INTERFEROMETRIC SEISMIC DATA PROCESSING

• US 20100265797A1
• Filed: 04/17/2009
• Published: 10/21/2010
• Est. Priority Date: 04/17/2009
• Status: Active Grant

• Current Assignee: WesternGeco LLC (Schlumberger NV)
• Original Assignee: WesternGeco LLC (Schlumberger NV)
• Inventors: Robertsson, Johan O. A., Rickett, James
• Granted Patent: US 9,075,163 B2
• Time in Patent Office: Days
• US Class Current: 367/43
• CPC Class Codes: G01V 1/366 by correlation of seismic signals
• CPC Class Codes: G01V 2210/675 Wave equation; Green's functions

Abstract

Implementations of various technologies for a method for generating a seismic image of a subsurface are described herein. Seismic data may be received from two sensors in a seismic survey. The seismic data below and equal to a predetermined frequency may be classified as low-frequency seismic data. The low-frequency seismic data may be re-sampled based on the predetermined frequency. A set of low-frequency Green'"'"'s functions may be calculated using interferometry on the re-sampled low-frequency seismic data. High-frequency seismic data of the seismic data may be processed to create a set of high-frequency Green'"'"'s functions at one or more source locations of the seismic survey. The set of high-frequency Green'"'"'s functions may be merged with the set of low-frequency Green'"'"'s functions to create a set of broad-band Green'"'"'s functions. The seismic image may be generated using the set of broad-band Green'"'"'s functions at the source locations.

Claims

1. A method for processing seismic data, comprising:

receiving the seismic data from two sensors in a seismic survey;

classifying the seismic data below and equal to a predetermined frequency as low-frequency seismic data;

calculating a set of low-frequency Green'"'"'s functions using interferometry on the low-frequency seismic data;

processing high-frequency seismic data of the seismic data to create a set of high-frequency Green'"'"'s functions at one or more source locations of the seismic survey;

merging the set of low-frequency Green'"'"'s functions and the set of high-frequency Green'"'"'s functions to create a set of broad-band Green'"'"'s functions at the source locations; and

generating a seismic image using the set of broad-band Green'"'"'s functions.

2. The method of claim 1, further comprising attenuating ground roll and surface waves in the low-frequency seismic data.

3. The method of claim 1, wherein the set of low-frequency Green'"'"'s functions comprises one or more reflection seismic data based on one or more cross-correlations between the two sensors, and wherein one of the two sensors is configured as a source of the reflection seismic data.

4. The method of claim 1, wherein the seismic data is classified using a low pass filter.

5. The method of claim 1, wherein generating the seismic image comprises:

producing a velocity model based on the set of broad-band Green'"'"'s functions; and

imaging the set of high-frequency Green'"'"'s functions using the velocity model.

6. The method of claim 5, wherein imaging the set of high-frequency Green'"'"'s functions comprises performing a reverse time migration using the velocity model and the set of high-frequency Green'"'"'s functions.

7. The method of claim 1, wherein the predetermined frequency ranges from about 4 Hz to about 5 Hz.

8. The method of claim 1, wherein the seismic data are obtained through continuous recording for the seismic data and surrounding noise.

9. The method of claim 8, wherein the surrounding noise comprises environmental noise at a surface of the earth.

10. The method of claim 8, wherein the surrounding noise comprises noise from earthquake, oceans or both.

11. The method of claim 1, further comprising re-sampling the low-frequency seismic data based on the predetermined frequency, and wherein the set of low-frequency Green'"'"'s functions is calculated using Interferometry on the re-sampled low-frequency seismic data.

12. The method of claim 11, wherein the low-frequency seismic data are re-sampled according to a time interval and a spatial interval based on the predetermined frequency, and a Nyquist sampling theorem.

13. The method of claim 12, wherein the Nyquist sampling theorem specifies that the spatial interval is less than v*(2*f)⁻

1, where v=the ground roll in the recorded seismic data and f=the predetermined frequency.

14. A method for processing seismic data comprising:

receiving the seismic data from two sensors in a seismic survey;

classifying the seismic data above and equal to a predetermined frequency as high-frequency seismic data and below and equal to the predetermined frequency as low-frequency seismic data;

re-sampling the low-frequency seismic data based on the predetermined frequency;

calculating a set of low-frequency Green'"'"'s functions using interferometry on the re-sampled low-frequency seismic data;

processing the high-frequency seismic data to form a set of high-frequency Green'"'"'s functions at one or more source locations of the seismic survey;

merging the set of low-frequency Green'"'"'s functions with the set of high-frequency Green'"'"'s functions to generate a set of broad-band Green'"'"'s functions at the source locations; and

inverting for one or more subsurface parameters using the set of broad-band Green'"'"'s functions.

15. The method of claim 14, wherein the set of low-frequency Green'"'"'s functions comprises one or more reflection seismic data based on one or more cross-correlations between the two sensors, and wherein one of the two sensors is configured as a source of the reflection seismic data.

16. The method of claim 14, wherein merging the set of low-frequency Green'"'"'s functions with the set of high-frequency Green'"'"'s functions comprises calibrating the set of low-frequency Green'"'"'s functions with the set of high-frequency Green'"'"'s functions at the predetermined frequency where the low-frequency seismic data and the high-frequency seismic data overlap.

17. The method of claim 16, wherein calibrating the set of low-frequency Green'"'"'s functions comprises:

interpolating one or more virtual source locations in the set of low-frequency Green'"'"'s functions to one or more locations of actual sources used to record the high-frequency seismic data.

18. A system, comprising:

a processor; and

a memory having program instructions configured to cause the processor to;

receive seismic data obtained through continuous recording for the seismic data and surrounding noise by one or more seismic sensors;

classify, using a low pass filter, the seismic data above and equal to a predetermined frequency as high-frequency seismic data and below and equal to the predetermined frequency as low-frequency seismic data;

re-sample the low-frequency seismic data based on the predetermined frequency;

attenuate ground roll and surface waves in the re-sampled low-frequency seismic data;

calculate a set of low-frequency Green'"'"'s functions using interferometry on the attenuated low-frequency seismic data;

index the high-frequency seismic data by one or more sources of the high-frequency seismic data to generate an active source seismic dataset; and

generate a seismic image using the active source seismic dataset and the set of low-frequency Green'"'"'s functions at one or more locations of the seismic sensors.

19. The system of claim 18, wherein the image is generated using a full waveform inversion on the active source seismic data set.

20. The system of claim 18, wherein the image is generated using a prestack depth migration on the active source seismic data set.

21. The system of claim 18, wherein the image is generated using an impedance inversion on the active source seismic data set.