Dating of Coal Bed Methane Reservoir and Surface Waters in the Raton Basin, Colorado and the Susitna Basin, Alaska

Paul R. Oldaker, Consulting Hydrologist/Hydrogeologist, P. O. Box 775048, Steamboat Springs, CO 80477, phone: 970-879-0082, [email protected] and Udo Fehn, Dept. Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, University of Rochester, Rochester, NY 14627.

Dating of coal bed methane (CBM) reservoir, surface, and near surface waters provides a test of the hydraulic connection between CBM reservoirs and surface hydrologic systems. Tritium and carbon 14 were used to date surface and near surface waters. In both basins surface and near surface waters were less than 60 years old. The CBM waters were greater than 60 years old. Carbon 14 could not be used to date CBM waters since the coal itself may contaminate the sample. Chlorine 36 was used to date CBM waters. The age for the Raton Basin sample was at least 1,300,000 years old at a depth of 1,850 feet. The age for the Susitna Basin sample was at least 1,200,000 years old at a depth of 2,600 feet. No modern water was found in the CBM reservoir indicating no hydraulic connection to surface hydrologic systems. For reservoir engineers this conclusion indicates the CBM reservoir water volume is finite and the reservoir can be de-pressurized. For environmental managers this conclusion indicates no direct connection between CBM water production and surface water supplies.