Analysis of the Hydrogeological Conditions Affecting Fault Response to
Nearby Hydraulic Fracturing
Abstract
The response of critically stressed dormant faults to fluid
perturbation, by oil and gas production, has been a major public concern
because of its link to induced seismicity. 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, 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 for 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.