Claims
- 1. A method for determining from measured reflection data on a plurality of trace positions a plurality of subsurface parameters, said method comprising the steps of:
(a) preprocessing the measured reflection data into a plurality of partial or full stacks; (b) specifying one or more initial subsurface parameters defining an initial subsurface model; (c) specifying a wavelet or wavelet field for each of the partial or full stacks of the measured reflection data; (d) calculating synthetic reflection data based on the specified wavelets and the initial subsurface parameters; (e) optimizing an objective function, comprising the weighted difference between measured reflection data and synthetic reflection data; and (f) outputting the optimized subsurface parameters.
- 2. The method according to claim 1, wherein the step of optimizing the objective function comprises minimizing the objective function:
- 3. The method according to claim 2, wherein the objective function comprises one or more stabilization terms and/or one or more correction terms.
- 4. The method according to claim 3, wherein a stabilization term is a measure for the deviation of the reflectivity away from 0.
- 5. The method according to claim 4, wherein said measure comprises
- 6. The method according to claim 3, wherein a stabilization term is a measure for the parameter contrast.
- 7. The method according to claim 6, wherein said measure comprises
- 8. The method according to claim 3, wherein a stabilization term is a measure for the deviation of the subsurface parameters from the initial subsurface parameters.
- 9. The method according to claim 8, wherein said measure comprises
- 10. The method according to claim 7, wherein a stabilization term is a measure for the deviation of the calculated subsurface parameters from a priori specified functional relationships between subsurface parameters.
- 11. The method according to claim 10, wherein said measure comprises
- 12. The method according to claim 3, wherein a stabilization term is a measure for the lateral variability of the parameters.
- 13. The method according to claim 12, wherein said measure comprises
- 14. The method according to claim 13, wherein the parameter difference dj,l,n is defined as
- 15. The method according to claim 1, wherein a correction term is a measure for the differential time shifts between traces of measured reflection data stacks.
- 16. The method according to claim 15, wherein said measure comprises
- 17. The method according to claim 1, wherein a stabilization term is a measure for the parameter differences between reflection data acquisition surveys taken at different points in time.
- 18. The method according to claim 17, wherein said measure comprises
- 19. The method according to claim 1, wherein the minimization is performed for each trace position separately.
- 20. The method according to claim 1, wherein the minimization is performed for a plurality of trace positions simultaneously.
- 21. The method according to claim 1, wherein constraints and/or constraint functions are applied to one or more of the subsurface parameters.
- 22. The method according to claim 1, wherein constraints and/or constraint functions are applied to control changes of subsurface parameters between surveys taken on different times.
- 23. The method according to claim 22, wherein constraints and/or constraint functions constrain outside a specified subsurface zone the parameter changes between surveys to small values relative to changes expected within the specified subsurface zone.
- 24. The method according to claim 23, wherein constraints and/or constraint functions constrain the minimization by setting the subsurface parameters outside a specified subsurface zone from survey to survey at the same value.
- 25. The method according to claim 1, wherein for optimizing the objective function outside a specified subsurface zone only one or one set of different subsurface parameters are specified.
- 26. The method according to claim 1, comprising the generation of quality control information.
- 27. The method according to claim 26, wherein the quality information includes synthetic data based on the optimized subsurface parameters.
- 28. The method according to claim 26, wherein the quality control information includes residual data obtained by subtracting the synthetic data from the measured reflection data.
- 29. The method according to claim 26, wherein the quality control information includes deviation data obtained by determining the deviations away from the initial subsurface parameters.
- 30. The method according to claim 26, wherein the quality control information includes deviation data obtained by determining the deviations away from the corresponding functional relations.
- 31. The method according to claim 26, wherein the quality control information includes deviation data obtained by determining the deviations away from well log data.
- 32. The method according to claim 1, wherein the reflection data is seismic data.
- 33. The method according to claim 1, wherein the reflection data is time lapse data.
- 34. The method according to claim 1, wherein the subsurface parameters comprise elastic parameters.
- 35. The method according to claim 34, wherein the elastic parameters comprise pressure wave velocities and/or shear wave velocities and/or densities in the subsurface.
- 36. The method according to claim 34, wherein the subsurface parameters comprise any mathematical relation between pressure wave velocities and/or shear wave velocities, and/or densities.
- 37. The method according to claim 1, wherein the subsurface parameters comprise compositional parameters representing the rock and fluid composition of the subsurface.
- 38. The method according to claim 36, wherein the seismic data comprises at least two seismic partial or full stacks containing different angle dependant information on seismic reflections in the subsurface.
- 39. The method according to claim 33, wherein the time lapse data at each survey time comprises at least one seismic partial or full stack.
- 40. The method according to claim 2, wherein the adjustable norm LP of a variable x for variable x comprises
- 41. The method according to claim 40, wherein the norm LP is normalized by exponentiation with 1/P.
- 42. The method according to claim 40, wherein the norm Lp is further normalized with the number of samples.
- 43. The method according to claim 40, wherein the norm Lp is further normalized with the square roof of the variance of x.
- 44. The method according to claim 32, wherein the seismic reflection data is determined from at least one of the following source-receiver combinations:
P-wave source and P-wave receiver, P-wave source and S-wave receiver, S-wave source and P-wave receiver, S-wave source and S-wave receiver.
- 45. The method according to claim 1, wherein the reflection data is echo-acoustic data and the subsurface is human or mammal tissue or any other material.
- 46. A device for determining from measured reflection data on each trace position a plurality of parameters of a subsurface, said device comprising:
(a) input means for inputting at least the measured reflection data and the initial subsurface parameters; (b) processing means for processing the measured reflection data and initial subsurface parameters according to the method of claim 1; and (c) output means for outputting optimized subsurface parameters and preferably quality control information.
Priority Claims (2)
Number |
Date |
Country |
Kind |
PCT/EP00/10464 |
Oct 1999 |
IB |
|
99 203 477.7 |
Oct 1998 |
EP |
|
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of International patent application No. PCT/EP00/10464, filed Oct. 22, 1999, and designating, inter alia, the United States, which claims priority to European Application No. 99203477.7, filed Oct. 22, 1998.