How does coalbed methane occur in the coal?
Because coal beds serve as both the source rocks and the reservoir rocks, gas storage in coal beds is more complex than in most conventional reservoirs (e.g., carbonate and sandstone). Although coalbed methane can (and does) migrate to non-coal reservoir rocks, once the gas leaves the coal beds it is no longer considered coalbed methane. Gas reservoirs composed of coal contain unique properties for gas storage that are not present in other reservoirs.
