State of In Situ Stress and Implications for Fault Slip Potential in the Montney Play, Western Canada

Abstract We investigate slip potentials of major faults in the North Montney Trend (NMT) and the Kiskatinaw Seismic Monitoring and Mitigation Area (KSMMA) in the Western Canada Sedimentary Basin. The KSMMA and NMT are seismic monitoring areas implemented by the British Columbia Energy Regulator (BCER) in 2018 following concerns about the increasing number of felt seismic events during hydraulic fracture treatments within the Montney Play, including the largest recorded () event in the NMT, and another three events () in the KSMMA. Our objective is to explain the observed seismicity from a geomechanics point of view. We first estimate full in situ stresses for the Montney Formation. Magnitude estimation of the maximum horizontal stress is subject to a large uncertainty. We therefore estimate a range of probable values based on the poroelastic stress model, combined with strain corrections inversely proportional to the distance from the Rocky Mountain Fold and Thrust Belt, as well as commonly used constraints from the borehole measurements and the possibility of a critical stress state. Finally, we estimate the likelihood of slip given known fault orientations in the area. We find that a reverse faulting to transpressional stress state exists within the NMT, transitioning to a transtensional to normal faulting regime in the east of KSMMA. The recorded seismicity mainly occurred at transitional in situ stress regime locations, as in these cases fault reactivation can occur on multiple planes. The amount of overpressure has a significantly smaller influence. Our findings help explain observed source mechanisms of moderate‐sized induced earthquakes.