As a result of these geologic differences, the target depth for coal bed methane extraction extends from very
shallow depths that sometimes intersect drinking water aquifers to depths that are similar to those for Marcellus Shale gas drilling. The target depth for gas extraction has a narrow range, changing vertically–at most–around
500 ft. in a 25 mile radius. However, in a coal bed over the same 25 mile radius, the target depth for methane
extraction can range from around 400 to 4,000 feet, and multiple depths may be targeted. Shallow coal
beds (less than 450 ft deep) are not only home to sources of methane, but sometimes are the source of potential
drinking water