The lacustrine shale of deep Shahezi Formation in the Songliao basin has great gas potential,but its pore evolution,heterogeneity,and connectivity characteristics remain unclear.In this work,total organic carbon analy...The lacustrine shale of deep Shahezi Formation in the Songliao basin has great gas potential,but its pore evolution,heterogeneity,and connectivity characteristics remain unclear.In this work,total organic carbon analysis,rock pyrolysis,X-ray diffraction field emission scanning electron microscopy,the particle and crack analysis system software,low-temperature nitrogen adsorption experiment,fractal theory,high-pressure mercury injection experiment and nuclear magnetic resonance experiment were used to study the Shahezi shale from Well SK-2.The result indicated that the organic pores in Shahezi shale are not developed,and the intergranular and intragranular pores are mainly formed by illitedominated clay.As the burial depth increases,the pore size and slit-shaped pores formed by clay decrease,and dissolved pores in the feldspar and carbonate minerals and dissolved fractures in the quartz increase.The pore evolution is affected by clay,compaction,and high-temperature corrosion.Based on the pore structure characteristics reflected by the pore size distribution and pore structure parameters obtained by multiple experimental methods,the pore development and evolution are divided into three stages.During stageⅠandⅡ,the pore heterogeneity of the shale reservoirs increases with the depth,the physical properties and pore connectivity deteriorate,but the gas-bearing property is good.In stageⅢ,the pore heterogeneity is the highest,its gas generation and storage capacity are low,but the increase of micro-fractures makes pore connectivity and gas-bearing better.展开更多
Shale oil can be extracted from shale by using interconnected pore networks.The migration of hydrocarbon molecules within the shale is controlled by pore connectivity.However,assessing the pore connectivity of shale o...Shale oil can be extracted from shale by using interconnected pore networks.The migration of hydrocarbon molecules within the shale is controlled by pore connectivity.However,assessing the pore connectivity of shale oil reservoirs is uncommon.To characterize pore connectivity and clarify its controlling factors,this study used spontaneous imbibition(SI)combined with nuclear magnetic resonance(NMR)T_(2)and T_(1)-T_(2)technologies on shale oil reservoirs selected from the Shahejie Formation in the Dongying Sag,Bohai Bay Basin.According to the findings,the SI processes of shales include fast-rising,slow-rising,and stable stages.The fast-rising stage denotes pore connectivity.The shales studied have poor connectivity,with lower imbibition slopes and connected porosity ratios,but large effective tortuosity.During the SI process,micropores have the highest imbibition saturation,followed by mesopores and macropores.Furthermore,n-dodecane ingested into micropores appears primarily as adsorbed,whereas n-dodecane appears primarily as free states in mesopores and macropores during the SI process.The pore connectivity of the shales under study is primarily controlled by inorganic minerals.Quartz and feldspar develop large and regular pores,resulting in better pore connectivity,whereas clay minerals and calcite with plenty of complex intragranular pores do not.Organic matter negatively influences pore connectivity because the dissolution of calcite by organic acid produced during hydrocarbon generation leads to a more complex and heterogeneous pore structure.This study sheds light on the pore connectivity and controlling factors of the shale oil reservoir and aids in the understanding of shale oil mobility.展开更多
Subsoiling is widely used to improve soil productivity in the North China Plain(NCP).However,its effects on pore network-based hydraulic properties and their relationship with water use efficiency(WUE)are far from cle...Subsoiling is widely used to improve soil productivity in the North China Plain(NCP).However,its effects on pore network-based hydraulic properties and their relationship with water use efficiency(WUE)are far from clear.In this study,we evaluated the effects of three tillage systems(rotary tillage at 15 cm depth,RT15;subsoiling at 40 cm depth,SS40;and subsoiling at 35 cm depth,SS35)on soil pore structure,hydraulic properties,and WUE during the 2022-2024 winter wheat seasons.Results showed that the effects of SS40 and SS35 were similar in optimizing the soil pore structure and hydraulic properties.Compared with RT15,SS40 and SS35 increased the soil macroporosity ratio,the soil pore connectivity,and the soil water storage.Structural equation modeling revealed that optimized soil pore structure under subsoiling directly and positively influenced the WUE or indirectly increasing the soil water storage.As a result,compared with RT15,SS40 and SS35 increased the spike number,kernel number per spike,and 1000-grain weight,and ultimately improved the yield(35.59% and 39.32%,respectively)and WUE(36.69% and 41.55%,respectively).Overall,the results revealed the mechanism of high-efficiency water use from the perspective of pore network-based hydraulic properties,providing a theoretical basis for food security.展开更多
The connectivity of shale pores and the occurrence of movable oil in shales have long been the focus of research.In this study,samples from wells BX7 and BYY2 in the Eq3^4-10 cyclothem of Qianjiang Formation in the Qi...The connectivity of shale pores and the occurrence of movable oil in shales have long been the focus of research.In this study,samples from wells BX7 and BYY2 in the Eq3^4-10 cyclothem of Qianjiang Formation in the Qianjiang depression,were analyzed.A double mercury injection method was used to distinguish between invalid and effective connected pores.The pore characteristics for occurrence of retained hydrocarbons and movable shale oil were identified by comparing pore changes in low temperature nitrogen adsorption and high pressure mercury injection experiments before and after extraction and the change in the mercury injection amounts in the pores between two separate mercury injections.The results show that less than 50%of the total connected pores in the Eq34-10 cyclothem samples are effective.The development of effective connected pores affects the mobility of shale oil but varies with different lithofacies.The main factor limiting shale oil mobility in Well BX7 is the presence of pores with throat sizes less than 15 nm.In Well BYY2,residual mercury in injection testing of lamellar dolomitic mudstone facies was mainly concentrated in pores with throats of 10-200 nm,and in bulk argillaceous dolomite facies,it was mainly concentrated at 60-300 nm.The throats of hydrocarbon-retaining pores can be 5 nm or even smaller,but pores with movable shale oil in the well were found to have throat sizes greater than 40 nm.Excluding the influence of differences in wettability,the movability of shale oil is mainly affected by differences in lithofacies,the degree of pore deformation caused by diagenesis,the complexity of pore structures,and the connectivity of pore throats.Dissolution and reprecipitation of halite also inhibit the mobility of shale oil.展开更多
Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial...Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial development.Resistivity logging serves as a valuable approach for achieving these goals.Nevertheless,due to inadequate comprehension of the electrical conductivity mechanism in hydrate-bearing sediments,existing data processing models still encounter certain challenges.This study conducts both core-scale and pore-scale simulation experiments to examine the relationship between resistivity variations and the distribution of gas hydrate porosity.The results indicate that the characteristics of resistivity variation is associated with the gas hydrate formation process,and the gas hydrate saturation index,denoted as‘n',varies between 0 and 3 depending on different gas hydrate distribution patterns.As the saturation increases,gas hydrate distribution in pore spaces transitions from floating to contacting and cementing patterns.It is proposed that the aqueous pore tortuosity can be utilized to correct the saturation index‘n'in Archie's equation.Based on the analysis of experimental data,a correction method for Archie's equation is suggested,and its effectiveness in controlling relative error has been validated.展开更多
Liquid nitrogen fracturing is one of the potential feasible technologies for improving the stimulation efficiency of coalbed methane(CBM)reservoirs.At present,the visualization of pore-throat connectivity and microsco...Liquid nitrogen fracturing is one of the potential feasible technologies for improving the stimulation efficiency of coalbed methane(CBM)reservoirs.At present,the visualization of pore-throat connectivity and microscopic seepage characteristics in coal rocks under liquid nitrogen thermal shock is still lack of studying.Hence,the influence of liquid nitrogen thermal shock on the micro-nano pore structure and mechanical property of coal rocks are not understood clearly.In order to provide theoretical basis for the stimulation behavior of liquid nitrogen fracturing in coal beds,this paper investigates the change of micro-nano pore structure and mechanical property of coal rocks before and after liquid nitrogen treatment means of CT scanning and atomic force microscope(AFM).In addition,the influence of liquid nitrogen thermal shock on the seepage routes of coal rock are revealed.The following research results can be obtained.First,the number and scales of pores in the coal increase after liquid nitrogen thermal shock.In this experiment,porosity is increased by 200%,micro-fracture is dominant and its volume proportion is increased to 90.0% from 7.7% before liquid nitrogen treatment.Second,the three-dimensional pore structure reconstruction model obtained by CT shows that after the liquid nitrogen treatment,the number,total length and total volume of throats in the coal rock are increased by 170%,140% and 130% and the pore connectivity is improved greatly.Third,after liquid nitrogen treatment,the sample's absolute permeability is improved significantly.In this experiment,the absolute permeability of coal after liquid nitrogen treatment is 77 times higher than that before liquid nitrogen cooling.The micro-fractures induced by thermal stress are the main percolation routes in coal after liquid nitrogen cooling.Fourth,pores and fractures are newly formed on both matrix and mineral domains,and the surface roughness is increased.In the meantime,the elastic modulus in matrix and mineral domains of coal drops,and the average elastic modulus drops by 81% and 91%,respectively.In conclusion,liquid nitrogen thermal shock leads to the increase of microscopic defects in coal and the deterioration of mechanical property.Liquid nitrogen fracturing is expected to be a new kind of efficient and green CBM reservoir stimulation technology.展开更多
It is difficult to stimulate coal reservoirs in physical approaches,and the recovery factor of coalbed methane(CBM)can be enhanced by applying strong oxidizers through oxidation to stimulate coal reservoirs.At present...It is difficult to stimulate coal reservoirs in physical approaches,and the recovery factor of coalbed methane(CBM)can be enhanced by applying strong oxidizers through oxidation to stimulate coal reservoirs.At present,however,there have been very few studies on the oxidation of CBM and fewer experimental studies for systematically evaluating the effect of oxidation on the seepage capacity of coal reservoirs.In this paper,the coal samples taken from coal seams of the Jurassic Xishanyao Formation in the Heishan Coal Mine,Toksun,Xinjiang,were selected as the study objects.Hydrogen peroxide solution immersion experiments were carried out on columnar and powdered coal samples,respectively to measure the permeability of columnar coal samples,the dissolution rate of powdered coal samples and the property parameters of hydrogen peroxide solution.Then,the reaction mechanisms between coal samples and hydrogen peroxide and the mechanisms to improve the seepage capacity of coal reservoirs were analyzed by means of X-ray diffraction(XRD),scanning electron microscope(SEM),infrared spectrum and wetting angle measurement.Finally,the stimulation effect of oxidation was compared with that of acidification.The following research results were obtained.(1)The permeability of coal samples is increased significantly after oxidation to 1.4–3.2 times the original permeability.(2)A large number of micro-fractures and dissolved pores are formed in the coal samples after oxidation,and consequently pore connectivity is improved greatly.Thus,the amount of associative hydroxyl and carboxyl functional groups on the surface of the coal samples increases,and the water wettability on the surface reduces.(3)Organic matters and pyrites are oxidized and consumed easily,and the generated H+and micro-molecular aliphatic acids further dissolve inorganic mineral components.(4)Oxidation also has the advantage of acidification for dissolving inorganic mineral components,so there is a low and controllable probability of generating coal powder.In conclusion,applying strong oxidizers has the potential to become a new technology for coal reservoir stimulation.展开更多
Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivi...Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.展开更多
Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate,and it is an important basic material for sponge city construction.The presence of a large n...Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate,and it is an important basic material for sponge city construction.The presence of a large number of connected pores inside pervious concrete leads to a marked difference in durability failure mechanism compared with that of ordinary concrete.In this study,the frost resistance and anti-clogging of pervious concrete were introduced in detail,and the methods to improve their performance were summarized systematically.The cracking pattern of pervious concrete is influenced by geometric characteristics and three-dimensional morphological features of pores,resulting in its crack generation,development,and geometry being significantly different from those of ordinary concrete,thus leading to different freeze-thaw cycle mechanisms.In addition,due to its different pore structure compared to ordinary concrete,three types of clogging mechanisms,affecting the long-term permeability of pervious concrete were elaborated systematically(i.e.,physical clogging,biological clogging,and chemical clogging).And the ways to improve the anti-clogging of pervious concrete are systematically presented from multiple perspectives.Finally,in order to broaden the engineering applications of pervious concrete,some research proposals are presented in this study.展开更多
Hierarchical porous carbons are the most viable electrode material for supercapacitors because of their balanced capacitive performance and chemical stability.Their pore connectivity plays a pivotal role in electrolyt...Hierarchical porous carbons are the most viable electrode material for supercapacitors because of their balanced capacitive performance and chemical stability.Their pore connectivity plays a pivotal role in electrolyte transport,which is quantified by a new parameter,defined in this work as the longest possible pore separation(LPPS).Herein,we report hierarchical porous carbon nanospheres(HPC-NS)with a unique ball-in-ball structure,which is achieved by the pyrolysis of a supramolecular complex ofγ-cyclodextrin(γ-CD)/PEO-PPO-PEO(F127).This approach differs from the conventional softtemplating method in that,apart from the assembly of the monomicelles that leads to the host nanospheres(approximately 300 nm),theγ-CD-containing monomicelles themselves are converted to small porous carbon nanospheres(<10 nm),which results in an ultralow LPPS of 10 nm,representing the bestknown pore connectivity of the HPC family.The HPC-NS delivers a high specific capacitance(405 F g^(-1)at 1 A g^(-1)and 71%capacitance retention at 200 A g^(-1)),wide voltage window(up to 1.6 V),and simultaneously high energy and power densities(24.3 Wh kg^(-1)at a power density of 151 W kg^(-1)and 9 Wh kg^(-1)at 105 W kg^(-1))in aqueous electrolytes.This new strategy boosts the development of porous carbon electrodes for aqueous supercapacitors with simultaneously high power and energy densities.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42072168 and 41802156)the National Key R&D Program of China(Grant No.2019YFC0605405)the Fundamental Research Funds for the Central Universities(Grant Nos.2023ZKPYDC07 and 2022YQDC06)。
文摘The lacustrine shale of deep Shahezi Formation in the Songliao basin has great gas potential,but its pore evolution,heterogeneity,and connectivity characteristics remain unclear.In this work,total organic carbon analysis,rock pyrolysis,X-ray diffraction field emission scanning electron microscopy,the particle and crack analysis system software,low-temperature nitrogen adsorption experiment,fractal theory,high-pressure mercury injection experiment and nuclear magnetic resonance experiment were used to study the Shahezi shale from Well SK-2.The result indicated that the organic pores in Shahezi shale are not developed,and the intergranular and intragranular pores are mainly formed by illitedominated clay.As the burial depth increases,the pore size and slit-shaped pores formed by clay decrease,and dissolved pores in the feldspar and carbonate minerals and dissolved fractures in the quartz increase.The pore evolution is affected by clay,compaction,and high-temperature corrosion.Based on the pore structure characteristics reflected by the pore size distribution and pore structure parameters obtained by multiple experimental methods,the pore development and evolution are divided into three stages.During stageⅠandⅡ,the pore heterogeneity of the shale reservoirs increases with the depth,the physical properties and pore connectivity deteriorate,but the gas-bearing property is good.In stageⅢ,the pore heterogeneity is the highest,its gas generation and storage capacity are low,but the increase of micro-fractures makes pore connectivity and gas-bearing better.
基金This study was financially supported by the Natural Science Foundation of Shandong Province(ZR2020QD036,ZR2020QD037,and ZR2021QD072)the National Natural Science Foundation of China(41972123).
文摘Shale oil can be extracted from shale by using interconnected pore networks.The migration of hydrocarbon molecules within the shale is controlled by pore connectivity.However,assessing the pore connectivity of shale oil reservoirs is uncommon.To characterize pore connectivity and clarify its controlling factors,this study used spontaneous imbibition(SI)combined with nuclear magnetic resonance(NMR)T_(2)and T_(1)-T_(2)technologies on shale oil reservoirs selected from the Shahejie Formation in the Dongying Sag,Bohai Bay Basin.According to the findings,the SI processes of shales include fast-rising,slow-rising,and stable stages.The fast-rising stage denotes pore connectivity.The shales studied have poor connectivity,with lower imbibition slopes and connected porosity ratios,but large effective tortuosity.During the SI process,micropores have the highest imbibition saturation,followed by mesopores and macropores.Furthermore,n-dodecane ingested into micropores appears primarily as adsorbed,whereas n-dodecane appears primarily as free states in mesopores and macropores during the SI process.The pore connectivity of the shales under study is primarily controlled by inorganic minerals.Quartz and feldspar develop large and regular pores,resulting in better pore connectivity,whereas clay minerals and calcite with plenty of complex intragranular pores do not.Organic matter negatively influences pore connectivity because the dissolution of calcite by organic acid produced during hydrocarbon generation leads to a more complex and heterogeneous pore structure.This study sheds light on the pore connectivity and controlling factors of the shale oil reservoir and aids in the understanding of shale oil mobility.
基金supported in part by the National Key Research and Development Plan(2023YFD1902605)the Natural Science Foundation of Shandong Province,China(ZR2021MC123)the Shandong Province First-class Discipline Construction“811”Project。
文摘Subsoiling is widely used to improve soil productivity in the North China Plain(NCP).However,its effects on pore network-based hydraulic properties and their relationship with water use efficiency(WUE)are far from clear.In this study,we evaluated the effects of three tillage systems(rotary tillage at 15 cm depth,RT15;subsoiling at 40 cm depth,SS40;and subsoiling at 35 cm depth,SS35)on soil pore structure,hydraulic properties,and WUE during the 2022-2024 winter wheat seasons.Results showed that the effects of SS40 and SS35 were similar in optimizing the soil pore structure and hydraulic properties.Compared with RT15,SS40 and SS35 increased the soil macroporosity ratio,the soil pore connectivity,and the soil water storage.Structural equation modeling revealed that optimized soil pore structure under subsoiling directly and positively influenced the WUE or indirectly increasing the soil water storage.As a result,compared with RT15,SS40 and SS35 increased the spike number,kernel number per spike,and 1000-grain weight,and ultimately improved the yield(35.59% and 39.32%,respectively)and WUE(36.69% and 41.55%,respectively).Overall,the results revealed the mechanism of high-efficiency water use from the perspective of pore network-based hydraulic properties,providing a theoretical basis for food security.
基金supported by the National Natural Science Foundation of China(No.U19B6003)。
文摘The connectivity of shale pores and the occurrence of movable oil in shales have long been the focus of research.In this study,samples from wells BX7 and BYY2 in the Eq3^4-10 cyclothem of Qianjiang Formation in the Qianjiang depression,were analyzed.A double mercury injection method was used to distinguish between invalid and effective connected pores.The pore characteristics for occurrence of retained hydrocarbons and movable shale oil were identified by comparing pore changes in low temperature nitrogen adsorption and high pressure mercury injection experiments before and after extraction and the change in the mercury injection amounts in the pores between two separate mercury injections.The results show that less than 50%of the total connected pores in the Eq34-10 cyclothem samples are effective.The development of effective connected pores affects the mobility of shale oil but varies with different lithofacies.The main factor limiting shale oil mobility in Well BX7 is the presence of pores with throat sizes less than 15 nm.In Well BYY2,residual mercury in injection testing of lamellar dolomitic mudstone facies was mainly concentrated in pores with throats of 10-200 nm,and in bulk argillaceous dolomite facies,it was mainly concentrated at 60-300 nm.The throats of hydrocarbon-retaining pores can be 5 nm or even smaller,but pores with movable shale oil in the well were found to have throat sizes greater than 40 nm.Excluding the influence of differences in wettability,the movability of shale oil is mainly affected by differences in lithofacies,the degree of pore deformation caused by diagenesis,the complexity of pore structures,and the connectivity of pore throats.Dissolution and reprecipitation of halite also inhibit the mobility of shale oil.
基金financially supported by the National Natural Science Foundation of China(No.42376067)the Natural Science Foundation of Shandong Province(No.ZR202011030013)+1 种基金the Laoshan Laboratory(No.LSKJ202203506)the China Geological Survey Program(No.DD20230064)。
文摘Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial development.Resistivity logging serves as a valuable approach for achieving these goals.Nevertheless,due to inadequate comprehension of the electrical conductivity mechanism in hydrate-bearing sediments,existing data processing models still encounter certain challenges.This study conducts both core-scale and pore-scale simulation experiments to examine the relationship between resistivity variations and the distribution of gas hydrate porosity.The results indicate that the characteristics of resistivity variation is associated with the gas hydrate formation process,and the gas hydrate saturation index,denoted as‘n',varies between 0 and 3 depending on different gas hydrate distribution patterns.As the saturation increases,gas hydrate distribution in pore spaces transitions from floating to contacting and cementing patterns.It is proposed that the aqueous pore tortuosity can be utilized to correct the saturation index‘n'in Archie's equation.Based on the analysis of experimental data,a correction method for Archie's equation is suggested,and its effectiveness in controlling relative error has been validated.
基金Project supported by the National Natural Science Foundation of China for Research and Development Program for Major Research Instruments“Synthetic experimental system of radial jet drilling technology”(No.:51827804).
文摘Liquid nitrogen fracturing is one of the potential feasible technologies for improving the stimulation efficiency of coalbed methane(CBM)reservoirs.At present,the visualization of pore-throat connectivity and microscopic seepage characteristics in coal rocks under liquid nitrogen thermal shock is still lack of studying.Hence,the influence of liquid nitrogen thermal shock on the micro-nano pore structure and mechanical property of coal rocks are not understood clearly.In order to provide theoretical basis for the stimulation behavior of liquid nitrogen fracturing in coal beds,this paper investigates the change of micro-nano pore structure and mechanical property of coal rocks before and after liquid nitrogen treatment means of CT scanning and atomic force microscope(AFM).In addition,the influence of liquid nitrogen thermal shock on the seepage routes of coal rock are revealed.The following research results can be obtained.First,the number and scales of pores in the coal increase after liquid nitrogen thermal shock.In this experiment,porosity is increased by 200%,micro-fracture is dominant and its volume proportion is increased to 90.0% from 7.7% before liquid nitrogen treatment.Second,the three-dimensional pore structure reconstruction model obtained by CT shows that after the liquid nitrogen treatment,the number,total length and total volume of throats in the coal rock are increased by 170%,140% and 130% and the pore connectivity is improved greatly.Third,after liquid nitrogen treatment,the sample's absolute permeability is improved significantly.In this experiment,the absolute permeability of coal after liquid nitrogen treatment is 77 times higher than that before liquid nitrogen cooling.The micro-fractures induced by thermal stress are the main percolation routes in coal after liquid nitrogen cooling.Fourth,pores and fractures are newly formed on both matrix and mineral domains,and the surface roughness is increased.In the meantime,the elastic modulus in matrix and mineral domains of coal drops,and the average elastic modulus drops by 81% and 91%,respectively.In conclusion,liquid nitrogen thermal shock leads to the increase of microscopic defects in coal and the deterioration of mechanical property.Liquid nitrogen fracturing is expected to be a new kind of efficient and green CBM reservoir stimulation technology.
基金supported by National Natural Science Foundation of China-General Program“Study on acceleration of gas transmission by enhancing permeability through organic-rich shale fracturing due to oxidation”(No.:51674209).
文摘It is difficult to stimulate coal reservoirs in physical approaches,and the recovery factor of coalbed methane(CBM)can be enhanced by applying strong oxidizers through oxidation to stimulate coal reservoirs.At present,however,there have been very few studies on the oxidation of CBM and fewer experimental studies for systematically evaluating the effect of oxidation on the seepage capacity of coal reservoirs.In this paper,the coal samples taken from coal seams of the Jurassic Xishanyao Formation in the Heishan Coal Mine,Toksun,Xinjiang,were selected as the study objects.Hydrogen peroxide solution immersion experiments were carried out on columnar and powdered coal samples,respectively to measure the permeability of columnar coal samples,the dissolution rate of powdered coal samples and the property parameters of hydrogen peroxide solution.Then,the reaction mechanisms between coal samples and hydrogen peroxide and the mechanisms to improve the seepage capacity of coal reservoirs were analyzed by means of X-ray diffraction(XRD),scanning electron microscope(SEM),infrared spectrum and wetting angle measurement.Finally,the stimulation effect of oxidation was compared with that of acidification.The following research results were obtained.(1)The permeability of coal samples is increased significantly after oxidation to 1.4–3.2 times the original permeability.(2)A large number of micro-fractures and dissolved pores are formed in the coal samples after oxidation,and consequently pore connectivity is improved greatly.Thus,the amount of associative hydroxyl and carboxyl functional groups on the surface of the coal samples increases,and the water wettability on the surface reduces.(3)Organic matters and pyrites are oxidized and consumed easily,and the generated H+and micro-molecular aliphatic acids further dissolve inorganic mineral components.(4)Oxidation also has the advantage of acidification for dissolving inorganic mineral components,so there is a low and controllable probability of generating coal powder.In conclusion,applying strong oxidizers has the potential to become a new technology for coal reservoir stimulation.
基金supported by the Yalongjiang River Joint Fund by the National Natural Science Foundation of China(NSFC)Ertan Hydropower Development Company,LTD(Nos.50579091 and 50539090)+1 种基金NSFC(No.10772190)Major State Basic Research Project of China(No.2002CB412708)
文摘Physical mechanisms and influencing factors on the effective stress coefficient for rock/soil-like porous materials are investigated, based on which equivalent connectivity index is proposed. The equivalent connectivity index, relying on the meso-scale structure of porous material and the property of liquid, denotes the connectivity of pores in Representative Element Area （REA）. If the conductivity of the porous material is anisotropic, the equivalent connectivity index is a second order tensor. Based on the basic theories of continuous mechanics and tensor analysis, relationship between area porosity and volumetric porosity of porous materials is deduced. Then a generalized expression, describing the relation between effective stress coefficient tensor and equivalent connectivity tensor of pores, is proposed, and the expression can be applied to isotropic media and also to anisotropic materials. Furthermore, evolution of porosity and equivalent connectivity index of the pore are studied in the strain space, and the method to determine the corresponding functions in expressions above is proposed using genetic algorithm and genetic programming. Two applications show that the results obtained by the method in this paper perfectly agree with the test data. This paper provides an important theoretical support to the coupled hydro-mechanical research.
基金financially supported by the National Natural Science Foundation of China(52208246,U22A20122)the Natural Science Foundation of Hunan Province(2023JJ40142)+3 种基金the Natural Science Foundation of Changsha(kq2202160)the Provincial Special Project for the Construction of National Sustainable Development Agenda Innovation Demonstration Zone in Chenzhou City(2023sfq50)the Fundamental Research Funds for the Central Universities(531118010493)Training Program for Excellent Young Innovators of Changsha(kq2107010)。
文摘Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate,and it is an important basic material for sponge city construction.The presence of a large number of connected pores inside pervious concrete leads to a marked difference in durability failure mechanism compared with that of ordinary concrete.In this study,the frost resistance and anti-clogging of pervious concrete were introduced in detail,and the methods to improve their performance were summarized systematically.The cracking pattern of pervious concrete is influenced by geometric characteristics and three-dimensional morphological features of pores,resulting in its crack generation,development,and geometry being significantly different from those of ordinary concrete,thus leading to different freeze-thaw cycle mechanisms.In addition,due to its different pore structure compared to ordinary concrete,three types of clogging mechanisms,affecting the long-term permeability of pervious concrete were elaborated systematically(i.e.,physical clogging,biological clogging,and chemical clogging).And the ways to improve the anti-clogging of pervious concrete are systematically presented from multiple perspectives.Finally,in order to broaden the engineering applications of pervious concrete,some research proposals are presented in this study.
基金Natural Science Foundation of Guangdong Province,Grant/Award Number:2020A1515011127Shenzhen Government's Plan of Science and Technology,Grant/Award Numbers:JCYJ20190808121407676,20200813142301001+1 种基金Shenzhen University Initiative Research Program,Grant/Award Number:2019005Natural Science Foundation of China,Grant/Award Number:22178223。
文摘Hierarchical porous carbons are the most viable electrode material for supercapacitors because of their balanced capacitive performance and chemical stability.Their pore connectivity plays a pivotal role in electrolyte transport,which is quantified by a new parameter,defined in this work as the longest possible pore separation(LPPS).Herein,we report hierarchical porous carbon nanospheres(HPC-NS)with a unique ball-in-ball structure,which is achieved by the pyrolysis of a supramolecular complex ofγ-cyclodextrin(γ-CD)/PEO-PPO-PEO(F127).This approach differs from the conventional softtemplating method in that,apart from the assembly of the monomicelles that leads to the host nanospheres(approximately 300 nm),theγ-CD-containing monomicelles themselves are converted to small porous carbon nanospheres(<10 nm),which results in an ultralow LPPS of 10 nm,representing the bestknown pore connectivity of the HPC family.The HPC-NS delivers a high specific capacitance(405 F g^(-1)at 1 A g^(-1)and 71%capacitance retention at 200 A g^(-1)),wide voltage window(up to 1.6 V),and simultaneously high energy and power densities(24.3 Wh kg^(-1)at a power density of 151 W kg^(-1)and 9 Wh kg^(-1)at 105 W kg^(-1))in aqueous electrolytes.This new strategy boosts the development of porous carbon electrodes for aqueous supercapacitors with simultaneously high power and energy densities.
