Imaging below seafloor canyons and other rugose features

2017 ◽  
Vol 57 (2) ◽  
pp. 728
Author(s):  
Dominic Fell ◽  
Kiran Dyal ◽  
Tony Hallam ◽  
Sebastian Nixon
Keyword(s):  
Model Building ◽  
Model Updating ◽  
Depth Image ◽  
Earth Model ◽  
Structural Distortions ◽  
Building Process ◽  
Constrained Model ◽  
Marine Seismic ◽  
Mass Transport Deposits

Rugose seabed and near seafloor features in marine seismic datasets such as canyons, mass transport deposits and paleo-channels, present a major imaging challenge that can be overcome by a rigorous and careful approach in the earth model building process. To obtain an accurate image of the deeper target levels, a modelling and data driven update of the distinctive velocity characteristics of the overburden features are necessary. Without adequately addressing the complexity of the shallow velocity field, the final depth image of the target intervals can be poorly focussed and contaminated with non-geologic structural distortions. Inadequate corrections ultimately have an adverse impact upon the interpretation of the dataset. This paper presents a successful earth modelling approach used to obtain an accurate depth image for a marine dataset located on the shelf break in the Otway Basin. The case study area includes extensive seafloor canyons and associated paleo-channels, requiring the strategic use of several geologically constrained model updating technologies in order to obtain a final imaged section free of velocity related structural distortions.

Revitalizing Seismic Beyond Geometry Limitations: A Case Study of OBN Survey in Offshore Sabah

2021 ◽  
Author(s):  
Lee Sii Ngo ◽  
Wai Leng Cheah ◽  
Artem Sazykin ◽  
Gavin Menzel-Jones ◽  
Joyce Li Wong ◽  
...  
Keyword(s):  
Model Building ◽  
Waveform Inversion ◽  
Water Environment ◽  
Low Frequency ◽  
Earth Model ◽  
Ocean Bottom ◽  
Full Waveform ◽  
Seismic Acquisition ◽  
Marine Seismic

Abstract Ocean-bottom node (OBN) surveys are an increasingly common choice of method for marine seismic acquisition and offer several key advantages. These include recording wide-azimuth data and reliable low-frequency information. Since the start of OBN acquisition almost two decades ago, key challenges remain, not only on equipment handling and data management, but also on the data processing and imaging methodologies as these multicomponent workflows continue to evolve. We present a case study of an OBN survey acquired in offshore Sabah with a cross-spread geometry, in an ultra-shallow-water environment. This study discusses a few key processing challenges encountered due to this sparse acquisition including noise and multiple energy contamination and aliasing on data. We explain the challenges, how these were overcome, and the methodologies we used to enhance the data quality. As the main product for this project is a depth-imaged seismic volume, we also describe the earth model building workflow and imaging tools we used to leverage the advantage of full-azimuth data and multidirectional wavefield recorded in this survey. This includes full-waveform inversion, multi-azimuth tomography, and imaging with multiple.

An offshore Gabon full-waveform inversion case study

2016 ◽  
Vol 4 (4) ◽  
pp. SU25-SU39 ◽  
Author(s):  
Bingmu Xiao ◽  
Nadezhda Kotova ◽  
Samuel Bretherton ◽  
Andrew Ratcliffe ◽  
Gregor Duval ◽  
...  
Keyword(s):  
Model Building ◽  
Waveform Inversion ◽  
Velocity Model ◽  
Earth Model ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Velocity Model Building ◽  
Building Process ◽  
Model Building Process

Velocity model building is one of the most difficult aspects of the seismic processing sequence. But it is also one of the most important: an accurate earth model allows an accurate migrated image to be formed, which allows the geologist a better chance at an accurate interpretation of the area. In addition, the velocity model itself can provide complementary information about the geology and geophysics of the region. Full-waveform inversion (FWI) is a popular, high-end velocity model-building tool that can generate high-resolution earth models, especially in regions of the model probed by the transmitted (diving wave) arrivals on the recorded seismic data. The history of the South Gabon Basin is complex, leading to a rich geologic picture today and a very challenging velocity model-building process. We have developed a case study from the offshore Gabon area showing that FWI is able to help with the model-building process, and the resulting velocity model reveals features that improve the migrated image. The application of FWI is made on an extremely large area covering approximately 25,000 [Formula: see text], demonstrating that FWI can be applied to this magnitude of survey in a timely manner. In addition, the detail in the FWI velocity model aids the geologic interpretation by highlighting, among other things, the location of shallow gas pockets, buried channels, and carbonate rafts. The concept of actively using the FWI-derived velocity model to aid the interpretation in areas of complex geology, and/or to identify potential geohazards to avoid in an exploration context, is applicable to many parts of the world.

INTEGRATING DIGITAL MAPPING WITH CONSTRAINED MODEL BUILDING AND STRUCTURAL VALIDATION - CASE STUDY FROM WREN'S NEST

2020 ◽  
Author(s):  
Leah Swan ◽  
◽  
Alan P.M. Vaughan ◽  
Fiona McLean ◽  
Carl T. Stevenson ◽  
...  
Keyword(s):  
Model Building ◽  
Digital Mapping ◽  
Constrained Model ◽  
Structural Validation

The impact of acquisition geometry on full-waveform inversion updates

2021 ◽  
Vol 40 (5) ◽  
pp. 335-341
Author(s):  
Denes Vigh ◽  
Xin Cheng ◽  
Kun Jiao ◽  
Wei Kang ◽  
Nolan Brand
Keyword(s):  
Model Building ◽  
Waveform Inversion ◽  
Velocity Model ◽  
Depth Image ◽  
Earth Model ◽  
Full Waveform Inversion ◽  
Ocean Bottom ◽  
Full Waveform ◽  
Data Content ◽  
The Impact

Full-waveform inversion (FWI) is a high-resolution model-building technique that uses the entire recorded seismic data content to build the earth model. Conventional FWI usually utilizes diving and refracted waves to update the low-wavenumber components of the velocity model. However, updates are often depth limited due to the limited offset range of the acquisition design. To extend conventional FWI beyond the limits imposed by using only transmitted energy, we must utilize the full acquired wavefield. Analyzing FWI kernels for a given geology and acquisition geometry can provide information on how to optimize the acquisition so that FWI is able to update the velocity model for targets as deep as basement level. Recent long-offset ocean-bottom node acquisition helped FWI succeed, but we would also like to be able to utilize the shorter-offset data from wide-azimuth data acquisitions to improve imaging of these data sets by developing the velocity field with FWI. FWI models are heading toward higher and higher wavenumbers, which allows us to extract pseudoreflectivity directly from the developed velocity model built with the acoustic full wavefield. This is an extremely early start to obtaining a depth image that one would usually produce in much later processing stages.

scholarly journals High Resolution Anisotropic Earth Model Building on Conventional Seismic Data Using Full Waveform Inversion: A Case Study Offshore Australia

2015 ◽  
Vol 2015 (1) ◽  
pp. 1-5
Author(s):  
Bee Jik Lim ◽  
Denes Vigh ◽  
Stephen Alwon ◽  
Saeeda Hydal ◽  
Martin Bayly ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Model Building ◽  
Waveform Inversion ◽  
Earth Model ◽  
Full Waveform Inversion ◽  
Full Waveform
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