Multiple Attenuation for Ocean Bottom Seismic Data
Removal of noise is a critical first step in improving the seismic image. Multiples are a form of coherent noise that can be a challenge to overcome. With our unique tools, we apply industry leading techniques to help you image your target.
Ocean bottom seismic (OBS) data can be degraded by free-surface multiples, peg-leg, and interbed multiples. Therefore, data conditioning to remove multiples is critical for signal processing and imaging methods to work more effectively. ION offers a suite of algorithms and multiple removal workflows tailored to specific ocean bottom seismic acquisition issues and water depths. Multiples are addressed to preserve amplitude, control phase, and maintain frequency over a broad bandwidth in order to deliver images with greater clarity and resolution.
Having this rich toolbox allows us to apply our industry leading technology to your unique challenges. For multiples suppression, we use tools available in three domains, which include deconvolution/velocity-based approaches, model-based approaches and wavefield separation.
Deconvolution and Velocity-based Approaches
Deconvolution approaches include 2D/3D tau-p domain predictive deconvolution using the appropriate time lag and operator corresponding to the two-way travel-time of the multiple. Velocity-based approaches depend on the ability to differentiate the multiple from the primary based on differences in their move-out velocities.
3D surface related multiple elimination (3D SRME) is a robust technique for modeling and attenuating strong seafloor surface-related multiples even where the seafloor is irregular or steep. ION utilizes a wide azimuth approach well suited for 3D ocean bottom seismic acquisition datasets. Our technique of utilizing true 3D shot modeling eliminates potential directional effects common in less robust techniques that require multiple 2D passes in the model building phase. Subsequent adaptive subtraction provides excellent discrimination between primaries and multiples even in steeply dipping data.
For even greater resolution, interbed multiple attenuation (IMA) is an additional step to attenuate remaining interbed multiples after SRME processing. Strong reflection events such as those related to chalk or salt can generate significant interbed multiples. IMA uses information from identified events to model the interbed multiple and an adaptive subtraction process to attenuate the interbed multiples.
One of the advantages of recording OBS surveys is the ability to deliver high quality broadband images by suppressing ghost notches and receiver-side (i.e. down-going) water-column multiples. The opposite polarity response of down-going waves recorded by hydrophones and geophones present the unique opportunity to remove receiver-side multiples and very effectively de-ghost the data in the marine environment. The result is a broad frequency spectrum and improved overall quality of ocean bottom seismic data.
Regardless of the method used, our staff has the expertise to combine these methods to optimize inversion and imaging objectives.
- Offset Vector Tile Anisotropic Tomography and PreSDM of the Hild OBC - SPG Abstract (PDF)
- Noise Attenuation Techniques for Improving the Quality of Ocean Bottom Seismic Data - GeoIndia Abstract (PDF)