Method and apparatus for pre-stack deghosting of seismic data

Patent metadata

Field	Value
Publication number	US-9322943-B2
Application number	US-201313894036-A
Country	US
Kind code	B2
Filing date	May 14, 2013
Priority date	May 18, 2012
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

A method for deghosting seismic data collected with a seismic system, the seismic data being related to a subsurface of a body of water. The method includes receiving the seismic data recorded by detectors distributed along a variable-depth profile; calculating migrated (d 1 ) and mirror-migrated (d 2 ) gathers based on the seismic data, wherein the migrated and mirror-migrated gathers depend on a feature characterizing a configuration of the seismic system; applying a joint deconvolution model to the migrated and mirror-migrated gathers (d 1 , d 2 ) to calculate a single deghosted gather (dg); and generating a final image of the subsurface based on the single deghosted gather (dg). The feature is not present in a gather after a step of stacking that is performed prior to generating the final image.

First claim

What is claimed is:

1. A method for deghosting seismic data collected with a seismic system, the seismic data being related to a subsurface of a body of water, the method comprising:
receiving the seismic data recorded by detectors distributed along a variable-depth profile;
calculating migrated (d 1 ) and mirror-migrated (d 2 ) gathers based on the seismic data, wherein the migrated and mirror-migrated gathers depend on time and a feature characterizing a configuration of the seismic system;
applying pre-stack a joint deconvolution model to the migrated and mirror-migrated gathers (d 1 , d 2 ) to calculate a single deghosted gather (dg);
stacking the single deghosted gather (dg) to remove the feature; and
generating a final image of the subsurface based on the stacked single deghosted gather (dg).

2. The method of claim 1 , wherein the feature is an offset between a seismic source of the seismic system and the detectors.

3. The method of claim 1 , wherein the feature is an angle of an incident wave to a corresponding detector.

4. The method of claim 1 , wherein the step of applying a deconvolution model comprises:
defining a reflectivity (r) as a sum of a set of polynomials (T i ) multiplied by corresponding coefficients (a i );
parameterizing ghost (g min ) and mirror ghost (g max ) operators;
defining a cost function (C) based on the reflectivity (r) and the ghost (g min ) and mirror ghost (g max ) operators; and
minimizing the cost function (C) to determine the coefficients (a i ) and the ghost (g min ) and mirror ghost (g max ) operators.

5. The method of claim 4 , further comprising:
calculating the reflectivity (r); and
calculating a ghost model (g 1 ) and a mirror ghost model (g 2 ),
wherein the ghost model (g 1 ) is given by a convolution of the ghost operator (g min ) with the reflectivity (r) and then subtracting the reflectivity (r), and
the mirror ghost model (g 2 ) is given by the convolution of the mirror ghost operator (g max ) with the reflectivity (r) and then subtracting the reflectivity (r).

6. The method of claim 5 , wherein the ghost operator (g min ) is a causal, minimum-phase operator and the mirror ghost operator (g max ) is an anti-causal, maximum-phase operator.

7. The method of claim 5 , further comprising:
computing a deghosted gather (dg 1 ) based on the migrated gather (d 1 ) and the ghost model (g 1 ); and
computing a deghosted mirror gather (dg 2 ) based on the mirror migrated gather (d 2 ) and the mirror ghost model (g 2 ).

8. The method of claim 7 , further comprising:
calculating the single deghosted gather (dg) based on the deghosted gather (dg 1 ) and the deghosted mirror gather (dg 2 ).

9. A computing device for deghosting seismic data collected with a seismic system, the seismic data being related to a subsurface of a body of water, the computing device comprising:
an interface for receiving the seismic data recorded by detectors distributed along a variable-depth profile; and
a processor connected to the interface and configured to,
calculate migrated (d 1 ) and mirror-migrated (d 2 ) gathers based on the seismic data, wherein the migrated and mirror-migrated gathers depend on a feature characterizing a configuration of the seismic system,
apply pre-stack a joint deconvolution model to the migrated and mirror-migrated gathers (d 1 , d 2 ) to calculate a single deghosted gather (dg),
stack the single deghosted gather (dg) to remove the feature, and
generate a final image of the subsurface based on the stacked single deghosted gather (dg).

10. The computing device of claim 9 , wherein the feature is an offset between a vessel of the seismic system and the detectors.

11. The computing device of claim 9 , wherein the feature is an angle of an incident wave to a corresponding detector.

12. The computing device of claim 9 , wherein the processor is further configured to:
define a reflectivity (r) as a sum of a set of polynomials (T i ) multiplied by corresponding coefficients (a i );
parameterize ghost (g min ) and mirror ghost (g max ) operators;
define a cost function (C) based on the reflectivity (r) and the ghost (g min ) and mirror ghost (g max ) operators; and
minimize the cost function (C) to determine the coefficients (a i ) and the ghost (g min ) and mirror ghost (g max ) operators.

13. The computing device of claim 12 , wherein the processor is further configured to:
calculate the reflectivity (r); and
calculate a ghost model (g 1 ) and a mirror ghost model (g 2 ),
wherein the ghost model (g 1 ) is given by a convolution of the ghost operator (g min ) with the reflectivity (r) and then subtracting the reflectivity (r), and
the mirror ghost model (g 2 ) is given by the convolution of the mirror ghost operator (g max ) with the reflectivity (r) and then subtracting the reflectivity (r).

14. The computing device of claim 13 , wherein the ghost operator (g min ) is a causal, minimum-phase operator and the mirror ghost operator (g max ) is an anti-causal, maximum-phase operator.

15. The computing device of claim 13 , wherein the processor is further configured to:
compute a deghosted gather (dg 1 ) based on the migrated gather (d 1 ) and the ghost model (g 1 ); and
compute a deghosted mirror gather (dg 2 ) based on the mirror migrated gather (d 2 ) and the mirror ghost model (g 2 ).

16. The computing device of claim 15 , wherein the processor is further configured to:
calculate the single deghosted gather (dg) based on the deghosted gather (dg 1 ) and the deghosted mirror gather (dg 2 ).

17. A non-transitory computer readable medium including computer executable instructions, wherein the instructions, when executed by a computer, implement a method for deghosting seismic data collected with a seismic system, the seismic data being related to a subsurface of a body of water, the method comprising:
receiving the seismic data recorded by detectors distributed along a variable-depth profile;
calculating migrated (d 1 ) and mirror-migrated (d 2 ) gathers based on the seismic data, wherein the migrated and mirror-migrated gathers depend on a feature characterizing a configuration of the seismic system;
applying pre-stack a joint deconvolution model to the migrated and mirror-migrated gathers (d 1 , d 2 ) to calculate a single deghosted gather (dg);
stacking the single deghosted gather (dg) to remove the feature; and
generating a final image of the subsurface based on the single deghosted gather (dg).

18. The medium of claim 17 , wherein the feature is an offset between a seismic source of the seismic system and the detectors or an angle of an incident wave to a corresponding detector.

Assignees

• Cggveritas Services Sa

Inventors

• Soubaras Robert

Classifications

• G01V1/282 Primary

  Application of seismic models, synthetic seismograms · CPC title

• G01V1/366 Primary

  by correlation of seismic signals · CPC title

• G01V2210/56

  De-ghosting; Reverberation compensation · CPC title

• G01V1/38

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

• G01V1/362 Primary

  Effecting static or dynamic corrections; Stacking · CPC title