Assessment of environmental health and safety issues associated with the commercialization of unconventional gas recovery: methane from coal seams

Unconventional gas recovery: state of knowledge document

“…This is a conservative estimate that may be extended as additional information becomes available on the thickness and continuity of other deeper formations. Coal beds considered too thin to be minable can still contain significant volumes of methane gas that may be recoverable (Ethridge, et. al.…”

“…When it is intersected by mining, the overburden fractures and the methane that would normally be released into the waste material is drawn to the surface. Such holes can remove as much as one million scfd of methane from a mine and reduce underground emissions of methane by more than 50% (Ethridge, et. al.…”

“…This technique consists of drilling small diameter horizontal boreholes into the virgin coal as the working face is advanced. The methane drained from these boreholes is conducted by pipeline to the surface (Ethridge, et. al.…”

“…is the narrow target zone. The coal bed must be penetrated at a very acute angle since the average coal bed thickness is between 3.9 and 5.9 feet (Ethridge, et. al.…”

“…The information presented in this document was obtained primarily from a series of four technology assessments of the potential environmental, health and safety impacts of unconventional gas resource recovery operations (Ethridge, et. al.…”