Accurate structural characterization of nanopores in coal by cryo-FIB-SEM
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Abstract
The structural characteristics of nanopores are known to significantly affect the wetting effect in coal seam water injection. Currently, the three-dimensional characterization of nanopores in coal relies mainly on digital images, whereas poor image resolution and segmentation methods pose significant challenges. Therefore, using coal samples from Wudong Coal Mine in China as an example, cryo-focused ion beam scanning electron microscopy (cryo-FIB-SEM) and deep learning segmentation methods were implemented to accurately characterize the nanopores and water distribution. In the obtained pore structure, the number of isolated pores was higher than that of connected pores, while the volume of connected pores was significantly larger than that of isolated pores, comprising the key path and storage space for external water to enter the coal body. The water content of isolated pores mainly depends on the permeability of the coal matrix. The connectivity of single pores can be characterized by the coordination number, whose increase leads to the number of pores exponentially decreasing. The connectivity of pore clusters depends on the number of internal branches. The number of branches in the pore cluster increases exponentially with the increasing total length, total volume and average radius of the cluster, and the connectivity is correspondingly enhanced. The increase in pore size enhances the shape factor, surface area and connectivity of pores while reducing tortuosity, which in turn facilitates coal wetting. The accurate characterization of coal nanopores in this study helps to scientifically evaluate the effect of coal seam water injection, highlighting the importance of increased pore size and improved pore connectivity for enhanced water injection effectiveness.
Document Type: Original article
Cited as: Wang, G., Chen, X., Wang, G., Zhang, H., Wang, J., Xu, H. Accurate structural characterization of nanopores in coal by cryo-FIB-SEM. Advances in Geo-Energy Research, 2024, 14(3): 187-200. https://doi.org/10.46690/ager.2024.12.04
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Andrew, M. A quantified study of segmentation techniques on synthetic geological XRM and FIB-SEM images. Computational Geosciences, 2018, 22(6): 1503-1512.
Bailey, J. J., Wade, A., Boyce, A. M., et, al. Quantitative assessment of machine-learning segmentation of battery electrode materials for active material quantification. Journal of Power Sources, 2023, 557: 232503.
Čalkovský, M., Müller, E., Meffert, M., et, al. Comparison of segmentation algorithms for FIB-SEM tomography of porous polymers: Importance of image contrast for machine learning segmentation. Materials Characterization, 2021, 171: 110806.
Capua-Shenkar, J., Varsano, N., Itzhak, N.-R., et, al. Examining atherosclerotic lesions in three dimensions at the nanometer scale with cryo-FIB-SEM. Proceedings of the National Academy of Sciences of the United States of America, 2022, 119(34): e2205475119.
De Winter, M., Mesman, R. J., Hayles, M. F., et, al. Ion beam preparation and transmission-SEM imaging of frozen-hydrated, vitreous lamellas prepared by the Cryo-FIB-SEM: An all-in-one instrument. Microscopy and Microanalysis, 2013, 19(S2): 878-879.
Guan, X., Liu, Y., Ren, C., et, al. Characterization and comparison of pore structure and connectivity of anthracite based on CT three-dimensional reconstruction. Unconventional Oil & Gas, 2023, 10(1): 69-76. (in Chinese)
Guo, Y., Zhang, T., Du, J., et, al. Evaluating the chloride diffusion coefficient of cement mortars based on the tortuosity of pore structurally-designed cement pastes. Microporous and Mesoporous Materials, 2021, 317: 111018.
Jacob, A., Peltz, M., Hale, S., et, al. Simulating permeability reduction by clay mineral nanopores in a tight sandstone by combining computer X-ray microtomography and focussedion beam scanning electron microscopy imaging. Solid Earth, 2021, 12(1): 1-14.
Jantschke, A., Pinkas, I., Schertel, A., et, al. Biomineralization pathways in calcifying dinoflagellates: Uptake, storage in MgCaP-rich bodies and formation of the shell. Acta Biomaterialia, 2020, 102: 427-439.
Jiang, J., Yang, W., Cheng, Y., et, al. Pore structure characterization of coal particles via MIP, N2 and CO2 adsorption: Effect of coalification on nanopores evolution. Powder Technology, 2019, 354: 136-48.
Jiao, K., Yao, S., Liu, C., et, al. The characterization and quantitative analysis of nanopores in unconventional gas reservoirs utilizing FESEM-FIB and image processing: An example from the lower Silurian Longmaxi Shale, upper Yangtze region, China. International Journal of Coal Geology, 2014, 128-129: 1-11.
Kazak, A., Simonov, K., Kulikov, V. Machine-learning-assisted segmentation of focused ion beam-scanning electron microscopy images with artifacts for improved void-space characterization of tight reservoir rocks. SPE Journal 2021, 26(4): 1739-1758.
Li, H., Cao, J., Lu, J., et, al. Effect of microwave-assisted cyclic oxidation on the coal internal and surface structure based on NMR and AFM. Energy, 2024a, 288: 129872.
Li, K., Tian, H., Liang, Y., et, al. The molecular model of organic matter in coal-measure shale: Structure construction and evaluation based on experimental characterization. Molecules, 2023, 28(13): 5203.
Li, L., Zhang, D., Su, Y., et al. Microfluidic insights into CO2 sequestration and enhanced oil recovery in laminated shale reservoirs: Post-fracturing interface dynamics and micro-scale mechanisms. Advances in Geo-Energy Research, 2024b, 13(3): 203-217.
Liu, H., Li, Z., Yang, Y., et, al. Role of moisture content in coal oxidation during the spontaneous combustion latency. Energy, 2024, 291: 130336.
Liu, R., Ji, D., Zhou, G., et, al. Electrospun nanofibers for personal protection in mines. Chemical Engineering Journal, 2021a, 404: 126558.
Liu, S., Sang, S., Hu, Q., et, al. Characteristics of high-rank coal structure parallel and perpendicular to the bedding plane via NMR and X-ray CT. Petroleum Science, 2020, 17(4): 925-938.
Liu, W., Wang, G., Han, D., et, al. Accurate characterization of coal pore and fissure structure based on CT 3D reconstruction and NMR. Journal of Natural Gas Science and Engineering, 2021b, 96: 104242.
Li, X., Kang, Y., Haghighi, M. Investigation of pore size distributions of coals with different structures by nu clear magnetic resonance (NMR) and mercury intrusion porosimetry (MIP). Measurement, 2018, 116: 122-128.
Li, Z. Evolution of pores and fractures in coal reservoirs and their impact on microscopic flow of coalbed methane. Beijing, China University of Mining and Technology (Beijing), 2018.
Lubelli, B., de Winter, D. A. M., Post, J. A., et, al. Cryo-FIB-SEMandMIPstudy of porosity and pore size distribution of bentonite and kaolin at different moisture contents. Applied Clay Science, 2013, 80-81: 358-365.
Mazumder, M., Bal, A., Tripathy, A., et, al. Multiscale assessment of transformation in pore system of shale during combustion: An insight into poromechanical response and sorption dynamics. Energy & Fuels, 2024, 38: 17510 17524.
Qin, W., Zhang Y. Relation of pore distribution of coal with water infusion increment in seams. Journal of China Coal Society, 2000(5): 514-517. (in Chinese)
Qin, X., Cai, J., Wang, G. Pore-scale modeling of pore structure properties and wettability effect on permeability of low-rank coal. International Journal of Mining Science and Technology, 2023, 33(5): 573-584.
Raguin, E., Weinkamer, R., Schmitt, C., et, al. Logistics of bone mineralization in the chick embryo studied by 3D Cryo FIB-SEM imaging. Advanced Science, 2023, 10(22): 2301231.
Röding, M., Fager, C., Olsson, A., et, al. Three-dimensional reconstruction of porous polymer films from FIB-SEM nanotomography data using random forests. Journal of Microscopy, 2021, 281(1): 76-86.
Saif, T., Lin, Q., Butcher, A., et, al. Multi-scale multidimensional microstructure imaging of oil shale pyrolysis using X-ray micro-tomography, automated ultra-high res olution SEM, MAPS Mineralogy and FIB-SEM. Applied Energy, 2017, 202: 628-647.
Schlüter, S., Sheppard, A., Brown, K., et, al. Image processing of multiphase images obtained via X-ray microtomography: A review. Water Resources Research, 2014, 50(4): 3615-3639.
Sun, Y., Zhao, Y., Wang, X., et, al. Synchrotron radiation facility-based quantitative evaluation of pore structure heterogeneity and anisotropy in coal. Petroleum Exploration and Development, 2019, 46(6): 1195-1205.
Tang, X., Jiang, Z., Jiang, S., et, al. Heterogeneous nanoporosity of the Silurian Longmaxi Formation shale gas reser voir in the Sichuan Basin using the QEMSCAN, FIB-SEM, and nano-CT methods. Marine and Petroleum Geology, 2016, 78: 99-109.
Vierrath, S., Zielke, L., Moroni, R., et, al. Morphology of nanoporous carbon-binder domains in Li-ion batteries A FIB-SEM study. Electrochemistry Communications, 2015, 60: 176-179.
Vranjes-Wessely, S., Misch, D., Issa, I., et, al. Nanoscale pore structure of Carboniferous coals from the Ukrainian Donets Basin: A combined HRTEM and gas sorption study. International Journal of Coal Geology, 2020, 224: 103484.
Wang, C., Li, X., Liu, L., et, al. Dynamic effect of gas initial desorption in coals with different moisture contents and energy-controlling mechanism for outburst prevention of water injection in coal seams. Journal of Petroleum Science and Engineering, 2023, 220: 111270.
Wang, G., Chen, X., Cheng, W., et, al. Multi-scale characterization of coal pore and fractures and its influence on permeability-taking 14 large coal bases in China as examples. Journal of Chongqing University, 2024, 47(4): 34-50. (in Chinese)
Wang, G., Chen, X., Wang, S., et, al. Influence of fracture connectivity and shape on water seepage of low-rank coal based on CT 3D reconstruction. Journal of Natural Gas Science and Engineering, 2022, 102: 104584.
Wang, G., Shen, J., Liu, S., et, al. Three-dimensional modeling and analysis of macro-pore structure of coal using combined X-ray CT imaging and fractal theory. International Journal of Rock Mechanics and Mining Sciences, 2019, 123: 104082.
Wang, H., Cheng, X., Tian, J., et, al. Permeability enhancement of low rank coal through acidization using H2S solution: An experimental study in the Kuqa-Bay Coal field, Xinjiang, China. Journal of Petroleum Science and Engineering, 2020, 185: 106476.
Wang, W., Teng, T. Experimental study on anisotropic fracture characteristics of coal using notched semi-circular bend specimen. Theoretical and Applied Fracture Mechanics, 2022, 122: 103559.
Wu, J., Yuan, Y., Niu, S., et, al. Multiscale characterization of pore structure and connectivity of Wufeng-Longmaxi shale in Sichuan Basin, China. Marine and Petroleum Geology, 2020, 120: 104514.
Yang, W., Lu, C., Si, G., et, al. Coal and gas outburst control using uniform hydraulic fracturing by destress blasting and water-driven gas release. Journal of Natural Gas Science and Engineering, 2020, 79: 103360.
Yu, B., Dijkstra, T. A., Fan, W., et, al. Advanced multiscale characterization of loess microstructure: Integrating µXCT and FIB-SEM for detailed fabric analysis and geotechnical implications. Engineering Geology, 2024, 341: 107727.
Zang, J., Liu, J., He, J., et, al. Characterization of the pore structure in Chinese anthracite coal using FIB-SEM tomography and deep learning-based segmentation. Energy, 2023, 282: 128686.
Zhang, C., Jia, S., Wang, F., et, al. An experimental research on the pore and fracture evolution characteristics and its driving mechanism for coal samples under water-rock interaction. Journal of Basic Science and Engineering, 2023, 31(1): 185-96.
Zhang, R., Liu, S., San-Miguel, A., et, al. Nanoscale coal deformation and alteration of porosity and pore orientation under uniaxial compression: An in situ SANS study. Rock Mechanics and Rock Engineering, 2021, 54(7): 3593-608.
Zhang, X. Fractal character of coal nanopore and effect of deviation corrected, coal rank, and gas adsorption. Microporous and Mesoporous Materials, 2024, 367: 112972.
Zhao, Y., Sun, Y., Liu, S., et, al. Application of fractal theory to predict the coal permeability of multi-scale pores and fractures. Energy Reports, 2018, 7(2): 10-18.
Zheng, L. Mechanism and engineering application of hydraulic fracturing, permeability enhancement, wetting and dust suppression in difficult-to-inject coal seams. Chongqing, Chongqing University, 2022.
Zhou, F., Oraby, M., Luft, J., et, al. Coal seam gas reser voir characterisation based on high-resolution image logs from vertical and horizontal wells: A case study. Inter national Journal of Coal Geology, 2022, 262: 104110.
Zhou, H., Liu, Z., Zhao, J., et, al. In-situ observation and modeling approach to evolution of pore-fracture structure in coal. International Journal of Mining Science and Technology, 2023, 33: 265-274.
Zhou, Y., Zhong, X., Nie, X. Identification and parameter characterization of pores and fractures in shales based on multi-scale digital core data. Advances in Geo-Energy Research, 2024, 13(2): 146-160.
DOI: https://doi.org/10.46690/ager.2024.12.04
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