Method and application of extending seismic vibrator bandwidth toward low frequency

Abstract

Low-frequency content of the output signal is very helpful in seismic exploration. In this study, method and application are conducted to extend the bandwidth of a seismic vibrator toward low frequency. Factors limiting vibrator’s low-frequency extension are studied, and stroke load capacity and pump-displacement load capacity are proposed and act as vibrator’s low-frequency performance evaluation indexes. Low-frequency performances of five seismic vibrators available in the market are analyzed. Then, multi-objective optimization is used to extend low frequency, and a newly designed seismic vibrator EV56 is developed based on this method. Results show that stroke load capacities of these vibrators are not much different, and all are beyond 5 Hz at 100% level. Moreover, none of the vibrators reaches a frequency lower than 8 Hz at a full pump-displacement load capacity. Through the optimization, the ground force increases by 8.55%, and the standard deviation of the ground force is reduced by 32.99%. Compared to other five vibrators, the EV56 vibrator generates more than twice the output force at 70% drive force level of 3 Hz and improves more than one full-load capacity octave. Field test shows that compared to a conventional seismic vibrator, the EV56 vibrator is more helpful to discover and reflect the underground structure.