Seepage law and permeability calculation of coal gas based on Klinkenberg effect

WANG Deng-ke(王登科)^{1, 2, 3}, WEI Jian-ping(魏建平)^{1, 2, 3}, FU Qi-chao(付启超)^{1, 2}, LIU Yong(刘勇)^{1, 2}, XIA Yu-ling(夏玉玲)⁴

(1. State Key Laboratory Cultivation Base for Gas Geology and Gas Control (Henan Polytechnic University),
Jiaozuo 454003, China;
2. School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China;
3. Collaborative Innovation Center of Coal Safety Production of Henan Province, Jiaozuo 454003, China;
4. College of Computer Science and Technology, Henan Polytechnic University, Jiaozuo 454003, China;)

Abstract:Focused on the Klinkenberg effect on gas seepage, the independently developed triaxial experimental system of gas seepage was applied to conduct research on the seepage characteristics of coal seam gas. By means of experimental data analysis and theoretical derivation, a calculation method of coal seam gas permeability was proposed, which synthesized the respective influences of gas dynamic viscosity, compressibility factor and Klinkenberg effect. The study results show that the Klinkenberg effect has a significant influence on the coal seam gas seepage, the permeability estimated with the method considering the Klinkenberg effect is correct, and this permeability can fully reflect the true seepage state of the gas. For the gas around the standard conditions, the influences of dynamic viscosity and compressibility factor on the permeability may be ignored. For the gas deviating far away from the standard conditions, the influences of dynamic viscosity and compressibility factor on the permeability must be considered. The research results have certain guiding significance in forming a correct understanding of the Klinkenberg effect and selecting a more accurate calculation method for the permeability of coal containing gas.

Key words:coalbed gas; seepage law; Klinkenberg effect; gas adsorption-desorption; permeability