A study titled CSG Water Re-injection Impacts: Modelling, Uncertainty and Risk Analysis, undertaken by scientists from CSIRO’s Gas Industry Social & Environmental Research Alliance has concluded that it is possible to re-inject water produced from CSG extraction into aquifers to benefit existing water users and water-dependent industries.
After it is treated to remove salts and other chemicals, the water was found to be of equal or better quality to that already in the target aquifers.
In particular, the study sought to investigate the effects of large scale re-injection of treated CSG water into the Precipice Sandstone in the Surat Basin (QLD).
Four models were created to simulate groundwater flow in the area and the passage of possible contaminants. The impacts on groundwater were then simulated.
The study found that although the re-injected water could increase groundwater pressure, the maximum increase in groundwater level in stock and domestic sites was expected to be minimal. Such an increase could also occur naturally, even without any re-injection, so may not necessarily be a risk.
Potential changes in groundwater quality were also identified, with the results showing that re-injected, treated CSG-water would be diluted to 1% or less of the original concentration, within 5km of the injection well. As there were no domestic and stock bores located within the 5km radius, the risk of contamination of such bores located in the Precipice Sandstone from re-injecting treated CSG water was considered insignificant.
This suggests, that with the right monitoring, water produced in the CSG extraction process could be re-injected into aquifers to replenish groundwater or possibly be put to other uses.