Method of seismic surveying

• US 7,376,046 B2
• Filed: 10/11/2006
• Issued: 05/20/2008
• Est. Priority Date: 04/06/2002
• Status: Expired due to Term

• Current Assignee: WesternGeco LLC
• Original Assignee: WesternGeco LLC
• Inventors: Jeffryes, Benjamin Peter
• Primary Examiner(s): Keith; Jack
• Assistant Examiner(s): Hughes; Scott A.
• Application Number:
  US11/548,521
• Publication Number:
  US 20070091721A1
• Time in Patent Office: 587 Days
• Field of Search: 367/14, 367 39- 41, 181/107, 181/111, 181/114
• US Class Current: 367/41
• CPC Class Codes: G01V 1/005 with exploration systems emitting special signals, e.g. frequency swept signals, pulse sequences or slip sweep arrangements

Abstract

The present invention provides a seismic surveying method in which vibrators in a first vibrator group are actuated at time T0 and vibrators in a second vibrator group are actuated at time T1, where T0<T1<T0+S1+L and S1 is the sweep time of the first group and L is the listening time. This method enables the time required to complete a seismic survey to be reduced. In other embodiments, vibrators in the first vibrator group may be actuated at time T2, where T1<T2<T1+S2+L and S2 is the sweep time of the first group, and vibrators in the second vibrator group at time T3 where T2<T3<T2+S1+L and T3−T2≠T1−T0. Such embodiments providing that by appropriately combining the shot records noise may be eliminated.

Claims

1. A method of seismic surveying using slip sweep technique having at least a first vibrator group and a second vibrator group, the method comprising:

actuating a vibrator in the first vibrator group at time T0 with a fundamental sweep;

actuating a vibrator in the second vibrator group at time T1 with a fundamental sweep, where T0<

T1<

T0+S1+L, where S1 is the sweep time of the first vibrator group and L is the listening time and wherein T1−

T0>

(n−

1)*S1*f₁/(n*(f₁−

f₀)), where n is a natural number, f₀ is the lower frequency limit of the vibrator sweep and f₁ is the upper frequency limit of the vibrator sweep;

recording the earth responses as seismic surveying data;

correlating the seismic surveying data with the fundamental sweep;

correlating the seismic survey data with a harmonic frequency sweep;

estimating the noise due to the harmonic frequency sweep; and

removing the noise due to the harmonic frequency sweep from the seismic survey data.

2. The method of claim 1 wherein the correlated data is Fourier transformed.

3. The method of claim 1 wherein the correlated data is time windowed.

4. The method of claim 1, wherein the estimate of the harmonic noise of one shot is subtracted from the data acquired during a preceding shot.

5. The method of claim 1, wherein the seismic surveying data is correlated with the fundamental sweep of the last shot first;

wherein the correlated seismic surveying data of the last shot is used to estimate the harmonic noise in the correlated seismic surveying data of one shot earlier.

6. The method of claim 1, wherein the harmonic frequency sweep comprises the second harmonic of the fundamental sweep.

7. The method of claim 6, wherein the harmonic frequency sweep comprises the third harmonic of the fundamental sweep.

8. A method of processing seismic data acquired using slip sweep technique having at least a first vibrator and a second vibrator, wherein a first vibrator is actuated with a fundamental sweep and to be listened at T0, wherein a second vibrator is actuated at time T1 with a fundamental sweep, where T0<

T1<

T0+S1+L, where S1 is the sweep time of the first vibrator group and L is the listening time and wherein T1−

T0>

(n−

1)*S1*f₁/(n*(f₁−

f₀)), where n is a natural number, f₀ is the lower frequency limit of the vibrator sweep and f₁ is the upper frequency limit of the vibrator sweep;

the method comprising;

having the seismic data;

correlating the seismic surveying data with the fundamental sweep;

correlating the seismic survey data with a harmonic frequency sweep;

estimating the noise due to the harmonic frequency sweep; and

removing the noise due to the harmonic frequency sweep from the seismic survey data.

9. The method of claim 8 wherein the correlated data is Fourier transformed.

10. The method of claim 8 wherein the correlated data is time windowed.

11. The method of claim 8, wherein the estimate of the harmonic noise of one shot is subtracted from the data acquired during a preceding shot.

12. The method of claim 8, wherein the seismic surveying data is correlated with the fundamental sweep of the last shot first;

wherein the correlated seismic surveying data of the last shot is used to estimate the harmonic noise in the correlated seismic surveying data of one shot earlier.

13. A seismic data processing system utilizing a slip sweep technique having at least a first vibrator and a second vibrator, wherein a first vibrator is actuated with a fundamental sweep and to be listened at T0, wherein a second vibrator is actuated at time T1 with a fundamental sweep, where T0<

T1<

T0+S1+L, where S1 is the sweep time of the first vibrator group and L is the listening time and wherein T1−

T>

(n−

1)*S1*f₁/(n*(f₁−

f₀)), where n is a natural number, f₀is the lower frequency limit of the vibrator sweep and f₁ is the upper frequency limit of the vibrator sweep;

the system comprising;

a memory stored on a computer readable medium having the seismic data;

a data processor coupled to the memory, wherein the data processor accesses the seismic data in the memory;

correlates the seismic surveying data with the fundamental sweep;

correlates the seismic survey data with a harmonic frequency sweep;

estimates the noise due to the harmonic frequency sweep; and

removes the noise due to the harmonic frequency sweep from the seismic survey data; and

stores the seismic survey data in the memory.

14. The system of claim 13 further comprising,

a storage with storage medium, an input interface and an output interface coupled to the data processor.

15. The system of claim 13 wherein the correlated data is Fourier transformed.

16. The system of claim 13 wherein the correlated data is time windowed.

17. The system of claim 13, wherein the estimate of the harmonic noise of one shot is subtracted from the data acquired during a preceding shot.

18. The system of claim 13, wherein the seismic surveying data is correlated with the fundamental sweep of the last shot first;

wherein the correlated seismic surveying data of the last shot is used to estimate the harmonic noise in the correlated seismic surveying data of one shot earlier.