3D prestack seismic data migration method
First Claim
Patent Images
1. A method of performing prestack migration of seismic events for imaging a part of an underground zone from a series of a number Ns of seismic reflection cycles, comprising successive emission of elementary wavefields, each elementary wavefield defined by association of a seismic signal W(t) and of a point of emission defined in a series of points of emission Si with 1≦
- i≦
Ns, seismic receivers located in positions Rji receiving seismic signals reflected by the underground zone in response to each of the wavefields, with signals received by each seismic receiver being recorded as time-dependent seismic traces dji(t), wherein for a given velocity model, the method comprises the following steps;
a) defining a slowness vector p having components p1 and p2 assuming a series of previously defined values;
b) defining, for a given slowness vector p and for a given point of emission Si, a time lag function t0(p, i);
c) applying the time lag function t0(p, i) to each elementary wavefield associated with point of emission Si and forming a surface composite wavefield by spatiotemporal superposition of elementary wavefields to which such a time lag is applied;
d) applying the time lag function t0(p, i) to seismic traces dji(t) marked by a pair (i,j) and forming a surface composite trace field by spatiotemporal superposition of the seismic traces to which the time lag is applied, e) performing migration of the surface composite trace field using the surface composite wavefield, by modelling propagation of the surface composite wavefield and retropropagation of the surface composite trace field, and combining the modelled propagation of the surface composite wavefield and the retropropagation of the surface composite trace field at any point of the zone to be imaged, f) repeating steps c) to e) for all values assumed by the components p1 and p2 of the vector p, and g) for any set value of the second component p2 of the vector p, stacking the results of combinations of the surface composite wavefield and the retropropagation of the surface composite tracer field to obtain a migrated image associated with the set value of p2, to thereby perform prestack migration.
1 Assignment
0 Petitions
Accused Products
Abstract
A prestack migration method allowing imaging of an underground zone, for a given velocity model of arbitrary complexity. By means of conventional wave propagation and retropropagation modelling tools, the method allows to obtain elementary migrated images associated with the values assumed by a parameter and the sum of the images obtained for the different values of the parameter (post-migration stacking), in the depth domain as well as in the time domain. This migration is obtained at an attractive price (calculation cost) because it is independent of the volume of the results calculated and of the number of seismic traces recorded. Only the volume of the zone in which the waves are propagated, the complexity of the events to be imaged and the desired accuracy have an effect on the calculation cost. Volume images are thus obtained by taking account of all the seismic traces. It is thus possible to implement a plane wave migration procedure in cases where acquisition does not allow synthesis of the subsurface response to a plane wave excitation, a response required from the outset in conventional plane wave migration algorithms. The method can be applied for imaging of geologic interfaces or heterogeneities of a part of an underground zone.
55 Citations
39 Claims
-
1. A method of performing prestack migration of seismic events for imaging a part of an underground zone from a series of a number Ns of seismic reflection cycles, comprising successive emission of elementary wavefields, each elementary wavefield defined by association of a seismic signal W(t) and of a point of emission defined in a series of points of emission Si with 1≦
- i≦
Ns, seismic receivers located in positions Rji receiving seismic signals reflected by the underground zone in response to each of the wavefields, with signals received by each seismic receiver being recorded as time-dependent seismic traces dji(t), wherein for a given velocity model, the method comprises the following steps;a) defining a slowness vector p having components p1 and p2 assuming a series of previously defined values;
b) defining, for a given slowness vector p and for a given point of emission Si, a time lag function t0(p, i);
c) applying the time lag function t0(p, i) to each elementary wavefield associated with point of emission Si and forming a surface composite wavefield by spatiotemporal superposition of elementary wavefields to which such a time lag is applied;
d) applying the time lag function t0(p, i) to seismic traces dji(t) marked by a pair (i,j) and forming a surface composite trace field by spatiotemporal superposition of the seismic traces to which the time lag is applied, e) performing migration of the surface composite trace field using the surface composite wavefield, by modelling propagation of the surface composite wavefield and retropropagation of the surface composite trace field, and combining the modelled propagation of the surface composite wavefield and the retropropagation of the surface composite trace field at any point of the zone to be imaged, f) repeating steps c) to e) for all values assumed by the components p1 and p2 of the vector p, and g) for any set value of the second component p2 of the vector p, stacking the results of combinations of the surface composite wavefield and the retropropagation of the surface composite tracer field to obtain a migrated image associated with the set value of p2, to thereby perform prestack migration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
forming a final image representative of post-migration stacking of the surface composite trace fields obtained for all values p2 of vector p.
- i≦
-
3. A method as claimed in claim 1 wherein:
- steps a) to g) are used to directly perform post-migration stacking.
-
4. A method as claimed in claim 1, further comprising:
updating of velocities of the seismic signals W(t) by analysis of deformations obtained when a value p2 of vector p is varied.
-
5. A method as claimed in claim 1, wherein:
a migrated image of a part of the zone to be imaged is formed by using a wave conversion phenomenon, by definition of at least a part of a velocity field in P waves and S waves.
-
6. A method as claimed in claim 2, wherein:
a migrated image of a part of the zone to be imaged is formed by using a wave conversion phenomenon, by definition of at least a part of a velocity field in P waves and S waves.
-
7. A method as claimed in claim 3, wherein:
a migrated image of a part of the zone to be imaged is formed by using a wave conversion phenomenon, by definition of at least a part of a velocity field in P waves and S waves.
-
8. A method as claimed in claim 4, wherein:
a migrated image of a part of the zone to be imaged is formed by using a wave conversion phenomenon, by definition of at least a part of a velocity field in P waves and S waves.
-
9. A method as claimed in claim 5, comprising
using preprocessing to separate seismic events. -
10. A method as claimed in claim 6, comprising:
using preprocessing to separate seismic events.
-
11. A method as claimed in claim 7, comprising:
using preprocessing to separate seismic events.
-
12. A method as claimed in claim 8, comprising:
using preprocessing to separate seismic events.
-
13. A method as claimed in claim 1, wherein:
steps a) to g) are used to determine a gradient of a cost function involved in an inverse seismic problem.
-
14. A method in accordance with claim 1 wherein:
the migration of a surface composite trace field is a time migration.
-
15. A method in accordance with claim 2 wherein:
the migration of a surface composite trace field is a time migration.
-
16. A method in accordance with claim 3 wherein:
the migration of a surface composite trace field is a time migration.
-
17. A method in accordance with claim 4 wherein:
the migration of a surface composite trace field is a time migration.
-
18. A method in accordance with claim 5 wherein:
the migration of a surface composite trace field is a time migration.
-
19. A method in accordance with claim 6 wherein:
the migration of a surface composite trace field is a time migration.
-
20. A method in accordance with claim 7 wherein:
the migration of a surface composite trace field is a time migration.
-
21. A method in accordance with claim 8 wherein:
the migration of a surface composite trace field is a time migration.
-
22. A method in accordance with claim 9 wherein:
the migration of a surface composite trace field is a time migration.
-
23. A method in accordance with claim 10 wherein:
the migration of a surface composite trace field is a time migration.
-
24. A method in accordance with claim 11 wherein:
the migration of a surface composite trace field is a time migration.
-
25. A method in accordance with claim 12 wherein:
the migration of a surface composite trace field is a time migration.
-
26. A method in accordance with claim 13 wherein:
the migration of a surface composite trace field is a time migration.
-
27. A method in accordance with claim 1 wherein:
the migration of a surface composite trace field is a depth migration.
-
28. A method in accordance with claim 2 wherein:
the migration of a surface composite trace field is a depth migration.
-
29. A method in accordance with claim 3 wherein:
the migration of a surface composite trace field is a depth migration.
-
30. A method in accordance with claim 4 wherein:
the migration of a surface composite trace field is a depth migration.
-
31. A method in accordance with claim 5 wherein:
the migration of a surface composite trace field is a depth migration.
-
32. A method in accordance with claim 6 wherein:
the migration of a surface composite trace field is a depth migration.
-
33. A method in accordance with claim 7 wherein:
the migration of a surface composite trace field is a depth migration.
-
34. A method in accordance with claim 8 wherein:
the migration of a surface composite trace field is a depth migration.
-
35. A method in accordance with claim 9 wherein:
the migration of a surface composite trace field is a depth migration.
-
36. A method in accordance with claim 10 wherein:
the migration of a surface composite trace field is a depth migration.
-
37. A method in accordance with claim 11 wherein:
the migration of a surface composite trace field is a depth migration.
-
38. A method in accordance with claim 12 wherein:
the migration of a surface composite trace field is a depth migration.
-
39. A method in accordance with claim 13 wherein:
the migration of a surface composite trace field is a depth migration.
Specification
-
- Resources
Litigation Campaign Assessment
Thank you for your request. You will receive a custom alert email when the Litigation Campaign Assessment is available.
×
-
Current AssigneeInstitut Francais Du Petrole
-
Original AssigneeInstitut Francais Du Petrole
-
InventorsEhinger, Andreas, Duquet, Bertrand, Lailly, Patrick
-
Primary Examiner(s)McElheny, Jr., Donald E.
-
Application NumberUS09/408,515Time in Patent Office761 DaysField of Search702/14, 702/16, 702/17, 702/18, 367/38, 367/50-53US Class Current702/18CPC Class CodesG01V 1/301 for determining seismic cro...
