A new academic study reveals two ways hydraulic fracturing by oil and gas operators can cause earthquakes in Alberta, Canada. Researchers at the University of Calgary’s Department of Geoscience have discovered that tremors induced by hydraulic fracturing can occur through pore pressure increases and by stress changes. The study “Fault Activation by Hydraulic Fracturing” has been published in Science, one of the world’s leading peer‑reviewed academic journals.
The study has been described as revealing an “exquisitely detailed picture” of the timing and dynamics of seismic events in an area about 30 kilometers west of the town of Fox Creek, Alberta. The area has recently had small earthquakes which researchers and regulators believe are attributable to extensive hydraulic fracturing of oil and gas wells in the area.
The study’s authors, Professor David Eaton and Dr. Xuewei Bao, collected and analyzed seismic data from public and private seismograph stations and reportedly were able to link seismic events to specific operations at individual wells. They also discovered a previously undetected fault system running parallel to two horizontally drilled wells. Their analysis showed that small earthquakes were triggered when hydraulic fracturing of those wells imposed mechanical stresses on the rocks underlying the hydrocarbon-bearing zone, causing slippage in the fault. This seismicity ended when the hydraulic fracturing ended. However, more than two weeks later, a magnitude 3.9 earthquake occurred. The research indicates that that event appears to have been associated with the subsequent infiltration of the fracture fluids into part of the fault.
This research may lead to new ways to assess risk and to mitigate the hazards of earthquakes caused by hydraulic fracturing, as well as to help regulators develop regulations informed by science.