A fractal approach to fully-couple coal deformation and gas flow

Guannan Liu, Jishan Liu, Liu Liu, Dayu Ye, Feng Gao

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Although the impact of matrix microstructures on the evolution of coal permeability is significant, this impact has not been included in the analysis of coupled multiple processes during the extraction of coal seam gas. Previous studies normally investigate the relation between microstructures and coal porosity or permeability through imaging characterization techniques. In this study, we developed a fractal permeability model that defines coal permeability as a function of effective stress. In this model, coal microstructure is characterized by three fractal parameters: (1) fractal dimension of pore size; (2) fractal dimension of throat tortuosity; and (3) maximum pore size. These fractal dimensions may evolve with the effective stress through porosity. We applied this fractal permeability model to fully couple coal deformation and gas flow. Model results illustrate the significant differences between the fractal approach and the classical cubic model between permeability and porosity. When the porosity remains unchanged, the permeability calculated by the classical cubic model remains as a constant. However, the fractal permeability changes due to different microstructural parameters. These results show that the macroscopic permeability of coal is directly proportional to the fractal dimension and the maximum pore size, and is inversely proportional to the fractal dimension of the throat tortuosity. These characteristics cannot be captured by the classical cubic porosity-permeability model.

Original languageEnglish
Pages (from-to)219-236
Number of pages18
JournalFuel
DOIs
Publication statusPublished - 15 Mar 2019

Fingerprint

Coal
Fractals
Flow of gases
Fractal dimension
Porosity
Pore size
Microstructure
Imaging techniques

Cite this

Liu, Guannan ; Liu, Jishan ; Liu, Liu ; Ye, Dayu ; Gao, Feng. / A fractal approach to fully-couple coal deformation and gas flow. In: Fuel. 2019 ; pp. 219-236.
@article{58df7d547e024d55a79a952e6bc3ce3b,
title = "A fractal approach to fully-couple coal deformation and gas flow",
abstract = "Although the impact of matrix microstructures on the evolution of coal permeability is significant, this impact has not been included in the analysis of coupled multiple processes during the extraction of coal seam gas. Previous studies normally investigate the relation between microstructures and coal porosity or permeability through imaging characterization techniques. In this study, we developed a fractal permeability model that defines coal permeability as a function of effective stress. In this model, coal microstructure is characterized by three fractal parameters: (1) fractal dimension of pore size; (2) fractal dimension of throat tortuosity; and (3) maximum pore size. These fractal dimensions may evolve with the effective stress through porosity. We applied this fractal permeability model to fully couple coal deformation and gas flow. Model results illustrate the significant differences between the fractal approach and the classical cubic model between permeability and porosity. When the porosity remains unchanged, the permeability calculated by the classical cubic model remains as a constant. However, the fractal permeability changes due to different microstructural parameters. These results show that the macroscopic permeability of coal is directly proportional to the fractal dimension and the maximum pore size, and is inversely proportional to the fractal dimension of the throat tortuosity. These characteristics cannot be captured by the classical cubic porosity-permeability model.",
keywords = "Coal microstructure, Coal swelling, Coupled model, Fractal permeability, Gas sorption",
author = "Guannan Liu and Jishan Liu and Liu Liu and Dayu Ye and Feng Gao",
year = "2019",
month = "3",
day = "15",
doi = "10.1016/j.fuel.2018.11.140",
language = "English",
pages = "219--236",
journal = "Fuel",
issn = "0016-2361",
publisher = "Elsevier",

}

A fractal approach to fully-couple coal deformation and gas flow. / Liu, Guannan; Liu, Jishan; Liu, Liu; Ye, Dayu; Gao, Feng.

In: Fuel, 15.03.2019, p. 219-236.

Research output: Contribution to journalArticle

TY - JOUR

T1 - A fractal approach to fully-couple coal deformation and gas flow

AU - Liu, Guannan

AU - Liu, Jishan

AU - Liu, Liu

AU - Ye, Dayu

AU - Gao, Feng

PY - 2019/3/15

Y1 - 2019/3/15

N2 - Although the impact of matrix microstructures on the evolution of coal permeability is significant, this impact has not been included in the analysis of coupled multiple processes during the extraction of coal seam gas. Previous studies normally investigate the relation between microstructures and coal porosity or permeability through imaging characterization techniques. In this study, we developed a fractal permeability model that defines coal permeability as a function of effective stress. In this model, coal microstructure is characterized by three fractal parameters: (1) fractal dimension of pore size; (2) fractal dimension of throat tortuosity; and (3) maximum pore size. These fractal dimensions may evolve with the effective stress through porosity. We applied this fractal permeability model to fully couple coal deformation and gas flow. Model results illustrate the significant differences between the fractal approach and the classical cubic model between permeability and porosity. When the porosity remains unchanged, the permeability calculated by the classical cubic model remains as a constant. However, the fractal permeability changes due to different microstructural parameters. These results show that the macroscopic permeability of coal is directly proportional to the fractal dimension and the maximum pore size, and is inversely proportional to the fractal dimension of the throat tortuosity. These characteristics cannot be captured by the classical cubic porosity-permeability model.

AB - Although the impact of matrix microstructures on the evolution of coal permeability is significant, this impact has not been included in the analysis of coupled multiple processes during the extraction of coal seam gas. Previous studies normally investigate the relation between microstructures and coal porosity or permeability through imaging characterization techniques. In this study, we developed a fractal permeability model that defines coal permeability as a function of effective stress. In this model, coal microstructure is characterized by three fractal parameters: (1) fractal dimension of pore size; (2) fractal dimension of throat tortuosity; and (3) maximum pore size. These fractal dimensions may evolve with the effective stress through porosity. We applied this fractal permeability model to fully couple coal deformation and gas flow. Model results illustrate the significant differences between the fractal approach and the classical cubic model between permeability and porosity. When the porosity remains unchanged, the permeability calculated by the classical cubic model remains as a constant. However, the fractal permeability changes due to different microstructural parameters. These results show that the macroscopic permeability of coal is directly proportional to the fractal dimension and the maximum pore size, and is inversely proportional to the fractal dimension of the throat tortuosity. These characteristics cannot be captured by the classical cubic porosity-permeability model.

KW - Coal microstructure

KW - Coal swelling

KW - Coupled model

KW - Fractal permeability

KW - Gas sorption

UR - http://www.scopus.com/inward/record.url?scp=85057597844&partnerID=8YFLogxK

U2 - 10.1016/j.fuel.2018.11.140

DO - 10.1016/j.fuel.2018.11.140

M3 - Article

SP - 219

EP - 236

JO - Fuel

JF - Fuel

SN - 0016-2361

ER -