Energy Center - CCTR

INTRODUCTION

Underground coal gasification (UCG) is a technology that has potential to complement or even replace traditional methods for coal mining and surface gasification. New commercial UCG projects have started recently in several countries such as Australia, China, and India, and more projects are being considered. Appropriate site selection and application of the best UCG technology is a complex process, and a variety of technical and geological factors must be taken into consideration to evaluate each site being considered.

A review of the UCG technologies worldwide and their possible application for use in the in-situ gasification Indiana coals was the subject of a recent preliminary assessment sponsored by the Indiana Center for Coal Technology Research (CCTR). Taking into account both the operational experiences of UCG projects and the geological characteristics of Indiana coals, the thickness and depth of target coal seams were recommended to be used as the primary screening criteria in selecting the areas that have the most potential for further evaluation for UCG.

The Springfield and the Seelyville Coal Members were selected as the primary targets for assessment. For these coals, maps were generated that show thickness, depth, and other characteristics, such as moisture and heating value. Based on these maps, several of the most promising zones were identified. Based on these maps and other geological and infrastructure data, preliminary recommendations on the future selection of a suitable location for UCG operations were made. That study emphasized, however, that the available information on the coals and overlying rock characteristics was insufficient for use in selecting individual sites for engineering and design studies for the construction of a UCG plant. Consequently, additional follow-up site evaluation of the areas determined in the initial assessment would be required.

The intent of this evaluation is to provide more detailed geological analysis of the potential areas or sites that were derived in the previous assessment. Some modifications of the proposed areas were made to make best use of data coverage and to account for the changes in land use. This geological analysis includes: (1) a detailed characterization of coal properties in order to better predict the nature of the produced syngas and the kinetics of the underground gasification process; (2) a generalized investigation of the lithological characteristics of the overlying rock strata in an effort to understand the risk to underground sources of drinking water as well as the availability of water for the gasification process; and (3) a preliminary general evaluation of the overlying rock characteristics in an effort to understand their influence on potential roof collapse and on the subsidence of the ground surface.