Signal enhancement using diversity shot stacking for reverse time migrations (DeSSeRT)
View Patent ↗A method of processing seismic data so as to provide an image of a subsurface region, comprises providing plurality of migrated shot gathers that contain information about the region, summing portions of the migrated shot gathers to provide a pilot stack, partitioning the plurality of gathers into a plurality of groups and summing the gathers in each group to provide a substack, wherein each group includes at least two migrated shots and wherein a substack is generated from each group, applying an amplitude normalization algorithm to the pilot stack so as to generate an amplitude-normalized pilot stack, calculating a weight function by comparing each substack to the normalized pilot stack, weighting each substack using the weight function so as to generate a plurality of weighted substacks, summing overlapping portions of the weighted substacks so as to generate a output stack, and using the output stack to generate an image.
1. A method of processing seismic data so as to provide an image of a subsurface region and to produce hydrocarbons from said subsurface region, comprising the steps of:
a) providing plurality of migrated shot gathers that contain information about the subsurface region;
b) summing the overlapping portions of the migrated shot gathers to provide a pilot stack;
c) partitioning the plurality of migrated shot gathers into a plurality of groups, and summing the gathers in each group to provide a substack, wherein each group includes at least two migrated shots and wherein a substack is generated from each group;
d) applying an amplitude normalization algorithm to the pilot stack so as to generate an amplitude-normalized pilot stack;
e) calculating a weight function by comparing each substack to the amplitude-normalized pilot stack;
f) weighting each substack using the weight function so as to generate a plurality of weighted sub stacks;
g) summing the overlapping portions of the weighted substacks so as to generate an output stack;
h) using the output stack to generate an image of said subsurface region; and
i) producing, from said subsurface region, hydrocarbons that are detected with said image.
2. The method of claim 1 wherein the comparing in step e) consists of at least one of correlating, multiplying, dividing, subtracting, and adding.
3. The method of claim 1 , further including the step of using the weight function to construct or update a velocity model.
4. The method of claim 1 wherein step e) includes computing a least squares match filter.
5. The method of claim 1 wherein the weight function has a length between 1 and 50,000 data points.
6. The method of claim 1 wherein step f) comprises at least one calculation selected from the group of correlation, convolution, multiplication, division, and combinations thereof.
7. The method of claim 1 wherein step c) comprises partitioning the migrated shot gathers into at least 40 groups.
8. The method of claim 1 wherein step c) comprises partitioning the migrated shot gathers depending on their vector distances.
9. The method of claim 1 wherein step c) comprises partitioning the migrated shot gathers depending on their respective quadrants.
10. The method of claim 1 wherein step c) comprises partitioning the migrated shot gathers into conical volumes depending on their azimuth, image depth and distance.
11. The method of claim 10 wherein the migrated shot gathers are partitioned into muting cones that are expressed as percentages of X=Z, where X is distance and Z is image depth.
12. The method of claim 1 wherein step f) includes using an amplitude-based weighting algorithm.
13. The method of claim 1 wherein step f) includes using an illumination-based weighting algorithm.
14. The method of claim 1 , further including repeating steps d) through g) at least once, using the output stack as the pilot stack.