Multiple Attenuation
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This section describes some of the techniques used for multiple attenuation based on move out filtering, wave equation based methods and deconvolution.
For shallow-water marine surveys a standard processing sequence will typically use Tau-p deconvolution to attenuate short period multiples, followed by high-resolution Radon and/or 2D SRME targeted at the longer period multiples. For deep-water marine, 2D SRME followed by high-resolution Radon would typically be applied. For land data, de-multiple would normally use a combination of deconvolution and high-resolution Radon.
Higher-Resolution Radon de-multiple: XRMULT
XRMULT uses a constrained least squares version of the parabolic transform. The representation of the data in the Radon domain is better focused than with the conventional Radon transform (PMULT). It focuses energy along both the p and time axes. It is designed to overcome some of the limitations of the conventional transform. It is able to preserve primary amplitudes better as a function of offset whilst simultaneously giving a more complete multiple attenuation. It also is somewhat resistant to spatial aliasing and can therefore reduce the need for trace interpolation before the transform. The algorithm also honors the true offset of the data, so that it can be accurately applied even in irregularly sampled data from land or sea-floor acquisition geometries.
Targeted multiple attenuation: TMA
Adaptive subtraction is used to identify and remove specific, targeted pegleg or water bottom multiples from an isolated primary reflection (multiple generator). The user provides a design window containing the primary and a second application window containing the multiples from that event. The technique is based on the assumption that a multiple contains the imprint of the lateral variation or lateral ‘pattern’, of the multiple generator. The process uses the lateral amplitude and phase variation of the multiple generator to design operators that detect and remove events in the application window with the same lateral variations. The operators may be designed using either a 2D or 3D window. The program may be run on stack or common offset volumes