Abstract
The pore structure and microfracture evolution characteristics of coal in high gas mine are worthy of studying to make clear the mechanism of coal and gas outburst. Samples were collected from 2# coal seam (high gas coal seam) in Dongpang Coal Mine, China. Two groups of samples were divided: one was cut from the intact coal blocks which was roughly a cube with the particle size less than 1 cm, and the other was the pulverized coal drilled from the working face. Mercury intrusion porosimetry (MIP) and gas absorption were used to investigate the pore size distributions (PSDs) of coal samples. The experimental results display that the compressibility of coal matrix has a significant influence on the pore volume of coal specimens especially when the pressure is greater than 20 MPa. Macropores in both intact and pulverized coal samples account for the largest proportion but the average micropore volume for the pulverized coal is 2.67 times that of the intact coal. The greater pore tortuosity of pulverized coal indicates that it has worse pore connectivity overall. Multi-fractal analysis result shows the PSDs of pulverized coal are more homogeneous than intact coal. During the process of mining, the vertical loading and horizontal unloading cause the opening and propagation of microfractures and increase the difference of the PSDs between the intact and pulverized coal. It results in the not smooth of gas flow from pulverized coal area. Gas might be prone to accumulate in the area with more pulverized coal.
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References
Beamish BB, Crosdale PJ (1998) Instantaneous outbursts in underground coal mines: an overview and association with coal type. Int J Coal Geol 35:27–55. https://doi.org/10.1016/S0166-5162(97)00036-0
Cai Y, Liu D, Pan Z et al (2013) Pore structure and its impact on CH4 adsorption capacity and flow capability of bituminous and subbituminous coals from Northeast China. Fuel 103:258–268. https://doi.org/10.1016/j.fuel.2012.06.055
Caniego FJ, Martín MA, San José F (2003) Rényi dimensions of soil pore size distribution. Geoderma 112:205–216. https://doi.org/10.1016/S0016-7061(02)00307-5
Carniglia SC (1986) Construction of the tortuosity factor from porosimetry. J Catal 102:401–418. https://doi.org/10.1016/0021-9517(86)90176-4
Chen D, Pan Z, Liu J et al (2013) An improved relative permeability model for coal reservoirs. Int J Coal Geol 109–110:45–57. https://doi.org/10.1016/j.coal.2013.02.002
Cheng Y, Lei Y (2021) Causality between tectonic coal and coal and gas outbursts. J China Coal Soc 46:180–198. https://doi.org/10.13225/j.cnki.jccs.YG20.1539
Chhabra A, Meneveau C, Jensen R et al (1989) Direct determination of the f(α) singularity spectrum and its application to fully developed turbulence. Phys Rev A 40:5284–5294. https://doi.org/10.1103/physreva.40.5284
Ferreiro JP, Vázquez VE (2010) Multifractal analysis of Hg pore size distributions in soils with contrasting structural stability. Geoderma 160:64–73. https://doi.org/10.1016/j.geoderma.2009.11.019
Friesen W, Mikula R (1988) Mercury porosimetry of coals: pore volume distribution and compressibility. Fuel 67:1516–1520. https://doi.org/10.1016/0016-2361(88)90069-5
Fu XH, Qin Y, Xue XQ et al (2001) Research on fractals of pore and fracture-structure of coal reservoirs. J China Univ Min Technol (Engl Ed) 30: 225-228. https://doi.org/10.3321/j.issn:1000-1964.2001.03.003
Gauden PA, Terzyk AP, Rychlicki G (2001) New correlation between microporosity of strictly microporous activated carbons and fractal dimension on the basis of the Polanyi-Dubinin theory of adsorption. Carbon N Y 39:267–278. https://doi.org/10.1016/S0008-6223(00)00122-6
Giffin S, Littke R, Klaver J et al (2013) Application of BIB-SEM technology to characterize macropore morphology in coal. Int J Coal Geol 114:85–95. https://doi.org/10.1016/j.coal.2013.02.009
Guo J, Kang T, Kang J et al (2014) Effect of the lump size on methane desorption from anthracite. J Nat Gas Sci Eng 20:337–346. https://doi.org/10.1016/j.jngse.2014.07.019
Guo B, Li Y, Jiao F et al (2018) Experimental study on coal and gas outburst and the variation characteristics of gas pressure. Geomech Geophys Geo-Energy Geo-Resources 4:355–368. https://doi.org/10.1007/s40948-018-0092-8
Halsey TC, Jensen MH, Kadanoff LP et al (1987) Fractal measures and their singularities: the characterization of strange sets. Nuclear Phys B Proc Suppl 2:501–511. https://doi.org/10.1016/0920-5632(87)90036-3
Jin K, Cheng Y, Liu Q et al (2016) Experimental investigation of pore structure damage in pulverized coal: Implications for methane adsorption and diffusion characteristics. Energy Fuels 30:10383–10395. https://doi.org/10.1021/acs.energyfuels.6b02530
Karacan CO, Okandan E (2001) Adsorption and gas transport in coal microstructure: investigation and evaluation by quantitative X-ray CT imaging. Fuel 80:509–520. https://doi.org/10.1016/S0016-2361(00)00112-5
Khabbazi AE, Hinebaugh J, Bazylak A (2016) Determining the impact of rectangular grain aspect ratio on tortuosity–porosity correlations of two-dimensional stochastically generated porous media. Sci Bull 61:601–611. https://doi.org/10.1007/s11434-016-1020-3
Li YH, Lu GQ, Rudolph V (1999) Compressibility and fractal dimension of fine coal particles in relation to pore structure characterization using mercury porosimetry. Part Part Syst Charact 16:25–31. https://doi.org/10.1002/(SICI)1521-4117(199905)16:1%3c25::AID-PPSC25%3e3.0.CO;2-T
Li H, Ogawa Y, Shimada S (2003) Mechanism of methane flow through sheared coals and its role on methane recovery. Fuel 82:1271–1279. https://doi.org/10.1016/S0016-2361(03)00020-6
Li W, Liu H, Song X (2015) Multifractal analysis of Hg pore size distributions of tectonically deformed coals. Int J Coal Geol 144–145:138–152. https://doi.org/10.1016/j.coal.2015.04.011
Mandelbrot BB (1967) How long is the coast of Britain? Statistical self-similarity and fractional dimension. Science 156(3775):636–638. https://doi.org/10.1126/science.156.3775.636
Martínez FSJ, Martín MA, Caniego FJ et al (2010) Multifractal analysis of discretized X-ray CT images for the characterization of soil macropore structures. Geoderma 156:32–42. https://doi.org/10.1016/j.geoderma.2010.01.004
Muller J, McCauley JL (1992) Implication of fractal geometry for fluid flow properties of sedimentary rocks. Transp Porous Media 8:133–147. https://doi.org/10.1007/BF00617114
Nie B, Liu X, Yang L et al (2015) Pore structure characterization of different rank coals using gas adsorption and scanning electron microscopy. Fuel 158:908–917. https://doi.org/10.1016/j.fuel.2015.06.050
Suggate RP, Dickinson WW (2004) Carbon NMR of coals: the effects of coal type and rank. Int J Coal Geol 57:1–22. https://doi.org/10.1016/S0166-5162(03)00116-2
Sun B, Yang Q, Zhu J et al (2020) Pore size distributions and pore multifractal characteristics of medium and low-rank coals. Sci Rep 10:1–12. https://doi.org/10.1038/s41598-020-79338-3
Thommes M (2016) Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure and Applied Chemistry 87:25-25. https://doi.org/10.1515/ci-2016-0119
Wang Z, Cheng Y, Qi Y et al (2019) Experimental study of pore structure and fractal characteristics of pulverized intact coal and tectonic coal by low temperature nitrogen adsorption. Powder Technol 350:15–25. https://doi.org/10.1016/j.powtec.2019.03.030
Xu J, Liu D, Peng S et al (2010) Experimental research on influence of particle diameter on coal and gas outburst. Chinese J Rock Mech Eng 29:1231–1237. https://doi.org/CNKI:SUN:YSLX.0.2010-06-020
Zhu J, He F, Zhang Y et al (2019) Fractal analysis in pore size distributions of different bituminous coals. Sci Rep 9:1–12. https://doi.org/10.1038/s41598-019-54749-z
Zhuo Q, Liu W, Xu H et al (2020) Effect of particle size distribution on filter cake pore structure and coal slurry dewatering process. Int J Coal Prep Util 00:1–16. https://doi.org/10.1080/19392699.2020.1781830
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This research was supported by the National Nature Science Foundation of China (52074297) and the Fundamental Research Funds for the Central Universities (2022YJSLJ03).
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Zhu, J., Yang, Y., Shao, T. et al. Pore Size Distributions and Multi-Fractal Characteristics of the Intact and Pulverized Coal in High Gas Mine. Geotech Geol Eng 40, 4943–4959 (2022). https://doi.org/10.1007/s10706-022-02192-9
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DOI: https://doi.org/10.1007/s10706-022-02192-9