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Natural gas produced from coal beds (coal-bed methane, CBM) accounts for about 7.5 percent of the total natural gas production in the United States. Along with this gas, water is also brought to the surface. The amount of water produced from most CBM wells is relatively high compared to conventional natural gas wells because coal beds contain many fractures and pores that can contain and transmit large volumes of water.

How is coalbed methane extracted from coal?

When water is removed from a coal seam, it lowers the reservoir pressure. Methane that was held in place by water pressure tends to follow the water as it is pumped to the surface, where it is captured and transported through pipelines to storage facilities or shipped. This relatively inexpensive and straightforward procedure has made coalbed methane a useful, easily accessible form of energy.

Estimates of the amount of recoverable CBM have increased from about 90 trillion cubic feet (TCF) 10 years ago to about 141 TCF, spurred by advances in technology, exploration, and production (Nelson, 1999). As the number of CBM wells increases, the amount of water produced will also increase.

Water coproduced with methane is not reinjected into the producing formation to enhance recovery as it is in many oil fields.  Instead it must be disposed of or used for beneficial purpose.

(Science Education Research Center, USGS)