43 Analysis of the Coal-Bed Methane Mass Development

Based on underground hydrodynamic principle, this paper analyzed the production mechanism of coal-bed methane well. The production process of CBM well might be divided into two stages: the initial constant rate stage and the late constant head stage. The drawdown of CBM well is mainly subject to water production rate, coefficient of storage, pumping time, permeability and effective radius. For a single CBM well, the effective radius and the drawdown intensity are limited, which directly leads to low gas production.

According to superposition principle, the pressure interference among CBM wells enhances the drawdown and gas production. Therefore, by large-scale development the daily production per well and accumulative outputs of the CBM wells will increase. At last this paper compared the gas production of different scale CBM well groups by using the COMET2 coal bed methane simulator, and concluded that the smallest reasonable number of wells in a group is 60–80 for CBM ground mass development.