LARGEO is one of the leaders in advanced marine data processing including processing of big-scale 3D offshore seismic projects. We apply GXT processing software built around Landmark’s ProMAX® processing system. GXT has enhanced the database-related tools in improving its functionality and allowing it to better accommodate large projects.
- 3D SRME
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LARGEO is the only Russian company that has been applying 3D Surface-Related Multiple Attenuation technology for processing of big-scale offshore projects (several Black Sea projects, Sakhalin and Venezuela shelf). GXT's SRME algorithm is suitable for the attenuation of water bottom and other surface related multiples. It works equally well in both deep and shallow water marine environments. The algorithm is production streamlined to efficiently handle large data volumes. It includes options for 2D and 3D cross equalized adaptive matching using L2 or L1 norm operators.
Field of seismograms with multiples:
a) Seismogram before attenuation;
b) the multiple model obtained using 3D SRME;
c) The result of subtracting a multiple of the wave.Single-channel cross section
a) before suppressing of multiples
b) after the suppression of multiples using 2D SRME and
c) after the suppression of multiples using 3D SRME.
- Data Regularization and Interpolation
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using GXT technology. Regularization attempts to adjust the recorded data to more nearly match the assumptions of the migration algorithms, with a consequent improvement in amplitude fidelity and reduction in noise. GXT current implementation on marine 3D imposes regular spatial sampling on each cross line. Traces are adjusted to bin centre and empty bins interpolated from neighbouring data. The method works in the frequency domain and employs a combination of compressive anti-leakage and anti-aliasing conditioning technology to handle both regularization and high bandwidth interpolation. LARGEO has successfully applied the method for Black sea, Sakhalin and Venezuela offshore data.
Comparing in the direction of the cross-section:
a) the result of migration, without compensation to the multiplicity of technologies;
b) the result of migration using the technology of the multiplicity of compensation;
c) The result of migration using the technology of regularization
a) the cut after the migration with compensation for multiplicity;
b) the cut after the migration with the use of regularization - De-multiple techniques
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LARGEO applies GXT de-multiple techniques including HR Radon and HR “Beam” Radon. Variety of different parabolic RADON multiple attenuation GXT algorithms include the true “high resolution” varieties. A Gaussian Beam option is available for improved handling of aliased and sub-optimally spatially sampled datasets. This algorithm avoids the need to precede the transform with a dedicated interpolation.GXT HR Radon routine applies two-pass non-iterative approach (Sacchi 1995). First pass uses Least Squares to compute “low” resolution weight estimation. Second pass solves using Conjugate Gradient & FFT (fast way to solve a pseudo-Toeplitz matrix). High Resolution Radon improves boundary artifacts, but does not handle badly aliased input data. It usually requires a dedicated spatial de-aliasing step (interpolation). High resolution “beam” radon overcomes these limitations and can solve smaller subsets and better discriminates between aliased multiple & primary with no interpolation is required. LARGEO successfully applied HR Beam Radon method was for Sakhalin and Venesuela offshore datasets.
- ASMA
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Apex Shifted Multiple Attenuation algorithm developed by GXT. Very effective “diffracted” multiple attenuation method that exploits the fact that in the CDP domain, the apex of a diffracted multiple occurs at non-zero offset. The method operates in the CMP domain and is designed to remove multiples that have different moveouts from primary reflections but don’t necessarily have their apex at the zero offset. This type of moveout is associated with steeply dipping diffractions and reflections. LARGEO successfully applied the method for processing of Columbian offshore data.
