Study on the evolution of solid–liquid–gas in multi-scale pore methane in tectonic coal

doi:10.1016/j.cjche.2024.02.012

Abstract

Abstract: The rich accumulation of methane (CH₄) in tectonic coal layers poses a significant obstacle to the safe and efficient extraction of coal seams and coalbed methane. Tectonic coal samples from three geologically complex regions were selected, and the main results obtained by using a variety of research tools, such as physical tests, theoretical analyses, and numerical simulations, are as follows: 22.4–62.5 nm is the joint segment of pore volume, and 26.7–100.7 nm is the joint segment of pore specific surface area. In the dynamic gas production process of tectonic coal pore structure, the adsorption method of methane molecules is “solid–liquid adsorption is the mainstay, and solid–gas adsorption coexists”. Methane stored in micropores with a pore size smaller than the jointed range is defined as solid-state pores. Pores within the jointed range, which transition from micropore filling to surface adsorption, are defined as gaseous pores. Pores outside the jointed range, where solid–liquid adsorption occurs, are defined as liquid pores. The evolution of pore structure affects the methane adsorption mode, which provides basic theoretical guidance for the development of coal seam resources.

Key words: Tectonic coal, Multiscale pore structure, Methane adsorption, Micropore filling, Monolayer, Molecular simulation

摘要： The rich accumulation of methane (CH₄) in tectonic coal layers poses a significant obstacle to the safe and efficient extraction of coal seams and coalbed methane. Tectonic coal samples from three geologically complex regions were selected, and the main results obtained by using a variety of research tools, such as physical tests, theoretical analyses, and numerical simulations, are as follows: 22.4–62.5 nm is the joint segment of pore volume, and 26.7–100.7 nm is the joint segment of pore specific surface area. In the dynamic gas production process of tectonic coal pore structure, the adsorption method of methane molecules is “solid–liquid adsorption is the mainstay, and solid–gas adsorption coexists”. Methane stored in micropores with a pore size smaller than the jointed range is defined as solid-state pores. Pores within the jointed range, which transition from micropore filling to surface adsorption, are defined as gaseous pores. Pores outside the jointed range, where solid–liquid adsorption occurs, are defined as liquid pores. The evolution of pore structure affects the methane adsorption mode, which provides basic theoretical guidance for the development of coal seam resources.

关键词: Tectonic coal, Multiscale pore structure, Methane adsorption, Micropore filling, Monolayer, Molecular simulation

Junjie Cai, Xijian Li, Hao Sui, Honggao Xie. Study on the evolution of solid–liquid–gas in multi-scale pore methane in tectonic coal[J]. Chinese Journal of Chemical Engineering, 2024, 71(7): 122-131.

Junjie Cai, Xijian Li, Hao Sui, Honggao Xie. Study on the evolution of solid–liquid–gas in multi-scale pore methane in tectonic coal[J]. 中国化学工程学报, 2024, 71(7): 122-131.

References

[1] J.C. Zhang, X.L. Li, Q.Z. Qin, Y.B. Wang, X. Gao, Study on overlying strata movement patterns and mechanisms in super-large mining height stopes, Bull. Eng. Geol. Environ. 82 (4) (2023) 142.
[2] C.S. Zheng, B.Y. Jiang, S. Xue, Z.W. Chen, H. Li, Coalbed methane emissions and drainage methods in underground mining for mining safety and environmental benefits: A review, Process. Saf. Environ. Prot. 127 (2019) 103-124.
[3] X.F. Liu, X.Q. Jia, Y. Niu, B.S. Nie, C.P. Zhang, D.Z. Song, Alterations in coal mechanical properties and permeability influenced by liquid CO₂ phase change fracturing, Fuel 354 (2023) 129254.
[4] G.W. Lu, C.T. Wei, J.L. Wang, R.Y. Meng, L. Soh Tamehe, Influence of pore structure and surface free energy on the contents of adsorbed and free methane in tectonically deformed coal, Fuel 285 (2021) 119087.
[5] H.S. Song, B.B. Li, J.H. Li, P.P. Ye, S.L. Duan, Y.N. Ding, An apparent permeability model in organic shales: Coupling multiple flow mechanisms and factors, Langmuir 39 (11) (2023) 3951-3966.
[6] S. Giffin, R. Littke, J. Klaver, J.L. Urai, Application of BIB-SEM technology to characterize macropore morphology in coal, Int. J. Coal Geol. 114 (2013) 85-95.
[7] Y.X. Zhao, S.M. Liu, D. Elsworth, Y.D. Jiang, J. Zhu, Pore structure characterization of coal by synchrotron small-angle X-ray scattering and transmission electron microscopy, Energy Fuels 28 (6) (2014) 3704-3711.
[8] B.S. Nie, X.F. Liu, L.L. Yang, J.Q. Meng, X.C. Li, Pore structure characterization of different rank coals using gas adsorption and scanning electron microscopy, Fuel 158 (2015) 908-917.
[9] S.M. Liu, H.T. Sun, D.M. Zhang, K. Yang, X.L. Li, D.K. Wang, Y.N. Li, Experimental study of effect of liquid nitrogen cold soaking on coal pore structure and fractal characteristics, Energy 275 (2023) 127470.
[10] X.Q. He, X.F. Liu, B.S. Nie, D.Z. Song, FTIR and Raman spectroscopy characterization of functional groups in various rank coals, Fuel 206 (2017) 555-563.
[11] M.M. Labani, R. Rezaee, A. Saeedi, A. Al Hinai, 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. Petrol. Sci. Eng. 112 (2013) 7-16.
[12] M.L. Wang, Q.C. Yu, Pore structure characterization of Carboniferous shales from the eastern Qaidam Basin, China: Combining helium expansion with low-pressure adsorption and mercury intrusion, J. Petrol. Sci. Eng. 152 (2017) 91-103.
[13] S.M. Liu, X.L. Li, Experimental study on the effect of cold soaking with liquid nitrogen on the coal chemical and microstructural characteristics, Environ. Sci. Pollut. Res. Int. 30 (13) (2023) 36080-36097.
[14] X.G. Kong, M.Z. Zhan, Y.C. Cai, C.L. Zhang, E.Y. Wang, S.G. Li, S.R. Yang, D. He, Experimental and simulation researches of loaded stress and gas environment on dynamics properties of gas-bearing coal during impact failure process, Bull. Eng. Geol. Environ. 83 (1) (2023) 16.
[15] X.G. Kong, D. He, X.F. Liu, E.Y. Wang, S.G. Li, T. Liu, P.F. Ji, D.Y. Deng, S.R. Yang, Strain characteristics and energy dissipation laws of gas-bearing coal during impact fracture process, Energy 242 (2022) 123028.
[16] K. Jian, X.H. Fu, Y.M. Ding, H.D. Wang, T. Li, Characteristics of pores and methane adsorption of low-rank coal inChina, J. Nat. Gas Sci. Eng. 27 (2015) 207-218.
[17] Y.D. Cai, D.M. Liu, Z.J. Pan, Y.B. Yao, J.Q. Li, Y.K. Qiu, Pore structure and its impact on CH₄adsorption capacity and flow capability of bituminous and subbituminous coals from Northeast China, Fuel 103 (2013) 258-268.
[18] C. Peng, C.C. Zou, Y.Q. Yang, G.H. Zhang, W.W. Wang, Fractal analysis of high rank coal from southeast Qinshui Basin by using gasadsorption and mercury porosimetry, J. Petrol. Sci. Eng. 156 (2017) 235-249.
[19] L. Zhou, J.S. Zhang, Y.P. Zhou, A simple isotherm equation for modeling the adsorption equilibria on porous solids over wide temperature ranges, Langmuir 17 (18) (2001) 5503-5507.
[20] M.N. Nounou, H.N. Nounou, Multiscale estimation of the Freundlich adsorption isotherm, Int. J. Environ. Sci. Technol. 7 (3) (2010) 509-518.
[21] I.E. Men’shchikov, A.A. Fomkin, A.B. Arabei, A.V. Shkolin, E.M. Strizhenov, Description of methane adsorption on microporous carbon adsorbents on the range of supercritical temperatures on the basis of the Dubinin-Astakhov equation, Prot. Met. Phys. Chem. Surf. 52 (4) (2016) 575-580.
[22] S. Ozawa, S. Kusumi, Y. Ogino, Physical adsorption of gases at high pressure. IV. An improvement of the Dubinin-Astakhov adsorption equation, J. Colloid Interface Sci. 56 (1) (1976) 83-91.
[23] K.R. Matranga, A.L. Myers, E.D. Glandt, Storage of natural gas by adsorption on activated carbon, Chem. Eng. Sci. 47 (7) (1992) 1569-1579.
[24] S.G. Li, Y. Bai, H.F. Lin, C.M. Shu, M. Yan, L.W. Bin, Molecular simulation of adsorption of gas in coal slit model under the action of liquid nitrogen, Fuel 255 (2019) 115775.
[25] K. Mosher, J.J. He, Y.Y. Liu, E. Rupp, J. Wilcox, Molecular simulation of methane adsorption in micro- and mesoporous carbons with applications to coal and gas shale systems, Int. J. Coal Geol. 109-110 (2013) 36-44.
[26] H.X. Hu, L. Du, Y.F. Xing, X.C. Li, Detailed study on self- and multicomponent diffusion of CO₂-CH₄gas mixture in coal by molecular simulation, Fuel 187 (2017) 220-228.
[27] X.F. Sun, Y.Y. Zhang, K. Li, Z.Y. Gai, A new mathematical simulation model for gas injection enhanced coalbed methane recovery, Fuel 183 (2016) 478-488.
[28] G.W. Yue, C.L. Zeng, X.J. Zheng, L.P. Huo, Prediction for CH₄adsorption isotherm based on DA model, Chin. J. Process. Eng. 18 (5) (2018) 1045-1051.
[29] S.W. Zhou, H.Y. Wang, H.Q. Xue, W. Guo, X.B. Li, Supercritical methane adsorption on shale gas: Mechanism and model, Chin. Sci. Bull. 62 (35) (2017) 4189-4200.
[30] S. Zhang, S. Tang, S. Meng, D. Xin, Y. Zhang. X. Wang, Water-bearing characteristics of coal reservoirs and its control mechanism on coalbed methane production, J. China Coal Society (2023) 1-20. (in Chinese).
[31] J. Xiong, X.J. Liu, L.X. Liang, M. Lei, Improved Dubibin-Astakhov model for shale-gas supercritical adsorption, Acta Petrolei Sin. 36 (7) (2015) 849-857.
[32] V.A. Astakhov, M.M. Dubinin, Development of the concept of volume filling of micropores in the adsorption of gases and vapors by microporous adsorbents, Bull. Acad. Sci. USSR Div. Chem. Sci. 20 (1) (1971) 13-16.
[33] Suyang, Z., Chuanliang, L.I., Zhimin, D.U., Xiaolong, P. Discussion on Liquid Phase Adsorption of Coalbed Methane, Xinjiang Petroleum Geology 36 (05) 2015 620-623. (in Chinese).
[34] S.Y. Zhu, C.L. Li, Z.M. Du, Z., X.L. Peng, Compound desorption model of coalbed methane, Journal of China University of Mining & Technology, 45 (02) 2016 319-327. (in Chinese).
[35] Q.Y. Tu, Y.P. Cheng, T. Ren, Z.Y. Wang, J. Lin, Y. Lei, Role of tectonic coal in coal and gas outburst behavior during coal mining, Rock Mech. Rock Eng. 52 (11) (2019) 4619-4635.
[36] H.F. Lin, J.T. Bu, M. Yan, Y. Bai, Joint analysis of pore structure characteristics of middle and low rank coal with nitrogen adsorption and mercury intrusion method, J. Xi'an Univ. Sci. Technol. 39 (1) (2019) 1-8.
[37] L. Tian, Molecular simulation study of the adsorption of methane and carbon dioxide in bituminous coal model, Master Thesis, China Uni. Min. Tec., China, 2014. (in Chinese).
[38] P. Billemont, B. Coasne, G. De Weireld, Adsorption of carbon dioxide, methane, and their mixtures in porous carbons: Effect of surface chemistry, water content, and pore disorder, Langmuir 29 (10) (2013) 3328-3338.
[39] P. Billemont, B. Coasne, G. De Weireld, An experimental and molecular simulation study of the adsorption of carbon dioxide and methane in nanoporous carbons in the presence of water, Langmuir 27 (3) (2011) 1015-1024.