METHOD OF ATTENUATING MIGRATION ARTIFACTS
Methods and systems are disclosed. The methods may include obtaining vertical seismic profile (VSP) data and a seismic velocity model for a subterranean region of interest and determining, using the seismic velocity model and reverse time migration, a pre-stacked migrated seismic image based on the VSP data. The pre-stacked migrated seismic image includes seismic slices. The methods may further include, for each of the seismic slices in turn, determining a coherency map, determining a weighting map based on the coherency map, and determining a corrected seismic slice by applying the weighting map to each of the seismic slices. The methods may still further include determining a post-stacked corrected migrated seismic image based on the corrected seismic slices and determining a location of a geological feature within the subterranean region of interest based, at least in part, on the post-stacked corrected migrated seismic image.
1 . A method comprising:
obtaining vertical seismic profile (VSP) data and a seismic velocity model for a subterranean region of interest;
determining, using the seismic velocity model and reverse time migration, a pre-stacked migrated seismic image of the subterranean region of interest based on the VSP data,
wherein the pre-stacked migrated seismic image comprises a plurality of seismic slices;
for each of the plurality of seismic slices in turn:
determining a coherency map for each of the plurality of seismic slices,
determining a weighting map based, at least in part, on the coherency map, and
determining a corrected seismic slice by applying the weighting map to each of the plurality of seismic slices;
determining a post-stacked corrected migrated seismic image based on the plurality of corrected seismic slices; and
determining a location of a geological feature within the subterranean region of interest based, at least in part, on the post-stacked corrected migrated seismic image.
2 . The method of claim 1 , further comprising planning a wellbore path that penetrates a hydrocarbon reservoir within the subterranean region of interest based, at least in part, on the location of the geological feature.
3 . The method of claim 2 , further comprising drilling a wellbore guided by the wellbore path.
4 . The method of claim 1 , wherein the VSP data comprises seismic traces organized into a plurality of common shot gathers, and
wherein determining the pre-stacked migrated seismic image comprises applying the reverse time migration to each of the plurality of common shot gathers.
5 . The method of claim 1 , wherein each of the plurality of seismic slices comprises a plurality of seismic traces organized into a source-offset domain common-image gather.
6 . The method of claim 1 , wherein determining the coherency map further comprises:
determining a spectral seismic slice by applying a transform to each of the plurality of seismic slices;
determining a filtered spectral seismic slice by applying a filter to the spectral seismic slice; and
determining a filtered seismic slice by applying an inverse transform to the filtered spectral seismic slice.
7 . The method of claim 6 , wherein the transform comprises a dual-tree complex wavelet transform.
8 . The method of claim 6 , wherein the filter is a function of a scale factor and orientation.
9 . The method of claim 6 , wherein the inverse transform comprises an inverse complex wavelet transform.
10 . The method of claim 1 , wherein the coherency map comprises a value of semblance at each position within each of the plurality of seismic slices.
11 . The method of claim 1 , wherein determining the weighting map comprises applying a weight function to the coherency map, and
wherein the weight function assigns each value within the coherency map to a group based on a plurality of threshold values.
12 . A system comprising:
a seismic processing system configured to:
receive vertical seismic profile (VSP) data and a seismic velocity model for a subterranean region of interest,
determine, using the seismic velocity model and reverse time migration, a pre-stacked migrated seismic image of the subterranean region of interest based on the VSP data,
wherein the pre-stacked migrated seismic image comprises a plurality of seismic slices,
for each of the plurality of seismic slices in turn:
determine a coherency map for each of the plurality of seismic slices;
determine a weighting map based, at least in part, on the coherency map; and
determine a corrected seismic slice by applying the weighting map to each of the plurality of seismic slices, and
determine a post-stacked corrected migrated seismic image based on the plurality of corrected seismic slices; and
a seismic interpretation workstation configured to:
determine a location of a geological feature within the subterranean region of interest based, at least in part, on the post-stacked corrected migrated seismic image.
13 . The system of claim 12 , further comprising a wellbore planning system configured to plan a wellbore path that penetrates a hydrocarbon reservoir within the subterranean region of interest based, at least in part, on the location of the geological feature.
14 . The system of claim 13 , further comprising a drilling system configured to drill a wellbore guided by the wellbore path.
15 . The system of claim 12 , further comprising a VSP acquisition system configured to obtain the VSP data.
16 . The system of claim 12 , wherein the seismic processing system is further configured to determine the seismic velocity model based, at least in part, on the VSP data.
17 . The system of claim 12 , wherein the seismic processing system is further configured to:
determine a spectral seismic slice by applying a transform to each of the plurality of seismic slices;
determine a filtered spectral seismic slice by applying a filter to the spectral seismic slice; and
determine a filtered seismic slice by applying an inverse transform to the filtered spectral seismic slice.
18 . A non-transitory computer-readable memory having computer-executable instructions stored thereon that, when executed by a computer processor, perform steps comprising:
receiving vertical seismic profile (VSP) data and a seismic velocity model for a subterranean region of interest;
determining, using the seismic velocity model and reverse time migration, a pre-stacked migrated seismic image of the subterranean region of interest based on the VSP data,
wherein the pre-stacked migrated seismic image comprises a plurality of seismic slices;
for each of the plurality of seismic slices:
determining a coherency map for each of the plurality of seismic slices,
determining a weighting map based, at least in part, on the coherency map, and
determining a corrected seismic slice by applying the weighting map to each of the plurality of seismic slices;
determining a post-stacked corrected migrated seismic image based on the plurality of corrected seismic slices; and
determining a location of a geological feature within the subterranean region of interest based, at least in part, on the post-stacked corrected migrated seismic image.
19 . The non-transitory computer-readable memory of claim 18 , wherein determining the coherency map further comprises:
determining a spectral seismic slice by applying a transform to each of the plurality of seismic slices;
determining a filtered spectral seismic slice by applying a filter to the spectral seismic slice; and
determining a filtered seismic slice by applying an inverse transform to the filtered spectral seismic slice.
20 . The non-transitory computer-readable memory of claim 18 , wherein determining the weighting map comprises applying a weight function to the coherency map,
wherein the weight function assigns each value within the coherency map to a group based on a plurality of threshold values.