Coal bed methane gas producers must pump water from the coal seam in order to extract methane gas!

Water flows through fractures (or cleats) in the coal seam. Coal bed methane gas moves with the ground water in the coal seam. In order to extract the gas, the water pressure in the coal seam must be reduced in order for the gas to be released. CBM gas has a very low solubility in water and quickly separates from the water as pressure decreases, allowing the gas to be piped out of the well separately from the water. The gas migrates from the coal seam to the well bore as the water moves to the well bore, thus moving the water also moves the gas.

It is really not the intention of CBM producers to dewater the coal seam, but rather they seek to decrease the water pressure, also called the head pressure, in the coal seam to just above the top of the seam, and to migrate the gas toward the well bore. Unfortunately, in order to reduce the water pressure and to more rapidly migrate the gas to the well bore, there is no alternative but to pump the water out of the coal seam. If the CBM producer wants to sell gas from a well they must do something with the water in order for the well to produce gas. If the CBM operator can not get rid of the water the well will become "stranded".

CBM operators do NOT want stranded capital wells. Stranded capital CBM wells are wells that have required a great deal of capital to plan, permit and drill, but still are not producing, and thus not selling gas. It is not uncommon for a CBM operator to wind up with a well that does not produce gas or that can not be drilled at all because of water handling issues. Often it takes over a year to obtain the required permits for surface discharge of water, as well as very large infrastructure costs, to handle the water that will be produced by a single well. Often permits are not obtainable due to water balancing issues related to the surface discharge of the water, leaving an operator stuck with property they can not drill. As of December 2008, there have been 27,396 CBM wells drilled for Coal Bed Methane in the Wyoming Powder River Basin of which 18,039 are producing gas, but leaving over 9,357 wells shut-in or stranded and not producing gas.

The traditional methods for handling CBM produced water have involved bringing the water to the ground surface, and then discharging the water in some fashion. That may include:

1. impounding the water for evaporation,
2. using the water for irrigation during summer months,
3. atomization and treatment of the water and then sending the water directly down a drainage such as a river or a creek,
4. or piping the water to a central location for "high pressure deep well injection"(hyperlink to new page called "Deep Well Injection").

Each of these methods listed above has both environmental and economic limitations while there is another method, ARID, that used on its own or in combination with the older methods of water handling offers a viable solution.

Industry and governmental agencies have known for years that the water quality in coals seams, especially in the Powder River Basin, is quite good. Coal seams are the most regionally continuous geologic unit in the Powder River Basin and have aquifer characteristics equal to or better than sandstones, so are frequently targeted for water-well completions. In fact, coal seam produced water has greatly enhanced livestock operations, through the development of watering areas in previously unused or under-used pastures. At the same time, over the last decade, the shallow sand aquifer systems have been depleted due to drought in the late 1990’s and early 2000’s when normally these aquifers are recharged through precipitation.

Thus, it has been concluded that:

1. the water in coal seams is often quite good and
2. shallower aquifers often are in a position to be recharged

The ARID System offers the most feasible, environmentally friendly, and cost effective method for handling water produced from Coal Bed Methane wells by using viable coal seam water to recharge depleted aquifer systems.