Evolution of coal permeability under unconstrained swelling: Contribution of matrix-fracture interaction

Zhongwei Chen, Jishan Liu, Derek Elsworth, Shugang Wang, Yu Wu

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Coal permeability model is needed to define the transient characteristics of coal permeability evolution due to adsorbing gas injection. A broad variety of models have evolved to represent the effects of sorption, swelling/shrinkage and effective stresses on the evolution of permeability. This work evaluated the performance of these models against analytical solutions for both unconstrained swelling and constrained swelling conditions. Constrained model predictions are apparently consistent with typical laboratory measurements. Nevertheless, this consistency is due to the mismatch between model boundary condition (constrained) and experiment boundary condition (unconstrained), demonstrating that current permeability models can hardly explain net reductions in coal permeability where swelling is unconstrained. To explore the possible reason, a full coupling approach was applied to explicitly model the interactions of coal matrix-fracture and translate these interactions into the permeability change. In this approach, the important non-linear responses of coal matrix to the effective stress are quantified through the incorporation of heterogeneous distributions of coal properties into complex mechanical coupling with gas transport. When swelling coefficient and modulus vary spatially relative to the fracture void, a net reduction in coal permeability is achieved from the initial no-swelling state to the final equilibrium state. These modeling results are consistent with the observed responses under the unconstrained swelling conditions, which demonstrates the contribution of this work.

Original languageEnglish (US)
Title of host publication47th US Rock Mechanics / Geomechanics Symposium 2013
Number of pages11
StatePublished - 2013
Event47th US Rock Mechanics / Geomechanics Symposium 2013 - San Francisco, CA, United States
Duration: Jun 23 2013Jun 26 2013

Publication series

Name47th US Rock Mechanics / Geomechanics Symposium 2013


Other47th US Rock Mechanics / Geomechanics Symposium 2013
Country/TerritoryUnited States
CitySan Francisco, CA

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology


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