Natural gas in coal seams is held in place by the pressure of groundwater. The water is pumped to the surface by wells, relieving this pressure and allowing gas to flow and be collected.
CSG produced water is distinct from water found in other non-coal seam aquifers and has different properties to normal artesian water. CSG production water tends to be relatively saline (usually it is brackish, like estuarine water).
With the ability to extract groundwater comes the obligation to treat the water for beneficial use and to “make good” any impact on existing water users.
Disposal and use of CSG production water
Gas producers are usually required to treat CSG associated water and make it available for beneficial use.
The quality of associated water can vary greatly in different areas and different types of treatment can be required.
Some companies are already treating their associated water by reverse osmosis and other methods so that it can be used for beneficial uses, such as:
Untreated associated water also has beneficial uses, including coal washing and cooling of power stations. Water from some coal seams is – even without treatment – suitable for stock watering, irrigation or reinjection into aquifers.
CSG production and groundwater
For more information on how CSG production can affect groundwater, see this webpage.