System for estimating azimuthal variations in seismic data
First Claim
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1. A method for processing seismic data comprising:
- forming a gather of seismic data traces;
selecting a plurality of time windows in said seismic data gather;
within each selected time window, successively selecting seismic data traces in said gather and determining a time shift for each selected seismic data trace that achieves maximum correlation of the selected seismic data trace with a pilot trace formed by summing a plurality of traces within a spatial window of said gather of seismic data traces, said spatial window being spatially related to the selected seismic data trace; and
utilizing the time shifts determined for said selected seismic data traces in each selected time window to adjust said selected seismic data traces for velocity anisotropy in the earth'"'"'s subsurface.
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Abstract
The invention comprises a system for processing seismic data to estimate time shift resulting from velocity anisotropy in the earth'"'"'s subsurface. A gather of seismic data traces is formed and selected seismic data traces included in said gather within selected time windows are cross-correlated to estimate the time shift in the seismic data traces included in said gather resulting from velocity anisotropy in the earth'"'"'s subsurface.
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Citations
16 Claims
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1. A method for processing seismic data comprising:
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forming a gather of seismic data traces;
selecting a plurality of time windows in said seismic data gather;
within each selected time window, successively selecting seismic data traces in said gather and determining a time shift for each selected seismic data trace that achieves maximum correlation of the selected seismic data trace with a pilot trace formed by summing a plurality of traces within a spatial window of said gather of seismic data traces, said spatial window being spatially related to the selected seismic data trace; and
utilizing the time shifts determined for said selected seismic data traces in each selected time window to adjust said selected seismic data traces for velocity anisotropy in the earth'"'"'s subsurface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
within selected time windows of said seismic data, adjusting the center point of seismic data traces included in said gather in accordance with the determined time shift and adjusting other locations in seismic data traces included in said gather by interpolation between the center points.
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9. The method of claim 1 wherein the element of utilizing the determined time shifts further comprises:
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within selected time windows of said seismic data utilizing the determined time shifts to calculate velocity variation for seismic data traces included in said gather as a function of azimuth and reflection angle;
within selected time windows of said seismic data adjusting the time positions of seismic data traces included in said gather in accordance with the calculated velocity variation.
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10. The method of claim 1 further comprising performing a surface consistent statics solution on said adjusted traces.
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11. The method of claim 1 further comprising:
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performing a surface consistent statics solution on said adjusted traces; and
repeating the acts of (a) within each selected time window, successively selecting seismic data traces in said gather and determining a time shift for each selected seismic data trace that achieves maximum correlation of the selected seismic data trace with a pilot trace formed by summing a plurality of traces within a spatial window of said gather of seismic data traces, said spatial window being spatially related to the selected seismic data trace and utilizing the time shifts determined for said selected seismic data traces in each selected time window to adjust said selected seismic data traces for velocity anisotropy in the earth'"'"'s subsurface, and (b) performing a surface consistent statics solution on said adjusted traces until convergence of the determined time shifts has occurred.
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12. The method of claim 8 further comprising utilizing a least squares analysis to estimate errors associated with the calculation of time shift variation in said selected seismic data traces.
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13. The method of claim 9 further comprising utilizing a least squares analysis to estimate errors associated with the calculation of velocity variation in said selected seismic data traces.
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14. A digital computer programmed to utilize seismic data traces obtained over a region of the earth'"'"'s subsurface to perform a process comprising the steps of:
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forming a gather of seismic data traces;
selecting a plurality of time windows in said seismic data gather;
within each selected time window, successively selecting seismic data traces in said gather and determining a time shift for each selected seismic data trace that achieves maximum correlation of the selected seismic data trace with a pilot trace formed by summina a plurality of traces within a spatial window of said gather of seismic data traces, said spatial window beina spatially related to the selected seismic data trace; and
utilizing the time shifts determined for said selected seismic data traces in each selected time window to adjust said selected seismic data traces for velocity anisotropy in the earth'"'"'s subsurface.
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15. A device which is readable by a digital computer having instructions defining the following process and instructions to the computer to perform said process:
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forming a gather of seismic data traces;
selecting a plurality of time windows in said seismic data gather;
within each selected time window, successively selecting seismic data traces in said gather and determining a time shift for each selected seismic data trace that achieves maximum correlation of the selected seismic data trace with a pilot trace formed by summing a plurality of traces within a spatial window of said gather of seismic data traces, said spatial window being spatially related to the selected seismic data trace; and
utilizing the time shifts determined for said selected seismic data traces in each selected time window to adjust said selected seismic data traces for velocity anisotropy in the earth'"'"'s subsurface. - View Dependent Claims (16)
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Specification