3D microfracture network and seepage characteristics of low-volatility bituminous coal based on nano-CT

Shi, Xinghua; Pan, Jienan; Pang, Longlong; Wang, Rui; Li, Guofu; Tian, Jijun; Wang, Haichao

doi:10.1016/j.jngse.2020.103556

Cited by 47 publications

(19 citation statements)

References 45 publications

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“…However, the complex pore and fracture structure makes the application of this model for fluid seepage and other simulations very computationally intensive. In order to optimize the calculation process, a simplified equivalent pore network model with topological structure was developed. , …”

Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

“…3D visualization of microfractures: (a) reconstructed microfracture network and (b) pore network model skeleton of the microfractures. [Reproduced with permission from ref . Copyright 2020, Elsevier B.V.]…”

Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

“…In order to optimize the calculation process, a simplified equivalent pore network model with topological structure was developed. 58,59 The equivalent pore network model effectively includes the geometric features of pores and fractures in coal (Figure 4b). Its establishment not only solves the problem of excessive computation during the simulation, but also enables the statistics of parameters such as throat length and coordination number, which are important for studying the connectivity of coal.…”

Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

See 2 more Smart Citations

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

et al. 2022

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Characterization of microscopic structure and macroscopic physical property are the basis for better understanding of coalbed methane reservoirs. X-ray computed tomography (CT), as an nondestructive measurement, has been widely and successfully applied to characterize the internal structure of coal. In this study, we introduce the principle of CT imaging and the microstructure recognition. A summary of CT imaging-based coal microstructure characterization follows, including three-dimensional (3D) microstructure reconstruction, pore and mineral quantification, and equivalent pore network model construction. We review the methods used to evaluate the macroscopic properties of coal, including porosity calculation, gas adsorption/diffusion rate test, permeability simulation, and mechanical behavior evaluation. This study discusses the application of CT to investigate the evolutionary mechanisms of microstructure and macroscopic properties during gas adsorption, temperature change, and damage deformation. We conclude this review with a summary of the challenges and application perspectives of CT. The small scanning range, limited observation accuracy, functional limitations, lengthy testing process, and high cost are some of the major hurdles in the broad application of CT for coal characterization. In the future, CT should be combined with other techniques to establish full-scale pore and fracture models, identify mineral types in microstructures, and effusively use the advantages of CT by selecting the key points in the evolutionary mechanisms of microstructure and macroscopic properties.

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Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

Section: Quantitative Characterization Of Microstructurementioning

confidence: 99%

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Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

et al. 2022

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“…花岗岩残积土作为一种典型结构性土，具有孔隙比大、遇水易失结构性等特点 [1] 。研究表明，当孔隙孔径较大时，在降雨等作用下水流可通过孔隙绕过大部分基质土壤，快速到达土壤深层，即产生孔隙流 [2,3] ，而能传导孔隙流的孔隙被定义为大孔隙。同时，孔隙流的出现常常诱发降雨型边坡失稳、渗透变形等不良地质灾害，甚至威胁人民生命和财产安全 [1] 。孔隙结构特征直接影响着水分在土体中渗透能力的强弱。传统试验观察方法会不可避免地对土体原有结构产生影响，因此很难对真实孔隙结构进行三维 (3D)定量表征。近年来，研究人员主要使用计算机断层扫描(CT 扫描) [4][5][6] 和核磁共振(NMR) [7,8] 等先进技术进行土体孔隙结构的无损表征。其中 CT 扫描技术按照尺度又可分为为毫米级、微米级和纳米级三类；微、纳米级 CT 扫描可以更清晰地观察土体中微、纳米孔的分布和连通情况；但其对试样要求更加严格，扫描费用昂贵，且样品扫描区域较小，对含大孔隙土体代表性不佳。而核磁共振技术虽然不受样品尺寸限制，但需通过流体的氢核横向驰豫时间(T 2 )间接反映孔隙结构特征，且部分孔隙表征效果较差。因此，为获取土体中大孔隙结构特征，并平衡土样大小与分辨率之间的矛盾，毫米级工业 CT 扫描技术是一种更优的选择 [9] 。土体广布于自然界，是一种三相体，即固相(土体基质)、液相(水溶液)和气相(空气) [10] 。水流在土体中入渗实质上是水在入渗过程中驱赶空气的两相流问题，而由于大孔隙的存在，水分和溶质在迁移过程中，孔隙壁的毛细屏蔽使其优先在大孔隙通道中快速迁移，因此深入了解大孔隙流动对揭示土壤中流体在孔隙中的运移机制极为重要。传统的两相流研究多采用试验方法，如玻璃刻蚀、薄片平面驱替等二维方法 [11] ；岩心驱替物理试验、宏观驱替 CT 扫描等三维方法 [12] ，但以上试验研究成本较高，操作较繁琐困难，且一般情况精度无法满足工程需要，更不利于重复性开展研究。因此，为克服上述试验方法的不足，一些细观尺度下的数值模拟方法得到了迅速发展和应用 [13][14][15][16] [17] ，国内外学者也已有应用 [18][19][20] ，但由于量化技术、地域性差异等原因，多集中在二维孔隙结构模型层面，对 REV 尺度原状花岗岩残积土的真实 [22,23] ，本文参考以往学者对大孔隙的界定方法及范围 [24,25] [26] 。其中，通过拟合法 [27] [28][29][30][31]…”

Section: 引言unclassified

3D quantitative characterization and flow simulation of granite residual soil based on CT scanning

Cai¹,

Que²,

Jiang³

et al. 2022

Sci. Sin.-Tech.

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“…Nano-Computed Tomography (Nano-CT) technique can provide lossless observation images of three-dimensional microstructures. Shi et al [ 5 ] used Nano-CT to characterize the three-dimensional micro-crack structure of low-volatile coal and simulated the permeability characteristics of single-phase water flow in the micro-crack network using COMSOL. Zhao et al [ 6 ] studied the pore structure characteristics of coal via Nano-CT, discussed the computational fluid dynamics simulation method based on the micro-nano pore structure, and then carried out the permeability simulation of the reconstructed microstructure.…”

Section: Introductionmentioning

confidence: 99%

Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC

et al. 2022

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Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a microstructure model of CL was first reconstructed using images acquired by Nano-computed tomography (Nano-CT) of a real sample of CL. Then, the multiphysics dynamic distribution (MPDD) simulation, which is inherently a multiscale approach made of a combination of pore-scale and homogeneous models, was conducted on the reconstructed microstructure model to compute the corresponded heat and mass transport, electrochemical reactions, and water phase-change processes. Considering a computational domain with the size of 4 um and cube shape, this model consisting of mass and heat transport as well as electrochemical reactions reached a stable solution within 3 s as the convergence time. In the presence of sufficient oxygen, proton conduction was identified as the dominant factor determining the strength of the electrochemical reaction. Additionally, it was concluded that current density, temperature, and the distribution of water all exhibit similar distribution trends, which decrease from the interface between CL and the proton-exchange membrane to the interface between CL and the gas-diffusion layer. The present study not only provides an in-depth understanding of the mass and heat transport and electrochemical reaction in the CL microstructure, but it also guides the optimal design and fabrication of CL components and structures, such as improving the local structure to reduce the number of dead pores and large agglomerates, etc.

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3D microfracture network and seepage characteristics of low-volatility bituminous coal based on nano-CT

Cited by 47 publications

References 45 publications

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

Review on Applications of X-ray Computed Tomography for Coal Characterization: Recent Progress and Perspectives

3D quantitative characterization and flow simulation of granite residual soil based on CT scanning

Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC

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