The calculated depth to top values were extracted from Viewlog and used to calculate the gas content using the following formula:

Gas content dry, ash-free basis (daf)was calculated for the coal zone using the equations:

1) For depth to top > 200 m: gas concentration (cc/g, daf)=Lv x (depth x grad)/(depth x grad)+(Lp x 0.70)

and

2) For depth to top < 200 m: gas concentration (cc/g, daf)=Lv x (depth x grad)/(depth x grad)+(Lp x 0.40)

where Lv is Langmuir volume (cc/g, daf) and Lp is Langmuir pressure (Mpa), both obtained from isotherm analyses; depth is depth to top of coal zone (m); grad is pressure gradient (Mpa); daf is dry, ash free basis; and 0.70 and 0.40 are gas saturation values. Saturation percent determined by comparing gas adsorption capacity (langmuir parameters) to measured desorbed gas content.

Note: Langmuir volume and pressure were determined by laboratory analysis on Alberta coal samples from each coal zone in question according to Langmuir, I.: “The Adsorption of Gases on Plane Surfaces of Glass, Mica, and Platinum,” Journal of the American Chemical Society, Vol. 40 (1918) pp. 1,361-1,403.

From the above calculations, a gas content estimate (cc of gas per g of coal) on a dry, ash-free basis for the Ardley coal zone was generated.

Results were gridded and contoured in Viewlog using its Simple Kriging method. Contour lines were exported from Viewlog as a DXF file. This was then imported into ArcGIS and exported as a shapefile.