Porosity and Fracture Changes of Coal under Uniaxial Strain Conditions Based on the X-ray Microscopic Imaging Technology

Qi, Yang; Yu, Yanbin; Cheng, Weimin; Cui, Wenbin; Xin, Qilin; Gao, Chengwei; Zheng, Lei

doi:10.1021/acs.energyfuels.1c03463

Cited by 7 publications

(5 citation statements)

References 40 publications

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“…26 There are also studies on analyzing the fracture volume change and the crushing process of coal under axial stress through a 3-D model. 27 In addition, according to the digital core 3-D model, selecting a suitable permeability calculation model and combining the seepage experiment can find the correlation between permeability and the porosity resolved by X-ray CT. 28 In coal, the seepage capacity and stress sensitivity of different types of fractures are different. 29 Based on lattice Boltzmann and pore network models, Avizo software can simulate the coal seepage path and velocity under effective stress.…”

Section: Introductionmentioning

confidence: 99%

“…For the stress sensitivity of coal, the 2-D image of coal constructed by X-ray CT clarifies the law of fracture aperture and distributed evolution as effective stress increases . There are also studies on analyzing the fracture volume change and the crushing process of coal under axial stress through a 3-D model . In addition, according to the digital core 3-D model, selecting a suitable permeability calculation model and combining the seepage experiment can find the correlation between permeability and the porosity resolved by X-ray CT .…”

Section: Introductionmentioning

confidence: 99%

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Stress Sensitivity of Coal: A Digital Core Analysis

Zhou

Zhao

et al. 2022

Energy Fuels

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Identifying the variation of fracture structure and coal permeability with effective stress is important for protecting coalbed methane (CBM) reservoirs and formulating a reasonable drainage system. This study characterizes the coal fracture and permeability variations with effective stress using three-dimensional (3-D) micro-CT and digital core techniques. Dual-resolution scanning is adopted to characterize the variation of three types of fractures with effective stress and to clarify the stress sensitivity of the porosity of each type of fracture. Type-A fractures (>109 μm3) are most sensitive to effective stress and tend to close as effective stress increases. Moreover, the porosity of this fracture has a negative exponential relationship with effective stress. Type-B fractures (107–109 μm3) are moderately sensitive to effective stress and have the highest contribution of total porosity at high effective stress. Type-C fractures (<107 μm3) are least sensitive to effective stress, and the porosity of this fracture changes slightly. The seepage simulation in the two directions with digital core techniques confirms that the permeability of coal samples presents an exponential decrease with effective stress and shows an anisotropic behavior with space. Combined with the quantitative analysis of variation of pore–fracture models, the compression model of coal under effective stress can be established, which can reveal the reason that the permeability loss rate in the y-axis is more than that in the z-axis. The sensitivity of porosity and permeability is stronger under low stress and weaker under high stress. Therefore, digital core technology can quantitatively analyze the stress sensitivity of coal fracture structure and permeability based on 3-D models. This method is more intuitive to study the stress sensitivity of coal compared with traditional methods.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stress Sensitivity of Coal: A Digital Core Analysis

Zhou

Zhao

et al. 2022

Energy Fuels

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Section: Dynamic Evolution Of Microstructure and Macroscopic Properti...mentioning

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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“…Therefore, it is very important to construct a three-dimensional real meso-model of porous media, which can be used to analyze the spatial distribution characteristics of pores from the meso-scale. Three-dimensional reconstruction technology refers to reproducing the original three-dimensional image of the detected object by performing segmentation processing, such as boundary recognition, on a series of two-dimensional images, and using visual processing to display the three-dimensional spatial structure distribution and morphological characteristics of BFRC [30][31][32]. In this paper, the 3D model was obtained after the 3D reconstruction of the series of binary images which were segmented according to the above threshold, allowing a series of operations, such as pore segmentation, to be carried out.…”

Section: Pore Network Modelmentioning

confidence: 99%

Quantifying Computed Tomography of Basalt Fiber-Reinforced Concrete under Unconfined Compression

et al. 2022

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The macroscopic aspects of adding basalt fiber (BF) to concrete has been the subject of studies that document great increases in compression strength. Research into the microscopic aspects of the reinforcement mechanism is still in an exploratory stage, and the quantitative analysis and visual observation of fibers in the concrete matrix are difficult. In this paper, the reinforcement effect of fiber on concrete is studied by means of computed tomography (CT) scanning technology and digital image processing (DIP) technology, combined with the macro-mechanical properties obtained from the unconfined compression strength test, and quantitative analysis from the micro point of view. At the same time, the fiber visualization is realized with the help of Avizo. The results show that with the increase in fiber dosage, the peak stress of concrete first increases and then decreases. When the fiber dosage is 3 kg/m3, the peak stress is 44.4 MPa, which is 41.85% higher than that of ordinary concrete. Additionally, the proportion of macropores is the least, which is the best fiber dosage. It is found that when the fiber dosage is 3 kg/m3, the angular distribution of φ is relatively uniform, and the uniform distribution of fibers forms a dense network structure, which significantly increases the peak stress of concrete. However, when the fiber dosage is too high, it will lead to the accumulation of fibers and produce macropores, and these excess fibers mainly appear in the horizontal direction and do not contribute to the compression strength.

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Porosity and Fracture Changes of Coal under Uniaxial Strain Conditions Based on the X-ray Microscopic Imaging Technology

Cited by 7 publications

References 40 publications

Stress Sensitivity of Coal: A Digital Core Analysis

Stress Sensitivity of Coal: A Digital Core Analysis

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

Quantifying Computed Tomography of Basalt Fiber-Reinforced Concrete under Unconfined Compression

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