Diffusion models for gas production from coals: Application to methane content determination

✍ Scribed by Douglas M. Smith; Frank L. Williams

• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 632 KB
• Volume: 63
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(84)90046-2

✦ Synopsis

Experimental studies of methane diffusion from coal cuttings have been analysed with both a unipore diffusion model and a bi-disperse pore structure diffusion model to determine the time range of each model's validity. Initial desorption, during the first 50% of volume desorbed, can be adequately described by the unipore model. For Fruitland coals of the San Juan Basin, the unipore diffusion coefficient varied by less than a factor of 2 from a value of 1 x 1 OW5 s-' despite large variations in sample depth and location. The unipore diffusion model has been successfully incorporated into a lost-gascorrection-factor determination as part of a new technique to delineate coal-bed methane. To describe methane diffusion over the full timescale of desorption, a more complex model which more accurately represents the observed bi-disperse pore structure of coal is required. Using that model the observed desorption rate is described over all the desorption. This model is especially applicable as a source term in describing overall well production.

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