Visco-Elastic Full-Waveform Inversion and Imaging Using Ocean-Bottom Node Data

Abstract

Summary Full-waveform inversion (FWI) has demonstrated tremendous potential to provide high-resolution models of the subsurface in different geological settings. However, in complex environments such as salt and subsalt, relying on acoustic approximations in FWI limits the accuracy of Earth models derived from modern field data, and may require complex workflows to mitigate the challenges associated with large elastic parameter variations. Recent case studies highlight this issue and suggest that more accurate models can be produced by elastic FWI using simpler workflows in these areas. In addition to elasticity, wave propagation in the subsurface undergoes anelastic (viscous) effects, especially through absorption in gas-charged layers. Although anelastic effects are known to be significant in many visco-acoustic case studies, few examples consider both elastic and anelastic effects in FWI. In this paper, we present a visco-elastic FWI to invert for P-wave velocity and associated viscosity. We demonstrate our approach using ocean-bottom node data from the Central North Sea in a complex area associated with strong velocity contrasts and shallow absorption anomalies. Results in this area demonstrate that visco-elastic FWI can provide high-resolution viscosity and velocity models, and an FWI Image with improved event continuity, resolution, and signal-to-noise ratio compared to visco-acoustic FWI.