UNDERGROUND COAL GASIFICATION: EXAMPLES FROM THE EASTERN PART OF THE ILLINOIS BASIN

A renewed interest in the technology of underground coal gasification (UCG) has great potential to complement or replace traditional methods of converting coal to power via coal mining, combustion or surface gasification. Selection of the most effective UCG technology is a complex process, and a variety of technical and geological factors must be taken into consideration for each site being evaluated.

In this study, potential for UCG in the eastern part of the Illinois Basin (Indiana) has been evaluated. Based on the review of the existing UCG projects and the geological characteristics of Indiana coals, screening criteria have been established, with the thickness and depth of coal seams selected as the most important. Coal properties considered to be important include heating value, moisture content, ash/sulfur content, and swelling characteristics. Because of the size and position within the basin, the evaluation focused on the Pennsylvanian Springfield and Seelyville Coal Members. For these coals, a series of maps of selected coal parameters were generated. These maps were basis for selection of the most optimal areas with regard to geological criteria. In addition, for the most promising areas, more detailed maps, which also show available infrastructure (power plants, pipelines, towns, etc.) were generated. Analysis of these maps and additional information identified nine promising zones for UCG in Indiana (four for the Springfield and five for the Seelyville Coal. A follow-up study is now ongoing and focuses on more detailed characterization of the selected areas, including an assessment of geomechanical (subsidence risk) and hydrological (groundwater protection) properties of the overlying rock strata as well as chemical characteristics (kinetic analysis) of the coals in the most promising localities.