Borehole Vibration Response to Hydraulic Fracture Pressure

Passive-seismic recordings in cased wellbores, including data acquired to monitor hydraulic fracture treatments, can be used to detect resonant vibrations of the casing. The resonant vibrations are linked to the geometry of geophone arrays, which are clamped to the borehole casing with sufficient force to affect the fundamental casing vibration frequency. Using field examples from western Canada, we document temporal variations of vibration frequency that occur over the course of a multistage hydraulic fracture treatment. Finite-element simulations suggest that vibrational frequency is sensitive to local stress conditions. We propose that this effect can be used for in situ monitoring of stress variations.