METHOD AND DEVICE FOR WAVE FIELDS SEPARATION IN SEISMIC DATA

• US 20130021873A1
• Filed: 07/18/2011
• Published: 01/24/2013
• Est. Priority Date: 07/18/2011
• Status: Active Grant

• Current Assignee: CGG Services (U.S.), Inc. (CGG)
• Original Assignee: CGGVeritas Services US Inc (Cgg S.A.)
• Inventors: MATTOCKS, Bruce, DE MEERSMAN, Kristof
• Granted Patent: US 9,116,256 B2
• Time in Patent Office: Days
• US Class Current: 367/24
• CPC Class Codes: G01V 1/36 Effecting static or dynamic corrections on records, e.g. correcting spread; Correlating seismic signals; Eliminating effects of unwanted energy
• CPC Class Codes: G01V 1/38 specially adapted for water-covered areas G01V1/28 takes precedence
• CPC Class Codes: G01V 2210/144 with functionally associated receivers, e.g. hydrophone and geophone pairs
• CPC Class Codes: G01V 2210/46 Radon transform
• CPC Class Codes: G01V 2210/56 De-ghosting; Reverberation compensation

Abstract

Apparatus, computer instructions and method for processing seismic data related to a subsurface of a body of water. The method includes receiving input data for a vertical direction and radial direction and/or from a hydrophone, applying a radon transform to the input data, separating primary signals from ghosts signals based on the vertical and radial components, applying an inverse radon transform to determine up-going and down-going wave fields in a time-distance domain, and separating interfering up-going and down-going wave fields that are recorded by the same receivers.

Claims

1. A method for ZX separating up-going and down-going wave fields in seismic data related to a subsurface of a body of water, the method comprising:

receiving as input vertical and radial components, wherein the vertical component is related to a particle velocity measured along a depth direction relative to a surface of the water and the radial component is related to the particle velocity measured along a radial direction parallel to the surface of the water and substantially perpendicular to the depth direction and the radial direction and the vertical direction define a plane in which the wave fields propagate;

applying a radon transform to the vertical and radial components to transform the vertical and radial components from a time-distance domain to a tau-apparent slowness domain, wherein the apparent slowness is the sine of an incidence angle divided by a speed of the wave fields in water;

calculating the up-going wave fields as a first combination of the radon transformed vertical and radial components multiplied by a scaling factor;

calculating the down-going wave fields as a second combination of the radon transformed vertical and radial components multiplied by the scaling factor; and

applying an inverse radon transform to the up-going wave fields and the down-going wave fields to obtain up-going wave fields and down-going wave fields in the time-distance domain.

2. The method of claim 1, wherein the input vertical and radial components are determined from geophone or accelerometer sensors.

3. The method of claim 2, wherein the geophone or accelerometer sensors are provided under water at a given depth.

4. The method of claim 1, wherein the up-going wave fields U are given by:

U=s(V sin(θ

)+R cos(θ

)),

where V is the vertical component, R is the radial component, θ

is an angle between a line substantially perpendicular to the surface of the water and a direction of propagation of the up-going wave fields U, and s is the scaling factor and it is equal to

5. The method of claim 1, wherein the up-going wave fields U are given by:

6. The method of claim 5, wherein μ

and α

are parameters selected to avoid singularities at angles θ

around 0° and

90°

for a predetermined water velocity.

7. The method of claim 1, wherein the down-going wave fields D are given by:

D=s(V sin(θ

)−

R cos(θ

)),

where V is the vertical component, R is the radial component, θ

is an angle between a line substantially perpendicular to the surface of the water and a direction of propagation of the down-going wave fields D, and s is the scaling factor and it is equal to

8. The method of claim 1, wherein the down-going wave fields D are given by:

9. The method of claim 8, wherein μ

and α

are parameters selected to avoid singularities at angles θ

around 0° and

90°

for a given water velocity.

10. The method of claim 1, further comprising:

calculating a time shift

11. A method for PZX separating up-going and down-going wave fields in seismic data related to a subsurface of a body of water, the method comprising:

receiving as input vertical and radial components and a hydrophone component, wherein the vertical component is related to a particle velocity measured along a depth direction relative to the surface of the water, the radial component is related to the particle velocity measured along a direction parallel to the surface of the water and substantially perpendicular to the depth direction, the radial direction and the vertical direction define a plane in which the wave fields propagate, and the hydrophone component is related to a pressure measured in the body of water by the hydrophone at a predetermined depth;

applying a radon transform to the vertical and radial components and to the hydrophone component to transform the vertical and radial components and the hydrophone component from a time-distance domain to a tau-apparent slowness domain, wherein the apparent slowness is the sine of an incidence angle divided by a speed of the wave fields in water;

calculating the up-going wave fields as a first combination of the radon transformed vertical and radial components and the radon transformed hydrophone component, the first combination being multiplied by a scaling factor;

calculating the down-going wave fields as a second combination of the radon transformed vertical and radial components and the radon transformed hydrophone component, the second combination being multiplied by the scaling factor; and

applying an inverse radon transform to the up-going wave fields and the down-going wave fields to obtain up-going wave fields and down-going wave fields in the time-distance domain.

12. The method of claim 11, wherein the input vertical and radial components are determined from geophone or accelerometer sensors.

13. The method of claim 11, wherein the up-going wave fields U are given by

14. The method of claim 11, wherein the down-going wave fields D are given by:

15. The method of claim 11, where the vertical component, the radial component, and the hydrophone component are measured and the up-going and down-going wave fields are calculated.

16. The method of claim 11, further comprising:

calculating a time shift

17. A method for weighted PZX separation of up-going and down-going wave fields in seismic data related to a subsurface of a body of water, the method comprising:

receiving as input vertical and radial components and a hydrophone component, wherein the vertical component is related to a particle velocity measured along a depth direction relative to the surface of the water, the radial component is related to the particle velocity measured along a direction parallel to the surface of the water and substantially perpendicular to the depth direction, the radial direction and the vertical direction define a plane in which the wave fields propagate, and the hydrophone component is related to a pressure measured in the body of water by the hydrophone at a predetermined depth;

applying a radon transform to the vertical and radial components and to the hydrophone component to transform the vertical and radial components and the hydrophone component from a time-distance domain to a tau-apparent slowness domain, wherein the apparent slowness is the sine of an incidence angle divided by a speed of the wave fields in water;

applying a weighting matrix to the radon transformed vertical and radial components and to the radon transformed hydrophone component, the weighting matrix having a parameter β

that has a value between 0 and 1;

calculating the up-going wave fields as a first combination of the radon transformed vertical and radial components and the radon transformed hydrophone component, the first combination being multiplied by a scaling factor;

calculating the down-going wave fields as a second combination of the radon transformed vertical and radial components and the radon transformed hydrophone component, the second combination being multiplied by the scaling factor; and

applying an inverse radon transform to the up-going wave fields and the down-going wave fields to obtain up-going wave fields and down-going wave fields in the time-distance domain.

18. The method of claim 17, wherein the up-going wave fields U are given by

19. The method of claim 17, wherein the down-going wave fields D are given by:

20. The method of claim 17, wherein the weighting matrix is diagonal, and a sum of the squares of the diagonal elements is one.

21. The method of claim 17, wherein if β

=0, the hydrophone weight is zero and the up-going and down-going wave fields take into account only the vertical and radial components and if β

=1, the weighting matrix is one and the method is similar to an unweighted PZX method.

22. The method of claim 17, further comprising:

calculating a time shift