Cleat structure analysis and permeability simulation of coal samples based on micro-computed tomography (micro-CT) and scan electron microscopy (SEM) technology

Roslin, Alexandra; Pokrajac, Dubravka; Zhou, Yingfang

doi:10.1016/j.fuel.2019.05.162

Cited by 65 publications

(38 citation statements)

References 35 publications

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“…CT scanning is quite a fast, comprehensive and nondestructive technology [42,43]. The scanning resolution of the industrial CT scanning system depends on the size of coal specimens.…”

Section: Ct Scanning Results Under Thermal Shocksmentioning

confidence: 99%

“…From the above result analysis, under thermal shocks effect, the propagation rule of microcracks obtained by analyzing CT images was consistent with that by analyzing SEM images. Previously, studies to investigate the internal structure of microcracks in geological materials were carried out by using CT and SEM images [43,60,62]. For instance, Roslin [43] used CT scan and SEM techniques to study the characteristic of cleat structures in coal in order to predicate coal permeability with Lattice Boltzmann method.…”

Section: Plos Onementioning

confidence: 99%

“…Previously, studies to investigate the internal structure of microcracks in geological materials were carried out by using CT and SEM images [43,60,62]. For instance, Roslin [43] used CT scan and SEM techniques to study the characteristic of cleat structures in coal in order to predicate coal permeability with Lattice Boltzmann method. In this paper, CT scanning focused on the internal microcracks change and whereas SEM scanning focused on the surface microcracks change.…”

Section: Plos Onementioning

confidence: 99%

“…Scanning electron microscope (SEM) and computer tomography (CT) scanning technologies are effective means to investigate the growth and expansion of cracks in geological materials under thermal treatments [42,43]. Cai et al and Qin et al studied the crack propagation in coal using SEM tests and found that LN 2 freezing stretched and increased the number of cracks, and accordingly improved the initial damage degree of the coal [5,[8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Microcrack evolution and permeability enhancement due to thermal shocks in coal

Zhang

Wang

et al. 2020

PLoS ONE

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To understand the effects of thermal shock on microcrack propagation and permeability in coal, thermal shock tests were conducted on coal specimens by using a constant temperature drying oven (105˚C) and a SLX program controlled cryogenic tank. The growth and propagation of microcracks were measured with computer tomography (CT) scanning and scanning electron microscope (SEM) tests. Results showed that thermal shocks improved the permeability of coal significantly. Notably, the permeability of coal after thermal shocks increased from 211.31% to 368.99% and was positively correlated with temperature difference. CT scanning images revealed that thermal shocks increased the crack number, crack volume and crack width as well as smoothened and widened the gas flow paths, thereby enhancing coal permeability. Moreover, SEM images showed that heating-cooling shocks created more new microcracks, forming more complex crack propagation paths and better connectivity among microcracks in coal compared to cooling shocks. We proposed a crack propagation criterion for coal to explain the mechanism of crack failure and propagation during thermal shocks. Our experiment results and theoretical analysis indicate that the heating-cooling shock is more effective in damaging and breaking coal than the cooling shock. Thus, it can be used as an alternative approach to enhance coal permeability in the production of coalbed methane (CBM).

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“…CT scanning is quite a fast, comprehensive and nondestructive technology [42,43]. The scanning resolution of the industrial CT scanning system depends on the size of coal specimens.…”

Section: Ct Scanning Results Under Thermal Shocksmentioning

confidence: 99%

Section: Plos Onementioning

confidence: 99%

Section: Plos Onementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Microcrack evolution and permeability enhancement due to thermal shocks in coal

Zhang

Wang

et al. 2020

PLoS ONE

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“…Kluge et al (12) analysed the discrepancy between numerical simulation of fluid flow and analytical solution of Navier- For the purpose of the research described in this paper it was decided to apply cubic law in order to calculate permeability for a cylinder with diameter and height 2.5mm, compare the results with the outcomes of numerical simulation for the same volume, make corrections and use the resulted "updated" cubic law for a cylinder with diameter and height 2.5cm. This study relies on the previous study by the authors which focused on micro-CT image resolution improvement and permeability numerical simulation (25). Validation of the final results is performed by comparison with laboratory data obtained for the studied or similar samples.…”

Section: Introductionmentioning

confidence: 99%

Permeability Upscaling Using the Cubic Law Based on the Analysis of Multiresolution Micro Computed Tomography Images of Intermediate Rank Coal

2019

Self Cite

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This paper presents a method for upscaling permeability of fractured coal by using cubic law to quantify permeability of fractures system. The version of the cubic law that incorporates the length/tortuosity effect available in the literature was modified by including a connectivity parameter. All parameters of the modified cubic law (fracture aperture, porosity, length, and connectivity) were estimated for a set of coal samples using quantitative methods available in the literature. The geometry of the fracture system within the coal samples was determined from Micro-CT scans. Parameters of the modified cubic law estimated from the scans were validated by comparison of the resulting permeability with the numerical simulation of single phase fluid flow in fractures, which was developed at the previous stage of this study. The modified cubic law was then used for upscaling of permeability from millimetre scale to centimetre scale. It produced the results that match the literature data for the coal from the same region as well as the experimental data for the studied area.

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The combined effect of fractures and mineral content on coal hydromechanical response

Bahaaddini

Masoumi

et al. 2022

Bull Eng Geol Environ

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The hydromechanical behaviour of fractured coal is a complex function of interaction between coal bulk and fracture deformation driven by fluid pressure and external stress. Despite the research studies conducted to date, the combined effect of mineral content and fracture structure on hydromechanical behaviour of sorptive fractured coal remains unexplored. To study this combined effect, we performed a series of X-ray computed tomography (XRCT) imaging on a range of coal specimens with non-sorbing (helium) and sorbing (CO2) gases at different effective stress paths using a newly developed X-ray transparent triaxial system. The compressibility of system components was obtained from processed 3D XRCT images which were used to interpret the results. The results of this study show that coal matrix/solid compressibility has a positive nonlinear relation with mineral content irrespective of mineral type. Effective stress coefficient is also a strong function of both mineral content and fracture porosity. Furthermore, the increase in mineral content leads to less fracture opening by an increase in helium pressure. Interestingly, the effect of mineral content on the bulk strength of coal is more significant than the effect of fracture porosity. Finally, coal with more open fractures shows less bulk swelling by gas adsorption under external stress due to damping effect of fracture volume on developed internal volumetric swelling strain.

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Cleat structure analysis and permeability simulation of coal samples based on micro-computed tomography (micro-CT) and scan electron microscopy (SEM) technology

Cited by 65 publications

References 35 publications

Microcrack evolution and permeability enhancement due to thermal shocks in coal

Microcrack evolution and permeability enhancement due to thermal shocks in coal

Permeability Upscaling Using the Cubic Law Based on the Analysis of Multiresolution Micro Computed Tomography Images of Intermediate Rank Coal

The combined effect of fractures and mineral content on coal hydromechanical response

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