How do they estimate the amount of methane gas that will come from a region underlain by coal?
There are two popular methods for estimating recoverable methane gas from a coal seam. One method requires estimating methane reserves by boring a hole through the coal seam, extracting a core from the bore hole, then trapping the amount of methane from the coal core. If a number of cores are drilled and methane gas release is observed, one can get a rough idea of the amount of gas available in a region. The limitations to this method are: 1) there is much disturbance to the coal seam core before gas release is finally measured; 2) it is expensive and 3) not every region of potential CBM development has been drilled and explored. Another method of estimating the amount of methane in a region underlain by coal is through a series of calculations based on information we already know about the coal in the region and the feasibility of CBM development. For instance, the Montana Bureau of Mines and Geology estimated the amount of recoverable CBM in the Powder River Basin using the following
