CHARACTERIZATION OF A POTENTIAL UNDERGROUND COAL GASIFICATION SITE IN SOUTHERN INDIANA
The potential UCG site was selected based on various geologic criteria, including the thickness, depth, and quality of the coal seam, the mechanical and hydrological nature of the overburden, and isolation of the coal from freshwater aquifers. This study utilized geophysical logs, core analyses, coal properties, hydrologic features, and petrophysical data to develop a geologic framework for the Seelyville and the lithostratigraphic units above and below the coal. The results of this study indicate that the Posey County locale is highly favorable for further investigation of UCG potential.
The Posey County study area is approximately 9 square miles in extent, and the Seelyville in this area is found at depths from 830 to 1,100 ft below the surface. The coal seam varies in thickness from 0 to 15 ft. The coal has a persistent split of approximately two feet in thickness. Faulting in the area predates the Pennsylvanian, and the probability of hydraulic connectivity between the coal seam and the primary regional freshwater aquifer, the Inglefield Sandstone Member, that occurs at depths between 200 to 300 ft, is low. The units that separate the Seelyville from the Inglefield consist of interlayered fine-grained siliciclastic rocks, discontinuous thin limestones, and minor coal seams. Low porosities (3.29-8.48%) and permeabilities (0.002-0.042 mD) within the siliciclastic units result in hydraulic conductivities ranging from 1.15x10-4 to 5.48x10-6 ft/day, also suggesting a low probability of hydraulic connectivity between the coal seam and the Inglefield aquifer.