Induced hydraulic fractures or reactivated natural fractures? Modeling the response of natural fracture networks to stimulation treatments

Microseismicity induced by hydraulic fracture stimulation of a horizontal well was mapped with a near-surface buried array. Distinct linear trends of events were not parallel to the direction of fast shear wave polarization measured in the reservoir with a crossed-dipole anisotropy tool. Analysis of core from a nearby well revealed numerous calcite-filled fractures that did not induce shear wave polarization, but did significantly impact the failure behavior of the reservoir rock during the stimulation treatment. Hydraulic fracture simulation with DFN modeling and source mechanism analysis supports the interpretation of reactivated existing fractures rather than the formation of hydraulically-induced tensile fractures.