Method for simulating local prestack depth migrated seismic images

• US 20050088913A1
• Filed: 04/16/2003
• Published: 04/28/2005
• Est. Priority Date: 04/09/2003
• Status: Active Grant

• Current Assignee: Norsar
• Original Assignee: Norsar
• Inventors: Lecomte, Isabelle
• Granted Patent: US 7,376,539 B2
• Time in Patent Office: Days
• US Class Current: 367/51
• CPC Class Codes: G01V 1/282 Application of seismic models, synthetic seismograms
• CPC Class Codes: G01V 1/286 Mode conversion
• CPC Class Codes: G01V 2210/512 Pre-stack
• CPC Class Codes: G01V 2210/614 Synthetically generated data

Abstract

Method simulating local prestack depth seismic migrated images from target models, without using either real or synthetic recorded data. The input is a background model and some surveys, with the possibility of defining some acquisition surfaces to describe any acquisition geometry of potential surveys. In addition, detailed target models are given, generated from different type of input, such as parameter grids, interpreted time- or depth-horizons with attributes reservoir models, and other models. In the most efficient application of the invention, a point in the background model is chosen by the user and will act as a node for Green'"'"'s functions calculation between the surveys/acquisition surfaces and that point. Green'"'"'s functions can be calculated in many ways (classic ray tracing, Wavefront Construction, and Eikonal solvers are possible methods), the mandatory information being slowness vectors to form a sum vector called the scattering wavenumber. According to some survey choices, the scattering wavenumbers are extracted, with various sub-selections, sorting, re-ordering, and used to create filters in the scattering wavenumber domain. Amplitudes, pulses, scattering pattern, Fresnel-zone effects, and other effects can be included in the filters. The latter are then applied to each target model to give a simulated prestack local image in depth after some transformation, like Fast Fourier Transform, from the wavenumber domain to the space domain. For better accuracy, local images for neighboring Green'"'"'s functions nodes can be merged to form a classic prestack depth migrated section. A variant of the present invention is to simulate seismic traces in the time domain. The inner core of the invention, with application of scattering wavenumbers to build filters to apply to target models, can be applied in other domains, such as Ground Penetrating Radar, and possibly acoustical and medical imaging.

Claims

1. Method simulating local prestack depth migrated images on basis of a selected GF-node comprising:

extracting at the GF-node scattering wavenumbers K;

creating at the GF-node K-filters in a scattering wavenumber domain;

applying the K-filters to a target model in the scattering wavenumber domain; and

obtaining a simulated local image by transformation from the K-domain to a space domain.

2. Method according to claim 1, wherein the extraction of the K is done with different sub-selections in source/receiver locations, and/or locally in the dip/azimuth/reflection angle domain at the GF-node.

3. Method according to claim 2, wherein re-sampling of the K distribution is done with interpolation to get regular distribution, in order to improve the quality of the simulated local image and speed-up the following mapping process in the K-domain.

4. Method according to claim 2, wherein other GF parameters are extracted in parallel to the K.

5. Method according to claim 4, wherein amplitudes are extracted.

6. Method according to claim 4, wherein traveltimes are extracted.

7. Method according to claim 4, further comprising using amplitudes for creating the K-filters.

8. Method according to claim 1, wherein the K-filters are created by mapping the K on a grid suited for a summation process in terms of efficiency and quality, mapping techniques for which many public and registered techniques existing in the Synthetic Aperture Radar domain, can be used.

9. Method according to claim 8, wherein the mapping of the K on a regular grid is done by the nearest-point mapping.

10. Method according to claim 9, wherein the mapping includes taking care of the Jacobian of the transformation between the original K coordinate system, polar in 2D and spherical in 3D, and the one used for the integration, the simplest being counting the number of K assigned to a sample and dividing the total result by this number.

11. Method according to claim 8, wherein the values assigned to each K sample is a function of factors, such as propagation amplitudes to simulate non-preserving amplitude PSDM, angle-dependent reflectivity, Fresnel-zone factor to get the frequency-dependent “

lateral”

smoothing effect done by PSDM when working with band-limited signals, and other scattering-pattern factors such as Born or Kirchhoff.

12. Method according to claim 8, wherein the values assigned to each K sample is multiplied by a pulse to get the band-limited signal effect on the resolution across the reflectors, this pulse being the source-signature if no source correction is to be considered, or the deconvolved pulse if deconvolution is supposed to be done prior to the imaging, or a pulse used to test resolution improvements with the simulated process.

13. Method according to claim 1, wherein target models to study are defined from various types of input, such as parameter grids, interpreted horizons—

either in time and depth—

with attributes, models for any type of modeling like ray-tracing or finite-differences, reservoir models, and are created in the same coordinate system than the one used for the K-filters, the target model parameter to map depending on the type of PSDM to simulate, like reflectivity in classic PSDM or object function in Born approaches.

14. Method according to claim 1, wherein the final transformation from the K-domain to the space-domain is done by a numerical summation method.

15. Method according to claim 1, wherein the numerical summation method is a FFT summation method.

16. Ground Penetrating Radar imaging apparatus operating according to a method as recited in claim 1.

17. Acoustical imaging apparatus operating according to a method as recited in claim 1.

18. Medical imaging apparatus operating according to a method as recited in claim 1.

19. An article of manufacture comprising:

a computer usable medium having computer readable program code embodied therein for simulating local prestack depth migrated images on basis of a selected GF-node, the computer readable program code in said article of manufacture comprising;

computer readable program code for causing a computer to extract at the GF-node scattering wavenumbers K;

computer readable program code for causing a computer to create at the GF-node K-filters in a scattering wavenumber domain;

computer readable program code for causing a computer to apply the K-filters to a target model in the scattering wavenumber domain;

computer readable program code for causing a computer to obtain a simulated local image by transformation from the K-domain to a space domain.

20. Data set representing the simulated prestack local images produced by:

extracting at the GF-node scattering wavenumbers K;

creating at the GF-node K-filters in a scattering wavenumber domain;

applying the K-filters to a target model in the scattering wavenumber domain; and

obtaining a simulated local image by transformation from the K-domain to a space domain.

21. Method simulating seismic traces on basis of a selected GF-node comprising extracting at the GF-node scattering wavenumbers K and traveltime;

creating at the GF-node and along a given K, 1D K-filters, also called ID K-signals, in a frequency domain;

applying the 1D K-signals to a target model along a given K and in the frequency domain;

and obtaining a simulated seismic trace by transformation from the frequency domain to a time domain.

22. Method according to claim 21, further comprising using amplitudes for creating the 1D K-signals.

23. Method according to claim 21, wherein the K-signals are created by mapping the K along a frequency line suited for a summation process in terms of efficiency and quality.

24. Method according to claim 23, wherein the mapping of the K along a frequency line is done by the nearest-point mapping.

25. Method according to claim 23, wherein the values assigned to each frequency sample of a 1D K-signal is a function of factors, such as propagation amplitudes to simulate non-preserving amplitude PSDM, angle-dependent reflectivity, and other scattering-pattern factors such as Born or Kirchhoff.

26. Method according to claim 23, wherein the values assigned to each frequency sample is multiplied by a pulse to get the band-limited signal effect, this pulse being the source-signature if no source correction is to be considered, or the deconvolved pulse if deconvolution is supposed to be done prior to the imaging, or a pulse used to test resolution improvements with the simulated process.

27. Method according to claim 21, wherein the final transformation from the frequency domain to the time domain is done by a numerical summation method.

28. Method according to claim 27, wherein the numerical summation method is a FFT summation method.

29. Ground Penetrating Radar Imaging apparatus operating according to a method as recited in claim 21.

30. Acoustical imaging apparatus operating according to a method as recited in claim 21.

31. Medical imaging apparatus operating according to a method as recited in claim 21.

32. An article of manufacture comprising:

a computer usable medium having computer readable program code embodied therein for simulating seismic traces on basis of a selected GF-node, the computer readable program code in said article of manufacture comprising;

computer readable program code for causing a computer to extract at the GF-node scattering wavenumbers K and traveltime;

computer readable program code for causing a computer to create at the GF-node and a long a given K, 1D K-filters also called 1D K-signals in a frequency domain;

computer readable program code for causing a computer to apply the 1D) K-signals to a target model along a given K in the frequency domain;

computer readable program code for causing a computer to obtain a simulated seismic trace by transformation from the frequency domain to a time domain.

33. Data set representing the simulated seismic traces produced by:

extracting at the GF-node scattering wavenumbers K and traveltime;

creating at the GF-node and a long a given K, 1D K-filters, also called 1D K-signals, in a frequency domain;

applying the 1D K-signals to a target model along a given K in the frequency domain; and

obtaining a simulated seismic trace by transformation from the frequency drain to a time domain.