Noise Suppression Technology
PGS’ Suite of Noise Attenuation Technologies
Perhaps the most important step in the processing of seismic data is the removal of coherent and incoherent noise. According to the ageless signal processing mantra “rubbish in, rubbish out”, however sophisticated your imaging algorithms may be, if your signal is lost under a sea of noise then no useful seismic image will be produced. Noise on seismic datasets can appear as a result of many different physical processes and, consequently, with many different seismic characteristics. One of the most complex challenges in seismic data processing is attenuating these different noise types while preserving the character of the underlying data. As may be expected, the diversity of noise types and characteristics leads to a requirement for a diverse array of noise attenuation tools. PGS’ noise attenuation technology suite is composed of tools suitable for use on many different data-types and in many different noise environments.
The table below gives an overview of some of the multi-channel noise technology that is available from PGS. Click on the underlined processes for more details of the technology.
Seismic Interference Noise Killer (SINK)*
*U.S. Patent
SINK is designed to attenuate both swell noise and seismic interference.
SINK designs scalars across ensembles which scale down energy bursts to the median "mean absolute amplitude" in a given window.
The main features of SINK:
The ability to "self-heal" the holes created, either by:
Easy design and application within a limited frequency range
Integrated QC tools
Interleave streamers to attenuate consistently bad channels
Input data (left) and after SINK (right) (courtesy of Talisman Norge).
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Water Interference Prediction & Elimination (WIPE)*
*U.S. Patent
Surface diffraction (from obstructions such as rigs, seabed structures etc.) and ship noise removal are combined in a single process: WIPE
The main features of WIPE:
Single process for both types of noise
Iterative solution for the noise source location
Easy QC output options
Tightly integrated with PGS’ 2-D and 3-D visualization packages
A natural complement to the tight 3D spatial sampling provided by PGS' HD3D acquisition technology, ensuring artifact-free imaging, high resolution, and optimum data quality
Data contaminated by ship noise (left) and after WIPE (right) .
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Noise attenuation by 3-D Weighted Slant Stacks (NS3D)*
* U.S. Patent
Using 3-D weighted slant stacks, NS3D can attenuate three different types of noise: coherent, incoherent and impulsive
- NS3D can be attenuated pre-stack, post-stack or post-migration
- NS3D has proven successful on land, marine and OBC (seafloor) data
Land input data before (left) and after NS3D (right).
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Dual-wavefield noise attenuation (DWNA)*
* U.S. Patent pending
Dual Wavefield Noise Attenuation (DWNA) offers a significant improvement in the signal-to-noise (S/N) ratio of dual sensor OBC (seafloor) data.
- DWNA is not limited by the spatial aliasing issues associated with conventional coherent noise rejection
- DWNA addresses the noise on the near traces where there is no moveout differentiation between primary and noise
- DWNA improves the effectiveness of subsequent processing by preserving the bandwidth and improving the S/N ratio of the data being processed
A single-fold cube generated from a single shot and receiver line orthigonal to each other,
before (left) and after DWNA + FK filtering(right).
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Multiple diffraction attenuation (MDA)
Multiple diffraction attenuation (MDA) is an innovative processing technique designed to attenuate high-energy reverberations of near-surface diffractions. The method utilizes a pattern recognition technique to separate the high-amplitude diffracted multiple arrivals from the underlaying primary energy. The separation is based on the difference in frequency, amplitude and phase characteristics of the two types of events. By utilizing all these characteristics, the process may be finely tuned to particular nature of the diffracted multiple energy in any given geological regime.
Multiple diffraction attenuation is routinely used and particular in deeper waters to remove multiple energy not removed in the demultiple process. Stack after demultiple is shown on left will the result after application of MDA is shown on right.
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