The perforation of the borehole casing and cement is the final stage in a well-completion procedure to establish a connection with the reservoir for hydraulic fracturing purposes. Although they have been neglected to date, the generated seismic expressions of these explosions in the stimulation well display a very characteristic signature. A Fayetteville Shale stimulation concurrently monitored using a downhole and surface seismic array was analyzed to develop a better understanding of the perforation arrivals and to identify the influence of reservoir properties, using a combination of data processing and forward modeling. The perforation shots typically give rise to multiple P- and S-wave arrivals. Comparison of observed and modeled arrivals reveals the importance of incorporating two crucial geologic parameters: a 1.6° subsurface dip and a strong anisotropy in the Fayetteville Shale, typically between 40% and 50%. Of equal importance are shot-generated tube waves traveling through the treatment well, which convert into body waves after interaction with the perforation plugs that seal off the borehole and give rise to secondary high-amplitude, low-frequency seismic events. Hence, the waveforms related to source, propagation, and treatment operation effects become strongly interlinked and need careful separation and interpretation to allow for the correct identification of primary and secondary perforation arrivals and for the reliable derivation of velocity models for surface microseismic monitoring.

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