Title: Investigations of coal permeability under the influence of stress, matrix-fracture adsorption induced strain and volumetric strain

Authors: Haizeng Pan; Chaoyu Xu; Xiaochuan Wang

Addresses: School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, Hubei, China ' School of Power and Mechanical Engineering, Wuhan University, Wuhan, 430072, Hubei, China ' The Institute of Technological Sciences, Wuhan University, Wuhan, 430072, Hubei, China

Abstract: The evolution and distribution of coal seam permeability have a significant role to play during CBM extraction. Many permeability models assume that coal is isotropic, however, the assumption has received a lot of scepticism. In this study, an improved fracture permeability model is established, considering the anisotropy of coal. The relationship among matrix adsorption strain, fracture adsorption strain, and volume strain of coal is defined. Fracture permeability is a feature of pressure and strain caused by fracture and matrix adsorption. At the same time, the permeability model is validated by experimental data, and the results are in good accordance with the experimental data. The simulation results show that the fracture permeability in the compression direction is smaller than in the tensile direction, and the peak fracture pressure will be delayed in the non-Darcy condition. Cracks are the main passage of CBM. Therefore, studying the permeability of fractures in different directions can better improve the production of coalbed methane. [Received: January 12, 2023; Accepted: May 8, 2023]

Keywords: permeability; anisotropic; adsorption induced strain; numerical model; coalbed methane; CBM.

DOI: 10.1504/IJOGCT.2024.136027

International Journal of Oil, Gas and Coal Technology, 2024 Vol.35 No.1, pp.53 - 74

Received: 11 Jan 2023
Accepted: 08 May 2023
Published online: 12 Jan 2024 *

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