Amplitude-versus-angle analysis for quantitative interpretation

1. A method, comprising:

updating, by a machine, a velocity model and adjusting corresponding anisotropy parameters via tomography to solve for relatively longer wavelengths in the velocity model;

performing, by the machine, full waveform inversion to solve for relatively shorter wavelengths in the velocity model;

using, by the machine, the velocity model after full waveform inversion to migrate up-going wavefields and down-going wavefields including primaries and multiples;

creating, by the machine, a plurality of angle gathers from the migration, thereby imaging a subsurface location with multiples in a near-offset range and with primaries outside the near-offset range, wherein the subsurface location is shallow such that primaries are not received from the subsurface location for a near-offset range; and

applying, by the machine, an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the shallow subsurface location.

2. The method of claim 1 , wherein, the quantitative interpretation comprises at least one of a group of quantitative interpretations comprising:

a property of the subsurface location;

a prediction of a lithology of the subsurface location; and

a prediction of a fluid at the subsurface location.

3. The method of claim 2 , wherein the property of the subsurface location comprises one of the group of properties comprising:

a direct hydrocarbon indicator; and

an existence of a reservoir.

4. The method of claim 1 , further comprising separating recorded seismic data into the up-going wavefields and the down-going wavefields including the primaries and the multiples.

5. The method of claim 1 , further comprising creating the plurality of angle gathers from imaging the subsurface location with multiples outside the near-offset range.

6. The method of claim 1 , further comprising applying a deconvolution imaging condition at the subsurface location to reduce crosstalk from unrelated correlation of the primaries and the multiples.

7. A non-transitory machine-readable medium storing instructions executable by a processing resource to, comprising:

perform separated wavefield imaging, including separating recorded seismic data into up-going wavefields and down-going wavefields recorded in a non-transitory machine-readable medium, to provide seismic data for a near-offset range;

wherein providing seismic data for the near-offset range includes illuminating angles in the near-offset range to improve discrimination of amplitude with angle for an amplitude-versus-angle analysis;

migrate the up-going wavefields and the down-going wavefields to the subsurface location;

apply a deconvolution imaging condition at the subsurface location after the migration to create a plurality of angle gathers from imaging a subsurface location with multiples over a plurality of angles, wherein the subsurface location is shallow such that primaries are not received from the subsurface location for a near-offset range; and

apply the amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the shallow subsurface location, the quantitative interpretation comprising a direct hydrocarbon indicator.

8. The medium of claim 7 , further comprising instructions to apply a radial trace transform to a plurality of subsurface offset gathers to create the plurality of angle gathers.

9. The medium of claim 7 , wherein the quantitative interpretation includes at least one of the group of quantitative interpretations including:

a determination of a property of the subsurface location;

a prediction of a lithology of the subsurface location; and

a prediction of a fluid at the subsurface location.

10. The medium of claim 9 , wherein the property of the subsurface location comprises one of the group of properties comprising:

a direct hydrocarbon indicator; and

an existence of a reservoir.

11. A system, comprising hardware of a machine configured to:

update a velocity model and adjust corresponding anisotropy parameters via tomography to solve for relatively longer wavelengths in the velocity model;

perform full waveform inversion to solve for relatively shorter wavelengths in the velocity model;

use the velocity model after full waveform inversion to migrate up-going wavefields and down-going wavefields including primaries and multiples;

create a plurality of angle gathers from the migration and record the plurality of angle gathers in a non-transitory machine-readable medium, thereby imaging a subsurface location with multiples over a plurality of angles, wherein the subsurface location is shallow such that primaries are not received from the subsurface location for a near-offset range; and

apply an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the shallow subsurface location.

12. The system of claim 11 , wherein, the quantitative interpretation comprises at least one of a group of quantitative interpretations comprising:

a property of the subsurface location;

a prediction of a lithology of the subsurface location; and

a prediction of a fluid at the subsurface location.

13. The system of claim 12 , wherein the property of the subsurface location comprises one of the group of properties comprising:

a direct hydrocarbon indicator; and

an existence of a reservoir.

14. The system of claim 11 , wherein the multiples comprise down-going sea surface reflections in a near-offset range.

15. The system of claim 14 , wherein the hardware of the machine is configured to create the plurality of angle gathers from imaging the subsurface location with primaries outside of the near-offset range.

16. The system of claim 11 , wherein the recorded seismic data was recorded with multi-sensor seismic receivers in water having a depth less than 600 meters.

17. A method of generating a geophysical data product, the method comprising:

obtaining geophysical data;

processing the geophysical data, wherein processing the geophysical data comprises:

updating a velocity model and adjust corresponding anisotropy parameters via tomography to solve for relatively longer wavelengths in the velocity model;

performing full waveform inversion to solve for relatively shorter wavelengths in the velocity model;

using the velocity model after full waveform inversion to migrate up-going wavefields and down-going wavefields including primaries and multiples;

creating a plurality of angle gathers from the migration and record the plurality of angle gathers in a non-transitory machine-readable medium, thereby imaging a subsurface location with multiples over a plurality of angles, wherein the subsurface location is shallow such that primaries are not received from the subsurface location for a near-offset range;

applying an amplitude-versus-angle analysis to the plurality of angle gathers to produce a quantitative interpretation pertaining to the shallow subsurface location; and

recording the geophysical data product on a non-transitory machine-readable medium thereby creating the geophysical data product.

18. The method of claim 17 , wherein processing the geophysical data comprises processing the geophysical data offshore or onshore.

19. The method of claim 17 , wherein the quantitative interpretation includes at least one of the group of quantitative interpretations including:

a determination of a property of the subsurface location;

a prediction of a lithology of the subsurface location; and

a prediction of a fluid at the subsurface location.

20. The method of claim 19 , wherein the property of the subsurface location comprises one of the group of properties comprising:

a direct hydrocarbon indicator; and

an existence of a reservoir.