An assessment of viscoelastic finite-difference models applied to the Brazilian pre-salt
Fabrício O. A. AugustoRoger Matsumoto MoreiraMarco CetaleDanielle M. TostesDjalma Manoel Soares Filho
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Abstract:
Abstract Viscoelastic waves are modeled using a 3D time-domain finite-difference scheme with three classical rheological models – Maxwell (M), Kelvin-Voigt (KV), Standard Linear Solid (SLS) – each of them with a single relaxation mechanism. Attenuation and dispersion effects are introduced in terms of the quality factor \textit{Q} for a certain angular frequency $\omega$. Initially, seismic attenuation of the 2D poststack seismic data from Brazilian pre-salt is evaluated through a frequency analysis. After that, numerical results are validated with analytical solutions based on a homogeneous model with constant seismic properties. The behavior of each rheological model are discussed based on phase, wave amplitude and spectrum. A simplified multilayered geological model is proposed considering regions of the poststack seismic data from the Brazilian pre-salt, Búzios field. Synthetic data are then generated for each rheological model considering two approaches in terms of \textit{Q} distribution: a constant \textit{Q} and a varying \textit{Q} per layer. Both waveform and spectra are extracted from seismograms and compared with selected regions of Búzios poststack data. The amplitude spectra confirmed that the shallowest post-salt package is more dissipative than deeper regions. Moreover, based on the analysis of synthetic data, KV and SLS models proved to be effective to mimic seismic wave propagation at Búzios field. Synthetic results also show that a \textit{Q} distribution per layer can yield a seismic attenuation behavior similar to the one observed within the data.Keywords:
Seismogram