A marine dipole source for low frequency seismic acquisition

Meier, Mark A.; Duren, Richard E.; Lewallen, Kyle; Otero, J. D.; Heiney, Steve

doi:10.1190/segam2015-5920771.1

Cited by 9 publications

(3 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We also show that for streamer acquisition, when the sensors are at a shallow depth below the water surface, this results in better preservation of the low frequencies in the VAFWI adjoint fields compared to FWI adjoint fields, if receiver ghosts are present in the data. Meier et al (2015) show that vector data make no difference in the handling of the source ghost: instead of vector data at receivers, source de-ghosting requires directional (vector) sources. The main challenge in the creation of the directional sources lies in designing marine dipole source actuators capable of producing large enough energy at low frequencies that could be used in reflection seismic applications.…”

Section: Introductionmentioning

confidence: 97%

Vector acoustic full waveform inversion: taking advantage of de-aliasing and receiver ghosts

Zheglova¹,

Malcolm²

2019

Preprint

View full text Add to dashboard Cite

Data acquisition is changing to incorporate more components of the recorded wavefield. An example of this is so-called vector data in which both the pressure and particle velocity are recorded in marine data. We present a vector acoustic full waveform inversion (VAFWI) method. We demonstrate the connection of the VAFWI adjoint operator with inverse wavefield extrapolation and show that under the assumption of a plane wave propagating towards an infinite flat recording surface at normal incidence, the VAFWI adjoint is equivalent to inverse extrapolation of the normal derivative of the recorded field. Thus, unlike the conventional FWI adjoint, the VAFWI adjoint is an inverse wavefield extrapolation operator. If these assumptions are violated, this equivalence relation is no longer true and becomes an approximation. We argue that this has implications in the handling of receiver ghosts by the two inversion methods: in the VAFWI adjoint, the receiver ghosts interact constructively with the back-propagated reflected field. We show numerically that the de-aliasing property of vector data extends to VAFWI, which results in fewer artefacts in VAFWI images compared to conventional FWI when data are spatially undersampled and aliased. Additional information about the subsurface contained in properly handled receiver ghosts can be utilized to achieve further VAFWI image improvement.

show abstract

Section: Introductionmentioning

confidence: 97%

Vector acoustic full waveform inversion: taking advantage of de-aliasing and receiver ghosts

Zheglova¹,

Malcolm²

2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Dellinger et al (2016) present a vibratortype source, called Wolfspar, that is designed to create specific ultra-low frequencies needed for the computation of velocity models in full waveform inversion (FWI). A marine dipole source is illustrated by Meier et al (2015) which would change the ghost notches and hence would amplify the low frequency amplitudes. Ronen and Chelminski (2018) present a new pneumatic source, called the Tuned Pulse Source (TPS), that can use much larger volumes and lower operating pressures compared to conventional airguns.…”

Section: Introductionmentioning

confidence: 99%

On low frequencies emitted by air guns at very shallow depths — An experimental study

Wehner

Landrø²,

Amundsen

2019

GEOPHYSICS

View full text Add to dashboard Cite

In marine seismic acquisition, the enhancement of frequency amplitudes below 5 Hz is of special interest because it improves imaging of the subsurface. The frequency content of the air gun, the most commonly used marine seismic source, is mainly controlled by its depth and the volume. Although the depth dependency on frequencies greater than 5 Hz has been thoroughly investigated, for frequencies less than 5 Hz it is less understood. However, recent results suggest that sources fired very close to the sea surface might enhance these very low frequencies. Therefore, we conduct dedicated tank experiments to investigate the changes of the source signal for very shallow sources in more detail. A small-volume air gun is fired at different distances from the water-air interface, including depths for which the air bubble bursts directly into the surrounding air. The variations of the oscillating bubble and surface disturbances, which can cause changes of the reflected signal from the sea surface, are explored to determine whether an increased frequency signal below 5 Hz can be achieved from very shallow air guns. The results are compared with field measurements of a large-volume air gun fired close to the sea surface. The results reveal an increased signal for frequencies below 5 Hz of up to 10 and 20 dB for the tank and field experiments, respectively, for the source depth at which the air gun bubble bursts directly into the surrounding air. For large-volume air guns, an increased low-frequency signal might also be achieved for sources that are slightly deeper than this bursting depth. From these observations, new design considerations in the geometry of air-gun arrays in marine seismic acquisition are suggested.

show abstract

“…However, Pramik et al (2015) and Ozasa et al (2015) show promising results for this technique. Furthermore, Meier et al (2015) illustrate a marine dipole source that would especially increase the energy content at the low-frequency end of the spectrum. Recently, an "FWI-friendly" vibrator-type source that focuses on creating ultralow frequencies is presented by Dellinger et al (2016).…”

Section: Introductionmentioning

confidence: 99%

Low-frequency acoustic signal created by rising air-gun bubble

Wehner

Landrø

2017

GEOPHYSICS

View full text Add to dashboard Cite

In the seismic industry, there is increasing interest in generating and recording low frequencies, which leads to better data quality and can be important for full-waveform inversion. The air gun is a seismic source with a signal that consists of the (1) main impulse, (2) oscillating bubble, and (3) rising of this air bubble. However, there has been little investigation of the third characteristic. We have studied a low-frequency signal that could be created by the rising air bubble and find the contribution to the low-frequency content in seismic acquisition. We use a simple theory and modeling of rising spheres in water and compute the acoustic signal created by this effect. We conduct tank and field experiments with a submerged buoy that is released from different depths and record the acoustic signal with hydrophones along the rising path. The experiments simulate the signal from the rising bubble separated from the other two effects (1 and 2). Furthermore, we use data recorded below a single air gun fired at different depths to investigate if we can observe the proposed signal. We find that the rising bubble creates a low-frequency signal. Compared with the main impulse and the oscillating bubble effect of an air-gun signal, the contribution of the rising bubble is weak, on the order of 1/900 depending on the bubble size. By using large air-gun arrays tuned to create one big bubble, the contribution of the signal can be increased. The enhanced signal can be important for deep targets or basin exploration because the low-frequency signal is less attenuated.

show abstract

A marine dipole source for low frequency seismic acquisition

Cited by 9 publications

References 2 publications

Vector acoustic full waveform inversion: taking advantage of de-aliasing and receiver ghosts

Vector acoustic full waveform inversion: taking advantage of de-aliasing and receiver ghosts

On low frequencies emitted by air guns at very shallow depths — An experimental study

Low-frequency acoustic signal created by rising air-gun bubble

Contact Info

Product

Resources

About