Diffusion of methane through coal

✍ Scribed by Edward D. Thimons; Fred N. Kissell

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 894 KB
• Volume: 52
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(73)90057-4

✦ Synopsis

Both methane and helium flow through solid coal by Knudsen diffusion, even at relatively high pressures. Knudsen permeabilities were determined for samples of Pittsburgh, Pocahontas No.3, and Oklahoma Hartshorne coals. The average permeability for dry methane was I.3 X 10e6 cm2/s for Pittsburgh coal, 20 X 10e6 for Pocahontas No.3 coai, and 134 X 10-6 for Oklahoma Hartshorne coal. A molecular-sieve effect exists for methane in all three coals examined and it is very strong in Pittsburgh coal. If the methane is saturated with water vapour the permeability decreases by a factor of 3 to 25, depending on the coal. The Knudsen permeability of solid coal discs seems to bear no relation to coalbed permeability. Lag-time measurements indicate systems of both larger and finer pores and the presence of blind pores. This effect is again more pronounced in the Pittsburgh coal.