Fault Activation During Hydraulic Fracturing

Microseismic imaging was used to image hydraulic fracturing during a gas well stimulation. Some time after the end of the injection, there was an increase in the seismic deformation rate. Investigation of the frequency-magnitude characteristics during the pumping were consistent with other hydraulic fracture results, although the activity recorded after the end of pumping was more consistent with observations of natural seismic deformation along faults. The ratio of p- to s-wave amplitudes also varied for events recorded during the pumping compared to those occurring after the end of pumping, suggesting a different failure mechanism. In this example, it appears that the hydraulic fracture induced movement on a nearby fault. Geomechanical modeling was also performed to examine induced stresses associated with the stimulation, and investigate possible fault deformation.