Assessing fault reactivation tendency within and surrounding porous reservoirs during fluid production or injection

This paper investigates fault reactivation tendency within and surrounding reservoirs during fluid injection or production. Induced stress analysis is performed using Eshelby's theory of inclusions for a poroelastic material, and the concept of Coulomb failure stress change is implemented as a criterion for fault reactivation tendency. A methodology is developed to find the range of fault dip angles that tend towards reactivation in either thrust or a normal fault stress regimes. The results demonstrate that, during production from a reservoir in a normal fault stress regime, fault reactivation is likely to occur within the reservoir and adjacent to its flanks. For a thrust-fault stress regime, only faults located in rocks overlying and underlying the reservoir tend towards reactivation. The results for the analogous case of fluid injection are exactly the opposite. Sensitivity analyses show that the locations of the boundaries defining these regions of reactivation (or stabilization) tendency are not highly sensitive to the fault friction coefficient. The use of the proposed methodology is illustrated for a synthetic case study.