Evolution of Coal Permeability with Cleat Deformation and Variable Klinkenberg Effect

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• 作者：Yinbo Zhou ; Zenghua Li ; Yongliang Yang ; Lanjun Zhang…
• 关键词：Effective stress ; Methane sorption ; Coal deformation ; Coal permeability ; Klinkenberg effect
• 刊名：Transport in Porous Media
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：115
• 期：1
• 页码：153-167
• 全文大小：1,164 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Geotechnical Engineering
  Industrial Chemistry and Chemical Engineering
  Civil Engineering
  Hydrogeology
  Mechanics, Fluids and Thermodynamics
  
• 出版者：Springer Netherlands
• ISSN：1573-1634
• 卷排序：115

文摘

The characteristics of the gas flow in reservoir have a great impact on exploiting coalbed methane (CBM), so many researchers have carried out the experiments to test the coal sample permeability in the laboratory. The Klinkenberg effect is an important factor in the apparent permeability which is obtained in the laboratory, and it also be recognized as a constant value for a specific gas. From the principle of the Klinkenberg effect, the Klinkenberg coefficient is closely related to the width of the gas flowing path. The coal cleat width changes because of the compressibility and sorption-induced strain features. Therefore, the Klinkenberg coefficient can not be treated as a constant. By using the cubic conceptual model of coal, the deformation behaviors of the coal matrix and fracture are analyzed in this paper, and the influential factors of the Klinkenberg coefficient are obtained. The theoretical equation of methane’s Klinkenberg coefficient was also established. The evolution equation of the cleat width is derived by coupling the effective stress and gas sorption, and the Klinkenberg coefficient model is also rewritten. Using the parameters of the coal sample, some results are obtained. The Klinkenberg coefficient increases with the increase in the pore pressure because of the sorption-induced strain at the constant effective stress; The Klinkenberg coefficient varies with the increase in the pore pressure because of the competition between the stress–strain and sorption-induced strain at the constant mean stress; The Klinkenberg coefficient increases with the increase in the mean stress at a constant pore pressure. The results improve the understanding of the Klinkenberg effect for the gas flow in a coalbed and provide theoretical guidance for CBM exploitation.