Evidence of a Horizontal Hydraulic Fracture at Depth Due to Stress Rotations Across a Thrust Fault

摘要

Microseismic imaging of a hydraulic fracture stimulation showed significant fracture reorientation across a thrust fault. Fracture orientations were identified through a combination of alignment of event locations, polarization of the seismic waves and injection details. Stimulation below the fault indicated a near horizontal fracture geometry. Above the fault, a near vertical fracture geometry was observed. A change in fault orientation was supported by differences in the microseismic signal characteristics and the treatment injection data. This difference in fracture geometry was attributed to rotations in the direction of minimum principle stress, which is consistent with observed differences in the injection pressures. The fracture reorientation suggests a significant difference in the stimulated permeable pathways for sands above, compared to below the fault.