Seismic P-wave velocity derived from vibrator control system

• US 6,982,928 B2
• Filed: 02/17/2004
• Issued: 01/03/2006
• Est. Priority Date: 04/21/2003
• Status: Active Grant

• Current Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Original Assignee: Saudi Arabian Oil Company (Government of Saudi Arabia)
• Inventors: Al-Ali, Mustafa Naser
• Primary Examiner(s): Gregory, Bernarr E.
• Assistant Examiner(s): Hughes, Scott A.
• Application Number:
  US10/781,130
• Publication Number:
  US 20050041527A1
• Time in Patent Office: 686 Days
• Field of Search: 367/54, 367/75, 367/50, 702/6, 702/18
• US Class Current: 367/54
• CPC Class Codes: G01V 1/005 with exploration systems emitting special signals, e.g. frequency swept signals, pulse sequences or slip sweep arrangements
• CPC Class Codes: G01V 1/303 for determining velocity profiles or travel times
• CPC Class Codes: G01V 1/362 Effecting static or dynamic corrections; Stacking
• CPC Class Codes: G01V 2210/53 Statics correction, e.g. weathering layer or transformation to a datum

Abstract

P-wave velocity in a near-surface region of a land area is estimated from a combination of seismic data based upon waves in the near-surface region generated in response to a shock in each of a plurality of upholes drilled in the land area and vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area.

Claims

1. A method of improving the estimation of P-wave velocity in a near-surface region of a land area, comprising:

a first step of gathering vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area;

a second step of deriving a P-wave velocity attribute from the vibrator dynamic data; and

a third step of estimating the P-wave velocity using the P-wave velocity attribute to interpolate between sparse velocity measurement points from an uphole data collection technique.

2. The method of claim 1, wherein the vibrator dynamic data includes both the ground stiffness data and the ground viscosity data.

3. The method of claim 1, wherein the vibrator dynamic data includes P-wave velocity information which is derived by the steps of calculating shear wave propagation velocity information from the ground stiffness data and the ground viscosity data and then calculating the P-wave velocity information from the calculated shear wave propagation velocity information in combination with an estimate of Poisson'"'"'s ratio.

4. The method of claim 1, further comprising an initial step of selecting the land area such that the land area includes adequate upholes to ensure good statistical representation of the selected land area near surface variations.

5. The method of claim 1, wherein said first step is conducted either with either a 2-dimensional seismic study in the land area, with a 3-dimensional seismic study in the land area, or as a stand-alone survey to obtain the vibrator dynamic data.

6. The method of claim 1, further comprising a step of gathering surface elevation information of the land area to be used in said third step.

7. The method of claim 1, wherein said third step includes the step of building either a 2-dimensional near-surface model or a 3-dimensional near-surface velocity model by the steps of:

deriving velocity attribute information from the vibrator dynamic data gathered in said first step;

obtaining velocity control points using the uphole data collection technique in said third step; and

integrating the control velocity points using collocated cokriging with the velocity attribute information.

8. The method of claim 7, wherein said building step further includes the steps of:

building either an initial 2-dimensional near-surface velocity model or an initial 3-dimensional near-surface velocity model by 2-dimensional or 3-dimensional kriging, respectively, of the velocity control points to generate additional information; and

using the additional information in said integrating step.

9. The method of claim 7, further comprising the step of computing seismic statics corrections to be used in seismic data processing to remove the effects of the rapidly varying near-surface velocity, thereby improving the 2-dimensional or 3-dimensional images of the earth subsurface.

10. The method of claim 7, further comprising the step of utilizing the integrated velocity models for estimating the P-wave velocity using a technique requiring a knowledge of a near-surface velocity model.

11. A method of estimating P-wave velocity in a near-surface region of a land area, comprising:

a first step of gathering control data for the near-surface region;

a second step of gathering vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area; and

a third step of estimating the P-wave velocity in response to both the control data and the vibrator dynamic data;

wherein the vibrator dynamic data includes at least one of ground stiffness data and ground viscosity data.

12. The method of claim 11, wherein the vibrator dynamic data includes both the ground stiffness data and the ground viscosity data.

13. The method of claim 12, wherein the vibrator dynamic data includes P-wave velocity information which is derived by the steps of calculating shear wave propagation velocity information from the ground stiffness data and the ground viscosity data and then calculating the P-wave velocity information from the calculated shear wave propagation velocity information in combination with an estimate of Poisson'"'"'s ratio.

14. The method of claim 12, further comprising an initial step of selecting the land area such that the land area includes adequate upholes to ensure good statistical representation of the selected land area near surface variations.

15. The method of claim 12, wherein said first step includes the step of uphole data preparation and quality assessment.

16. The method of claim 12, wherein said second step includes the step of conducting a 3-dimensional seismic study in the land area.

17. The method of claim 12, further comprising a step of gathering surface elevation information of the land area to be used in said third step.

18. The method of claim 11, wherein said first and second steps may be perfonned in any order and/or at least partially concurrently.

19. The method of claim 11, wherein the control data gathered in said first step is seismic data based upon waves in the near-surface region generated in response to a shock in each of a plurality of upholes drilled in the land area.

20. The method of claim 19, wherein said first and second steps may be performed in any order and/or at least partially concurrently.

21. A method of estimating P-wave velocity in a near-surface region of a land area, comprising:

a first step of gathering control data for the near-surface region;

a second step of gathering vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area; and

a third step of estimating the P-wave velocity in response to both the control data and the vibrator dynamic data;

wherein said third step includes the step of building a 3-dimensional near-surface velocity model by the steps of;

deriving uphole velocity information from the seismic data gathered in said first step;

deriving velocity attribute information from the vibrator dynamic data gathered in said second step; and

integrating the uphole velocity information using collocated cokriging with the velocity attribute information.

22. The method of claim 21, wherein said building step further includes the steps of:

building an initial 3-dimensional near-surface velocity model by 3-dimensional kriging of the uphole velocity information to generate additional information; and

using the additional information in said integrating step.

23. The method of claim 21, further comprising the step of applying static corrections to results from said integrating step.

24. A method of estimating P-wave velocity in a near-surface region of a land area, comprising:

a first step of gathering control data for the near-surface region;

a second step of gathering vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area; and

a third step of estimating the P-wave velocity in response to both the control data and the vibrator dynamic data;

wherein the control data gathered in said first step is seismic data based upon waves in the near-surface region generated in response to a shock in each of a plurality of upholes drilled in the land area; and

wherein the vibrator dynamic data includes at least one of ground stiffness data and ground viscosity data.

25. The method of claim 24, wherein the vibrator dynamic data includes both the ground stiffness data and the ground viscosity data.

26. The method of claim 25, wherein the vibrator dynamic data includes P-wave velocity information which is derived by the steps of calculating shear wave propagation velocity information from the ground stiffness data and the ground viscosity data and then calculating the P-wave velocity information from the calculated shear wave propagation velocity information in combination with an estimate of Poisson'"'"'s ratio.

27. The method of claim 25, further comprising an initial step of selecting the land area such that the land area includes adequate upholes to ensure good statistical representation of the selected land area near surface variations.

28. The method of claim 25, wherein said first step includes the step of uphole data preparation and quality assessment.

29. The method of claim 25, wherein said second step includes the step of conducting a 3-dimensional seismic study in the land area.

30. The method of claim 25, further comprising a step of gathering surface elevation information of the land area to be used in said third step.

31. A method of estimating P-wave velocity in a near-surface region of a land area, comprising:

a first step of gathering control data for the near-surface region;

a second step of gathering vibrator dynamic data generated in the near-surface region in response to vibrator action on the land area; and

a third step of estimating the P-wave velocity in response to both the control data and the vibrator dynamic data;

wherein the control data gathered in said first step is seismic data based upon waves in the near-surface region generated in response to a shock in each of a plurality of upholes drilled in the land area; and

wherein said third step includes the step of building a 3-dimensional near-surface velocity model by the steps of;

deriving uphole velocity information from the seismic data gathered in said first step;

deriving velocity attribute information from the vibrator dynamic data gathered in said second step; and

integrating the uphole velocity information using collocated cokriging with the velocity attribute information.

32. The method of claim 31, wherein said building step further includes the steps of:

building an initial 3-dimensional near-surface velocity model by 3-dimensional kriging of the uphole velocity information to generate additional information; and

using the additional information in said integrating step.

33. The method of claim 31, further comprising the step of applying static corrections to results from said integrating step.