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We presented a study on the estimation of the anisotropic velocity
parameters based on the residual moveout curves in anisotropic
angle-domain common image gathers.
We first performed a brief
theoretical study of the estimation problem by formulating it
mathematically as an inversion problem. We showed that provided that
the range of the aperture angles is not too small, the problem is well
posed with relatively small condition numbers, whatever the sampling
of the aperture-angle axis. The theory also highlighted the well-known
fact that the estimation of the horizontal velocity is poor when the
range of the aperture angles is small and that one should be careful when
trying to estimate anisotropic parameters when the range of aperture angle is large (significant noise propagation).
In a second part, we computed anisotropic velocity spectra from
synthetic angle-domain common-image gathers. This study showed that
velocity spectra can introduce some bias in the estimation of the
anisotropic parameters and that there are large trade-offs between the
different anisotropic parameters. However, picking the set of
anisotropic parameters that correspond to the maximum semblance,
proved to overall improve the anisotropic parameters' estimation.
Our future work will consists in the development of the two
following estimation techniques:
- The computation of the velocity spectra and the iterative
estimation of the anisotropic parameters have to be explored: is
there an optimal search path to determine the anisotropic parameters
(successive estimation of the different parameters or estimation of
several parameters at the same time)? This procedure will also have
to be tested on
real data estimation problem, for which some continuity constraints
will be key.
- The actual measure of the residual moveout (using an automatic
technique such as the one presented by (8)) and its
inversion is a way of
estimating the anisotropic parameters that has to be explored and
that could be very successful. It has the advantage of
better constraining the estimation of the anisotropic parameters to
the data, in comparison with the method developed by (1).
Next: Computation of anisotropic velocity
Up: Jousselin: Anisotropic velocity spectra
Previous: Trade-off between the different
Stanford Exploration Project
1/16/2007