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<p>A thorough understanding of gas storage and transport mechanisms in coal seams requires a precise characterization of pore structure evolution under dynamic conditions. Low-field nuclear magnetic resonance offers a rapid, non-destructive, and information-rich approach to quantify pore parameters, yet its application to highly metamorphosed coals under variable pressure regimes remains underexplored. In this study, we used low-field nuclear magnetic resonance to analyze five highly metamorphosed coal samples from distinct mining regions. Their pore structure, fractal dimensions, and pressure-dependent pore reorganization were systematically investigated. Our results demonstrated that pore development in the samples was dominated by micropores and small pores, with fractal dimensions below 2 revealing low structural heterogeneity. Increasing the pressure from 1 to 6.7&#xa0;MPa induced a 2%–7% reduction in porosity, accompanied by a redistribution of pore sizes: small pores were proliferated, while the proportion of medium and large pores diminished. These pressure-driven structural transformations provide critical insights into gas storage capacity and transport dynamics, with direct implications for optimizing coalbed methane extraction and CO<sub>2</sub> sequestration strategies.</p><p><b>Highlights</b><UnorderedList Mark="Bullet"> <ItemContent> <p>Dynamic Pore Structure Mapping: Applied low-field NMR to track pressure-induced pore reorganization in highly metamorphic coals, combining fractal dimension analysis with real-time pore size redistribution.</p> </ItemContent> <ItemContent> <p>Quantifying Pressure-Driven Heterogeneity: Revealing that increasing pressure (1–6.7&#xa0;MPa) reduces porosity by 2–7%, accompanied by structural transformations favoring small pores, a key determinant of natural gas storage and transportation efficiency.</p> </ItemContent> <ItemContent> <p>Blueprint for Sustainable Resource Management: Direct mechanistic insight into gas transport dynamics to provide tailored strategies for enhanced coalbed methane recovery and scalable CO<sub>2</sub> storage technologies.</p> </ItemContent> </UnorderedList></p>

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Pressure-Driven Pore Structure Evolution in Coal: Insights from Low-Field NMR

  • 期刊论文

  • 发表日期：

    2025年11月11日

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  • Lin Hong,
  • Hongkun Wang,
  • Dan Zheng,
  • Dameng Gao

摘要

A thorough understanding of gas storage and transport mechanisms in coal seams requires a precise characterization of pore structure evolution under dynamic conditions. Low-field nuclear magnetic resonance offers a rapid, non-destructive, and information-rich approach to quantify pore parameters, yet its application to highly metamorphosed coals under variable pressure regimes remains underexplored. In this study, we used low-field nuclear magnetic resonance to analyze five highly metamorphosed coal samples from distinct mining regions. Their pore structure, fractal dimensions, and pressure-dependent pore reorganization were systematically investigated. Our results demonstrated that pore development in the samples was dominated by micropores and small pores, with fractal dimensions below 2 revealing low structural heterogeneity. Increasing the pressure from 1 to 6.7 MPa induced a 2%–7% reduction in porosity, accompanied by a redistribution of pore sizes: small pores were proliferated, while the proportion of medium and large pores diminished. These pressure-driven structural transformations provide critical insights into gas storage capacity and transport dynamics, with direct implications for optimizing coalbed methane extraction and CO2 sequestration strategies.

Highlights

Dynamic Pore Structure Mapping: Applied low-field NMR to track pressure-induced pore reorganization in highly metamorphic coals, combining fractal dimension analysis with real-time pore size redistribution.

Quantifying Pressure-Driven Heterogeneity: Revealing that increasing pressure (1–6.7 MPa) reduces porosity by 2–7%, accompanied by structural transformations favoring small pores, a key determinant of natural gas storage and transportation efficiency.

Blueprint for Sustainable Resource Management: Direct mechanistic insight into gas transport dynamics to provide tailored strategies for enhanced coalbed methane recovery and scalable CO2 storage technologies.