3D Acoustic-Elastic Coupled Full Waveform Inversion
of Marine VSP Data from Fenja Field, Norway
3D Model Used by SPECFEM3D
We apply the state-of-the-art three-dimensional (3D) acoustic-elastic coupled seismic modeling, migration, and inversion techniques to deviated Rig Source Vertical Seismic Profile (RSVSP) data from the Fenja Field in Norway, to advance our understanding of subsurface structure. We first build the 3D initial S-wave speed (VS) and density (ρ) models from the legacy 3D P-wave speed (VP ) models based on the estimated 1D VP /VS ratio from sonic logs. Then the three-component (3C) synthetic seismic data are generated using a 3D acoustic-elastic coupled forward modeling method, which can account for the elastic effects like P-to-S conversions on the solid seabed. Next, we compared the synthetic data to the observed data to evaluate the accuracy of the current velocity model. Afterward, we apply the 3D acoustic-elastic coupled full-waveform inversion (FWI) methods on the deviated 3C RVSP data. Subsequently, 3D acoustic-elastic coupled reverse-time migration (RTM) was used to image the subsurface structure. Finally, the 3D RTM images are compared with the legacy 2D depth-domain migration images provided by Schlumberger and the 3D migration images from the surface seismic data.