Field testing the AquaVib: an alternate marine seismic source

Pramik, Bill; Bell, MC; Grier, Adam; Lindsay, Allen

doi:10.1190/segam2015-5925758.1

Cited by 11 publications

(4 citation statements)

References 3 publications

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“…Fortunately, different signatures of interfering sources provide an opportunity in deblending by using the different signatures as done in voice recognition (Pramik et al . ; Jennings and Ronen ).…”

Section: Geophysical Considerations and Implicationsmentioning

confidence: 97%

Research Note: Low‐frequency pneumatic seismic sources

Chelminski

Watson

Ronen

2019

Geophysical Prospecting

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Pneumatic seismic sources, commonly known as airguns, have been serving us well for decades, but there is an increasing need for sources with improved low‐frequency signal and reduced environmental impact. In this paper, we present a new pneumatic source that is designed to achieve these goals by operating with lower pressures and larger volumes. The new source will release more air creating larger bubbles with longer bubble periods than airguns. The release of the air will be tuned so that the rise time will be longer and the sound pressure level and its slope will be lower. Certain engineering features will eliminate cavitation. Larger bubbles increase low‐frequency content of the signal, longer rise times decrease mid‐frequency content and the elimination of cavitation reduces high‐frequency content. We have not yet built a full‐scale version of the new source. However, we have manufactured a small‐scale low‐pressure source incorporating most of the engineering features, and tested it in a lake. Here, we present the lake data that, as expected, show a significant reduction in the sound pressure level, increase in rise time, decrease in slope and decrease in high‐frequency content while maintaining the same low‐frequency content when the source prototype is operated at low pressure compared with high pressure. Synthetic data produced by numerical modelling of the full‐scale proposed pneumatic source suggest that the new source will improve the low‐frequency content and can produce geophysically useful signal down to 1 Hz.

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Section: Geophysical Considerations and Implicationsmentioning

confidence: 97%

Research Note: Low‐frequency pneumatic seismic sources

Chelminski

Watson

Ronen

2019

Geophysical Prospecting

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“…Pramik et al . ). However, common to all the methods referred to above is that they are based on considering the wavefields associated with specific source locations or a small area around such locations as individual wavefields.…”

Section: Introductionmentioning

confidence: 97%

“…Marine vibrators have also been proposed in order to spread the emitted signals out in time to reduce the impact on the environment (e.g. Pramik et al 2015). However, common to all the methods referred to above is that they are based on considering the wavefields associated with specific source locations or a small area around such locations as individual wavefields.…”

Section: Introductionmentioning

confidence: 99%

Making the transition from discrete shot records to continuous seismic records and source wavefields, and its potential impact on survey efficiency and environmental footprint

Hegna

Klüver

Lima

et al. 2018

Geophysical Prospecting

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A marine seismic method based on continuous source and receiver wavefields has been developed. The method requires continuous recording of the seismic data. The source that may consist of multiple source elements can emit signals continuously while moving. The ideal source wavefield to be used with this method should be as white as possible both in a temporal and a spatial sense to avoid deep notches in the spectrum enabling a stable multi‐dimensional deconvolution. White noise has such properties. However, equipment that can generate white noise does not exist. In order to generate a continuous source wavefield that is approaching the properties of white noise using existing equipment onboard marine seismic vessels, individual air‐guns can be triggered with short randomized time intervals in a near‐continuous fashion. The main potential benefits with the method are to reduce the environmental impact of marine seismic surveys and to improve acquisition efficiency. The peak sound pressure levels are significantly reduced by triggering one air‐gun at a time compared to conventional marine seismic sources. Sound exposure levels are also reduced in most directions. Since the method is based on continuous recording of seismic data and the air‐guns are triggered based on time and not based on position, there are less vessel speed limitations compared to conventional marine seismic data acquisition. Also, because the source wavefield is spread out in time, the wavefields emitted from source elements in different cross‐line positions can be designed such that the emitted wavefield is spatially white in this direction. This means that source elements in multiple cross‐line positions can be operated simultaneously, potentially improving the cross‐line sampling and/or the acquisition efficiency.

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“…Marine life, with the exception of whales that communicate with low frequency (15 -100 Hz) calls (Goldbogen et al, 2014;Stimpert et al, 2015;Watson et al, 2017b), is thought to be most sensitive to the non-geophysically useful high frequency component of air gun signals (Kastelein et al, 2014;Finneran, 2015). Therefore, there is significant interest in modifying existing seismic air gun designs or operating procedures (Coste et al, 2014;Chelminski et al, 0), or designing new marine seismic sources such as marine vibrators (Pramik et al, 2015), in order to reduce the amplitude of the high frequency components of the signal and minimize the environmental impact of marine seismic surveys. The amplitude of high frequency acoustic waves is related to the slope of the initial acoustic pressure pulse (Coste et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

What controls the initial peak of an air-gun source signature?

2019

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Seismic air guns are broadband sources that generate acoustic waves at many frequencies. The low frequency waves can be used for imaging while the high frequency waves are attenuated and/or scattered before they can reflect from targets of interest in the subsurface. It is desirable to reduce the amplitude of the high frequency acoustic waves as they are thought to be disruptive, and potentially damaging, to marine life and are not useful for geophysical purposes. The high frequency acoustic waves are primarily associated with the initial expansion of the air gun bubble and associated peak in the acoustic pressure time series, which is commonly referred to as the source signature of the air gun. Here, we develop a quasi-one-dimensional model of a seismic air gun coupled to a spherical bubble that accounts for gas dynamics and spatially variable depressurization inside the firing chamber in order to investigate controls on the initial peak of the source signature. The model is validated against data collected during field tests in Lake Seneca, New York. Simulations and field data both show that the initial peak is primarily dependent on the operating pressure. A lower gun pressure results in a smaller peak amplitude and a slower rise time. The slope, the amplitude of the initial peak divided by the rise time, is used as a proxy for environmental impact and can decrease by as much as 50% when the air gun pressure is reduced from 2000 psi to 1000 psi. The low frequencies are controlled by the total discharged mass, which is dependent upon gun volume and pressure. Decreasing the operating pressure while simultaneously increasing the gun volume will reduce the high frequencies while maintaining the desirable low frequency signals.

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Field testing the AquaVib: an alternate marine seismic source

Cited by 11 publications

References 3 publications

Research Note: Low‐frequency pneumatic seismic sources

Research Note: Low‐frequency pneumatic seismic sources

Making the transition from discrete shot records to continuous seismic records and source wavefields, and its potential impact on survey efficiency and environmental footprint

What controls the initial peak of an air-gun source signature?

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