Communities with CSG mining in their backyards have welcomed the development of a technique that can detect if methane from coal seam gas extraction sites is leaking into nearby groundwater.
A team of UNSW-led scientists devised the technique, which was tested for the first time in Dalby, Queensland, a growing hot-spot for CSG mining.
Gas extraction from the Walloon Coal Measures near Dalby in the south east of Queensland has expanded rapidly in the past decade, raising concerns among farmers that the groundwater level in the Condamine River Alluvial Aquifer will fall as a result of coal seam gas production.
The team compared the methane in the air near a coal seam gas water holding pond with the methane in groundwater pumped from the Condamine Alluvium at 19 locations.
UNSW’s Charlotte Iverach is lead author of the study, which appeared in journal
Nature Scientific Reports.
Iverach explains that the team compares the isotopic carbon “fingerprint” of the methane.
“Coal bed methane often has a different fingerprint from methane produced by other processes, such as microbial activity,” Iverach says.
After testing at 19 locations, two additional tests had to be passed to establish connectivity between the coal seam and groundwater.
The study has found the extent of hydrologic activity between the coal seam and the aquifer is low, project leader Associate Professor Bryce Kelly says.
“Using the technique for the first time in Queensland, we tested 19 irrigation bores and discovered four locations where the Walloon Coal Measures appear to be hydraulically connected to the Condamine River Alluvial Aquifer,” Kelly says.
“This study shows that the risk of any short-term impact from CSG production on groundwater resources used by the irrigation sector remains low, and farmers should not be concerned about the current scale of gas extraction to the north west of Cecil Plains.
“But if the industry were to expand considerably, more work would be needed to determine the possible impacts of gas extraction on the aquifer in the decades ahead.”
It is not yet known whether the hydraulic connections that allow methane from the coal seam to enter the aquifer are natural, such as a geological fault in the rock, or man-made, such as a leaky abandoned coal exploration well.
You can view the report
here.