The national agency responsible for Australia’s seismographic network is expanding its earthquake monitoring capability in the Northern Territory as the Federal Government continues its plans to expedite fracking in the Beetaloo Basin.
- A fracking inquiry in 2018 acknowledged “considerable evidence” that fracking could cause earthquakes
- The inquiry found the likelihood of such an event would be very low and unlikely to result in significant damage
- Scientists will aim to install real-time seismic monitoring before fracking potentially expands in the region
The Beetaloo Basin, about 500 kilometres south-east of Darwin, is one of five Australian gas fields the Government plans to open up under its post-pandemic “gas-led recovery”, with the Commonwealth spending more than $200 million since December 2020 to make the immense gas reserve ready for production by 2025.
Trevor Allen, a senior seismologist with Geoscience Australia, said it was imperative scientists began monitoring seismic activity in the basin now, before commercial production got underway.
“It’s really important for us in the Beetaloo region to deploy this seismic network before any large-scale industrial activity does start occurring in the region, so that we can really get a handle on the natural seismicity that might be occurring in the region that we just don’t know about because the earthquakes are too small,” he said.
“[Then] we can potentially see any changes that might occur in the sub-surface environment in the next few years as the [fracking] industry starts to really ramp up in the region.”
Mr Allen said the new network of seismic monitors, which will bolster a less-sophisticated temporary network already up and running in the Beetaloo region, will detect and locate natural seismic activity such as earthquakes in the area, as well as human-induced seismicity as a result of hydraulic fracturing.
“It’s really important to note that every basin, and even every injection well is different, and will respond differently to the gas recovery process,” Mr Allen said.
“We really don’t have any idea ahead of time whether to expect any earthquake activity in the Beetaloo Basin.
“However the monitoring … will help us identify any potential changes in the sub-surface environment that could occur in the future, given the likely expansion of industrial activity in the region.”
If the agency does not expand its monitoring system before fracking increases in the Beetaloo, Mr Allen said the cause of any seismic activity in the region would become much harder to identify.
Geoscience Australia aims to have the new system installed by the end of the current wet season.
The data captured by the system will be fed back to Geoscience Australia’s offices in Canberra in real time and will be openly accessible to researchers, industry and the public.
Does fracking potentially lead to earthquakes?
Earthquakes that have been attributed to hydraulic fracturing have occurred in Oklahoma in the US and in remote areas of British Columbia and Alberta in Canada, but Mr Allen said only a handful of instances worldwide have been recorded.
“We know that from a very small number of cases from around the world that the recovery of shale gas has triggered small to moderate earthquakes through the process of hydraulic fracturing,” he said.
“It’s much less than one per cent of hydraulic fracturing wells worldwide.”
But Mr Allen said scientists were often constrained by a lack of data when attributing the cause of earthquakes in regions proximal to fracking activity.
“It can be really difficult for seismologists to provide definitive evidence that the fracking is the cause of earthquakes when an earthquake might occur in a geological province that is subject to unconventional oil and gas recovery,” he said.
“This is where it’s really important for us at Geoscience Australia to capture some baseline information about the natural seismicity that might be occurring in the region before any large-scale industrial activity commences.”
Mr Allen said Geoscience Australia had not yet observed any incidences of earthquakes being caused by shale gas fracking in Australia.
The 2018 Inquiry into Hydraulic Fracturing in the Northern Territory acknowledged there was a low risk that fracking could trigger damaging earthquakes.
“There is now considerable evidence from the US and UK that low magnitude earthquakes may occur during hydraulic fracturing and that larger-scale (Richter scale magnitude greater than 2.0) earthquakes have occurred during the fracking process,” the inquiry stated.
“The seismicity caused by hydraulic fracturing mostly has very low magnitudes and is unlikely to be felt or cause infrastructure damage.”
To minimise the risk of seismic events occurring during hydraulic fracturing, the inquiry recommended the implementation of a UK-style “traffic light system”, which uses seismic monitoring to inform gas companies of induced seismicity occurring during hydraulic fracturing in real time.
The UK rules state that hydraulic fracturing must be stopped if minor earth tremors reach a threshold of magnitude-0.5 on the Richter scale.
It is this sort of monitoring capacity that Geoscience Australia will ensure is available.
“The network that we are planning to install will actually support the efforts of the Northern Territory regulator to develop the guidelines for the mitigation of induced seismicity in the Beetaloo region,” Mr Allen said.
A natural or induced earthquake?
With the convergence of three tectonic plates in the nearby Banda Sea, it is not uncommon to feel the impacts of earthquakes in the Northern Territory.
Mr Allen said with adequate monitoring seismologists were able to distinguish between natural events, like Banda Sea earthquakes, and seismic events potentially caused by human activity.
“The occurrence of natural earthquakes will generally tend to occur in more randomised positions,” he said.
“The locations of these earthquakes we cannot necessarily predict ahead of time — so that is often one way that we can identify any natural seismicity that is occurring.”
But Mr Allen said if seismologists can begin to detect patterns in seismic events near fracking fields then that is “an obvious indicator” that industrial activity is a cause.
“But again, I would like to stress that the likelihood of this work actually causing seismicity is very low, and it’s only in a very small number of cases worldwide where it has been observed,” he said.