13 small Alberta earthquakes caused by nearby wastewater injection well
A study by Alberta geo-physicists has established a link between oil and gas activity – a wastewater injection well – and small Alberta earthquakes for the first time.
Prof. Jeff Gu, Associate Professor of Geophysics, University of Alberta. Photo: UofA.
Prof. Jeff Gu, a seismologist at the University of Alberta, is one of three co-authors of a recently published study in the Journal of Geophysical Research that examined a “swarm” of earthquakes measuring up to 3.0 on the Richter scale. The research examined 13 small Alberta earthquakes over four years near an wastewater injection well in the Rocky Mountain House region of central Alberta.
Ryan Schultz and Virgina Stern co-authored the paper – “An investigation of seismicity clustered near the Cordel Field, west central Alberta, and its relation to a nearby disposal well” – and used seismograph data from the region to correlate the timing of the earthquakes with well-injection rates.
“What we found was a relatively compelling correlation between the two with some delays in the timing of the injection relative to the occurrence of the event,” Prof. Gu told Beacon News in an interview.
He says there is no need for Albertans to panic. In most cases, tremors from the earthquakes won’t be felt at surface and there will be no damage to buildings. But he says the incidence of Alberta earthquakes is increasing, which makes further research important.
“How big can these earthquakes get? And why are they occurring? There’s still a lot of unknowns about these events…the mechanisms for the events are not yet precisely known,” he said. “We’re working on that.”
Prof. Gu cautions that his study did not examine wells that were hydraulic fractured – fracking, as it is commonly known – and media reports suggesting his team did are incorrect.
“To be precise, it’s waste water injection,” not fracking, he said.
Prof. Gu says he and his colleagues are just beginning to study the relationship between fracking and induced small Alberta earthquakes. He says that earthquakes induced by fracking operations are very small, smaller than the ones created by the wastewater injection well.
“I would caution that there’s a difference between small events being caused by the fracking operation. As it happens, these are generally very tiny events. These are very small. So, people call these micro-seismic events,” he said.
While fracking-caused Alberta earthquakes may be under 2.0 now, he is researching how fracking might set up a “stress field” in the earth and induce a larger earthquake.
“Something that’s on the order of two or above. That’s certainly detectable by using seismograph.”
The BC government has been studying the relationship between fracking and earthquakes in the NE part of the province where natural gas production is ramping up. Beacon News reported two years ago that the BC Oil and Gas Commission found 272 minor seismic events.
The majority of the earthquakes registered between 2.3 and 3.1 on the Richter scale, according to Hardy Friedrich, spokesperson for the Commission. Only one was felt at ground level.
“No evidence has been found of induced seismicity affecting water wells in northeast British Columbia. Microseismic data were examined during this investigation and showed no evidence of microseismicity occurring significantly above target shale gas depths,” said Friedrich in the Beacon story.
“The Commission has high regulatory standards respecting wellbore integrity, and no vertical wellbore integrity issues were encountered.”
Prof. says the Alberta public should be concerned about fracking-induced earthquakes, but they are too small to worry about.
“I don’t think people should panic about these events yet,” he said. “But it’s certainly worth monitoring and studying.”