Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to stu...Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism.The results show that the tensileσ−εcurves of the porous FeAl with different porosities can be divided into four stages:elasticity,yielding,strengthening and failure,without necking phenomenon.The elastic modulus,ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%.A macroscopic brittle fracture appears,and the microscopic fracture mechanism is mainly intergranular fracture,depending on the Al content in the dense FeAl intermetallics.In addition,the stochastic porous model(SPM)with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language.Combined with the secondary development platform of finite element software ANSYS,the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values,which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.展开更多
The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnect...The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength.展开更多
Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore...Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore structure of coal rock is very important in the exploration and development of coalbed methane.In this study,we use a coal rock digital core and three-dimensional modeling to study the pore structure of coal rock.First,the micropore structure of coal rock is quantitatively analyzed using a two-dimensional thin-section image,and the quantitative information of the pore and fracture(cleat)structure in the coal rock is extracted.The mean value and standard deviation of the face porosity and pore radius are obtained using statistical analysis.The number of pores is determined using dichotomy and spherical random-packing methods based on compression.By combining with the results of the petrophysical analysis,the single-porosity structure model of the coal rock is obtained using a nonequal-diameter sphere to represent the pores of the coal rock.Then,an ellipsoid with an aspect ratio that is very much lesser than one is used to represent the fracture(cleat)in the coal rock,and a dual-pore structure model of the coal rock is obtained.On this basis,the relationship between the different pore aspect ratios and porosity is explored,and a fitting relationship is obtained.The results show that a nonlinear relationship exists between them.The relationship model can provide a basis for the prediction of coal rock pore structure and the pore structure parameters and provide a reference for understanding the internal structure of coalbed methane reservoirs.展开更多
The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was emp...The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was employed as an alternative approach to verify some theoretical aspects of NMR responses. Firstly, the basic principles of pore-scale NMR simulation based on random-walk method(RWM) were introduced. The RWM-simulated results were benchmarked with the analytical results for an ideal spherical pore model. Then, the effects of two numerical parameters, namely diffusion radius and walk numbers, were studied on the simulation accuracy. The simulation method is then applied to various pore models with different pore sizes and pore shapes filled with different fluids to study the microscopic NMR response characteristics. The numerical experiments are useful for understanding and interpreting NMR measurements and the simulation code provides a numerical tool to perform pixel-based digital rock analysis.展开更多
基金Project(11502307)supported by the National Natural Science Foundation of ChinaProject(2016JJ3187)supported by the Natural Science Foundation of Hunan Province,ChinaProject(50825102)supported by the National Natural Science Funds for Distinguished Young Scholar of China。
文摘Uniaxial tensile tests and scanning electron microscopy(SEM)experiments were carried out on the porous FeAl intermetallics(porosities of 41.1%,44.2%and 49.3%,pore size of 15−30μm)prepared by our research group to study the macroscopic mechanical properties and microscopic failure mechanism.The results show that the tensileσ−εcurves of the porous FeAl with different porosities can be divided into four stages:elasticity,yielding,strengthening and failure,without necking phenomenon.The elastic modulus,ultimate strength and elongation decrease with the increase of porosity and the elongation is much lower than 5%.A macroscopic brittle fracture appears,and the microscopic fracture mechanism is mainly intergranular fracture,depending on the Al content in the dense FeAl intermetallics.In addition,the stochastic porous model(SPM)with random pore structure size and distribution is established by designing a self-compiling generation program in FORTRAN language.Combined with the secondary development platform of finite element software ANSYS,the effective elastic moduli of the porous FeAl can be determined by elastic analysis of SPM and they are close to the experimental values,which can verify the validity of the established SPM for analyzing the elastic properties of the porous material.
基金Project(41672298) supported by the National Natural Science Foundation of ChinaProject(2017YFC0602901) supported by the National Key Research and Development Program of China
文摘The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength.
基金sponsored by the National Natural Science Foundation of China(No.41274129)National Science and Technology Major Project(No.2016ZX05026001-004)+2 种基金Key Research and Development Program of Sichuan Province(No.2020YFG0157)the 2018 Central Supporting Local Coconstruction Fund(No.80000-18Z0140504)the Construction and Development of Universities in 2019-Joint Support for Geophysics(Double First-Class center,80000-19Z0204).
文摘Coal rock is a type of dual-porosity medium,which is composed of matrix pores and fracture-cutting matrix.They play different roles in the seepage and storage capacity of coal rock.Therefore,constructing the micropore structure of coal rock is very important in the exploration and development of coalbed methane.In this study,we use a coal rock digital core and three-dimensional modeling to study the pore structure of coal rock.First,the micropore structure of coal rock is quantitatively analyzed using a two-dimensional thin-section image,and the quantitative information of the pore and fracture(cleat)structure in the coal rock is extracted.The mean value and standard deviation of the face porosity and pore radius are obtained using statistical analysis.The number of pores is determined using dichotomy and spherical random-packing methods based on compression.By combining with the results of the petrophysical analysis,the single-porosity structure model of the coal rock is obtained using a nonequal-diameter sphere to represent the pores of the coal rock.Then,an ellipsoid with an aspect ratio that is very much lesser than one is used to represent the fracture(cleat)in the coal rock,and a dual-pore structure model of the coal rock is obtained.On this basis,the relationship between the different pore aspect ratios and porosity is explored,and a fitting relationship is obtained.The results show that a nonlinear relationship exists between them.The relationship model can provide a basis for the prediction of coal rock pore structure and the pore structure parameters and provide a reference for understanding the internal structure of coalbed methane reservoirs.
基金Project(265201248) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(41172130) supported by the National Natural Science Foundation of China+2 种基金Project(2011ZX05014-001) supported by the Major State S&T Special Fund,ChinaProject(201205002) supported by the China Scholarship CouncilProject(2011D-5006-0305) supported by the China National Petroleum Co.Innovation Foundation,China
文摘The microscopic response characteristics of nuclear magnetic resonance(NMR) are widely used for characterizing complex pore structures of rocks. Due to the prohibitive NMR experiment cost, numerical simulation was employed as an alternative approach to verify some theoretical aspects of NMR responses. Firstly, the basic principles of pore-scale NMR simulation based on random-walk method(RWM) were introduced. The RWM-simulated results were benchmarked with the analytical results for an ideal spherical pore model. Then, the effects of two numerical parameters, namely diffusion radius and walk numbers, were studied on the simulation accuracy. The simulation method is then applied to various pore models with different pore sizes and pore shapes filled with different fluids to study the microscopic NMR response characteristics. The numerical experiments are useful for understanding and interpreting NMR measurements and the simulation code provides a numerical tool to perform pixel-based digital rock analysis.
