Seismic data processing including variable water velocity estimation and compensation therefor
AssigneeCgg Services SAS
InventorsRoss HAACKE, Robert ZIETAL
Life of this patent
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Abstract
Effects of time variability of water velocities in seismic surveys are addressed. Traveltime discontinuities in the input seismic data which are associated with the time-variable water velocities are determined. The input seismic data is transformed from a data space that contains the traveltime discontinuities into a model space which does not contain the traveltime discontinuities. Then the transformed seismic data is reverse transformed from the model space back into the data space.
Claims20
A method, stored in a memory and executing on a processor, for correcting input seismic data for time-variable water velocities comprising the steps of:
- determining traveltime discontinuities in the input seismic data which are associated with the time-variable water velocities;
- transforming the input seismic data from a data space that contains the traveltime discontinuities into a model space which does not contain the traveltime discontinuities;
- and
- reverse transforming the transformed seismic data from the model space back into the data space.
A computer system programmed to correct input seismic data for time-variable water velocities comprising:
- at least one memory device configured to store the input seismic data and computer program instructions;
- and
- at least one processor for executing the computer program instructions to:
- determine traveltime discontinuities in the input seismic data which are associated with the time-variable water velocities;
- transform the input seismic data from a data space that contains the traveltime discontinuities into a model space which does not contain the traveltime discontinuities;
- and
- reverse transform the transformed seismic data from the model space back into the data space.
A method for generating a time series of perturbed scalars which represent depth-insensitive time variability of water velocities in a region which has been surveyed to generate recorded seismic data, the method comprising:
- multiplying a perturbation function by a reference velocity to produce a depth-dependent velocity perturbation function;
- determining a maximum likelihood perturbation scalar associated with said depth dependent velocity perturbation function, for each of a plurality of shots associated with the recorded seismic data taken at different acquisition times, by minimising a cost function of travel time residuals;
- and
- averaging the resulting plurality of perturbation scalars to generate the time series of perturbed scalars which represent the depth-insensitive time variability of water velocities.
A computer system programmed to generate a time series of perturbed scalars which represent depth-insensitive time variability of water velocities in a region which has been surveyed to generate recorded seismic data, the system comprising:
- at least one memory device configured to store the input seismic data and computer program instructions;
- and
- at least one processor for executing the computer program instructions to:
- multiply a perturbation function by a reference velocity to produce a depth-dependent velocity perturbation function;
- determine a maximum likelihood perturbation scalar associated with said depth dependent velocity perturbation function, for each of a plurality of shots associated with the recorded seismic data taken at different acquisition times, by minimising a cost function of travel time residuals;
- and
- average the resulting plurality of perturbation scalars to generate the time series of perturbed scalars which represent the depth-insensitive time variability of water velocities.
Dependencies are inferred from the claim text.