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Vertical Wavespeed, Density and Attenuation Imaging by 3D Efficient Frequency-Domain FWI of Wide-Azimuth OBC Data - A North Sea Case Study
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
Summary
We present a North Sea case study of 3D efficient frequency-domain FWI for the joint reconstruction of the vertical wavespeed (v0), density and Q in the visco-acoustic VTI approximation. Frequency-domain seismic modelling is performed with sparse direct solver. Computational efficiency is achieved by sub-sampling the frequencies, hence degrading the redundancy of the wavenumber coverage in the model space. This frequency decimation questions the reliability of the frequency-domain multi-parameter FWI to manage parameter crosstalks. Using a frequency continuation, we perform a mono-parameter FWI and two (v0,density,Q) multiparameter FWIs by successive inversions of monochromatic and multi-frequency datasets. L-BFGS optimization is used to account for the Hessian. Overall the v0 models obtained with the three inversions compare well because the reconstruction of the long-to-intermediate wavelengths of the velocity is primarily tied to the need to fit the phase of the data. Moderate cross-talks between v0 and density can be removed by recombining the impedance a posteriori. The geometry of the Q reconstruction correlates well with that of v0 in the shallow sediments and well-documented low-velocity anomalies. Compared to the mono-frequency counterpart, the multi-frequency inversion removes efficiently acquisition footprint, provides more reliable estimation of density and Q, and improves time-domain data fit.
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