Estimating and Using Slowness Vector Attributes in Connection with a Multi-Component Seismic Gather

• US 20090003132A1
• Filed: 06/29/2007
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: WesternGeco LLC
• Original Assignee: WesternGeco LLC
• Inventors: Vassallo, Massimiliano, Kostov, Clement, Gonzalez, Alfonso
• Granted Patent: US 8,547,786 B2
• Time in Patent Office: Days
• US Class Current: 367/75
• CPC Class Codes: G01V 1/303 for determining velocity profiles or travel times
• CPC Class Codes: G01V 1/38 specially adapted for water-covered areas G01V1/28 takes precedence
• CPC Class Codes: G01V 1/3808 Seismic data acquisition, e.g. survey design
• CPC Class Codes: G01V 2210/61 Analysis by combining or comparing a seismic data set with other data
• CPC Class Codes: G01V 2210/6222 Velocity; travel time

Abstract

A technique includes determining at least one attribute of a slowness vector associated with a seismic gather based on pressure data and an indication of particle motion that is measured by at least one seismic sensor while in tow.

Claims

1. A method comprising:

determining at least one attribute of a slowness vector associated with a seismic gather based on pressure data and an indication of particle motion measured by at least one seismic sensor while in tow.

2. The method of claim 1, wherein the determining comprises determining a change in a pressure travel time with respect to a receiver offset.

3. The method of claim 1, wherein the determining comprises determining a spatial derivative of the pressure wave data based on said indication of the particle motion.

4. The method of claim 3, wherein the determining further comprises:

determining a time derivative of the pressure data; and

basing the determination of said at least one attribute on the determination of the time derivative of the pressure data and the determination of the spatial derivative of the pressure data.

5. The method of claim 1, wherein the indication of the particle motion comprises an indication of a velocity.

6. The method of claim 1, wherein the determining comprises determining a local slope, the method further comprising:

determining a slope error based on the determined local scope and a mathematical model of the slope.

7. The method of claim 6, further comprising:

determining a seismic event reliability measure based on the slope error.

8. The method of claim 7, further comprising:

further basing the seismic event reliability measure on a semblance-based coherency measure of the gather.

9. The method of claim 1, further comprising:

determining said at least one attribute of the slowness vector from a frequency range in which an associated signal-to-noise ratio is higher than a signal-to-noise ratio of a second frequency range; and

using said at least one attribute to improve a consistency of the pressure data and the indication of particle motion.

10. The method of claim 1, further comprising:

using said at least one attribute to replace a spatial derivative of a pressure wavefield in an interpolation determination.

11. The method of claim 1, further comprising:

determining a transform along a direction of the slowness vector.

12. The method of claim 1, further comprising:

rotating a coordinate frame associated with the indication of particle motion to a coordinate frame that includes the slowness vector as an axis that is directed along the slowness vector.

13. The method of claim 1, further comprising:

removing multiples from the seismic gather based on the slowness vector.

14. The method of claim 1, further comprising:

determining migration weights of a velocity model based on the slowness vector.

15. The method of claim 1, wherein the determining said at least one component of the slowness vector comprises:

determining an up going velocity based on the pressure wave data and the indication of particle motion;

determining a down going velocity based on the pressure wave data and the indication of particle motion; and

determining said at least one attribute of the slowness vector in response to a combination of the up going and down going velocities.

16. The method of claim 1, further comprising:

obtaining the pressure wave data and the indication of particle motion from a densely sampled point receiver system.

17. A system comprising:

an interface to receive pressure data and an indication of particle motion measured by at least one seismic sensor in tow; and

a processor to determine at least one attribute associated with a seismic gather based on the pressure data and the indication of the particle motion.

18. The system of claim 17, further comprising:

at least one towed streamer comprising at least one seismic sensor to indicate the pressure data.

19. The system of claim 18, wherein said at least one towed streamer comprises at least one multi-component sensor to provide an indication of the particle motion.

20. The system of claim 18, further comprising:

at least one vessel to tow said at least one towed streamer.

21. The system of claim 17, wherein the processor is adapted to determine a change in a pressure wave travel time with respect to a receiver offset.

22. The system of claim 17, wherein the processor is adapted to determine a spatial derivative of the pressure data based on said indication of the particle motion.

23. The system of claim 22, wherein the processor is further adapted to:

determine a time derivative of the pressure data; and

base the determination of said at least one attribute on the determination of the time derivative of the pressure data and the determination of the spatial derivative of the pressure data.

24. The system of claim 17, wherein the indication of the particle motion comprises an indication of a velocity.

25. The system of claim 17, wherein the processor is adapted to determine a local slope error based on said at least one attribute of the slowness vector and a mathematical model of the attribute.

26. The system of claim 25, wherein the processor is adapted to determine a seismic event reliability measure based on the slope error.

27. The system of claim 26, wherein the processor is adapted to further base the seismic event reliability measure on a semblance-based coherency measure of the gather.

28. The system of claim 17, wherein the processor is adapted to:

determine said at least one attribute from a frequency range in which an associated signal-to-noise ratio is higher than a signal-to-noise ratio of a second frequency range; and

use said at least one component to improve a consistency of the pressure data and the indication of particle motion.

29. The system of claim 17, wherein the processor is adapted to:

use said at least one attribute to replace a spatial derivative of a pressure wavefield in an interpolation determination.

30. The system of claim 17, wherein the processor is adapted to:

determine a transform along a direction of the slowness vector.

31. The system of claim 17, wherein the processor is adapted to:

rotate a coordinate frame associated with the indication of particle motion to a coordinate frame that includes the slowness vector as an axis that is directed along the slowness vector.

32. The system of claim 17, wherein the processor is adapted to:

remove multiples from the seismic gather based on the slowness vector.

33. The system of claim 17, wherein the processor is adapted to:

determine migration weights of a velocity model based on the slowness vector.

34. The system of claim 17, wherein the processor is adapted to:

determine an up going velocity based on the pressure data and the indication of particle motion;

determine a down going velocity based on the pressure data and the indication of particle motion; and

determine said at least one attribute in response to a combination of the up going and down going velocities.

35. The system of claim 17, wherein the pressure data and the indication of particle motion are obtained from a densely sampled point receiver system.

36. An article comprising a computer accessible storage medium to store instructions that when executed by a processor-based system cause the processor-based system to:

determine at least one attribute of a slowness vector associated with a seismic gather based on pressure wave data and an indication of particle motion measured by at least one seismic sensor while in tow.

37. The article of claim 36, the storage medium storing instructions that when executed cause the processor-based system to determine a change in a pressure wave travel time with respect to a receiver offset.

38. The article of claim 36, the storage medium storing instructions that when executed cause the processor-based system to determine a spatial derivative of the pressure wave data based on said indication of the particle motion.

39. The article of claim 38, the storage medium storing instructions that when executed cause the processor-based system to:

determine a time derivative of the pressure wave data; and

base the determination of said at lease one attribute on the determination of the time derivative of the pressure wave data and the determination of the spatial derivative of the pressure wave data.

40. The article of claim 36, the storage medium storing instructions that when executed cause the processor-based system to determine local slope error based on said at least one attribute and a mathematical model of the attribute.

41. The article of claim 40, the storage medium storing instructions that when executed cause the processor-based system to determine a seismic event reliability measure based on the slope error.