A multi-field coupling model of gas flow in fractured coal seam

Dayu Ye, Guannan Liu, Feng Gao, Rongguang Xu, Fengtian Yue

Abstract view|464|times       PDF download|294|times


The structure of fractures and pores has a dominant impact on the heat transfer-seepage-deformation process of a coal seam. Previous models have primarily used the cubic permeability model to characterize coal seam permeability properties. In this study, we developed a new multi-field coupling model, which includes fracture and pore structure, coal seam temperature, effective stress and gas seepage. Two major extraction scenarios were simulated: the unconstrained plane strain state and the uniaxial plane strain state. In addition, two microstructural parameters were applied to characterize coal permeability: maximum fracture length and the fractal dimension for the fracture. The results show that the fractal seepage model provides a more realistic and reliable characterization of resource migration and extraction processes in unconventional reservoirs than the cubic-law permeability model. Compared with the cubic-law permeability model, the permeability calculated by the model proposed in this paper changes about 17.09%-91.56%. Furthermore, coal seam permeability is proportional to the maximum fracture length and the fractal dimension for the fracture. The permeability changes about 17.09% and 17.18% with the different fractal dimension, and about 87.17% and 91.56% with the different maximum fracture length. However, the fractal dimension and coal seam permeability are inversely proportional to seam temperature.

Cited as: Ye, D., Liu, G., Gao, F., Xu, R., Yue, F. A multi-field coupling model of gas flow in fractured coal seam. Advances in Geo-Energy Research, 2021, 5(1): 104-118, doi: 10.46690/ager.2021.01.10


Fractal; coal permeability; gas sorption; coal microstructure; thermal conduction

Full Text:



Arand, F., Hesser, J. Accurate and efficient maximal ball algorithm for pore network extraction. Computers & Geosciences, 2017, 101: 28-37.

Au, P. I., Liu, J., Leong, Y. K. Yield stress and microstructure of washed oxide suspensions at the isoelectric point: Experimental and model fractal structure. Rheologica Acta, 2016, 55(10): 847-856.

Barton, C. C., Hsieh, P. A. Physical and hydrologic-flow properties of fractures. Paper Presented at 28th International Geological Congress, Washington DC, 9-19 July, 1989.

Bustin, R. M., Clarkson, C. R. Geological controls on coalbed methane reservoir capacity and gas content. International Journal of Coal Geology, 1998, 38(1-2): 3-26.

Cai, J., Wei, W., Hu, X., et al. Fractal characterization of dynamic fracture network extension in porous media. Fractals, 2017, 25 (2): 1750023.

Cai, Y., Liu, D., Pan, Z. Partial coal pyrolysis and its implication to enhance coalbed methane recovery: A simulation study. Energy & Fuels, 2017, 31(5): 4895-4903.

Cui, X., Bustin, R. M. Volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams. AAPG Bulletin, 2005, 89(9): 1181-1202.

Durucan, S., Ahsanb, M., Shia, J. Q. Matrix shrinkage and swelling characteristics of European coals. Energy Procedia, 2009, 1(1): 3055-3062.

Harpalani, S., Schraufnagel, R. A. Shrinkage of coal matrix with release of gas and its impact on permeability of coal. Fuel, 1990, 69(5): 551-556.

He, J., Zhang, Y., Li, X., et al. Experimental investigation on the fractures induced by hydraulic fracturing using freshwater and supercritical CO2 in shale under uniaxial stress. Rock Mechanics and Rock Engineering, 2019, 52(10): 3585-3596.

Jafari, A., Babadagli, T. Estimation of equivalent fracture network permeability using fractal and statistical network properties. Journal of Petroleum Science and Engineering, 2012, 92: 110-123.

Kulatilake, P., Shou, G., Huang, T. H., et al. New peak shear strength criteria for anisotropic rock joints. International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, 1995, 32(7): 673-697.

Li W., Liu J., Zeng J., et al. A fully coupled multidomain and multiphysics model for evaluation of shale gas extraction. Fuel, 2020, 278: 118214.

Li, Z., Duan, Y., Fang, Q., et al. A study of relative permeability for transient two-phase flow in a low permeability fractal porous medium. Advances in Geo-Energy Research, 2018, 2(4): 369-379.

Liang, B. Study on temperature effects on the gas absorption performance. Journal of Heilongjiang Mining Institute, 2000, 10(1): 20-22. (in Chinese)

Liu, G., Liu, J., Liu, L., et al. A fractal approach to fully-couple coal deformation and gas flow. Fuel, 2019, 240: 219-236.

Liu, G., Ye, D., Gao, F., et al. A dual fractal poroelastic model for characterizing fluid flow in fractured coal masses. Geofluids, 2020, 2020: 2787903.

Liu, G., Yu, B., Gao, F., et al. Analysis of permeability evolution characteristics based on dual fractal coupling model for coal seam. Fractals, 2020, 28(7): 2050133.

Liu, G., Yu, B., Ye, D., et al. Study on evolution of fractal dimension for fractured coal seam under multi field coupling. Fractals, 2020, 28(4): 2050072.

McTigue, D. F. Thermoelastic response of fluid-saturated porous rock. Journal of Geophysical Research Atmospheres, 1986, 91(B9): 9533-9542.

Miao, T., Yang, S., Long, Z., et al. Fractal analysis of permeability of dual-porosity media embedded with random fractures. International Journal of Heat and Mass Transfer, 2015, 88: 814-821.

Miao, T., Yu, B., Duan, Y., et al. A fractal analysis of permeability for fractured rocks. International Journal of Heat and Mass Transfer, 2015, 81: 75-80.

Ni, X., Gong, P., Xue, Y. Numerical investigation of complex thermal coal-gas interactions in coal-gas migration. Advances in Civil Engineering, 2018, 2018: 9020872.

Øren, P. E., Bakke, S. Process based reconstruction of sandstones and prediction of transport properties. Transport in Porous Media, 2002, 46(2): 311-343.

Palmer, I. Permeability changes in coal: Analytical modeling. International Journal of Coal Geology, 2009, 77(1-2): 119-126.

Palmer, I., Mansoori, J. How permeability depends on stress and pore pressure in coalbeds: A new model. Paper SPE 36737 Presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, 6-9 October, 1996.

Qin, X., Zhou, Y., Sasmito, A. P. An effective thermal conductivity model for fractal porous media with rough surfaces. Advances in Geo-Energy Research, 2019, 3(2): 149-155.

Raeini, A. Q., Bijeljic, B., Blunt, M. J. Generalized network modeling: Network extraction as a coarse-scale discretization of the void space of porous media. Physical Review E, 2017, 96(1): 013312.

Tong, F., Jing, L., Zimmerman, R. W. A fully coupled thermohydro-mechanical model for simulating multiphase flow, deformation and heat transfer in buffer material and rock masses. International Journal of Rock Mechanics & Mining Sciences, 2010, 47(2): 205-217.

Wang, D., Lv, R., Wei, J., et al. An experimental study of the anisotropic permeability rule of coal containing gas. Journal of Natural Gas Science and Engineering, 2018, 53: 67-73.

Wang, H., Xue, S., Shi, R., et al. Investigation of fault displacement evolution during extraction in longwall panel in an underground coal mine. Rock Mechanics and Rock Engineering, 2020, 53(4): 1809-1826.

Yu, B., Lee, L. J., Cao, H. A fractal in-plane permeability model for fabrics. Polymer Composites, 2002, 23(2): 201-221.

Yu, B., Li, J. Some fractal characters of porous media. Fractals, 2001, 9(3): 365-372.

Zeng, J., Liu, J., Li, W., et al. Evolution of shale permeability under the influence of gas diffusion from the fracture wall into the matrix. Energy & Fuels, 2020, 34(4): 4393-4406.

Zhang, H., Liu, J., Elsworth, D. How sorption-induced matrix deformation affects gas flow in coal seams: A new FE model. International Journal of Rock Mechanics and Mining Sciences, 2008, 45(8): 1226-1236.

Zhu, W., Wei, C., Liu, J., et al. A model of coal-gas interaction under variable temperatures. International Journal of Coal Geology, 2011, 86(2-3): 213-221.


  • There are currently no refbacks.

Copyright (c) 2021 The Author(s)

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Copyright ©2018. All Rights Reserved