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) resources is found in evolving enhanced gas recovery (EGR) technologies using CO2 injection, somewhat similar to enhanced oil recovery (EOR). However, unlike CO2-EOR where CO2-breakthru eventually occurs, the injected 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 stage, has shown increased yields of produced CH4 over conventional CBM recovery. Future successful tuning of the process may allow the design of efficient null-greenhouse-gas-emission power plants which are fuelled by CBM from deep coal beds. In this closed CO2-cycle process, the waste CO2 produced by CH4-fuelled power plants is injected into CBM reservoirs to produce more CH4. Other scenarios are possible using offsets. A simple mass balance argument, based on a 2 to 1 coal-sorption-selectivity for CO2 over CH4, supports the feasibility of building and operating fossil-fuelled green power plants. (C) 1997 Elsevier Science Ltd.