Characterisation of creep in coal and its impact on permeability: An experimental study

Danesh, Nima N., Chen, Zhongwei, Connell, Luke D., Kizil, Mehmet S., Pan, Zhejun and Aminossadati, Saiied M. (2017) Characterisation of creep in coal and its impact on permeability: An experimental study. International Journal of Coal Geology, 173 200-211. doi:10.1016/j.coal.2017.03.003


Author Danesh, Nima N.
Chen, Zhongwei
Connell, Luke D.
Kizil, Mehmet S.
Pan, Zhejun
Aminossadati, Saiied M.
Title Characterisation of creep in coal and its impact on permeability: An experimental study
Journal name International Journal of Coal Geology   Check publisher's open access policy
ISSN 0166-5162
1872-7840
Publication date 2017-03-15
Year available 2017
Sub-type Article (original research)
DOI 10.1016/j.coal.2017.03.003
Open Access Status Not yet assessed
Volume 173
Start page 200
End page 211
Total pages 12
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Collection year 2018
Language eng
Abstract Creep is a time-dependent deformation that affects coal permeability and should be considered in the prediction of Coalbed Methane (CBM) production. This study experimentally characterises and quantifies the impact of creep on coal permeability. The experiments were conducted on a bituminous coal sample, excavated from Bowen Basin, Australia, using a triaxial gas rig equipped with strain and displacement transducers. Two different types of gases (helium and methane) were injected into the sample under various stress and pore pressure conditions. It was found that for the experiments with helium, creep caused permanent partial closure of cleats and pathways under constant effective stress, and hence a reduction in permeability. Under hydrostatic stress only, a Residual Deformation Ratio (RDR) of 14.1% and a Permeability Loss Ratio (PLR) of 71% were found following the removal of the axial load. This can be due to the damage to coal microstructure along with closure of cleats. For the experiments with methane, coal experienced an instantaneous elastic deformation, at the onset of pore pressure depletion, followed by consolidation and matrix shrinkage. Then, creep occurred when gas desorption ceased. A total permeability loss of 26% was achieved due to an increase of 1.91 MPa in effective stress caused by gas desorption. In addition, the model previously developed by authors was validated against the experimental permeability data. A good agreement was found between the model-predicted permeability data and the experimental permeability data, particularly for higher pore pressure ranges.
Keyword Coal permeability
Creep
Consolidation
Triaxial test
Gas desorption
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mechanical & Mining Engineering Publications
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Created: Sun, 12 Mar 2017, 23:02:44 EST by Zhongwei Chen on behalf of School of Mechanical and Mining Engineering