Quantifying the Effects of Faults on Induced Seismicity Potential
Description of the material:
This paper describes the application of a new workflow which combines several outputs of a validated geomechanical model to predict the areas of a given faulted region which are most susceptible to an induced seismic event.
Critical to the workflow, a continuum mechanics model is imparted with weaknesses (faults) and subjected to far-field stresses to reproduce local perturbations of the stress field due to the presence of said fault system. Outputs from this model are combined to map areas within the study regions most susceptible to an induced seismic event. Results are then validated with actual seismic events. This workflow highlights the mechanical effects of large-scale fault systems, and quantifies the possibility to develop areas of high potential for induced seismicity, even away from faults.
As larger and larger seismic events are triggered more and more frequently, it is the responsibility of operators to respond proactively, or face increased societal pushback to unconventional production.
A general workflow is introduced to evaluate a region with large-scale and complicated fault networks for its mechanical potential to express a seismic event as a result of stress field disturbances due to water injection.
Results, Observations, and Conclusions:
This new workflow is validated with a Woodford case study and then applied to a Montney study area. The potential for induced seismicity is predicted using a combination of outputs of the geomechanical model. In the case of the Woodford, with abundant seismic event data (larger than 3 magnitude), the spatial occurrence of earthquakes overlaid on the geomechanical output demonstrates conspicuous features. Blue areas (areas of low stress and shear) are devoid of seismic events, while red areas (high stress and shear) are consistently populated with seismic events. In some cases, these areas of elevated stress and shear occur even away from largescale faults, and sometimes form “corridors” through the large fault blocks. Understanding these trends will help mitigate induced seismic events, and bolster public confidence in unconventional resource production.
Significance of subject matter:
The ability to assess the mechanical stability of regions on and proximal to large-scale fault systems is critical to mitigating the risk of inducing a seismic event. Performing this assessment in a predictive capacity is even more powerful. When the social license to operate runs out, as induced seismic events rock rural and possibly even urban communities, we all lose.
AAPG Datapages/Search and Discovery Article #90250 © 2016 Southwest Section AAPG Annual Convention, Abilene, Texas, April 9-12, 2016