Coal beds are an attractive prospect for development because of their ability to retain large amounts of gas. Coal is able to store six to seven times more gas than an equivalent volume of rock common to conventional gas reservoirs.
On a daily basis, however, CBM wells typically do not produce as much gas as conventional wells. In most regions of the U.S., coalbed methane wells produce between 100 and 500 thousand cubic feet (Mcf) per day, while the average conventional well in the lower 48 states produces approximately 1.7 million cubic feet (MMcf) per day. There are, however, some extremely productive coalbed methane areas, such as the San Juan basin in Colorado and New Mexico, where some wells produce up to 3 MMcf of methane per day.
(Source : http://www.energyjustice.net/naturalgas/cbm)
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