Seismic mono-frequency workflow for direct gas reservoir detection
The present disclosure describes methods and systems, including computer-implemented methods, computer program products, and computer systems for direct gas reservoir detection using frequency amplitude. One computer-implemented method includes spectrally decomposing seismic data associated with a target area into a plurality of mono-frequency volumes. Further, the method includes based on a low-frequency volume of the plurality of volumes, generating a low frequency map of the target area. Yet further, the method includes based on a high-frequency volume of the plurality of volumes, generating a high frequency map of the target area. Additionally, the method includes dividing the low frequency map by the high frequency map to generate a frequency ratio map. The method also includes using the frequency ratio map to identify a subsurface gas reservoir in the target area.
1. A method comprising:
spectrally decomposing seismic data associated with a target area into a plurality of mono-frequency volumes;
based on (i) low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area;
based on (i) a high-frequency volume of the plurality of volumes, (ii) the reservoir interval in the target area, and (iii) the shadow zone in the target area, generating a high-frequency map of the target area;
dividing the low-frequency map by the high-frequency map to generate a frequency ratio map;
identifying, in the frequency ratio map, a frequency ratio greater than a threshold frequency ratio; and
determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area.
2. The method of claim 1 , wherein based on (i) a low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area comprises:
generating a reservoir interval low-frequency map;
generating a shadow zone low-frequency map; and
dividing the reservoir interval low-frequency map by the shadow zone low-frequency map to generate the low-frequency map.
3. The method of claim 1 , wherein based on (i) a high-frequency volume of the plurality of volumes, (ii) the reservoir interval in the target area, and (iii) the shadow zone in the target area, generating a high-frequency map of the target area comprises:
generating a reservoir interval high-frequency map;
generating a shadow zone high-frequency map;
and dividing the reservoir interval high-frequency map by the shadow zone high-frequency map to generate the high-frequency map.
4. The method of claim 1 , wherein the seismic data is a Relative Amplitude Preserved (RAP) processed three-dimensional (3D) Pre-Stack Time Migration (PSTM) seismic data volume.
5. The method of claim 1 , wherein determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area comprises:
designating an area associated with the identified frequency ratio as the subsurface gas reservoir.
6. The method of claim 1 , further comprising:
displaying the frequency ratio map on a display device.
7. A device comprising:
a memory; and
a processing unit that is arranged to perform operations including:
spectrally decomposing seismic data associated with a target area into a plurality of mono-frequency volumes;
based on (i) a low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area;
based on (i) a high-frequency volume of the plurality of volumes, generating a high-frequency map of the target area;
dividing the low-frequency map by the high-frequency map to generate a frequency ratio map;
identifying, in the frequency ratio map, a frequency ratio greater than a threshold frequency ratio; and
determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area.
8. The device of claim 7 , wherein based on (i) a low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area comprises:
generating a reservoir interval low frequency map;
generating a shadow zone low-frequency map; and
dividing the reservoir interval low-frequency map by the shadow zone low-frequency map to generate the low-frequency map.
9. The device of claim 7 , wherein based on (i) a high-frequency volume of the plurality of volumes, (ii) the reservoir interval in the target area, and (iii) the shadow zone in the target area, generating a high-frequency map of the target area comprises:
generating a reservoir interval high-frequency map;
generating a shadow zone high-frequency map; and
dividing the reservoir interval high-frequency map by the shadow zone high-frequency map to generate the high-frequency map.
10. The device of claim 7 , wherein the seismic data is a Relative Amplitude Preserved (RAP) processed three-dimensional (3D) Pre-Stack Time Migration (PSTM) seismic data volume.
11. The device of claim 7 , wherein determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area comprises:
designating an area associated with the identified frequency ratio as the subsurface gas reservoir.
12. The device of claim 7 , the operations further comprising:
displaying the frequency ratio map on a display device.
13. A non-transitory computer-readable medium storing instructions executable by a computer system to perform operations comprising:
spectrally decomposing seismic data associated with a target area into a plurality of mono-frequency volumes;
based on (i) low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area;
based on (i) a high-frequency volume of the plurality of volumes, (ii) the reservoir interval in the target area, and (iii) the shadow zone in the target area, generating a high-frequency map of the target area;
dividing the low-frequency map by the high-frequency map to generate a frequency ratio map;
identifying, in the frequency ratio map, a frequency ratio greater than a threshold frequency ratio; and
determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area.
14. The non-transitory computer-readable medium of claim 13 , wherein based on (i) a low-frequency volume of the plurality of volumes, (ii) a reservoir interval in the target area, and (iii) a shadow zone in the target area, generating a low-frequency map of the target area comprises:
generating a reservoir interval low frequency map;
generating a shadow zone low-frequency map; and
dividing the reservoir interval low-frequency map by the shadow zone low-frequency map to generate the low-frequency map.
15. The non-transitory computer-readable medium of claim 13 , wherein based on (i) a high-frequency volume of the plurality of volumes, (ii) the reservoir interval in the target area, and (iii) the shadow zone in the target area, generating a high-frequency map of the target area comprises:
generating a reservoir interval high-frequency map;
generating a shadow zone high-frequency map; and
dividing the reservoir interval high-frequency map by the shadow zone high-frequency map to generate the high-frequency map.
16. The non-transitory computer-readable medium of claim 13 , wherein the seismic data is a Relative Amplitude Preserved (RAP) processed three-dimensional (3D) Pre-Stack Time Migration (PSTM) seismic data volume.
17. The non-transitory computer-readable medium of claim 13 , wherein determining that the identified frequency ratio is indicative of a subsurface gas reservoir in the target area comprises:
designating an area associated with the identified frequency ratio as the subsurface gas reservoir.