How do they estimate the amount of methane gas which will come from a region underlain by coal?
There are two popular methods of estimating recoverable methane gas from a coal seam. One method requires estimating methane reserves by boring to the top of the coal seam, then extracting a core from the coal. The amount of methane recovered from the coal core is used to estimate gas content per unit volume of coal. If a number of cores are drilled and methane gas release is observed, one can estimate 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 measured; 2) it is expensive and 3) not every region of potential CBM development has been drilled and explored. Another method of estimation is through a series of calculations based on information already known about the coal in the region and the feasibility of CBM development.
