Production Potential of Coalbed Methane from the Foothills and Plains of Alberta, Canada
Beaton, Andrew P.
Alberta Geological Survey, Edmonton, AB
Alberta contains vast coal resources. Maximum CBM gas-in-place for the Plains and Foothills has been estimated to be greater than 500 tcf however little is known about producibility of this resource. Exploration and research are underway to quantify gas potential, identify key geological factors that maximize CBM potential, and identify ‘most favourable’ areas for CBM production. Current investigations from areas showing favourable CBM potential will be presented.
Increased potential from stimulated wells in the Ardley Coal Zone is indicated by permeability enhancement. New data from the equivalent Coalspur Fm. coals of the Foothills contains saturated gas concentrations averaging 4.3 cc/g, double previously reported gas concentrations.
Subbituminous Horseshoe Canyon Formation coals were thought to have sub-economic gas concentrations. It is these coals, however, that host Alberta’s first commercial CBM production projects. Seams are thin, discontinuous and difficult to correlate. Adjacent wells have significantly different production rates. Different seams within a wellbore contribute differently to overall production; furthermore, correlatable seams between adjacent wells have differing contributions to production. Limited data indicate the gas contents of the underlying Belly River Group coals are slightly higher than that of the overlying Horseshoe Canyon coals.
The deeper, thick and widespread Mannville coals have some of the highest gas concentrations of Alberta coals; however, they have lower permeability than the overlying Belly River, Horseshoe Canyon and Ardley coals. Locally, Mannville coals can have enhanced permeability, and several of these areas are undergoing production pilots.