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Coalbed Methane Potential in Illinois-Regional Mapping Data



Illinois State Geological Survey, Champaign, IL


     Data for major Illinois coals have been compiled to identify areas that have the best potential for coalbed methane development.  The thicknesses and depths to the following major coals have been mapped: Danville, Herrin, Springfield,  Jamestown, Colchester, Dekoven-Davis and Seeleyville.  In addition an aggregate average Illinois coal thickness map illustrates the variation in total coal distribution across Illinois.  The greatest total coal thickness occurs in the eastern and southern parts of the state.  Individual coals range in thickness from their pinchouts to as much as 10 feet, whereas, the total thickness of all major coal beds may exceed 35 feet locally.

     Gas content varies geographically from coal to coal and with coal rank.  The first major coal deposited in the basal Carbondale formation, the Seeleyville coal, occurs mainly in eastern Illinois and splits into the Dekoven and Davis coals in southern Illinois.  The Seeleyville/Dekoven-Davis coal interval is about 1400 feet below the ground surface at the deepest part of the Illinois coal basin.  In our recent test hole drilling program, we encountered the Seeleyville at 817 feet in eastern Illinois and the Dekoven-Davis at 1054-1077 feet in southern Illinois.  The most mature Illinois coals have the high-volatile bituminous A rank and occur in the extreme southeastern part of the Illinois coal field.  Coal rank decreases to high-volatile bituminous B and then to high-volatile bituminous C from southeast to northwest and north across the coal field.