Some similarities can be drawn between coal bed methane extraction and Marcellus Shale methane extraction, but in detail, the similarities are few. Because of the different physical characteristics that dictate how and
where natural gas is stored in the rock types, the permeability of the rock units, and their proximity to potential drinking water sources, the likelihood of fractures propagating beyond their target zone(s) in coal bed methane extraction is much higher than in the Marcellus Shale.