Importance of In-situ Stress Estimation in the Understanding of Induced Seismicity
Description:
In this study, we investigate slip potentials of variously oriented major faults in the North Montney Trend (NMT) and the Kiskatinaw Seismic Monitoring and Mitigation Area (KSMMA) in the Western Canada Sedimentary Basin (WCSB). The KSMMA and NMT are seismic monitoring areas implemented by the British Columbia Energy Regulator in 2018 following the concerns about the increasing number of felt seismic events during hydraulic fracture treatments within the Montney Play. The largest recorded MW=4.6 event occurred on August 17, 2015, in the NMT, and another three events (ML=3.6~4.3) occurred on November 30, 2018, near the southern margin of the Fort St. John Graben (FSJG) in 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 (FTB), 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.
It is observed that the stress regimes transition from reverse to transpressional to strike-slip in the NMT, and from strike-slip to transtensional/normal faulting in the KSMMA. We found from more than 7000 recorded seismicity locations (magnitude of 1.5 or higher, British Columbia Energy Regulator, 2024) that seismicity does not necessarily occur in areas with the highest pore pressures. Most recorded seismicity occurred close to locations where two principal stresses are close in magnitudes because in these cases fault reactivation can occur on multiple planes. Our findings help explain the range of observed source mechanisms of induced earthquakes in both areas.
Session: Mechanistic Insights into Fluid-induced Earthquakes from the Laboratory to the Field - I
Type: Oral
Date: 4/15/2025
Presentation Time: 02:30 PM (local time)
Presenting Author: Hongxue
Student Presenter: No
Invited Presentation:
Poster Number:
Authors
Hongxue Han Presenting Author Corresponding Author hongxue2@ualberta.ca University of Alberta |
Mirko van der baan mirko.vanderbaan@ualberta.ca University of Alberta |
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Importance of In-situ Stress Estimation in the Understanding of Induced Seismicity
Category
Mechanistic Insights into Fluid-induced Earthquakes from the Laboratory to the Field