Analysis of Pore Structure and Fractal Characteristics of Coal Samples in Pingdingshan Mining Area Based on N2/CO2 Adsorption
DOI:
https://doi.org/10.54097/dbws0w72Keywords:
Coalbed methane, coal pore structure, gas adsorption, FHH model, fractal characteristicsAbstract
In order to reveal the multi-scale pore structure and fractal characteristics of coal samples in Pingdingshan mining area, typical medium metamorphic coal samples were selected to carry out low-temperature N2 adsorption and low-temperature CO2 adsorption experiments. Combined with FHH fractal model and Sierpinski fractal model, the pore volume, specific surface area, pore size distribution and fractal dimension of coal samples were analyzed. The results show that the coal samples in the study area have the characteristics of medium-low ash, low volatile matter and high fixed carbon. The macerals are mainly vitrinite, followed by inertinite. The results of low temperature N2 adsorption show that the pore volume in the 2-300 nm pores of coal samples is mainly contributed by micropores and mesopores, among which mesopores have more obvious control effect on reservoir space. The specific surface area is mainly controlled by 2-10 nm micropores. The adsorption-desorption isotherm is type IV and superimposed type II. The hysteresis loop reflects the development of composite pore structures such as ink bottle pores, slit pores and fissure pores in the coal body. The results of CO2 adsorption show that the ultramicropores of coal samples are relatively developed, and the pore size is mainly concentrated in 0.40-0.80 nm, of which about 0.52 nm pores are dominant, which is the main space for gas adsorption and occurrence. The fractal analysis shows that the fractal dimension D1 of N2 adsorption is 2.28-2.58, D2 is 2.55-2.67, and most samples D2 > D1, indicating that the pore complexity of coal samples is mainly controlled by the heterogeneity of three-dimensional pore network. The fractal dimension Dm of supermicropores for CO2 adsorption is 2.32-2.38, indicating that the structure of supermicropores is relatively simple and the connectivity is weak. According to the research, the gas occurrence of coal samples in Pingdingshan mining area is mainly controlled by the adsorption space of ultra-micropores, while the gas diffusion and migration are restricted by the complexity of micropore-mesopore pore network.
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[1] Zou G, Chau K W. Energy consumption, economic growth and environmental sustainability: Evidence from China [J]. Energy Reports, 2023, 9: 106-116.
[2] Labani M M, Rezaee R, Saeedi A, et al. Evaluation of pore size spectrum of gas shale reservoirs using low pressure nitrogen adsorption, gas expansion and mercury porosimetry: A case study from the Perth and Canning Basins, Western Australia [J]. Journal of Petroleum Science and Engineering, 2013, 112: 7-16.
[3] Qin L, Li S, Zhai C, et al. Changes in the pore structure of lignite after repeated cycles of liquid nitrogen freezing as determined by nitrogen adsorption and mercury intrusion [J]. Fuel, 2020, 267: 117214.
[4] Jia M, Huang W, Li Y. Quantitative characterization of pore structure parameters in coal based on image processing and SEM technology [J]. Energies, 2023, 16(4): 1663.
[5] He Shanshan, Zhao Difei, Liu Jing, et al. Characterization of adsorption pore structure and fractal characteristics of anthracite based on low-temperature nitrogen adsorption [J]. Coal Technology, 2019, 38(1): 66-69.
[6] Shen Yanjun, Wang Xu, Zhao Chunhu, et al. Multi-scale pore structure characteristics of oil-rich coal in Yushenfu mining area [J]. Coalfield Geology and Exploration, 2021, 49(3): 33-41.
[7] Fu Xuehai, Qin Yong, Zhang Wanhong, et al. Coal pore fractal classification and natural classification based on CBM migration [J]. Science Bulletin, 2005(S1): 51-55.
[8] Lang Weiwei, Song Zhimin, Liu Gaofeng, et al. Pore distribution and fractal characteristics of deformed coal based on low temperature liquid nitrogen adsorption experiment [J]. Journal of Henan Institute of Technology (Natural Science Edition), 2015, 27(2): 34-37.
[9] Hao Jinwei, Li Yang. Research on multi-scale fractal characterization and influencing factors of pore structure of tectonic coal [J]. Coal Science and Technology, 2020, 48(8): 164-174.
[10] Zhang Shaofeng, Li Yage, Qin Xinglin. Fractal characteristics of coal reservoir pores in Qinshui Basin and its influence on gas adsorption [J]. Coal Science and Technology, 2019, 47(3): 163-167.
[11] Lu Hongwei, Xu Hongjie, Yang Yichao, et al. Heterogeneity characteristics of pore structure and methane adsorption energy change in coal reservoir [J]. Science Technology and Engineering, 2023, 23(30): 12817-12826.
[12] Chen Liuyu, Li Xijian, Shen Zhonghui, et al. Study on pore structure and fractal characteristics of outburst coal in northern Guizhou [J]. China Safety Science Journal, 2020, 30(2): 66-72.
[13] Yang Y, Jin Y, Song H, et al. Shape and size effects on adsorption performance of methane from pores in coal [J]. Energy, 2025, 318: 134814.
[14] Li Yanhe, Wang Baoyu, Liu Shunxi, et al. Sedimentary environment of coal-bearing strata and its control on coal-measure gas accumulation in Pingdingshan mining area, Henan Province [J]. Journal of Palaeogeography, 2024, 26(6).
[15] An Cheng, Liu Guangdi, Sun Mingliang, et al. Analysis of shale pore structure characteristics based on nitrogen adsorption experiment and fractal FHH model: A case study of Chang 7 Member in Huachi area, Ordos Basin [J]. Petroleum Geology & Experiment, 2023, 45(3): 576-586.
[16] Peng Xin, Jiang Zebiao, Li Bobo, et al. Experimental study on the influence of carbon dioxide fracturing on the fractal characteristics of coal pore surface [J]. Journal of Safety Science and Technology, 2019, 15(2): 111-117.
[17] Zhang Kun, Meng Zhaoping, Jin Yi, et al. Fractal characteristics of pore structure of coal with different coal structure and its research significance [J]. Coal Science and Technology, 2023, 51(10): 198-206.
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