Abstract:
The response of critically stressed dormant faults to fluid perturbation, by oil and gas
production activities, has been a major public concern because of its link to induced
seismicity (IS). In this paper, we study the hydrogeological factors that affect a nearby
fault response, during and after hydraulic fracturing (HF) operations, evaluated by the
change in Coulomb Failure Stress (CFS) through coupling solid deformation and fluid
flow. We take the Duvernay formation in Alberta, Western Canada as a base study case
for our analysis. Our results show that the injection rate and the fault’s distance to HF
operations play an important role in increasing the CFS and hence the probability of
fault reactivation. When the fault is far from the operations, its damage zones allow
lateral diffusion and prevent pore pressure build up in its upper part, which stabilizes it.
The lower part, however, will be under a lower normal stress and its failure may be
triggered by an increase in shear stress. This is not the case of the close faults where the
damage zones act as conduits for pressure diffusion and the possible triggering failure
mechanism will be the increase in pore pressure. Moreover, we show that the width of
the HF zone does not affect the activation mechanisms or the stability of the fault unless
it is hydraulically connected to its damage zone. Therefore, serious attention should be
given to the fault position, its architecture, and the volume of fluid injected to help
reduce the potential for induced seismicity from HF.
