“Zero‐field” air‐gun measurements for improved efficiency in marine seismic acquisition

Estimating source signatures from source-over-spread marine seismic data

Geophysics ◽

10.1190/geo2017-0789.1 ◽

2018 ◽

Vol 83 (6) ◽

pp. P39-P48

Author(s):

Kristian Svarva Helgebostad ◽

Martin Landrø ◽

Vetle Vinje ◽

Carl-Inge Nilsen

Keyword(s):

Field Data ◽

Forward Modeling ◽

Inversion Algorithm ◽

Surface Reflection ◽

Air Gun ◽

Recent Developments ◽

Seismic Acquisition ◽

The Difference ◽

Marine Seismic ◽

Bubble Oscillations

Recent developments in marine seismic acquisition include deploying a source vessel above a towed-streamer spread. We have developed an inversion algorithm to estimate source signatures for such acquisition configurations, by minimizing the difference between the recorded and a modeled direct wave. The forward modeling is based upon a physical modeling of the air bubble created by each air gun in the source array, and a damped Gauss-Newton approach is used for the optimization. Typical inversion parameters are empirical damping factors for the bubble oscillations and firing time delays for each air gun. Variations in streamer depth are taken into account, and a constant sea-surface reflection coefficient is also estimated as a by-product of the inversion. For data acquired in shallow waters, we have developed an extension of the forward modeling to include reflections from the water bottom to stabilize the inversion. The algorithm is tested on synthetic- and field-data examples, and the estimated source signature for the field-data example is used in a designature processing flow.

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Marine seismic acquisition: efficiency and environment, new technologies applied in Australia

The APPEA Journal ◽

10.1071/aj16072 ◽

2017 ◽

Vol 57 (2) ◽

pp. 704 ◽

Cited By ~ 1

Author(s):

Martin Bayly ◽

Michelle Tham ◽

Peter Watterson ◽

Binghui Li ◽

Kevin Moran

Keyword(s):

Environmental Impact ◽

New Technologies ◽

New Technology ◽

Seismic Exploration ◽

Exposure Level ◽

North West ◽

Optimal Output ◽

Air Gun ◽

Seismic Acquisition ◽

Marine Seismic

The design of successful marine seismic surveys is driven by many factors, two prime issues being efficiency and environmental impact. Efficiency is primarily driven by reduction of non-productive time and creating the largest sub-surface illumination area possible in the shortest time. In addition, public opinion and governmental regulations are requiring the industry to minimise their environmental impact. One aspect is reducing the overall sound exposure level (SEL) of the source into the marine environment. Using recent Australian examples, we will discuss and demonstrate the use of two new technology groups that address these concerns. The first is the use of a new type of seismic air-gun with optimal output over the range of frequencies commonly used in seismic exploration, while limiting potential environmental effects from unnecessary high-frequency emissions. The second is continuous data acquisition along the entire boat traverse, including the turns, thereby reducing non-productive vessel time. Both are described with examples from a recent survey acquired offshore north-west Australia.

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

Geophysics ◽

10.1190/geo2018-0687.1 ◽

2019 ◽

Vol 84 (5) ◽

pp. P61-P71 ◽

Cited By ~ 1

Author(s):

Daniel Wehner ◽

Martin Landrø ◽

Lasse Amundsen

Keyword(s):

Large Volume ◽

Field Experiments ◽

Field Measurements ◽

Seismic Source ◽

Sea Surface ◽

Frequency Signal ◽

Low Frequencies ◽

Air Gun ◽

Seismic Acquisition ◽

Marine Seismic

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.

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Shot repetition: An alternative seismic blending code in marine acquisition

Geophysics ◽

10.1190/geo2017-0649.1 ◽

2018 ◽

Vol 83 (6) ◽

pp. P29-P37 ◽

Cited By ~ 4

Author(s):

Sixue Wu ◽

Gerrit Blacquière ◽

Gert-Jan Adriaan van Groenestijn

Keyword(s):

Source Code ◽

Seismic Exploration ◽

Data Quality Control ◽

Time Data ◽

Alternative Source ◽

Seismic Surveys ◽

Air Gun ◽

Seismic Acquisition ◽

Marine Seismic ◽

Source Encoding

In blended seismic acquisition, or simultaneous source seismic acquisition, source encoding is essential at the acquisition stage to allow for separation of the blended sources at the processing stage. In land seismic surveys, the vibroseis sources may be encoded with near-orthogonal sweeps for blending. In marine seismic surveys, the sweep type of source encoding is difficult because the main source type in marine seismic exploration is the air-gun array, which has an impulsive character. Another issue in marine streamer seismic data acquisition is that the spatial source sampling is generally coarse. This hinders the deblending performance of algorithms based on the random time delay blending code that inherently requires a dense source sampling because they exploit the signal coherency in the common-receiver domain. We have developed an alternative source code called shot repetition that exploits the impulsive character of the marine seismic source in blending. This source code consists of repeated spikes of ones and can be realized physically by activating a broadband impulsive source more than once at (nearly) the same location. Optimization of the shot-repetition type of blending code was done to improve the deblending performance. As a result of using shot repetition, the deblending process can be carried out in individual shot gathers. Therefore, our method has no need for a regular dense source sampling: It can cope with irregular sparse source sampling; it can help with real-time data quality control. In addition, the use of shot repetition is beneficial for reducing the background noise in the deblended data. We determine the feasibility of our method on numerical examples.

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High-resolution 3D marine seismic acquisition and imaging in shallow waters: Application to shallow fault detection, Beppu-Bay, Japan

10.1190/segj2021-053.1 ◽

2021 ◽

Author(s):

Yosuke Teranishi ◽

Fumitoshi Murakami ◽

Shinji Kawasaki ◽

Motonori Higashinaka ◽

Kei Konno ◽

...

Keyword(s):

High Resolution ◽

Fault Detection ◽

Shallow Waters ◽

Seismic Acquisition ◽

Marine Seismic

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Variable separations for sources and streamers in marine seismic acquisition: a novel towing concept to improve survey efficiency

First Break ◽

10.3997/1365-2397.fb2021083 ◽

2021 ◽

Vol 39 (11) ◽

pp. 53-59

Author(s):

Karim Souissi ◽

Geir W. Simensen ◽

Mark Rhodes

Keyword(s):

Seismic Acquisition ◽

Marine Seismic

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Blended acquisition with dispersed source arrays

Geophysics ◽

10.1190/geo2011-0480.1 ◽

2012 ◽

Vol 77 (4) ◽

pp. A19-A23 ◽

Cited By ~ 46

Author(s):

A. J. Berkhout

Keyword(s):

High Frequency ◽

Spatial Sampling ◽

Acquisition Process ◽

Air Gun ◽

Seismic Acquisition ◽

Sampling Intervals ◽

Source Array

Blended source arrays are historically configured with equal source units, such as broadband vibrators (land) and broadband air-gun arrays (marine). I refer to this concept as homogeneous blending. I have proposed to extend the blending concept to inhomogeneous blending, meaning that a blended source array consists of different source units. More specifically, I proposed to replace in blended acquisition the traditional broadband sources by narrowband versions — imagine coded single air guns with different volumes or coded single narrowband vibrators with different central frequencies — together representing a dispersed source array (DSA). Similar to what we see in today’s audio systems, the DSA concept allows the design of dedicated narrowband source elements that do not suffer from the low versus high frequency compromise. In addition, the DSA concept opens the possibility to use source depths and spatial sampling intervals that are optimum for the low-, mid-, and high-frequency sources (multiscale shooting grids). DSAs are considered to be an important step in robotizing the seismic acquisition process.

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On the reconstruction of the shape of a seismic streamer

Geophysics ◽

10.1190/1.3267855 ◽

2010 ◽

Vol 75 (1) ◽

pp. H1-H6

Author(s):

Bruno Goutorbe ◽

Violaine Combier

Keyword(s):

A Priori ◽

Synthetic Data ◽

Seismic Survey ◽

Random Errors ◽

Generalized Inversion ◽

Reconstruction Methods ◽

Seismic Acquisition ◽

Marine Seismic ◽

Gps Devices ◽

Vessel Reconstruction

In the frame of 3D seismic acquisition, reconstructing the shape of the streamer(s) for each shot is an essential step prior to data processing. Depending on the survey, several kinds of constraints help achieve this purpose: local azimuths given by compasses, absolute positions recorded by global positioning system (GPS) devices, and distances calculated between pairs of acoustic ranging devices. Most reconstruction methods are restricted to work on a particular type of constraint and do not estimate the final uncertainties. The generalized inversion formalism using the least-squares criterion can provide a robust framework to solve such a problem — handling several kinds of constraints together, not requiring an a priori parameterization of the streamer shape, naturally extending to any configuration of streamer(s), and giving rigorous uncertainties. We explicitly derive the equations governing the algorithm corresponding to a marine seismic survey using a single streamer with compasses distributed all along it and GPS devices located on the tail buoy and on the vessel. Reconstruction tests conducted on several synthetic examples show that the algorithm performs well, with a mean error of a few meters in realistic cases. The accuracy logically degrades if higher random errors are added to the synthetic data or if deformations of the streamer occur at a short length scale.

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