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Outer Vøring Area, Norwegian Sea
This 2016 project (orange outline) was the first commercial survey acquired by Ramform Tethys deploying 129 km of in-sea recording cable. Today, this is still the biggest spread towed by a seismic vessel in Northern Europe. Globally, this achievement has only been matched by the sister vessels in the Ramform Titan-class fleet. Visit our data library for more information on data availability.
Reservoir targets in the area sit deeper than complex ooze bodies. In order to accurately image the targets the ooze bodies must be effectively resolved. Deep water and lack of refractions from strong negative velocity contrasts at the top of the ooze bodies mean that traditional FWI is not optimal. The ooze also causes strong scattering of the wavefield and results in distortions and amplitude diming effects which must also be addressed.
The PGS FWI solution includes reflections and refractions to provide deeper and higher resolution velocity models. Small-scale velocity variations and sharp velocity contrasts between the ooze bodies and surrounding lithology are captured. Q modeling is included to compensate for amplitude distortions and to ensure absorption is incorporated during the migration.
PSDM stack and 1 700 m depth slice for the initial (left) and final FWI velocity model overlays (right). Ooze bodies are much better resolved with reflections and refractions in PGS FWI.
High-resolution velocity models down to depths of 4 km have been generated due to the availability of FWI frequencies down to 2 Hz and the inclusion of reflections in the calculations. Targets beneath the ooze are better imaged as the high-resolution velocity models have been combined with detailed attenuation (Q) models in a Q-Kirchhoff prestack depth migration.
12 and 27 Hz velocity model overlays on a 1530 m Q-KPSDM section. Note the resolution of localized ooze features in the 27 Hz FWI velocity model.
Q-KPSDM run with a 12 Hz FWI velocity model versus Q-WEM run with a 27 Hz FWI velocity model and masked shallow Q model. Note the Q-WEM image is significantly less distorted below the thick ooze body. The resolution of faults and geological contacts and facies boundaries is improved.
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