A team of researchers led by University of Calgary seismologists has uncovered an earthquake-triggering mechanism linked to hydraulic fracturing.
According to a press release from the U of C, their new model shows that injection of fracturing fluids can lead to a slow slip on a fault. Over time, this puts enough strain on another section of the fault to cause it to slip suddenly – producing an earthquake.
“Based on our model, the earthquake initiates on a part of the fault where friction conditions are unstable,” said study lead author Dr. Thomas Eyre, PhD, post-doctoral researcher in the Department of Geoscience. “In the case we studied, the earthquake occurred hundreds of metres above the hydraulic fracturing zone.”
The discovery appears to reconcile discrepancies typically seen in a laboratory measurements that indicate earthquakes shouldn’t happen in the type of rock that is undergoing stimulation.
Current theories for fluids injection-induced earthquakes suggest that increased fluid pressure is the main triggering mechanism. This can occur directly – by reducing frictional resistance of the fault – or indirectly, by changing the fault loading conditions.
“Our model predicts that slow slip initiates significantly before an induced seismic event. This could lead to new ways to monitor and forecast felt seismic events,” Eyre says.
This interdisciplinary study was a team effort within University of Calgary’s Global Research Initiative in Sustainable Low Carbon Unconventional Resources.
“Industry collaboration is essential, including access to 3-D seismic data (provided by Calgary-based TGS Canada Corp.) that allow us to image fault locations,” says Dr. David Eaton, PhD, professor in the Department of Geoscience and NSERC/Chevron Industrial Research Chair in Microseismic System Dynamics.
Co-authors include doctoral students Marco Venieri and Ronald Weir, Drs. Megan Zecevic and Donald Lawton from the University of Calgary, and Dr. Dmitry Garagash, professor in the Civil and Resource Engineering Department at Dalhousie University.