In situ determination of desorbable methane content by use of three different decay functions.

摘要

The desorptive properties of methane in selected western coal seams were studied through actual field measurements using a manual bubble desorbometer and later verified through laboratory modeling. Data were reduced using a power decay function, a quadratic function, and an exponential function. Methane desorption characteristics from individual coal seams were shown theoretically to be a good estimator of a seams total methane content to within (+ or -)20%. A laboratory was set up and equipped to properly analyze and reduce field data, in addition to providing a controlled model for studying methane adsorption properties on coal. The results of the field tests indicate that all three theoretical desorption functions provide a satisfactory model of the desorption process based on estimated and actual gas contents, and on superior coefficient of regression. The estimated gas content for four western coal mines are presented based on computer reduction of data obtained from field and laboratory tests. One of the investigated coal seams is located in Colorado (B seam of the Dutch Creek Mine in Carbondale) and three are located in Central Utah (Rock Canyon seam of the Soldier Creek Mine), Lower Sunnyside (Sunnyside Coal Mines) and Sub 3 (Castle Gate Mine) seam. Their average methane content ranges from 1.8 cc/g to 5.5 cc/g. Graphic results from laboratory tests indicated the power function may provide a more accurate model of the desorption process than the other two theories discussed. 4 refs., 12 figs., 3 tabs.