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