A modeling exercise was performed investigating hydraulic fracture interaction with pre-existing fractures, based on a benchmark modeling exercise lead by ARMA (American Rock Mechanics Association). The modeled scenarios are based on interaction with two existing faults under different geomechanical conditions. Simulations were performed with a coupled hydraulic-geomechanical-seismological, discrete-element model. The results show that the hydraulic fracture aperture is restricted at the intersection with the faults, to a degree depending on the slip induced on the fault. The aperture restriction was found to also limit the extent of the proppant distribution. In scenarios with relatively more slip, the fault activation was found to occur above and below the injection layer and resulted in some hydraulic fracture height growth relative to the depth contained fracture occurring without fault activation. As expected, the fault slip and intensity of associated microseismicity is related to the geomechanical prepotency for slip. Fractures oriented at 30° to the hydraulic fracture and maximum principal stress direction, resulted in the largest microseismic magnitude and significant hydraulic fracture restriction at the fault intersection. With increasing angle, the magnitude decreased and the hydraulic fracture had a larger half-length. Increasing the differential stress resulted in increased magnitudes and decreased fracture half-length, as did the case of a weaker fault. The study demonstrates through a numerical-physics simulation how a hydraulic fracture system behalves as it interacts with a pre-existing fracture under various geomechanical conditions.

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