EARTHQUAKES have increased at an earth shattering rate in the US, and it is now officially recognised that a standard onshore gas wastewater disposal technique is to blame.
For the first time, the US Geological Survey (USGS), a scientific government body, said that reinjecting wastewater back underground into the deep aquifers can induce seismic activity.
NSW and Queensland list reinjection as a preferred disposal technique. If wastewater were pumped back into the coal seams, it could potentially remove the need to remove salt, which gas producers currently dispose of in landfill.
In Queensland, Origin returns highly treated wastewater to the Precipice Sandstone aquifer under low pressure.
Santos is trialling reinjection of treated wastwater deep underground at Arcadia Valley, and at the Roma shallow gas project.
There are no trials in NSW. The state’s chief scientist released a blueprint for CSG regulation in 2014, which recommended further studies if reinjection were to be implemented, including impacts to seismic activity.
But NSW has not developed regulations for the practice.
Gas lobby Australian Petroleum Production and Exploration Association said reinjection is low risk in Australia and can be beneficial, if properly regulated.
“In Australia, the risk of earthquakes caused by reinjection is very low. Australia is a geologically stable continent and earthquakes are infrequent,” said APPEA Queensland director Rhys Turner.
Western Australia, Victoria, South Australia and Queensland have used managed aquifer recharge techniques successfully.
Surface and reclaimed water is collected and held in ponds, where it infiltrates under low pressure into shallow aquifers for beneficial re-use.
In the US, Oklahoma experienced the greatest increase in earthquakes since 1980. Other areas in the region with reinjection also experienced more earthquakes, but far fewer than Oklahoma. North Texas had nine earthquakes above 2.7 magnitude in 2015, and 10 in 2013, but only one between 1980 and 2010.
Groundwater is produced during coal seam gas production. Water is liberated along with gas during the fracking process, which flows to the surface through the gas well.
USGS’ assessment of eastern and central US said reinjection causes underground pressure changes that can weaken a fault and bring it closer to failure.
“Most injection wells do not trigger felt earthquakes, suggesting that a combination of many factors contribute to such events,” the report stated.
In September 2016 USGS senior advisor for earthquakes William Leith advised in a Congressional research report that groundwater systems were not well understood.
"Scientists currently have limited capability to predict human-caused earthquakes for a number of reasons, including uncertainty in knowing the state of stress in the earth, rudimentary knowledge of how injected fluids flow underground after injection, poor knowledge of faults that could potentially slip and cause earthquakes."
The US has sunk more than 30,000 water disposal wells to date. The USGS is the first government agency to link reinjection with earthquakes, but in March 2016 the Federation of American Scientists found earthquakes above magnitude 3.0 had increased threefold since 2009.