Illinois Coalbed Methane Assessment

By

MORSE, DAVID G. and ILHAM DEMIR

Illinois State Geological Survey, Champaign, IL

     Illinois, with its huge 200 billion ton coal resource, has lagged behind other regions of the country in coalbed methane (CBM) development.  Recent core drilling by the Illinois State Geological Survey (ISGS) provides encouraging new data on the gas content and origin of CBM in the State.  Prior to this study limited published gas content values ranged from 8 to 118 ft³ gas per ton of coal.  ISGS drilled a continuously-cored, wireline-retrieved, test hole in each of Richland, Franklin, Clark, Macoupin and Bureau Counties.  All major coals and several black shales were cored and analyzed.  New gas content values are considerably greater than previously reported- some exceeding 150ft³/ton.  Thicker coals tend to have greater content values per ton of coal, and gas contents tend to increase modestly with depth of coal.  The highest gas contents were from coals in Franklin and Clark counties. Desorbed methane isotope values range from delta ¹³C_PDB of -55 to -70 parts per mil and delta D_SMOW of -230 to -200 parts per mil, indicating primarily a biogenic (CO2 reduction) mechanism for generating the methane with a small thermogenic overprint.

    CBM drilling activity is at an early stage in the Illinois Basin.  A coal mine project with co-generation of heat and electricity from mine gas combustion powers a hydroponic farm in Saline County; excess electricity is sold.  Another company has drilled into several abandoned  Franklin County mines and is completing gathering lines and pipelines for transmission pipeline sales.  Several companies have drilled coalbed wells, but the only production is from North Dugger field in west-central Indiana where more wells are planned.