UNDERGROUND COAL GASIFICATION; USA, ILLINOIS BASIN, AND ELSEWHERE

With difficulties facing traditional coal mining because of new environmental regulations, underground coal gasification (UCG) has potential to complement or replace traditional methods of converting coal to power via coal mining, and combustion or surface gasification. Selection of the most effective UCG technology is, however, a complex process, and a variety of technical and geological factors must be taken into consideration for each site being evaluated.

This presentation will briefly discuss the history of UCG and present the status of recent projects in the US. In addition we will review screening criteria used to evaluate UCG potential of the Pennsylvanian Springfield Coal Member of the Petersburg Formation and Seelyville Coal Member of the Linton Formation in the eastern part of the Illinois Basin. Geologically-related criteria such as thickness and depth of coal seams and coal properties such as heating value, moisture content, ash/sulfur content, and swelling characteristics typical of the Illinois Basin coals will be discussed and compared to those in other coal regions that use or plan to use UCG technologies. Assessment of geomechanical (subsidence risk) and hydrological (groundwater protection) properties of the overlying rock strata will also be provided for selected areas in Indiana. For the Seelyville Coal, in particular, low porosities (3.29-8.48%) and permeabilities (0.002-0.042 mD) within the siliciclastic units overlying the coal result in hydraulic conductivities ranging from 1.15*10^-4 to 5.48*10^-6 ft/day, suggesting a very low probability of hydraulic connectivity between the coal seam and the primary regional fresh water aquifer. Finally, on-going experimental research and basin-scale UCG evaluation sponsored by the European Union will be presented.