Composite far offset impulsive source activations for marine seismic surveying and processing

Patent metadata

Field	Value
Publication number	US-11815641-B2
Application number	US-202117523284-A
Country	US
Kind code	B2
Filing date	Nov 10, 2021
Priority date	Dec 4, 2020
Publication date	Nov 14, 2023
Grant date	Nov 14, 2023

Abstract

Techniques are described for utilizing far offset impulsive source activations in various contexts, including when performing marine seismic surveys, when manufacturing a geophysical data product in conjunction with such surveys, or when generating an image of geological features of a subsurface. According to some embodiments, near offset impulsive source activations are caused in a body of water at each of a plurality of near offset shot points, and composite far offset impulsive source activations are caused in the body of water at each of a plurality of far offset shot points. Each of the composite far offset impulsive source activations comprises a succession of component impulsive source activations occurring over a far offset shot length. The far offset shot length is short enough to satisfy a stationary source assumption for frequencies at or below a maximum frequency of interest for the far offset shot points.

First claim

What is claimed is:

1. A method of performing a marine seismic survey in a body of water over a subsurface, comprising:
causing near offset impulsive source activations in the body of water at each of a plurality of near offset shot points according to a near offset shot point interval;
causing composite far offset impulsive source activations in the body of water at each of a plurality of far offset shot points according to a far offset shot point interval, wherein each of the composite far offset impulsive source activations comprises a succession of component impulsive source activations occurring over a far offset shot length, and wherein the far offset shot length is not greater than one half wavelength for acoustic energy in the body of water at a maximum frequency of interest for the far offset shot points; and
recording signals, or representations thereof, generated by plural sensors or sensor groups responsive to the near offset impulsive source activations and the composite far offset impulsive source activations;
wherein the phrases “near offset” and “far offset” mean that, for any given one of the plural sensors or sensor groups, a distance between the far offset shot points and the given sensor or sensor group is larger than a corresponding distance between the near offset shot points and the given sensor or sensor group.

2. The method of claim 1 , wherein:
the maximum frequency of interest for the far offset shot points corresponds to a maximum frequency of interest for purposes of full waveform inversion.

3. The method of claim 2 , wherein:
the maximum frequency of interest for the far offset shot points is 15 Hz.

4. The method of claim 1 , wherein:
the maximum frequency of interest for the far offset shot points corresponds to a maximum frequency of interest for purposes of amplitude versus offset analysis.

5. The method of claim 4 , wherein:
the maximum frequency of interest for the far offset shot points is 50 Hz.

6. The method of claim 1 , wherein:
a largest near offset corresponding to the near offset impulsive source activations is smaller than a smallest far offset corresponding to the composite far offset impulsive source activations.

7. The method of claim 1 , wherein:
at least one of the component impulsive source activations in at least one of the successions generates insufficient energy to meet a signal energy requirement at a point of interest in the subsurface; and
a combined energy of all of the component impulsive source activations in the at least one succession equals or exceeds the signal energy requirement at the point of interest.

8. The method of claim 1 , wherein:
each of the component impulsive source activations generates energy at or below an environmental energy limit.

9. The method of claim 8 , wherein:
a single component impulsive source activation at or below the environmental energy limit would be insufficient to meet a signal energy requirement at a point of interest in the subsurface; and
a combined energy of all of the component impulsive source activations in a given succession equals or exceeds the signal energy requirement at the point of interest.

10. The method of claim 1 , wherein:
the far offset shot point interval is longer than the near offset shot point interval.

11. The method of claim 1 , wherein:
at least one of the successions of component impulsive source activations comprises a temporally irregular sequence of source activations.

12. The method of claim 11 , wherein:
the temporally irregular sequence comprises a random or a pseudo random sequence.

13. The method of claim 11 , wherein:
temporal gaps between the source activations in the sequence change monotonically from larger to smaller or from smaller to larger.

14. The method of claim 1 , further comprising:
towing one or more near offset impulsive sources with a near offset vessel and towing one or more far offset sources with a far offset vessel;
sailing the far offset vessel at a first speed when the far offset vessel is in between far offset shot points; and
sailing the far offset vessel at a second speed, different than the first speed, when the far offset vessel is causing the composite far offset impulsive source activations.

15. The method of claim 14 :
wherein the second speed is slower than the first speed.

16. The method of claim 1 , further comprising:
towing at least first and second far offset impulsive source subarrays; and
wherein at least a first one of the component impulsive source activations corresponds to an activation of the first subarray, and at least a second one of the component impulsive source activations corresponds to an activation of the second subarray.

17. The method of claim 1 :
wherein the succession of component impulsive source activations in at least one of the composite far offset impulsive source activations creates a far offset source signature; and
further comprising using the far offset source signature to identify, during a full waveform inversion procedure, energy associated with the at least one composite far offset impulsive source activation.

18. The method of claim 1 :
wherein the succession of component impulsive source activations in at least one of the composite far offset impulsive source activations creates a far offset source signature; and
further comprising using the far offset source signature to distinguish far offset shot energy from near offset shot energy.

19. A tangible non-volatile computer readable medium having instructions or data stored therein that, when executed or used by navigation and control equipment onboard one or more marine seismic survey vessels, cause the one or more vessels to perform a method comprising:
causing near offset impulsive source activations in the body of water at each of a plurality of near offset shot points according to a near offset shot point interval;
causing composite far offset impulsive source activations in the body of water at each of a plurality of far offset shot points according to a far offset shot point interval, wherein each of the composite far offset impulsive source activations comprises a succession of component impulsive source activations occurring over a far offset shot length, and wherein the far offset shot length is not greater than one half wavelength for acoustic energy in the body of water at a maximum frequency of interest for the far offset shot points; and
recording signals, or representations thereof, generated by sensors responsive to the near offset impulsive source activations and the composite far offset impulsive source activations;
wherein the phrases “near offset” and “far offset” mean that, for any given one of the plural sensors or sensor groups, a distance between the far offset shot points and the given sensor or sensor group is larger than a corresponding distance between the near offset shot points and the given sensor or sensor group.

20. The method of claim 19 , wherein:
the maximum frequency of interest for the far offset shot points corresponds to a maximum frequency of interest for purposes of full waveform inversion.

21. The medium of claim 19 , wherein:
the far offset shot point interval is longer than the near offset shot point interval.

22. The medium of claim 19 , wherein:
at least one of the successions of component impulsive source activations comprises a temporally irregular sequence of source activations.

23. The medium of

Assignees

• Pgs Geophysical As

Inventors

• Beitz Manuel

Classifications

• G01V1/3861 Primary

  control of source arrays, e.g. for far field control · CPC title

• G01V1/24

  Recording seismic data · CPC title

• G01V1/3843 Primary

  Deployment of seismic devices, e.g. of streamers (equipment for marine deployment in general B63B) · CPC title

• G01V1/3808 Primary

  Seismic data acquisition, e.g. survey design · CPC title

• G01V1/38 Primary

  specially adapted for water-covered areas (G01V1/28 takes precedence) · CPC title