Extending low frequency bandwidth using pseudorandom sweeps

Maxwell, Peter; Gibson, J. B.; Egreteau, A.; Lin, Forest; Baeten, G.; Sallas, John J.

doi:10.1190/1.3513020

Cited by 6 publications

(3 citation statements)

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“…In fact, the piston area is limited by the rated output and the bearing pressure of the hydraulic system, which should be treated as a constant. From equations (10) and (11), it can be seen that S r and D vibrator are inversely proportional to the reaction mass weight. In order to avoid double counting, equation (10) acts as the optimization objective function instead of taking both equations (10) and (11).…”

Section: Improvement Of Vibrator For Extending Low Frequencymentioning

confidence: 99%

“…Baeten 10 also proposed a method and system to generate a sweep signal with enhanced low-frequency content by generating a combination of a linear and nonlinear sweep and wherein the nonlinear sweep as a function of time is calculated by a predetermined algorithm. Maxwell et al 11 and Sallas et al 12 employed pseudorandom sweeps to extend the low-frequency bandwidth. Their field tests indicated that well-designed pseudorandom sweeps had the potential to provide a bit more output than maximum displacement sweep with lower start frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Method and application of extending seismic vibrator bandwidth toward low frequency

Wen

Ding³

et al. 2019

Advances in Mechanical Engineering

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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.

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Section: Improvement Of Vibrator For Extending Low Frequencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Method and application of extending seismic vibrator bandwidth toward low frequency

Wen

Ding³

et al. 2019

Advances in Mechanical Engineering

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“…Non‐linear sweeps that spend more time sweeping at low‐frequencies to overcome the inherently reduced amplitudes are one method to overcome these limitations (Bagaini, ). Sallas et al () (see also Maxwell et al., ) introduced the concept that pseudorandom sweeps could also be used to overcome this limitation by shaping the spectrum of the sweep to increase low‐frequency content. As the low frequencies are spread out over the full length of the sweep then we should be able to avoid exceeding the mechanical and hydraulic limitations of the vibrator.…”

Section: Motivations For the Use Of Pseudorandom Sweepsmentioning

confidence: 99%

The use of pseudorandom sweeps for vibroseis surveys

Dean¹

2013

Geophysical Prospecting

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A B S T R A C TPseudorandom vibroseis sweeps have long been suggested as an alternative to standard linear sweeps due to their potential for having superior orthogonality, a lower likelihood for infrastructure damage, and increased low-frequency content. In the past, they were also attractive as they have a better autocorrelation shape, although that is less important today. Their use has been limited but the increasing popularity of simultaneous acquisition techniques has rekindled interest as they offer the ability to reduce interference noise. A wide variety of methods for generating pseudorandom sweeps have been developed over the last 45 years. This paper gives an overview of the motivations for their use before classifying and describing the different sweep types. Finally, the sweeps will be compared in terms of their major attributes including their suitability for simultaneous surveys.

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