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2D Multi-parameter VTI Acoustic Full Waveform Inversion of Wide-aperture OBC Data from the Valhall Field
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 74th EAGE Conference and Exhibition incorporating EUROPEC 2012, Jun 2012, cp-293-00736
- ISBN: 978-90-73834-27-9
Abstract
We apply 2D VTI acoustic FWI to wide-aperture OBC data from the Valhall field. Initial models for FWI are determined by VTI reflection traveltime tomography. Mono-parameter and multi-parameter VTI FWI are applied to the hydroacoustic component for reconstruction of seismic wavespeeds and Thomsen parameters, while density and attenuation are kept at their initial values during FWI. Two types of inversions are considered: in the first one, we invert only for one velocity and we keep fixed two Thomsen parameters. In the second one, we invert for two velocities, while the extra Thomsen pa- rameter is kept fixed during FWI. As long as the two Thomsen parameters describe the long wavelength content of the subsurface, the first type of inversion succeeds in reconstructing the wavespeed with a high resolution. The second type of inversion succeeds in reconstructing the two wavespeeds, vertical or normal moveout and horizontal velocities, but with a lower resolution for the horizontal velocities. Reverse time migrations and common image gathers, which are computed in the initial and final FWI models, show that FWI models do not allow us to improve the deep part of the migrated images, where the footprint of anisotropy is shown.