay mineral content are relatively insignificant.
基金supported by the National Natural Science Foundation of China(No.52371052).
文摘High-temperature infrared-regulating ceramics are essentialfoerxtreme-environmentapplicationsrequiring broadband infrared reflection(1-6μm),such as spacecraft thermal protection,military stealth systems,and related fields.Precise control of pore structures is crucial for enhancing ceramic infrared reflectance,as pores directly influence the scattering intensity and scattering path of radiation.However,achieving broadband reflectance above 0.9 remains challenging because of unclear pore-radiation interaction mechanisms and insufficient structural control.This study employs optical simulations to systematically analyze how pore parameters enhance infrared reflectance.The results demonstrate that pore sizes matching the infrared wavelength,highaspect ratios,and aligned orientations synergistically enhance reflection.Guided by simulations,directional pore-structured yttria-stabilized zirconia(YSZ)ceramics were fabricated via a rolling extrusion method using graphite flakes as sacrificial templates.The optimized ceramics exhibited tailored pore parameters(size:0.2-6μm,aspect ratio:3.2-3.9,orientation angle:<30°),achieving exceptional infrared reflectance(>0.9).This study clarifies pore-radiation interactions and presents a scalable strategy to produce advanced thermal shielding materials.
基金Funded by the National Natural Science Foundation of China(Nos.5226804252468035)。
文摘To investigate the pore structure of graphene oxide modified polymer cement mortar(GOPM)under salt-freeze-thaw(SFT)coupling effects and its impact on deterioration,this study modifies polymer cement mortar(EMCM)with graphene oxide(GO).The micro-pore structure of GOPM is characterized using LF-NMR and SEM.Fractal theory is applied to calculate the fractal dimension of pore volume,and the deterioration patterns are analyzed based on the evolution characteristics of capillary pores.The experimental results indicate that,after 25 salt-freeze-thaw cycles(SFTc),SO2-4 ions penetrate the matrix,generating corrosion products that fill existing pores and enhance the compactness of the specimen.As the number of cycles increases,the ongoing formation and expansion of corrosion products within the matrix,combined with persistent freezing forces,and result in the degradation of the pore structure.Therefore,the mass loss rate(MLR)of the specimens shows a trend of first decreasing and then increasing,while the relative dynamic elastic modulus(RDEM)initially increases and then decreases.Compared to the PC group specimens,the G3PM group specimens show a 28.71% reduction in MLR and a 31.42% increase in RDEM after 150 SFTc.The fractal dimensions of the transition pores,capillary pores,and macropores in the G3PM specimens first increase and then decrease as the number of SFTc increases.Among them,the capillary pores show the highest correlation with MLR and RDEM,with correlation coefficients of 0.97438 and 0.98555,respectively.
基金The financial support from“The National Key Research and Development Program of China”(No.2017YFB0703200)“National Natural Science Foundation of China”(No.51702341)+1 种基金Chinese Academy of Sciences Innovative Funding(CXJJ-17-M169)“CAS Pioneer Hundred Talents Program”are greatly acknowledged.
文摘Reactive melt infiltration(RMI)is an effective method for fabrication of highly dense carbon fiber reinforced ultra-high temperature ceramic matrix composites(Cf/UHTCs).In this work,C_(f)/SiC-ZrC-ZrB_(2)composites were fabricated by infiltrating ZrSi_(2)melt into porous C_(f)/B_(4)C-C preforms,where the physical and chemical reactions involved during the RMI process were identified and analyzed.Inhomogeneous infiltration between the inter-and intra-bundle pores was revealed,and was found to be strongly related to the pore structures of the C_(f)/B_(4)C-C preform.It is indicated that the inhomogeneous infiltration can be mitigated remarkably with increasing porosity and pore size of the preform.The effect of pore size on the RMI process was also investigated by a quantitative model,which agrees very well with the experiment results.It further indicates that the inhomogeneous infiltration can also be relieved at elevated RMI temperature.However,excessive infiltration at elevated temperature or more porous preform may cause serious erosion on interphase and fibers,leading to mechanical properties deterioration of the final composites.
基金support received from the Hong Kong Research Grants Council(Project No:T22-502/18-R)The Hong Kong Polytechnic University(Project ID:P0039974 and 1-W18N).
文摘CO_(2)sequestration/storage shows considerable impacts on the pore structures and compressive strength of concrete.This paper presents a study in which coral aggregates were presoaked in Ca(OH)_(2) slurries with different solid-to-liquid ratios(i.e.0.2,0.4,and 0.6 g/mL)followed by accelerated carbonation.The effects of CO_(2)sequestration on the particle size distribution,cylinder compressive strength,water absorption,and apparent density of coral aggregate were investigated.The evolution of pore structures in coral aggregate concrete after CO_(2)sequestration was also studied.Additionally,the effect of CO_(2)sequestration on the development of compressive strength of coral aggregate concrete was explored.The results showed that CO_(2)sequestration affected the properties of coral aggregate.Moreover,the porosity of CaCO_(3) formed by CO_(2)sequestration was the highest in the concrete.With the increase of solidto-liquid ratio,the porosity of cement pastes and the CaCO_(3) increased,and more big pores existed in the cement pastes and CaCO_(3).Furthermore,the compressive strength of coral aggregate concrete when the solid-to-liquid ratio was 0.2 g/mL increased compared with that before CO_(2)sequestration,but the compressive strength reduced when the ratio increased to 0.6 g/mL.
文摘1 Introduction Immobilization of homogeneous catalysts onto polymer supports through covalent attachment has received wide attention because these materials offer advantage features of heterogeneous catalysis to homogeneous systems.The polymer-supported catalysts enhance their thermal stability,selectivity,recyclability and easy separation from reaction products leading to the operationally flexible[1-2].Such behaviour prompted us to know the effect of pore structures of polymer supporters on catalytic ...
基金supported by the National Science Foundation for Distin-guished Young Scholars of China (Grant No. 51125017)the National Natural Science Foundation of China (Grant No. 50974125)+1 种基金the ResearchFund for Doctoral Programs of Chinese Ministry of Education (Grant No.20110023110015)the National Basic Research Program of China("973" Project)(Grant Nos. 2010CB226804,2011CB201201)
文摘Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.
基金supported by the National Natural Science Foundation of China(41925014).
文摘The Lower Cambrian shales in the Sichuan Basin are considered one of the most promising shale gas resources in China.However,large-scale commercial development has not been achieved due to the relatively low and significantly variable gas contents of the drilled shales.Excitingly,the first major breakthrough in deep and ultra-deep Lower Cambrian shale gas was made recently in the well Z201 in the southern Sichuan Basin,with a gas yield exceeding 73×10^(4)m^(3)/d.The success of well Z201 provides a favorable geological case to reveal the distinct enrichment mechanism of deep and ultra-deep Lower Cambrian shale gas.In this study,at drilling site of well Z201,fresh shale core samples with different gasin-place contents were collected,and their geochemical,pore development and water-bearing characteristics were analyzed systematically.The results showed that the Z201 organic-rich shales reached an overmature stage,with an average Raman maturity of 3.70%.The Z201 shales with high gas-in-place contents are mainly located in the Qiongzhusi 12section and the upper Qiongzhusi 11section,with an average gas-in-place content of 10.08 cm^(3)/g.Compared to the shales with low gas-in-place contents,the shales with high gas-in-place contents exhibit higher total organic carbon contents,greater porosities,and lower water saturations,providing more effective pore spaces for shale gas enrichment.The effective pore structures of the deep and ultra-deep Lower Cambrian shales are the primary factors affecting their gas-in-place contents.Similar to the shales with high gas-in-place contents of well Z201,the deep and ultra-deep Lower Cambrian shales in the Mianyang-Changning intracratonic sag,especially in the Ziyang area,generally developed in deep-water shelf facies with high total organic carbon contents and thick sedimentary thickness,providing favorable conditions for the development and preservation of effective pores.Therefore,they are the most promising targets for Lower Cambrian shale gas exploration.
