A Technique for Suppressing Bubble Oscillations from an Air Gun during Shallow-Water Marine Seismic Surveying

2020 ◽  
Vol 75 (3) ◽  
pp. 305-308
Author(s):  
M. V. Aleshkin
Keyword(s):  
Shallow Water ◽  
Air Gun ◽  
Seismic Surveying ◽  
Marine Seismic ◽  
Bubble Oscillations

scholarly journals Streamer depth versus vessel and seismic interference noise

Geophysics ◽  
2017 ◽  
Vol 82 (4) ◽  
pp. P41-P51
Author(s):  
Toan Dao ◽  
Martin Landrø
Keyword(s):  
Noise Level ◽  
Cutoff Frequency ◽  
Normal Modes ◽  
Low Frequency ◽  
Data Set ◽  
The North ◽  
Interference Noise ◽  
Air Gun ◽  
Seismic Surveying ◽  
Marine Seismic

For marine seismic surveying, it is commonly assumed that the noise level decreases with depth. In addition, recent advances in broadband seismic have shown that a greater receiver depth is beneficial in preserving low-frequency data. However, in a heavily trafficked ocean, noise from other ships, including seismic interference, is a counteractive process in which the noise actually varies with depth. Normal modes can be used to explain and predict the ship noise and seismic interference noise level. We find that weather noise is dominant below the first mode’s cutoff frequency (approximately 6 Hz), ship noise is dominant from that frequency to the upper end of the useful seismic frequency band (80 Hz). We have used a data set in which the streamer was towed at 8, 45, and 60 m depths in three passes over the same area in the North Sea. The water depth is 135 m on average. We observe that the noise level at 45 and 60 m depth is approximately 1.6 times stronger than that at 8 m. We find that the air-gun energy is up to 46 dB stronger than the noise from the seismic vessel. However, the total noise from all the ships within several hundred kilometers radius can reduce the data quality.

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

Geophysics ◽  
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.

Some notes on air-gun development as a marine seismic source

2009 ◽  
Vol 28 (11) ◽  
pp. 1334-1335 ◽  
Author(s):  
Ben F. Giles
Keyword(s):  
Seismic Source ◽  
Air Gun ◽  
Marine Seismic

Design of Near-orthogonal Air-gun Sequences for Marine Seismic Source Encoding

2016 ◽  
Author(s):  
M.B. Mueller ◽  
D.F. Halliday ◽  
D.J. van Manen ◽  
J.O.A. Robertsson
Keyword(s):  
Seismic Source ◽  
Air Gun ◽  
Marine Seismic ◽  
Source Encoding

High-frequency signals from air-gun arrays

Geophysics ◽  
2011 ◽  
Vol 76 (4) ◽  
pp. Q19-Q27 ◽  
Author(s):  
M. Landrø ◽  
L. Amundsen ◽  
D. Barker
Keyword(s):  
High Frequency ◽  
Experimental Testing ◽  
Seismic Sources ◽  
Frequency Noise ◽  
Suggested Model ◽  
Frequency Effects ◽  
High Frequency Noise ◽  
Air Gun ◽  
Marine Seismic ◽  
High Frequency Effects

We suggest two different mechanisms for generation of high-frequency signals from seismic sources: one type that we interpret as being caused by high-frequency effects close to and within each individual air gun and another type caused by an effect that we refer to as ghost cavitation. The former one is found to have a steep decreasing amplitude trend with frequency, while the latter has a close to 1/f attenuation for frequencies above 1 kHz. A thorough understanding of the effects is of significant importance to quantify and estimate any environmental impact of marine seismic air-gun arrays. The proposed ghost-cavitation mechanism needs further experimental testing. However, given that the suggested model is proven, we think it is possible to attenuate the high-frequency noise generated by compact air-gun arrays by increasing the areal extent of the gun array.

Single water gun far‐field pressure signatures estimated from near‐field measurements

Geophysics ◽  
1985 ◽  
Vol 50 (2) ◽  
pp. 257-261 ◽  
Author(s):  
M. H. Safar
Keyword(s):  
High Resolution ◽  
Data Acquisition ◽  
Seismic Data ◽  
Near Field ◽  
Field Measurements ◽  
Reference Source ◽  
Far Field ◽  
Air Gun ◽  
Seismic Data Acquisition ◽  
Marine Seismic

An important recent development in marine seismic data acquisition is the introduction of the Gemini technique (Newman, 1983, Haskey et al., 1983). The technique involves the use of a single Sodera water gun as a reference source together with the conventional air gun or water gun array which is fired a second or two after firing the reference source. The near‐field pressure signature radiated by the reference source is monitored continuously. The main advantage of the Gemini technique is that a shallow high;resolution section is recorded simultaneously with that obtained from the main array.

Marine vibrators and the Doppler effect

Geophysics ◽  
1988 ◽  
Vol 53 (11) ◽  
pp. 1388-1398 ◽  
Author(s):  
William H. Dragoset
Keyword(s):  
Gulf Of Mexico ◽  
Doppler Effect ◽  
Synthetic Data ◽  
Simple Relationship ◽  
Phase Dispersion ◽  
Air Gun ◽  
Before And After ◽  
Doppler Factor ◽  
The Doppler Effect ◽  
Marine Seismic

Marine seismic data acquired with a moving vibrator suffer phase dispersion caused by Doppler shifting of the source sweep function. The dispersion for a particular reflection event depends upon frequency, the type of sweep function, and the Doppler factor associated with that event. Synthetic vibrator data show that, at typical ship speeds, the Doppler factors for steeply dipping events are big enough to cause phase dispersion as large as several hundred degrees. If unaccounted for, such dispersive effects could make a moving marine vibrator unacceptable for imaging steep dips. In a constant‐offset section, the Doppler factor for a reflection event is the product of ship speed and the event’s time dip. That key, simple relationship allows a two‐dimensional f-k filter to remove the phase dispersion caused by the Doppler effect. Comparisons of both synthetic data and Gulf of Mexico field data, before and after application of the phase‐correcting filter, show that the filter improves steep‐dip imaging in marine vibrator data. For the Gulf of Mexico line, steep dips are imaged just as well in the phase‐corrected vibrator data as in air‐gun data.

Acoustic Assessment of Populations of Common Dolphin Delphinus Delphis In Conjunction With Seismic Surveying

1996 ◽  
Vol 76 (3) ◽  
pp. 811-820 ◽  
Author(s):  
John C. Goold
Keyword(s):  
Seismic Survey ◽  
Avoidance Reaction ◽  
Common Dolphin ◽  
Survey Area ◽  
Delphinus Delphis ◽  
Air Gun ◽  
Before And After ◽  
Seismic Surveying ◽  
Acoustic Contact ◽  
Common Dolphins

Common dolphin, Delphinus delphis (bairdi), were monitored acoustically across a survey area of 2747 km2 during a three month period before, during and after an oil industry two dimensional (2D) seismic reflection survey. Over 900 h of audio survey data were collected and analysed, along with GPS positional data, to reveal trends in presence and distribution of animals. The presence of dolphins was determined from vocalization events on the survey recordings. Dolphin presence was assessed by a system of percentage acoustic contact. This was highest before and after the seismic survey, with common dolphins showing a clear south-westerly skew within the survey area and a probable south-westerly migration of animals between September and December. Acoustic contact with dolphins during the seismic survey also showed a south-westerly skew within the survey area, although percentages were lower. Monitoring during the period of seismic activity was restricted to the immediate vicinity (1–2 km) of the seismic vessel, so percentage contact most likely reflects the response of dolphins to such immediate activity. The overall result suggests an avoidance reaction by common dolphins to air gun emissions, although certain observations suggest tolerance to these sounds outside a 1 km radius of the guns.

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