Energy regulators should consider five-kilometre exclusion zones to protect critical infrastructure such as cities and dams from an increasing number of earthquakes caused by hydraulic fracturing, says one of Canada’s foremost experts on seismic hazards.
In addition to “no frack zones” around critical infrastructure, the oil and gas industry should also monitor earthquake activity within 25 kilometres of such facilities, proposes Gail Atkinson, the NSERC/TransAlta/Nanometrics Industrial Research Chair in Hazards from Induced Seismicity at Ontario’s Western University.
“I think that would be a sensible thing to do,” said Atkinson in an interview.
Atkinson, who has been studying a dramatic surge in industry-triggered earthquakes in Western Canada, recently wrote a paper on strategies to prevent damage from seismic activity triggered by the injection of fluids into the ground. It was published last April.
Over the last few years, the number of industry-triggered events large enough to be felt by people in Western Canada has increased by about a factor of 10, and most of these shaking events are quite shallow or no more than five kilometres deep.
Swarms of earthquakes near Fort St. John, British Columbia and Fox Creek, Alberta have rattled homes, disrupted weddings and even raised concerns about public safety among local politicians such as the mayor of Fox Creek.
That oil and gas community has been rattled by more than 300 seismic events since 2015. Natural Resources Canada has reported more than 10 seismic events near Fox Creek this month, including three events greater than magnitude 3.
In addition, officials at BC Hydro have also raised concerns about the risks posed by hydraulic fracturing to dams in northeastern B.C. since 2009.
But a five-kilometre exclusion zone is likely not the only action needed to reduce the risk of a damaging earthquake, especially considering the possible impacts of events greater than a magnitude 5 happening outside the zone, said Atkinson.
“We need good monitoring within 25 kilometres of critical facilities, coupled with a response protocol that will limit or adjust operations immediately if there is an increase in the number of small earthquakes greater than magnitude 2 triggered within that larger radius,” she said.
Atkinson would also like to see regulators put together an inventory of critical infrastructure for which “failure consequences are unacceptable.”
Exclusion zones could then be set up around such critical infrastructure. Such facilities might include pipelines, dams, cities, sour gas processing plants and mining tailing ponds.
“My central concern is that there could be the potential for significant damage if one of these induced events happened in the wrong place.”
Atkinson is not alone in her concerns. The U.S. Army Corps of Engineers has raised a variety of public safety issues posed by fracking technology and recently recommended a five-mile exclusion zone for injection wells near the Joe Pool Dam in Grand Prairie, Texas.
Atkinson explained that swarms of low-magnitude earthquakes set off by industry imply a potential for higher magnitude earthquakes over time.
Swarms of small earthquakes all preceded magnitude 3 or 4 or “felt” events near Fort St. John and Fox Creek in recent years.
“The rate of events is quite important and they follow a well-known trajectory. For every 10 events above magnitude 3 there will be, on average, a magnitude 4.”
Since 2001, the fracking of 14,000 oil and gas wells has been linked to more than 1,400 earthquakes in Canada. Several events have been larger than magnitude 4 while the largest quake in the country attributed to fracking was 4.8, a global record.
Ground motion from a magnitude 4 event could exceed the damage threshold for some infrastructure, said Atkinson.
Experts do not yet know how big an earthquake hydraulic fracking can actually trigger.
Unlike the U.S., where wastewater injection into the ground has triggered dramatic swarms of earthquakes in Oklahoma, hydraulic fracturing in Western Canada has been directly responsible for some of the largest earthquakes ever caused by the technology.
The injection of fluids into the ground to smash and fracture dense rock in shale formations can change pressure underground and re-activate existing faults and fractures in the ground.
Experts still don’t really know why fracturing has caused more recorded seismic activity in Canada than in the U.S.
“That’s the $64,000 question,” said Atkinson.
It may be related to differences in geology, poor data availability, or could be masked by the sheer number of seismic events caused by wastewater injection in the U.S.
The mega-scale of hydraulic fracturing in Canada might also be a factor.
“There may be more massive high-volume fracking operations in Canada than the United States,” said Atkinson.
One hydraulically fractured well associated with the 4.6 earthquake, for example, injected more than 160,000 cubic metres (42.3 million U.S. gallons) of water, chemicals and sand over a three-week period in 132 stages in northeastern B.C. Each stage creates fractures in rock.
“It is very hard to get data on volume of fluids used in fracking operations in Canada,” noted Atkinson.
Industry often treats the number as proprietary data that gives away information on the size and economics of a particular shale gas development.
“The more volume of fluid you put in the ground, the greater the likelihood the pressure will find its way to a critically stressed fault,” explained Atkinson.
One of the hazard’s posed by industry-triggered quakes is their proximity to the surface, enhancing the likelihood of strong ground motion.
Natural earthquakes typically originate deep in the earth about 10 kilometres from the surface, while seismic activity set-off by hydraulic fracturing and wastewater disposal originates closer to the surface between 2 and 5 kilometres.
“These events are just so much closer to the surface; you are likely to see strong ground motion because they are really close,” said Atkinson.
The seismic hazard expert compared the shallow ground motion from industry-made quakes to explosions.
“If you think of blast going off, you are more likely to get injured if you are closer than further away.”
At present, no computer model exists that can confidently predict just where and when hydraulic fracturing or wastewater injection will trigger an earthquake.
Moreover, there is a great deal of uncertainty about hazards posed by shallow ground motions caused by industry.
To date there has been limited discussion about Atkinson’s proposed strategies. “They would have to be taken up at a higher level by regulatory bodies,” she said.
She said the basic idea behind her proposals is to prod regulators and industry into devoting a little more thought about where “we might choose not to do hydraulic fracturing.... We don’t have to frack everywhere.”