Abstract Permeability research of coal seams has long been a primary area of interest in the domain of coalbed methane (CBM) mining. The variation of coal permeability is heavily influenced by the coal structure. For coal seams, the coal matrixes are not completely separated, resulting in only a portion of the matrix expansion strain affecting permeability variations. However, the evolution mechanism of the internal swelling coefficient (ISCM) is not explicit. In this study, the ISCM was evaluated by theoretical inversion and numerical simulation, and its underlying evolution mechanism was analyzed combining research from other scholars. The results indicate that matrix bridge properties such as width, height, and numbers are direct factors affecting the ISCM, and changes in other factors can alter the matrix bridge properties and consequently affect the ISCM. Under uniaxial strain conditions, the ISCM shows an increasing trend with an increasing pore pressure. Under constant external stress conditions, the ISCM shows an increasing trend initially followed by a decreasing trend with an increasing pore pressure. Under constant pore pressure conditions, the ISCM shows an increasing trend as the effective stress increases. Under constant effective stress conditions, the ISCM initially decreases and subsequently increases with an increasing pore pressure. The ISCM is influenced by various factors, and the conclusions of different scholars only show a certain trend in the variation of the ISCM. The variation of the ISCM within a certain range is reasonable. In addition, this study compares the theoretical inversion and numerical simulation results under four different conditions, and systematically reveals the basic evolution mechanism of ISCM, aiming to fill the existing research gaps. The results in this paper hold immense importance for the safe and efficient extraction of CBM mining. Highlights <UnorderedList Mark="Bullet"> <ItemContent> The internal swelling coefficient of matrix is evaluated by theoretical inversion and numerical simulation, and the evolution laws of the internal swelling coefficient of matrix is obtained. </ItemContent> <ItemContent> The gas adsorption process was simulated by COMSOL under different boundary conditions with variations of matrix bridge properties. </ItemContent> <ItemContent> The evaluation of the internal swelling coefficient of matrix is analyzed by numerical simulation results, and the underlying evolution mechanism of the internal swelling coefficient of matrix is discussed. </ItemContent> </UnorderedList>

Evolution Mechanism of Internal Swelling Induced by Gas Sorption of Coal Matrix: Theoretical Inversion and Numerical Simulation

期刊论文
发表日期：

2025年11月25日

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Shouqing Lu,
Yongfu Liu,
Jiang Shi,
Yujin Qin,
Congmeng Hao,
Zhanyou Sa,
Jie Liu,
Yongliang Zhang,
Rong Zhang,
Hao Zhang

摘要

Abstract

Permeability research of coal seams has long been a primary area of interest in the domain of coalbed methane (CBM) mining. The variation of coal permeability is heavily influenced by the coal structure. For coal seams, the coal matrixes are not completely separated, resulting in only a portion of the matrix expansion strain affecting permeability variations. However, the evolution mechanism of the internal swelling coefficient (ISCM) is not explicit. In this study, the ISCM was evaluated by theoretical inversion and numerical simulation, and its underlying evolution mechanism was analyzed combining research from other scholars. The results indicate that matrix bridge properties such as width, height, and numbers are direct factors affecting the ISCM, and changes in other factors can alter the matrix bridge properties and consequently affect the ISCM. Under uniaxial strain conditions, the ISCM shows an increasing trend with an increasing pore pressure. Under constant external stress conditions, the ISCM shows an increasing trend initially followed by a decreasing trend with an increasing pore pressure. Under constant pore pressure conditions, the ISCM shows an increasing trend as the effective stress increases. Under constant effective stress conditions, the ISCM initially decreases and subsequently increases with an increasing pore pressure. The ISCM is influenced by various factors, and the conclusions of different scholars only show a certain trend in the variation of the ISCM. The variation of the ISCM within a certain range is reasonable. In addition, this study compares the theoretical inversion and numerical simulation results under four different conditions, and systematically reveals the basic evolution mechanism of ISCM, aiming to fill the existing research gaps. The results in this paper hold immense importance for the safe and efficient extraction of CBM mining.

Highlights

The internal swelling coefficient of matrix is evaluated by theoretical inversion and numerical simulation, and the evolution laws of the internal swelling coefficient of matrix is obtained.

The gas adsorption process was simulated by COMSOL under different boundary conditions with variations of matrix bridge properties.

The evaluation of the internal swelling coefficient of matrix is analyzed by numerical simulation results, and the underlying evolution mechanism of the internal swelling coefficient of matrix is discussed.