This report provides information on the underground coal gasification process in terms of concept, history, applications, technical and environmental issues. It also presents worldwide commercial sites and an assessment on the Alberta coal resources suitable to the process.
Underground coal gasification (UCG) is a process that makes coal resources, which are not economically amendable through conventional mining, available through underground combustion. UCG is an alternative source of energy in several countries around the world. In Alberta, the process has been tested since the summer of 2008 at two locations: southwest of Edmonton targeting the Ardley coal zone and northwest of Edmonton where the Upper Mannville coals represent the target.
The UCG operates by drilling designs of injection-production systems enabling in-situ conversion of coal into syngas (synthesis gas) by pyrolysis, combustion and gasification. Syngas is a mixture of mainly carbon monoxide and hydrogen used as fuel in power generation, as well as feedstock for various chemical products and as synthetic pipeline gas, a replacement of natural gas. The main UCG by-products are in-situ deposits (roof rock fragments and ash-rubble) and released residue (flue gases and fly-ash), which are under-control captured, managed, or discarded.
In Alberta, the Cordilleran foreland holds approximately 40% of the Canadian estimates of coal underground resources, which at this stage, are not economically exploitable through conventional mining. Examination of preliminary evaluations of the coal potential in Alberta, suggests that the primary UCG targets are the Ardley, Horseshoe Canyon and Upper Mannville coal zones. One area with UCG potential within each of these coal zones has been selected, compared and discussed in terms of opportunities and challenges. The selected areas are south of Pigeon Lake for the Ardley coal zone, south and east of Edmonton for the Horseshoe Canyon and Upper Mannville coal zones, respectively.
The competition of UCG operations with CBM exploration/exploitation and CO2 storage in some areas may require a regional evaluation of the coal resources to define the coal zone's suitability to one or the other application and to prevent risks.
Pana, C. (2009): Review of underground coal gasification with reference to Alberta's potential; Energy Resources Conservation Board, ERCB/AGS, Open File Report 2009-10, 56 p.