Data Acquisition and Prestack Migration Based on Seismic Visibility Analysis

• US 20110273959A1
• Filed: 01/19/2009
• Published: 11/10/2011
• Est. Priority Date: 01/19/2009
• Status: Active Grant

• Current Assignee: Landmark Graphics Corporation (Halliburton Company)
• Original Assignee: Landmark Graphics Corporation (Halliburton Company)
• Inventors: Jin, Shengwen, Xu, Shiyong
• Granted Patent: US 9,329,288 B2
• Time in Patent Office: Days
• US Class Current: 367/38
• CPC Class Codes: G01V 1/003 Seismic data acquisition in general, e.g. survey design G01V1/3808, G01V1/42 take precedence
• CPC Class Codes: G01V 1/30 Analysis G01V1/50 takes precedence
• CPC Class Codes: G01V 1/345 Visualisation of seismic data or attributes, e.g. in 3D cubes
• CPC Class Codes: G01V 20/00 Geomodelling in general
• CPC Class Codes: G01V 2210/67 Wave propagation modeling
• CPC Class Codes: G01V 2210/673 Finite-element; Finite-difference
• CPC Class Codes: G01V 2210/675 Wave equation; Green's functions
• CPC Class Codes: G01V 2210/679 Reverse-time modeling or coalescence modelling, i.e. starting from receivers

Abstract

Seismic visibility analysis of selected subsurface structures is employed to determine surface locations offering high visibility of target events. These locations can then be used as a basis for acquiring additional seismic survey data and/or selecting existing traces for re-migration with more sophisticated migration methods. With either usage, the newly migrated data is expected to offer enhanced images of the target event. In some embodiments, the visibility determination includes using a wave equation based propagator to find, for each of multiple simulated shots, a reflection wavefield from the target event in a seismic model; and to calculate, for each of multiple receiver positions, a contribution signal from each reflection wavefield. The visibility determination further includes converting each contribution signal into a source-receiver visibility value. Because data acquisition and/or re-migration is limited to the selected region, the imaging effort for the target event is significantly reduced.

Claims

1. A seismic survey method that comprises:

determining visibility of a target event as a function of seismic source and receiver positions; and

acquiring seismic data in a region selected at least in part to include positions having visibility values above a threshold.

2. The method of claim 1, further comprising:

imaging the target event based on the acquired seismic data.

3. The method of claim 2, wherein said determining the visibility of a target event includes:

finding, for each of multiple simulated shots, a reflection wavefield from the target event in a seismic model;

calculating, for each of multiple receiver positions, a contribution signal from each reflection wavefield; and

converting each contribution signal into a source-receiver visibility value.

4. The method of claim 3, wherein the seismic model is determined based at least in part on migrated data from a seismic survey.

5. The method of claim 3, wherein the target event is a subsurface feature that is selected by a user as being inadequately imaged.

6. The method of claim 3, wherein the visibility value is an integrated square of the contribution signal.

7. The method of claim 1, wherein the threshold is selected to capture a predetermined fraction of the area under the multidimensional visibility function.

8. A seismic migration method that comprises:

determining visibility of a target event at the source and receiver positions of traces in an existing seismic survey; and

re-migrating traces having visibility values above a threshold to image the target event.

9. The method of claim 8, wherein said determining the visibility of a target event includes:

finding, for each of multiple simulated shots, a reflection wavefield from said target event in a seismic model;

calculating, for each of multiple receiver positions, a contribution signal from each reflection wavefield; and

converting each contribution signal into a source-receiver visibility value.

10. The method of claim 9, wherein the seismic model is determined based at least in part on migrated data from the existing seismic survey, wherein said migrated data is obtained using a first migration method.

11. The method of claim 10, wherein said converting includes determining an integrated square of the contribution signal.

12. The method of claim 10, wherein said visibility is determined using a second migration method different than the first migration method.

13. The method of claim 10, wherein said re-migration is performed using a second migration method different than the first migration method.

14. The method of claim 8, wherein the target event is a subsurface feature that is selected by a user as being inadequately imaged.

15. The method of claim 8, wherein the threshold is selected to capture a predetermined fraction of the area under the visibility function.

16. A visibility analysis system that comprises:

a memory that stores visibility analysis software; and

at least one processor coupled to the memory to execute the visibility analysis software, wherein the software configures the at least one processor to;

determine, for each of multiple shots, a reflection wavefield from at least one target event in a seismic model;

calculate, for each of multiple receiver positions, a contribution signal from each reflection wavefield; and

convert each contribution signal into a source-receiver visibility value.

17. The system of claim 16, wherein the software further configures the processor to visually map visibility as a function of at least one of source position and receiver position.

18. The system of claim 16, wherein the seismic model is determined based at least in part on migrated data from a seismic survey, wherein said migrated data is obtained using a first migration method.

19. The system of claim 18, wherein said visibility is determined using a second migration method different than the first migration method.

20. The system of claim 16, wherein the software further configures the processor to identify traces from an existing seismic survey for re-migration with an enhanced migration method, wherein the traces are identified based at least in part on their visibility values.

21. The system of claim 16, wherein the software further configures the processor to identify source and receiver positions for additional seismic data acquisition, wherein said positions are identified based at least in part on source-receiver visibility values.