Modelling of fault reactivation and fault slip in producing gas fields using a slip-weakening friction law.

Geomechanical numerical simulations were conducted to analyze the stability of faults during gas production. A FLAC3D model of a fault intersecting a producing gas reservoir was developed which incorporates the fully dynamic behavior of the fault and surrounding rock mass, and a fault frictional behavior based on a slip-weakening law. The simplified reservoir and fault geometry of the model are representative for the Dutch gas fields. Simulated fault slip displacements and fault slip lengths were used to calculate moment magnitudes of induced seismic events. In addition, results of the fully dynamic model with slip-weakening frictional behavior were compared to results of a static geomechanical model with slip-weakening. Comparison of model results shows that, for a first-order assessment of induced seismicity, the static models can be used as a simplified and computationally less expensive alternative to the fully dynamic fault rupture models.