Regulatory mechanism of microscopic pore structure on anisotropy of gas multimodal seepage in original coals

Guo, Xiaoyang; Liu, Yijia; Zhang, Lemei; Deng, Cunbao; Song, Liuni; Zhang, Yu

doi:10.1016/j.energy.2024.131611

Energy

2024

DOI: 10.1016/j.energy.2024.131611

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Regulatory mechanism of microscopic pore structure on anisotropy of gas multimodal seepage in original coals

Xiaoyang Guo,

Yijia Liu,

Lemei Zhang

et al.

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Cited by 2 publications

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Microscopic Structure of Coal through Liquid Nitrogen Treatment Based on Micro-CT and 3D Visualization of Permeability Simulation

Qiao,

Wang,

Fan

et al. 2024

Energy Fuels

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Liquid nitrogen (LN 2 ) fracturing effectively enhances the coal seam permeability. Utilizing micro-CT scanning and Avizo software, pore networks and topological models were reconstructed to analyze structural changes before and after LN 2 treatment. By examining pore and throat characteristics, correlations with seepage indicators were established. Numerical simulations visualized gas flow distribution, focusing on pressure and velocity fields, and studied permeability evolution under varying pressure gradients. The results show that after undergoing LN 2 treatment, the pore radius of the coal sample exhibited a significant increase within the range of 100−500 μm, with an increase of 155% compared to the dry coal sample. The pore area and volume exhibit a bimodal distribution, with the primary growth regions for pore area being between 1 × 10 4 −5 × 10 5 μm 2 and 7.5 × 10 5 −7.5 × 10 6 μm 2 , and for pore volume, the main growth region is within the range of 10 6 −2.5 × 10 8 μm 3 . Through the fitting of structural characteristic parameters and seepage characteristic parameters, it was found that the pore radius and coordination number, as well as the throat length and tortuosity, are positively correlated before and after LN 2 treatment. Conversely, the throat radius is negatively correlated with the coordination number. Based on the three-dimensional (3D) reconstructed model, the visualized gas seepage in the fracture space exhibits significant heterogeneity. The permeability of the coal body shows significant differences before and after LN 2 treatment. The seepage velocity along the Y-and Z-axes is significantly higher than that along the X-axis, and the permeability exhibits a nonlinear increase with a rising pressure gradient.

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Microscopic Structure of Coal through Liquid Nitrogen Treatment Based on Micro-CT and 3D Visualization of Permeability Simulation

Qiao,

Wang,

Fan

et al. 2024

Energy Fuels

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Mechanism of matrix–fracture equilibrium time lag property inducing coal sub-matrix mass transfer behavior and its effect on the coal seepage characteristics in CO2 sequestration

Lin,

Liu,

Zhu

et al. 2025

Physics of Fluids

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Diffusion and seepage collectively govern the mass transfer behavior of gases in the CO2 enhancing coalbed methane recovery (CO2-ECBM) process, significantly influencing both coalbed methane extraction efficiency and CO2 sequestration capacity. Conventional theoretical models typically assume a uniform gas distribution within the coal matrix during injection. However, extensive field studies have revealed inconsistent conclusions. This paper delves into the gas equilibrium time lag property during the CO2-ECBM process, introducing the concept of sub-matrix mass transfer behavior to describe the non-uniform distribution of pressure, and construct the modified binary gas flow control equations and the permeability evolution model that takes this behavior into account. This model is used to investigate how sub-matrix mass transfer influences gas seepage characteristics. Findings show that the equilibrium time lag property intensify with coalbed extension but diminish over time. Despite an increased sub-matrix proportion enhancing CO2 adsorption capacity, the difference fades away due to the decay of the gas equilibrium time lag property. Furthermore, fixed-point monitoring reveals that a higher sub-matrix proportion aggravates permeability evolution, constraining fluid flow capacity. Based on these observations, a hypothesis of multi-level diffusion behavior within the coalbed is proposed, alongside an exploration of optimized CO2 injection strategies, providing new theoretical insights for CO2 sequestration in deep coalbeds.

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Regulatory mechanism of microscopic pore structure on anisotropy of gas multimodal seepage in original coals

Cited by 2 publications

References 47 publications

Microscopic Structure of Coal through Liquid Nitrogen Treatment Based on Micro-CT and 3D Visualization of Permeability Simulation

Microscopic Structure of Coal through Liquid Nitrogen Treatment Based on Micro-CT and 3D Visualization of Permeability Simulation

Mechanism of matrix–fracture equilibrium time lag property inducing coal sub-matrix mass transfer behavior and its effect on the coal seepage characteristics in CO2 sequestration

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