Detection of Perforation Shots in Surface Monitoring: The Attenuation Effect Available to Purchase

Detection of the seismic signal from perforation or string shots is crucial for calibration of velocity model for surface or down-hole monitoring. While in borehole monitoring perforations have higher signal to noise ratio of the P-waves than microseismic events, in surface monitoring it is often opposite. We investigated amplitude spectra of microseismic events and perforations in downhole monitoring and found that amplitude ratio in the band of 20-30 Hz relative to band 100-200 Hz is stronger for the microseismic events. Thus we suggest that detectability of the perforations in surface monitoring is limited by attenuation of the higher frequency signal which increases exponentially with frequency. This suggests that longer duration of calibration shots can be improve detectability of string shots at surface monitoring.