Thermal Evolution Characteristics of the Pore Structure in Coal and Its Dominant Factor Conversion

Yi, Minghao; Wang, Liang; Cheng, Yuanping; Wang, Chenghao; Hu, Biao; Wang, Zhenyang

doi:10.1021/acs.energyfuels.1c01694

Cited by 5 publications

(6 citation statements)

References 59 publications

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“…For more data, the experimental data herein were augmented with data reported in the literature where samples were subjected to heat treatment under vacuum and air conditions. 52 The combined data comprise 16 sets of LPGA data classified into three categories. The results are presented in Table 7.…”

Section: Discussion Of the Indicative Impact Of Pore Heterogeneity On...mentioning

confidence: 99%

“…The Pearson correlation coefficient r is employed to establish correlations among these parameters. For more data, the experimental data herein were augmented with data reported in the literature where samples were subjected to heat treatment under vacuum and air conditions . The combined data comprise 16 sets of LPGA data classified into three categories.…”

Section: Discussion Of the Indicative Impact Of Pore Heterogeneity On...mentioning

confidence: 99%

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Fractal Analysis of Coal Pore Structure Based on Low-Pressure Gas Adsorption and Its Influence on Methane Adsorption Capacity: A Perspective from Micropore Filling Model

Wang,

Wu,

Han

et al. 2024

Energy Fuels

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Understanding pore structure heterogeneity is crucial for gaining insights into the occurrence, transport, and recovery of methane from the coal stratum. The pore structure of coal directly affects the spatial distribution of methane in coal. The influence of the pore structure on methane adsorption has attracted considerable research attention, primarily because of the multiscale characteristics of the pore system and its diverse adsorption behaviors. This study analyzes fractal characteristics to reveal the heterogeneity of the pore structure and pore surface via lowpressure gas adsorption experiments. An adsorption capacity calculation model based on micropore filling is applied and validated by using CH 4 isothermal adsorption experiments. Furthermore, the variation in gas adsorption with fractal dimensions is studied via correlation analysis. Results show that high-rank coal exhibits well-developed micropores with larger micropore fractal dimensions than low-rank coal, and low-rank coal exhibits more meso/macropores and higher meso/macropore fractal dimensions than high-rank coal. The fractal dimensions of meso/macropores and micropores could describe the surface and the volumetric properties of pore structure, respectively. The micropore filling model based on the pore structure can be used to quantitatively calculate the methane adsorption capacity of coal, with errors of −32.6, 2.9, 3.2, and 14.3%. This offers significant advantages over the monolayer adsorption hypothesis in understanding the adsorption behavior of coal. The fractal dimensions of the pore structure are positively correlated with the adsorption capacity in each adsorption form, with correlation coefficients of 0.792 and 0.842 in meso/macropores and 0.821 and 0.743 in micropores, respectively. Because most methane molecules are stored in micropores, the fractal dimensions of micropores play a critical role in governing the methane adsorption capacity of coal. These findings hold substantial implications for understanding the mechanisms that influence methane occurrence in coal under diverse geological conditions, contributing to subsequently assessing the risk of coal and gas outbursts and estimating coalbed methane resources.

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Section: Discussion Of the Indicative Impact Of Pore Heterogeneity On...mentioning

confidence: 99%

Section: Discussion Of the Indicative Impact Of Pore Heterogeneity On...mentioning

confidence: 99%

Fractal Analysis of Coal Pore Structure Based on Low-Pressure Gas Adsorption and Its Influence on Methane Adsorption Capacity: A Perspective from Micropore Filling Model

Wang,

Wu,

Han

et al. 2024

Energy Fuels

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“…Coal is a porous medium with simplified matrixes and a fractured network. − After drilling, the stress and gas adsorption–desorption environment of the coal seam is broken. The gas will be desorbed from the matrixes into the borehole through the fractures network.…”

Section: Methods and Theorymentioning

confidence: 99%

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Zhang

2022

ACS Omega

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Soft and low permeability tectonic coal seams (SLPTCSs) are widely distributed in China. In SLPTCSs, because of the difficulty of gas extraction, coal and gas outburst accidents occur frequently. In this paper, with the principle of stress unloading and permeability enhancement in SLPTCSs analyzed, it is put forward that the key technology to realize stress unloading and permeability enhancement in SLPTCSs is caverning by hydraulic flushing. In addition, the development of hydraulic flushing caverning technology and equipment in China is also further systematically studied. Field tests on the application of highly integrated equipment for caverning by hydraulic flushing have been carried out in the Shijiazhuang coal mine and Pingdingshan no. 8 coal mine. The results show that the widely used drilling and hydraulic flushing packaged equipment and drilling and mechanical cutting packaged equipment for caverning in coal seams can efficiently enlarge caverns in SLPTCSs, reduce the amount of workload for hole-drilling in the coal seam, improve the permeability of the coal seam by 23.9 times, and increase the concentration and pure volume of gas extracted in boreholes by more than two times. Highly integrated hydraulic flushing caverning equipment can realize high-efficiency stress unloading and permeability enhancement of the coal seam, which provides beneficial guidance for gas control of SLPTCSs.

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“…Since the fractal theory was introduced into geology, it has been widely applied and developed in geological tectonics, , mineral prospecting, pore distribution, , rock damage, and fragmentation . In addition, the self-similar linear fractal is often used to study the distribution of geological structures.…”

Section: Experiments and Geostatisticsmentioning

confidence: 99%

Implications of Geological Conditions on Gas Contents: A Case Study in the Pingdingshan Coalfield

et al. 2023

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Coalbed methane occurrence and its geological control factors are important for coal and gas co-mining. In recent years, more than 50% of the outburst accidents occurred near the faults and the thickening strips in Chinese mines. Therefore, studying the gas occurrence and its controlling factors is vital to prevent gas disasters in outburst mines with complex geology. In this paper, the distributions of faults, coal thickness, and gas content were characterized and analyzed based on fractal theory and geostatistics. Then, finer coal thickness inverted by the cross-layer boreholes for gas extraction was analyzed at a single working face. The geological control characteristics of gas contents were finally studied. The results show that coal thickness, burial depth, and fault complexity are the geological factors controlling gas contents from a regional to local scale. The sedimentary environment determines the regional coal thickness distribution and even stratification, which leads to higher gas content in the eastern thick-coal region than in the west. And the gas content varies linearly with burial depth in the same geological zonation. The fault fractal dimension is a quantitative representation of fault complexity. The dense distribution of minor faults is why the sizable fractal dimension in the local region is crucial in controlling the uneven enrichment of gas content. Therefore, more refined geological detection and characterization is the way to gas precision control in the future.

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Thermal Evolution Characteristics of the Pore Structure in Coal and Its Dominant Factor Conversion

Cited by 5 publications

References 59 publications

Fractal Analysis of Coal Pore Structure Based on Low-Pressure Gas Adsorption and Its Influence on Methane Adsorption Capacity: A Perspective from Micropore Filling Model

Fractal Analysis of Coal Pore Structure Based on Low-Pressure Gas Adsorption and Its Influence on Methane Adsorption Capacity: A Perspective from Micropore Filling Model

Research on the Development of Hydraulic Flushing Caverning Technology and Equipment for Gas Extraction in Soft and Low Permeability Tectonic Coal Seams in China

Implications of Geological Conditions on Gas Contents: A Case Study in the Pingdingshan Coalfield

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