An experimental and numerical study of gas transport and imbibition processes in coal matrix

Fengshuang Han, Andreas Busch, Bernhard M. Krooss, Zhenyu Liu, Jianli Yang

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

Abstract

The mixed transport and imbibition processes of gas in the coal seams are the fundamental phenomena in the process of CO2 sequestration in unminable coal seams and Enhanced Coal Bed Methane (CO2-ECBM) production process. The gas imbibition and transport processes in a waterwetted matrix-plug (cleat-free) under a confined stress of 20 MPa were experimentally investigated by applying pressure gradients of different single gas (He, Ar, CH4 and CO2) over the matrix-plug and monitoring the gas pressure changes with time in the closed up- And down-stream compartments. It was found that different gases presented different up- (P1) and down-stream (P2) pressure curves, which reflected the differences in their flow rates and imbibition mechanisms through the plug. In order to explain the experimental data and understand quantitatively the imbibition and transport processes, simple numerical approaches were established, in which two mechanisms, including gas dissolution and diffusion in the pore water, and gas sorption and diffusion in the coal matrix were considered. Unipore models (homogenous medium) with a linear boundary and a Langmuir sorption boundary were applied to interpret these two mechanisms, respectively. It was found that He diffuses through the micropores which are inaccessible to water in the matrix-plug, while Ar, CH 4 or CO2 travels in the matrix-plug mainly with a combined process of sorption and diffusion. The effective diffusion coefficients of He, Ar, CH4 and CO2 in the matrix-plug were 6.6×10 -10, 7.5×10-13, 5.0×10-13 and 1.2×10-12 m2·s-1, respectively. It seems that both Knudsen diffusion and surface diffusion govern the transport of He and Ar, CH4 and CO2 in the matrix-plug.

Original languageEnglish
Title of host publication30th Annual International Pittsburgh Coal Conference 2013
PublisherInternational Pittsburgh Coal Conference
Pages756-777
Number of pages22
Volume1
ISBN (Print)9781629934389
Publication statusPublished - 2013
Event30th Annual International Pittsburgh Coal Conference 2013 - Beijing, China
Duration: 15 Sep 201318 Sep 2013

Conference

Conference30th Annual International Pittsburgh Coal Conference 2013
CountryChina
CityBeijing
Period15/09/1318/09/13

Keywords

  • Coal
  • Diffusion
  • Numerical model

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geotechnical Engineering and Engineering Geology

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  • Cite this

    Han, F., Busch, A., Krooss, B. M., Liu, Z., & Yang, J. (2013). An experimental and numerical study of gas transport and imbibition processes in coal matrix. In 30th Annual International Pittsburgh Coal Conference 2013 (Vol. 1, pp. 756-777). International Pittsburgh Coal Conference.