DEEP COALBED METHANE IN ALBERTA, CANADA - A FUEL RESOURCE WITH THE POTENTIAL OF ZERO GREENHOUSE-GAS EMISSIONS

A huge incentive to develop Alberta's deep coalbed methane (CBM) resou rces is found in evolving enhanced gas recovery (EGR) technologies usi ng CO2 injection, somewhat similar to enhanced oil recovery (EOR). How ever, unlike CO2-EOR where CO2-breakthru eventually occurs, the inject ed CO2 is sequestered in the reservoir by sorption to the coal surface . The mechanism is that the CO2 displaces the sorbed CH4 from the coal surface, two molecules of CO2 being trapped for every molecule of CH4 released. Already this CO2-EGR process, although in an embryonic stag e, has shown increased yields of produced CH4 over conventional CBM re covery. Future successful tuning of the process may allow the design o f efficient null-greenhouse-gas-emission power plants which are fuelle d by CBM from deep coal beds. In this closed CO2-cycle process, the wa ste CO2 produced by CH4-fuelled power plants is injected into CBM rese rvoirs to produce more CH4. Other scenarios are possible using offsets . A simple mass balance argument, based on a 2 to 1 coal-sorption-sele ctivity for CO2 over CH4, supports the feasibility of building and ope rating fossil-fuelled green power plants. (C) 1997 Elsevier Science Lt d.