UNDERGROUND COAL GASIFICATION POTENTIAL OF COLORADO

Many new coal combustion technologies such as Integrated Gasification Combined Cycle (IGCC ) are limited in the Rocky Mountains due to high elevation. Efficiencies on the order of 20-30 percent encumber Colorado with technological constraints regarding alternative coal power plants. Consequently, potential IGCC sites in Colorado have been proposed at the lowest elevations near Holly, in southeast Colorado, and Loma, in west-central Colorado.

An alternative to this technology is underground coal gasification (UGC). This technology utilizes coal beds at depth with sufficient thickness and converts coal into a gas product. It is an in-situ process that involves the injection of oxidants. The syngas product can be used as chemical feedstock or can be utilized in power plants. The invaluable benefit is that it can utilize coal that might otherwise be unmineable or uneconomic for coalbed methane plays. These ‘stranded’ coal plays can be used for UCG.

The Colorado Geological Survey has characterized all coal resources in Colorado by depth and thickness. Total coal resources from the eight coal regions in Colorado exceed 394 billion metric tons (434 billion tons) to a depth of 1830 m (6,000 ft). Identified resources to a depth of 915 m (3,000 ft) are nearly 117 billion metric tons (129 billion tons). Most of this coal is not mineable due to land-use and technological restrictions. Much of this coal can be explored for coalbed methane (CBM), but significant CBM resources deeper than 3,000 ft are limited by poor fracture development.

Coal gasification utilizes coal at depths between 200 meters (656 ft) to 1 kilometer (3,280 ft). Optimum coal seam thicknesses for UCG are 5 meters (17 ft) to 20 meters (65 ft) thick. New developments in technology promote electricity generation with 10-20 percent less CO₂ emissions and also eliminate 30-50 percent of the capital costs of above ground coal gasification processes.

While most of the Cretaceous and Tertiary coal beds in Colorado are much less than 5 m thick, there are six locations in the Uinta, Green River, Denver, and North Park Coal Regions that maintain substantial thickness and critical depth to utilize this resource technology. It is estimated that nearly 10.9 billion metric tons (12 billion tons) of bituminous and sub-bituminous coal resources in Colorado can be utilized for UGC.