How is Water Managed in CBM Operations?
In Alberta, if water is removed from the coal seam, provincial regulations stipulate how it may be discharged. In most cases, the water must be re-injected back into the earth at a formation deeper than where it was removed. These formations are identified by the government as appropriate for re-injection because they are deeper and not connected to any fresh water sources. The risk of contamination is unlikely. In exceptional circumstances water may be permitted for discharge on the surface, this water must first meet health requirements for safe water salinity and all discharge must be approved by the Alberta Departments of Environment and/or Agriculture.
Unlike conventional oil operations, water injection for enhanced production is not used in CBM operations.
In some cases, particularly where water is not saturated within the coal, the injection of nitrogen (N) or carbon dioxide (Co2) has been used to displace methane along the coal cleats. Forcing these gases into the borehole helps displace methane as the new gas adsorbs into the coal.
In Alberta, the preferred gas for injection has been nitrogen although there are currently some pilot projects undertaken with federal and provincial assistance to explore the viability of Co2 injection. The use of Co2 injection would have an additional benefit 'the sequestration of Co2. Carbon dioxide is a common by-product of many industrial processes and is considered a green house gas. The sequestering of Co2 would help Canadian lower the amount of emissions in the air, helping us met our goals for carbon reductions As of January 2005, more research is needed into the process before it can be considered economically viable.