Are you concerned about the effects of coal seam gas mining in your area of the world? Dr Peter Stone from the CSIRO in sunny Australia provides the facts in a question and answer session. In the interview he touches on all the hot topics, including the controversial process of fracking and what it means for the environment? He also address concerns over water contamination. Let’s get the facts.
Q. What is known about the possible impacts of CSG plants and surrounding aquifers?
A. Extraction of methane from coal seams requires the extraction of large quantities of water, so across the industry, it may total between about 90 and 30 gigalitres of groundwater per year, or the equivalent of about three Olympic swimming pools for each well, each year. Basic sets of impacts that are broadly well understood are: the likely drawdown of aquifers; depressurisation of aquifers; risk groundwater contamination; risk of subsidence of the surface, and salt that is in the water of coal seams will be brought to the surface as well, in a quantity of about 1.8 million tonnes of salt per year.
Q. When talking about water contamination, do you refer to the chemicals that are used in the fracking process, or would that contamination happen even when there is no fracking involved?
A. There are several types of water contamination that are possible. One is through the injection of chemicals through the fracking process. Another is through chemicals that naturally exist in coal seams, being taken out of coal seams and exposed to other parts of the environment, and the third is just from the removal of large quantities of water from aquifers or coal seams. You can get a lateral flow of water and aquifers, and aquifers actually differ in their water quality throughout their extent, so just having that lateral flow in aquifers can lead to changes in water quality.
About the contamination risk, it’s important to know that the likelihood of contamination extending to the broader environment, and particularly to human health, is thought to be low, and the reason is that removing water from coal seams creates a negative pressure in the coal seam, which means that water will actually move from surrounding aquifers into coal seams — rather than having water moving from coal seams into surrounding aquifers. So the risk of groundwater contamination is thought to be low.
Q. How low?
A. Well, I can’t give you a number, because the risk is related to the probability of contamination occurring and the actual nature of the risk associated with that contamination, so it’s not something that can be answered with a simple number.
Q. When talking about risks, are you referring to the possibility of methane leaking into aquifers from the coal seams?
A. Methane leaking into surrounding aquifers is something that can occur naturally when there’s a close connection between the coal seams and the surrounding aquifers. It’s also something that can occur if the wells that go from the surface down into the coal seam aren’t properly sealed.
So, many of the potential risks that are associated with the environmental impacts of gas extraction are impacts that you would expect to occur if processes haven’t been followed properly. So things like not sealing wells properly, or having spillages and things like this are thought to be the means by which contamination events are likely to occur.