As the extraction of any natural resource results in some by products, so does coal bed methane. The by product here that needs to be taken care of so that there are no negative impacts on the environment is Coal bed Methane product water. This is the water from which the methane gas is separated from and then needs to be gotten rid of.
What is CBM water?
To extract methane form coal bed methane (CBM) it is required that large amounts of water are pumped underground so that the water pressure which holds the methane in place in the coal seams gets reduced. The methane gas gets propelled towards the bore wells where the gas gets piped out. The remaining water is called as coal bed methane product water which is very high is salinity and sodium levels that can be bad for plant and soil conditions. This is why it is important that gas companies take care of this product water without harming the environment. You can get some more information at http://www.metgasco.com.au which is the website for Metgasco which is Australia’s major Coal Seam Gas provider on the eastern shores.
What are the current management practices for the disposal of CBM product water?
Most companies use their own ways but these are some common ones used all over the world:
Discharged into a stream
Although this is not allowed anymore on new wells the existing operations that are here for generations still discharge directly into the water. There are some proposals underway that will allow the product water to be discharged under certain flow conditions.
Impounding
This involves the construction of large surface pools in which the product water is held or stored or is allowed to infiltrate to the subsurface. There are many names for these ponds like “infiltration ponds,” holding ponds” or zero discharge ponds. In the zero discharge ponds the ponds are lined so that the water does not infiltrate the land though many other ponds are not lined.
Water applied to crops or rangefield
Water is applied to the soil through various irrigation pipes for some certain crops that can withstand the saline water. Like
Salt Tolerant:
-Barley
-Sugarbeet
-Sunflower
Salt Tolerant Forages
-Tall wheatgrass (Alkar)
-Beardless wildrye (Shoshone)
-Altai wildrye (Prairie land)
-Slender wheatgrass (Revenue)
-Western wheatgrass (Rosana)
-Russian wildrye (Commercial)
-Barley (Steptoe
Semi tolerant:
-Wheat
-Oats
-Safflower
-Corn
Sensitive:
-Potatoes
-Field Bean
-Peas
-Lentils
Other uses
Coal bed methane water is also used for dust control and is also in some cases used by coal mines as well.
Treatment of CBM water:
It is possible to alter the salinity and the high sodium levels of coal bed methane water so that it can be reused. This can be done by diluting it with non saline water, salt precipitation or reverse osmosis. Salt precipitation is the process in which the water evaporated leaving behind the salt and traps the evaporated water. Reverse osmosis is expensive and salt precipitation is not economical with large quantities of salt water. Dilution is possible only of there is a large amount of non saline water.
It is possible to alter the chemistry of the water by adding calcium and magnesium. This only affects the salinity but does nothing for the sodium. But what it does do is that it changes the ratio of sodium to other salts thus decreasing the Sodium Adsorption Ratio (SAR). To make this process work the water will first have to de degassed of the carbonate which can become calcium carbonate (lime) by adding acid. Unfortunately the addition of more salts to the water may result in the conditions that the water is too saline for plant growth. All these processes are being used varyingly in different companies so that the environmental impact is the least and we can have more energy resources. For more details visit our website www.metgasco.com.au
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Randolph Stow has worked in the natural gas industry for the past 7 years and likes to write about his experiences and share his knowledge with everyone. www.metgasco.com.au
