Method of deriving statics corrections from common reflection point gathers

• US 5,157,638 A
• Filed: 01/13/1992
• Issued: 10/20/1992
• Est. Priority Date: 01/13/1992
• Status: Expired due to Fees

• Current Assignee: Conoco Incorporated (ConocoPhillips)
• Original Assignee: Conoco Incorporated (ConocoPhillips)
• Inventors: Stoeckley, Thomas R., Loumos, Gregory L., Wang, Shein S.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US07/819,894
• Time in Patent Office: 281 Days
• Field of Search: 367/38, 367/50, 367/51, 367/52, 367/53, 367/54, 367/36, 364/421
• US Class Current: 367/54
• CPC Class Codes: G01V 1/362 Effecting static or dynamic corrections; Stacking
• CPC Class Codes: G01V 2210/53 Statics correction, e.g. weathering layer or transformation to a datum

Abstract

A method for static correction includes a three step process which eliminates the problems of assuming hyperbolic moveout curves and forming base traces from common midpoint gathers while addressing long spatial wavelength variations. First, after calculating and applying an approximate high-frequency static correction to the individual shot and receivers (using traditional automatic methods), depth migration iterations are employed to coarsely tune the near-surface velocity layer. Second, after applying this correction, the remaining statics are incorporated into the model by tomography, which accounts for the velocity and thickness of the weathering layer and buried anomalies. Third, any residual misalignments are addressed using a multi-windowed statics adjustment within the common image point (CIP) gathers.

Claims

1. A method of deriving statics corrections from seismic data including common reflection point gathers and both migrated and unmigrated traces comprising the steps of:

receiving seismic data as a first gather having traces including a conventional static solution having frequency variations;

filtering said conventional statics solution for source and receiver to remove all but the highest frequency variations;

applying said highest frequency variations to unmigrated traces in a second gather;

performing a depth migration using a uniform weathering velocity on said unmigrated traces with said highest frequency variations applied to provide second migrated traces in said second gather;

calculating an initial stacking power of each gather by stacking all said second migrated traces in said second gather;

recording source and receiver locations of each said second migrated trace on a source list and receiver list;

sorting said source list and said receiver list in order;

selecting a predetermined source location for further processing;

changing said uniform weathering velocity of said predetermined source incrementally by dv;

combining said stacking power of all said second gathers to provide a total stacking power; and

choosing a velocity increment dv to maximize said total stacking power.

2. The method according to claim 1 also including the steps of:

selecting a second predetermined source location for further processing;

changing said uniform weathering velocity of said second predetermined source incrementally by dv;

combining said stacking power of all said second gathers to provide a second total stacking power; and

choosing a velocity increment dv to maximize said second total stacking power.

3. The method according to claim 2 also including the steps of:

selecting a predetermined receiver location for further processing;

changing said uniform weathering velocity of said predetermined receiver incrementally by dv;

combining said stacking power of all said second gathers to provide a third total stacking power; and

choosing a velocity increment dv to maximize said third total stacking power.

4. The method according to claim 3 also including the steps of:

selecting a second predetermined receiver location for further processing;

changing said uniform weathering velocity of said second predetermined receiver incrementally by dv;

combining said stacking power of all said second gathers to provide a fourth total stacking power; and

choosing a velocity increment dv to maximize said fourth total stacking power.

5. The method according to claim 4 also including the step of:

averaging and grading said weathering velocities to yield a single velocity profile having a new weathering velocity.

6. The method according to claim 5 also including the step of:

migrating said unmigrated traces using said new weathering velocity.

7. The method according to claim 6 also including the step of:

sorting the results of common offset depth migration into common image point (CIP) gathers.

8. The method according to claim 7 also including the step of:

handling each common image point gather as a common depth point (CDP) gather.

9. The method according to claim 8 also including the step of:

using a basement-consistent multi-windowed statics program to derive a set of adjustments optimizing event line-ups.

10. The method according to claim 9 also including the step of:

employing a preliminary hyperbolic correction whenever residual moveout prevents a predictable adaptive treatment.

11. A method of deriving statics corrections from seismic data including common reflection point gathers and both migrated and unmigrated traces comprising the steps of:

receiving seismic data as a first gather having traces including a conventional static solution having frequency variations;

filtering said conventional statics solution for source and receiver to remove all but the highest frequency variations;

applying said highest frequency variations to unmigrated traces in a second gather;

performing a depth migration using a uniform weathering velocity on said unmigrated traces with said highest frequency variations applied to provide second migrated traces in said second gather;

calculating an initial stacking power of each gather by stacking all said second migrated traces in said second gather;

recording source and receiver locations of each said second migrated trace on a source list and receiver list;

sorting said source list and said receiver list in order;

selecting a predetermined source location for further processing;

changing said uniform weathering velocity of said predetermined source incrementally by dv;

combining said stacking power of all said second gathers to provide a total stacking power;

choosing a velocity increment dv to maximize said total stacking power;

selecting a second predetermined source location for further processing;

changing said uniform weathering velocity of said second predetermined source incrementally by dv;

combining said stacking power of all said second gathers to provide a second total stacking power;

choosing a velocity increment dv to maximize said second total stacking power;

selecting a predetermined receiver location for further processing;

changing said uniform weathering velocity of said predetermined receiver incrementally by dv;

combining said stacking power of all said second gathers to provide a third total stacking power;

choosing a velocity increment dv to maximize said third total stacking power;

selecting a second predetermined receiver location for further processing;

changing said uniform weathering velocity of said second predetermined receiver incrementally by dv;

combining said stacking power of all said second gathers to provide a fourth total stacking power;

choosing a velocity increment dv to maximize said fourth total stacking power;

averaging and grading said weathering velocities incremented by dv to yield a single velocity profile having a new weathering velocity;

migrating said unmigrated traces using said new weathering velocity.

12. An apparatus for deriving statics corrections from seismic data including common reflection point gathers and both migrated and unmigrated traces comprising:

input means for receiving seismic data as a first gather having traces including a conventional static solution having frequency variations;

filtering means for filtering said conventional statics solution for source and receiver to remove all but the highest frequency variations;

applying means for applying said highest frequency variations to unmigrated traces in a second gather;

means for performing a depth migration using a uniform weathering velocity on said unmigrated traces with said highest frequency variations applied to provide second migrated traces in said second gather;

calculating means for calculating an initial stacking power of each gather by stacking all said second migrated traces in said second gather;

recording means for recording source and receiver locations of each said second migrated trace on a source list and receiver list;

sorting means for sorting said source list and said receiver list in order;

selection means for selecting a predetermined source location for further processing;

change means for changing said uniform weathering velocity of said predetermined source incrementally by dv;

combining means for combining said stacking power of all said second gathers to provide a total stacking power; and

means for choosing a velocity increment dv to maximize said total stacking power.

13. The apparatus according to claim 12 also including:

second selection means for selecting a second predetermined source location for further processing;

second change means for changing said uniform weathering velocity of said second predetermined source incrementally by dv;

second combining means for combining said stacking power of all said second gathers to provide a second total stacking power; and

second means for choosing a velocity increment dv to maximize said second total stacking power.

14. The method according to claim 13 also including the steps of:

receiver selection means for selecting a predetermined receiver location for further processing;

receiver change means for changing said uniform weathering velocity of said predetermined receiver incrementally by dv;

receiver combining means for combining said stacking power of all said second gathers to provide a third total stacking power; and

receiver means for choosing a velocity increment dv to maximize said third total stacking power.

15. The apparatus according to claim 14 also including:

second receiver selection means for selecting a second predetermined receiver location for further processing;

second receiver change means for changing said uniform weathering velocity of said second predetermined receiver incrementally by dv;

second receiver combining means for combining said stacking power of all said second gathers to provide a fourth total stacking power; and

second receiver means for choosing a velocity increment dv to maximize said fourth total stacking power.

16. The apparatus according to claim 15 also including:

averaging means for averaging and grading said weathering velocities to yield a single velocity profile having a new weathering velocity.

17. The apparatus according to claim 16 also including:

migrating means for migrating said unmigrated traces using said new weathering velocity.

18. The apparatus according to claim 17 also including:

sorting means for sorting the results of common offset depth migration into common image point (CIP) gathers.

19. The apparatus according to claim 18 also including:

means for treating each common image point gather as a common depth point (CDP) gather.

20. The apparatus according to claim 19 also including:

means for using a statics program to derive a set of adjustments to maximize event line-ups.