A new laboratory technique to estimate gas diffusion characteristics of coal
This paper describes a new experimental technique developed to measure the diffusion coefficient (D) for a coal-methane system using the transient flow mechanism, and examine its dependency on factors that change with continued flow-pressure and gas concentration. Although developed primarily for coalbed methane reservoirs and coal in the gob regions, it also has application in situations where a second gas is injected in coal since it utilizes the principle of counter-diffusion. The results show that there is a continuous decrease in the value of D with decreasing mean concentration of methane in coal. The logarithm of D varies directly with the pressure. Two effects may be responsible for this decrease. The first is a possible change in the flow mechanism with decreasing methane concentration due to the existence of varying pore sizes in coal. The other is the volumetric strain of solid coal matrix induced by desorption of gas, the so called shrinkage effect. This matrix shrinkage may be resulting in reduced pore sizes, and consequently, a decrease in the value of D.
- Research Organization:
- Univ. of Arizona, Tucson, AZ (US)
- Sponsoring Organization:
- Department of Interior
- OSTI ID:
- 20020946
- Resource Relation:
- Conference: 8th US Mine Ventilation Symposium, Rolla, MO (US), 06/11/1999--06/17/1999; Other Information: PBD: 1999; Related Information: In: Proceedings of the 8th US mine ventilation symposium, by Tien, J.C. [ed.], 740 pages.
- Country of Publication:
- United States
- Language:
- English
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