Induced seismicity and the Australian landscape
Britain’s announcement that it will impose a moratorium on hydraulic fracturing, citing a suspected connection between the use of hydraulic fracturing and earth tremors, is a disappointing outcome for a country seeking to boost domestic energy sources and reduce its reliance on natural gas imports.
The claim of induced seismicity has prompted the UK to call for more investigation on the safety of hydraulic fracturing in that country, but repeated investigations have found this issue not to be a significant concern in Australia.
It is worth investigating the available science and experience in Australia, where hydraulic fracturing has been used in onshore production for more than 50 years.
Multiple inquiries in Australia have considered the concept of induced seismicity from hydraulic fracturing and have concluded that the risk of it occurring, and of it having any negative effects, in Australia are low.
This is because Australia is a stable continent. Earthquakes are infrequent compared to those in plate boundary settings, such as parts of the US and Pacific Rim countries to Australia’s north.
The Independent Scientific Panel Inquiry into Hydraulic Fracture Stimulation in Western Australia considered the concept of induced seismicity and noted that:
‘Human activities are not capable of creating entirely new large faults in an intact rock mass, but they can influence patterns of natural seismicity.’
What we do know is that seismic events can be triggered by man-made activities, such as mining, dams and the extraction or injection of material below the ground. Small seismic events have been known to result from stress changes in the ground due to oil and gas activities. This is known as induced seismicity.
There is no evidence to suggest that this is a cause for concern in Australia.
The risks associated with induced seismicity is very low and no correlation has been found between any earthquakes recorded by Geoscience Australia’s Australian National Seismograph Network (ANSN) and oil and gas activities in Australia (link).
Here is what the independent and scientific inquiries and local experts found:
“Frankly, the potential for problems from fracking in the context of an earthquake are minimal if non-existent.” Dr Chris Pigram, CEO of Geoscience Australia, Senate Estimates
‘A site that is susceptible to induced earthquakes generally has a pre-existing susceptibility to natural earthquakes. This means that the worst-case scenario for a site is the same maximum credible magnitude earthquake that would have occurred eventually without any artificial trigger mechanism (without being induced).’ – Report for the NSW Chief Scientist Mary O?Kane
‘Finding 42: The Committee finds that the risk of induced seismicity associated with hydraulic fracturing of shale pays at any depth is negligible.’ – Implications for Western Australia of Hydraulic Fracturing for Unconventional Gas
‘Finding 45: The Committee finds that, given Western Australia’s geology and low background seismicity, the State is unlikely to experience any negative effects from induced seismicity as a result of hydraulic fracturing.’ – Implications for Western Australia of Hydraulic Fracturing for Unconventional Gas
‘The possibility of hydraulic fracturing causing earthquakes of sufficient magnitude to cause structural damage (2 or greater on the Richter scale) has been examined. Based on an extensive review of the evidence, the Panel has concluded that this is unlikely to occur as a result of hydraulic fracturing for onshore shale gas in the NT.’– Scientific Inquiry into Hydraulic Fracturing in the Northern Territory
‘Based upon experience in the US and UK, the extent of fracturing can be monitored using sophisticated micro-seismic technologies.’ – Scientific Inquiry into Hydraulic Fracturing in the Northern Territory
‘The seismicity caused by hydraulic fracturing mostly has very low magnitudes (typically between MW = -2-0) and is unlikely to be felt or cause infrastructure damage.’ – Scientific Inquiry into Hydraulic Fracturing in the Northern Territory
‘The evidence suggests that, provided appropriate monitoring programs are undertaken and a robust and transparent regulatory regime put in place (and enforced), there will be a low risk that shale gas production will result in contamination of aquifers, surface waters or the air, or that damaging induced seismicity will occur.’ – The Australian Council of Learned Academies, Engineering Energy: Unconventional Gas Production: A study of shale gas in Australia
‘Provided best practice is followed, including ensuring that there is comprehensive knowledge of the sub-surface, hydraulic fracturing is most unlikely to cause damaging induced seismic events or result in widespread, systemic impacts on drinking water resources, of which there is no evidence from hydraulic fracturing of shales in the US.’ – Australian Academy of Technology and Engineering
Furthermore, explorers and producers are doing their part to understand background microseismic activity in the areas in which they operate.
For example, in the Canning Basin, Buru Energy commissioned Hasting Micro-Seismic Consulting to undertake a monitoring program in the weeks leading up to the company’s 2015 hydraulic fracturing program. The Canning Basin was determined to be ‘seismically quiet’. The two arrays detected 19 regional and seven local events; none of these were related to petroleum activities.
But what about during the hydraulic fracturing process? The operator’s consultant measured that too, and found:
‘During fraccing operations, 15 acoustic receivers were located in an array around each well and were connected to microseismic recording equipment on the well site using radio telemetry, monitored in realtime in an on-site office.’
‘Fracture stimulation was not associated with any microseismic events above the safe operating thresholds specified.’
‘The recorded microseismic events were of insufficient magnitude to be felt at surface and did not exceed the threshold that might cause any hazard to the well or at the surface.’
Since 2011, 14 separate inquiries and investigations have been conducted in Australia into differing aspects of onshore gas activities, including induced seismicity. The learnings from these reports tells us that with the appropriate regulation in place and with good industry practice, the risks are low.