Geomechanical Analysis of Fault Reactivation Due to Hydraulic Fracturing

Felt induced seismicity due to hydraulic fracturing has been observed at many fields in the past few years. Though spatial and temporal correlations establish the link between hydraulic fracturing activities and felt induced seismicity, the underlying stress/pressure change mechanisms that cause fault reactivation are unclear. This study reports a systematic analysis of several felt induced seismicity field observations using geomechanical models to understand the mechanisms that cause the fault reactivation. The field observations indicate that felt induced seismicity occurs at 100s of meters to few kms away from the wellbore and there is a time delay of hours to days. The numerical modeling results of hydraulic fracturing in a low permeability homogeneous medium show that stress and pressure changes attenuate rapidly with distance, unable to explain reasons for the felt induced seismicity at few kms away from the wellbore. Also wells in close proximity, completed similarly produce vastly different seismicity, indicating that local heterogeneity is important. An alternative mechanism, such as a direct hydraulic connection between a hydraulic fracture and fault, found to be consistent with the field observations. The insights gained from the numerical modeling of fracture fault interaction models can be used to develop felt induced seismicity mitigation plans.