NATURAL GAS

Coalbed Methane
The most widely spread distribution of any fossil fuel source located on land is coal.  Generally found within coal is the presence of methane gas.  Due to the abundance of coal, as well as the presence of methane gas, coalbed methane is the most widely distributed commercial gas source.  The United States Geological Survey (USGS), currently 7.5 of natural gas production is coalbed methane.

Coal is produced by the conversion of organic materials under the pressure of the earths surface.  This conversion processes creates extensive quantities of methane gas that then becomes trapped within the coal.  Due to the large internal surface area of coal and the large volume of methane produced by this conversion process, coal is capable of storing large volumes of methane gas.  Coalbed's are permeated by water, resulting in pressure that traps the methane gas within the coal.  Coalbed methane can be released from a coal seam when that seam is either broken through the mining process or when the water is removed from the seam.  Coalbed methane was originally detected in coal mines.  The presence of methane gas within the mine makes the atmosphere both toxic, and possibly explosive.  When water has been removed from a coal seam, it becomes depressurized resulting in the release of the methane gas, which can then be collected.  

Due to the decline in conventional reservoirs, unconventional methods of natural gas production are becoming increasingly important.  When comparing conventional and unconventional reservoirs, conventional reservoirs are typically more financially sound and easier to access than unconventional reservoirs.  Coalbed methane is considered an unconventional reservoir, however, it is generally found at shallow depths, which in turn makes well drilling and completion more cost effective.  With technological advances or new processes making the resource more easily extractable, unconventional reservoirs may become conventional.       

In order to produce gas from the coal,  water must be drawn first, lowering the pressure so that the natural gas can flow out of the coal and into the well bore.  The water produced by this process varies in quality and must be disposed  in an environmentally sound manner.  (Below: Wells located in Slater Dome.)

The combustion of methane gas is environmentally beneficial as opposed  to the release of methane gas into the atmosphere.  According to the United States Geological Survey (USGS), "Production of methane from coal beds may actually reduce methane emissions to the atmosphere by removing the gas that is otherwise released during coal mining."  Methane burns to carbon dioxide and water with no other pollutants.  Carbon dioxide is significantly less potent as a greenhouse gas when compared to the potency of methane as a greenhouse gas.  The combustion of methane to carbon dioxide thus produces environmentally beneficial effects.