Seepage characteristics of fracture and dead-end pore structure in coal at micro- and meso-scales

Wang, Gang; Han, Dongyang; Jiang, Chenghao; Zhang, Zhenyu

doi:10.1016/j.fuel.2020.117058

Cited by 56 publications

(12 citation statements)

References 38 publications

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“…Studying coal characteristics using CT dates back to 1879, when scholars first used it to distinguish the organic and inorganic materials in coal . At present, in addition to the microstructural characterization of coal, CT is widely used for investigating gas adsorption, gas diffusion, permeability, mechanical behavior, and the evaluation of matrix deformation. − Previous reviews on CT application in coal characterization focused on pore and fracture characterization methods and 3D model establishment. , The influence of coal microstructures on macroscopic properties has been investigated by extensively studying the correlation between them, but the characterization of coal properties using CT has not been systematically reviewed yet.…”

Section: Introductionmentioning

confidence: 99%

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

et al. 2022

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Characterization of microscopic structure and macroscopic physical property are the basis for better understanding of coalbed methane reservoirs. X-ray computed tomography (CT), as an nondestructive measurement, has been widely and successfully applied to characterize the internal structure of coal. In this study, we introduce the principle of CT imaging and the microstructure recognition. A summary of CT imaging-based coal microstructure characterization follows, including three-dimensional (3D) microstructure reconstruction, pore and mineral quantification, and equivalent pore network model construction. We review the methods used to evaluate the macroscopic properties of coal, including porosity calculation, gas adsorption/diffusion rate test, permeability simulation, and mechanical behavior evaluation. This study discusses the application of CT to investigate the evolutionary mechanisms of microstructure and macroscopic properties during gas adsorption, temperature change, and damage deformation. We conclude this review with a summary of the challenges and application perspectives of CT. The small scanning range, limited observation accuracy, functional limitations, lengthy testing process, and high cost are some of the major hurdles in the broad application of CT for coal characterization. In the future, CT should be combined with other techniques to establish full-scale pore and fracture models, identify mineral types in microstructures, and effusively use the advantages of CT by selecting the key points in the evolutionary mechanisms of microstructure and macroscopic properties.

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Section: Introductionmentioning

confidence: 99%

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

et al. 2022

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“…Tao et al [15] analysed the porosity and fracture heterogeneity of coal using a variety of experimental methods (SEM, carbon dioxide and nitrogen adsorption, and CT scans) and proposed an index to quantitatively predict coal macrolithotypes. Wang et al [16][17][18] used CT scans to analyse the pore structure and seepage features of coal, which were then used to conduct a dynamic water injection simulation analysis. Wu et al analysed the fractal features of a coal fracture network to find that the porosity is exponentially related to fractal dimension.…”

Section: Introductionmentioning

confidence: 99%

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Li¹,

Pan³

et al. 2022

Mathematics

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Computed tomography (CT) scans were performed on samples of an outburst-prone coal seam at different loading stages. The area and roundness of the CT images were used to quantify the degree of the coal macroscopic deformation under different loads. A spatial matching algorithm was used to calculate the three-dimensional (3D) displacement fields of different regions of interest (ROIs, containing primary fractures, minerals, and only coal) under different loads. The presence of fractures and minerals were found to promote and inhibit displacement, respectively, and the 3D displacement field data followed a normal distribution. A meshfree numerical simulation was used to determine the 3D maximum principal stress, shear stress and displacement fields under different loads. The following results were obtained: fractures and minerals significantly affect the stress state and displacement field distribution features, the maximum principal stresses and shear stresses in different matrices differ significantly, and the presence of minerals and fractures induce a prevalent shear stress in coal and make coal prone to stress concentration.

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“…Coal is a complex porous media material. 1,2 The structure and number of pores and cracks on the surface and inside determine the physical and chemical properties of the coal itself. 3−5 Coal is sensitive to the temperature, and temperature changes will directly affect its pore and crack structure.…”

Section: Introductionmentioning

confidence: 99%

“…Coal is a complex porous media material. , The structure and number of pores and cracks on the surface and inside determine the physical and chemical properties of the coal itself. − Coal is sensitive to the temperature, and temperature changes will directly affect its pore and crack structure. , When the pore and crack structure of coal changes, the permeability of coal will change, which will affect the collection efficiency of coalbed methane. , The change of the pore and crack structure will produce geophysical signals, such as acoustic emission and electromagnetism . Before there is no open fire in the coal mine, the fire monitoring and prediction can be realized by collecting and analyzing such signals .…”

Section: Introductionmentioning

confidence: 99%

Study on the Pore and Crack Change Characteristics of Bituminous Coal and Anthracite after Different Temperature Gradient Baking

Zhuang

Zhang

et al. 2021

Energy Fuels

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At present, there are few studies on the development, evolution, and quantitative analysis of internal pores and cracks after heat treatment of coal. On the basis of this, low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray diffraction (XRD) experiments were carried out on five kinds of temperature-treated bituminous coal and anthracite. The pore cracks of coal samples were studied qualitatively and quantitatively using linear fitting and the fractal theory. Through the analysis of the original diffractograms in the XRD experiment, the quantitative analysis of mineral composition in coal was realized. The results show that, with the increase of the temperature, the thermal damage of coal changes obviously and the micromorphology of the coal surface changes from the initial compact structure to the appearance of pores and small cracks and then to the mutual connection and evolution into large cracks. The development of pores and cracks of bituminous coal is more obvious than that of anthracite. Because anthracite has better heat resistance, there is no expansion and crack in its internal structure during the experiment. Through the fractal calculation of the coal nitrogen adsorption capacity, it is obtained that the overall pore volume and specific surface area of bituminous coal and anthracite are positively correlated with the fractal dimension (D 1) of the pore structure and V daf is negatively correlated with the fractal dimension (D 2) of the pore surface. In the temperature range from a normal temperature to 100 °C, the mineral crystal structure inside the coal body changes significantly, a large number of pores appear on the coal surface, and the total pore volume increases accordingly to reach the measured maximum value. The research of this paper is of great significance to reveal the effect of the temperature on coal damage and deformation and crack evolution.

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Seepage characteristics of fracture and dead-end pore structure in coal at micro- and meso-scales

Cited by 56 publications

References 38 publications

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

Characterization of 3D Displacement and Stress Fields in Coal Based on CT Scans

Study on the Pore and Crack Change Characteristics of Bituminous Coal and Anthracite after Different Temperature Gradient Baking

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