Table 5: List of top 10 countries by recoverable shale gas

3.3.2. Coalbed Methane (CBM)

CBM is generated by the conversion of plant material to coal through burial and heating. As “coalification” progresses, increasingly dense coal is formed. Coal serves as both the source rock and the reservoir rock. Coal is extremely porous but has low permeability (connected openings). Much of the methane generated by the coalification process escapes to the surface or migrates into adjacent reservoir or other rocks, but a significant volume remains trapped within the coal itself.