Note: This video was created by students for a university project and does not necessarily represent the views of REDEVELOP and its collaborators.
Development of low-permeability hydrocarbon resources has increased during the past decade. In some areas, injection-induced seismicity has become a growing concern in the application of hydraulic fracturing of low-permeability reservoirs.
We examine the current state of knowledge in evaluating the seismic hazard of a geological formation or region; focus is given to the Duvernay Formation in Alberta, Canada. In literature, we find that factors such as pre-existing faults and permeable pathways for pressure diffusion and stress transfer, proximity to crystalline basement and reefs, as well as high rates of natural seismicity and pore fluid overpressures are potential indicators of seismic susceptibility.
We utilize 2D geomechanical modeling to gain insight into the impact of fault orientation relative to the minimum (θmin) and maximum (θmax) stresses, along with fault reactivation through hydraulic fracturing (HF). We find that during HF treatments, fracture growth is hindered for the critically angled fault (30°N from θmax) relative to the stable fault orientation (90°N from θmax). Moreover, a stable fault acts as a hydraulic conduit for injected fluids, whereas a critically angled fault acts as a fluid sink. Greater displacement magnitudes occur for critically angled faulaats, thus, greater fault slip occurs.
We examine two mitigation practices of skipping stages and HF at half the injection spacing. Skipping stages reduces the total injected volumes, whereas decreasing the injection spacing reduces the length of fracture growth. We find that for the critically angled fault effectiveness of mitigation methods is greatly reduced.
Finally, we summarize current policies and outline possible policy measures that could help minimize the risk of induced seismicity. Moving forward, we suggest that regulators establish minimum pre-operation induced seismicity risk assessment criteria to form a baseline of assessment. Additionally, we recommend that regulators explore expanding induced seismicity regulations to areas near population centers and critical infrastructure to lower the risk of high impact events.
