Systems and methods employing upward beam propagation for target-oriented seismic imaging

1. A computer-implemented method for processing seismic data representative of a subsurface volume of interest, the method comprising:

a. obtaining, at a computer processor, a seismic dataset and a geologic model representative of the subsurface volume of interest;

b. identifying a target based on the seismic dataset and the geologic model;

c. calculating a normal to represent a structural dip direction for at least one point on the target;

d. upward propagating, via the computer processor, a cluster of beams from the at least one point on the target to a surface representing an acquisition surface of the seismic data wherein the normal is used to enforce equality between incidence angles and reflection angles of the cluster of beams;

e. identifying valid source-receiver beam pairs that overlap shot gathers of the seismic dataset;

f. accumulating, via the computer processor, coverage of the valid source-receiver beam pairs;

g. identifying traces from the seismic dataset that fall within the accumulated beam pair coverage; and

h. performing, via the computer processor, a target-oriented reverse time migration using the identified traces to produce a seismic image.

2. The method of claim 1 further comprising using the seismic image to identify a hydrocarbon reservoir.

3. The method of claim 1 wherein the upward propagating uses a Gaussian beam algorithm.

4. The method of claim 1 , wherein said obtaining includes deriving the geologic model from the seismic dataset, the geologic model representing seismic horizons within the subsurface volume of interest.

5. The method of claim 4 , wherein said calculating a normal includes finding a tangent plane to a seismic horizon nearest the at least one point.

6. The method of claim 1 , wherein each beam in the cluster of beams is initially directed at a corresponding range of angles relative to the normal.

7. The method of claim 1 , wherein the accumulated beam-pair coverage is weighted based on accumulated beam energy, and wherein traces are identified as being within the accumulated beam-pair coverage if the weight at the trace location exceeds a predetermined threshold.

8. The method of claim 1 , further comprising storing the seismic image in a nontransient information storage medium; and displaying a visual representation of the seismic image.

9. The method of claim 1 , wherein the seismic dataset is organized into shot gathers, and wherein said identifying is performed as separate parallelizable tasks that each include iterating through the traces of a given shot gather.

10. The method of claim 1 , wherein the seismic dataset is organized into offset gathers, and wherein said identifying is performed as separate parallelizable tasks that each include iterating through the traces of a given offset gather.

11. An article of manufacture including a non-transitory computer readable medium having computer readable code on it, the computer readable code being configured to implement a method for processing seismic data, the method comprising:

a. obtaining, at a computer processor, a seismic dataset and a geologic model representative of the subsurface volume of interest;

b. identifying a target based on the seismic dataset and the geologic model;

c. calculating a normal to represent a structural dip direction for at least one point on the target;

d. upward propagating, via the computer processor, a cluster of beams from the at least one point on the target to a surface representing an acquisition surface of the seismic data wherein the normal is used to enforce equality between incidence angles and reflection angles of the cluster of beams;

e. identifying valid source-receiver beam pairs that overlap shot gathers of the seismic dataset;

f. accumulating, via the computer processor, coverage of the valid source-receiver beam pairs;

g. identifying traces from the seismic dataset that fall within the accumulated beam pair coverage; and

h. performing, via the computer processor, a target-oriented reverse time migration using the identified traces to produce a seismic image.

12. The article of claim 11 , wherein the accumulated beam-pair coverage is weighted based on accumulated beam energy, and wherein traces are identified as being within the accumulated beam-pair coverage if the weight at the trace location exceeds a predetermined threshold.

13. The article of claim 11 , wherein the method further comprises: storing the seismic image in a nontransient information storage medium; and displaying a visual representation of the seismic image.

14. The article of claim 11 , wherein the seismic dataset is organized into shot gathers, and wherein said identifying is performed as separate parallelizable tasks that each include iterating through the traces of a given shot gather.