Pre-salt reservoirs of Búzios oil field are overlaid by a thick and complex sedimentary packcage (3500-4000m) which causes important scattering and severe attenuation of seismic signal.The present work performs a spectral analysis of a 3D Kirchhoff Pre-Stack Depth Migration (PSDM) seismic data from Búzios field, investigating the frequency content variation vertically and horizontally, to better understand the frequency attenuation process as the seismic wave travels through the sediments from the sea bottom down to the reservoir base in this area.To perform the spectral analysis in frequency domain, the PSDM volume was converted to time domain using the same interval velocity volume used to depth-migrate the data.The variation of frequency band as the signal propagates through the sediment package was analyzed dividing a crossline section in 12 layers of 200 ms each, from sea bottom down to the base of pre-salt reservoir formations (2700 to 5000 ms).Preliminary results suggest that most part of higher frequency loss has been occurred in post-salt package, specifically from 3600 to 3800 ms.This fact may be an indication of strong viscoelastic behavior of this interval.After that, higher frequency content is lost slowly from 3800ms down to the last layer located inside pre-salt formation.Very slight frequency spectrum variation between 4200 ms to 5000 ms indicates elastic behavior of the salt formation and underling pre-salt formation in this interval.
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