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States of in-situ stress in the Duvernay East Shale Basin and Willesden Green of Alberta, Canada: variable in-situ stress states effect fault stability
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  • Luyi W Shen,
  • Douglas Ray Schmitt,
  • Ruijia Wang,
  • Tyler E. Hauck
Luyi W Shen
Department of Physics, University of Alberta, Department of Physics, University of Alberta

Corresponding Author:luyi@ualberta.ca

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Douglas Ray Schmitt
Purdue University, Purdue University
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Ruijia Wang
University of New Mexico, University of New Mexico
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Tyler E. Hauck
Alberta Geological Survey, Alberta Geological Survey
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Induced earthquakes in some areas of the Duvernay Formations (i.e., of areas near the city of Red Deer and Fox Creek) due to Hydraulic fracturing (HF) operations nearby and seismic quiescence of the other areas (of a similar level of HF activities) warrants geomechanical investigations. Here, we start by quantitatively constraining the magnitudes and orientations of minimum (Sh), maximum (SH) horizontal stresses, vertical stress (SV) utilizing both borehole measurements and earthquake’s focal-mechanism (FM) solutions for a study area where a newly emerging swarm of HF induced earthquakes are reported (near the city of Red Deer, Canada). The apparent pore pressures (PP) are also assessed through several transient well testing results targeting the unconventional reservoirs. This knowledge allows the fault stabilities for the high-profile HF induced Red Deer (ML 4.2/MW 3.8) earthquake to be assessed. The N-S (or E-W) aligned fault, revealed by the FM solution, appears to be stable at a hydrostatic fluid pressure but unstable when fluid pressure is increased to the level of ambient unconventional reservoir pore pressures. The slip-tendency of the faults in the region studied is assessed by calculating the required fluid pressures to activate hypothetical faults; we find that the HF-induced clusters geographically overlap with the zones of higher susceptibility. High ambient pore pressure does not correlate with high susceptibility, and large deviatoric stress is needed to cause HF-induced earthquakes.
Jun 2021Published in Journal of Geophysical Research: Solid Earth volume 126 issue 6. 10.1029/2020JB021221