Method and system of processing seismic data by providing surface aperture common image gathers
The method processes, for each of a plurality of shots at respective source locations, seismic traces recorded at a plurality of receiver locations. Common-mid-point-modulated data are also computed by multiplying the seismic data in each seismic trace by a horizontal mid-point. A depth migration process is applied to the seismic data to obtain a first set of migrated data, and to the mid-point-modulated data to obtain a second set of migrated data. For each shot, aperture values are estimated and associated with respective subsurface positions. A migrated value for a depth and an aperture in a surface aperture common image gather at a horizontal position is a migrated value of the first set of migrated data for a shot such that the estimated aperture value associated with that subsurface position is the aperture.
1. A method of processing seismic data, comprising:
inputting a seismic data including, for each of a plurality of shots at respective source locations, a plurality of seismic traces recorded at a plurality of receiver locations;
applying a depth migration process to the seismic data to obtain a first set of migrated data including, for each shot, a first migrated value respectively associated with a plurality of subsurface positions;
computing a mid-point-modulated data by multiplying the seismic data in each seismic trace by a function of a center of the source and receiver locations for said seismic trace;
applying the depth migration process to the mid-point-modulated data to obtain a second set of migrated data including, for each shot, a second migrated values respectively associated with the plurality of subsurface positions;
applying a subtraction process comprising a projection of a lateral distance between an image position and a common mid-point location;
for each shot, estimating an aperture value respectively associated with at least some of the subsurface positions, by a division process performed in a Radon domain applied to the first and second sets of migrated data; and
estimating an aperture indexed common image gather at a horizontal position, comprising respective migrated values for a parameter pair, each including a depth parameter and an aperture parameter,
wherein the migrated value for the parameter pair in the common image gather at said horizontal position is a first migrated value of the first set of migrated data associated with a subsurface position determined by said horizontal position and the depth parameter of said parameter pair for a shot such that the estimated aperture value associated with said subsurface position is the aperture parameter of said parameter pair.
2. The method as claimed in claim 1 , wherein the division process used for estimating the aperture values associated with a subsurface position comprises minimizing a cost function defined by an aperture variable and local values of the first and second migrated values in a neighborhood of said subsurface position.
3. The method as claimed in claim 1 , wherein the depth migration process is a reverse-time migration process.
4. The method as claimed in claim 1 , wherein the depth migration process is a wave equation pre-stack depth migration process.
5. A system for processing seismic data, comprising computer resource configured to carry out a method as claimed in claim 1 .
6. A computer program product for a system for processing seismic data, comprising instructions to carry out a method as claimed in claim 1 when said program product is run in a computer processing unit of the system for processing seismic data.