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Inverting for Water Column Velocities in Seismic ExplorationNormal access

Authors: M. Cvetkovic, C. Saint-Andre and P. Blanvillain
Event name: 81st EAGE Conference and Exhibition 2019
Session: Velocity Model Estimation I
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201901525
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.29Mb )
Price: € 20

Summary:
Propagation of sound waves in water can vary both in time and space but velocity inversion and updates in water column for seismic surveys has been mostly been limited to 4D streamer and 3D OBN surveys. Seismic reflectors in the water column are often seen on conventional seismic acquisition but remained generally unexploited. The seismic features recorded in the water layer are primarily images of vertical water temperature variations restricted to the resolution scale of the seismic source wavelet. We will show 2 approaches for inverting water column seismic velocities. First we show examples obtained with conventional seismic data and fit for purpose processing to optimize the imaging of the inner water reflections in time domain. These subtle structures in the water column are created by the strong oceanic current affecting the area and can be inverted from preconditioned seismic data to allow a high resolution automated velocity analysis. The second example is reflection based tomographic inversion where we are correcting for PSDM image gather flatness of water bottom for regional water model. Here variation in the water column is a product of extreme water properties variations caused by interaction between warm and cold currents meeting offshore Argentina.


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