Salt Reconstruction in Full Waveform Inversion with a Parametric Level-Set Method

TL;DR

This paper introduces a parametric level-set method for seismic full-waveform inversion to accurately reconstruct salt-body geometries, using a dynamic boundary width adjustment for improved convergence and stability.

Contribution

It presents a novel parametric level-set approach with adaptive boundary width for efficient salt geometry reconstruction in seismic inversion.

Findings

Method is stable against noise.

Adaptive boundary width improves convergence.

Effective in joint inversion of velocity and salt geometry.

Abstract

Seismic full-waveform inversion tries to estimate subsurface medium parameters from seismic data. Areas with subsurface salt bodies are of particular interest because they often have hydrocarbon reservoirs on their sides or underneath. Accurate reconstruction of their geometry is a challenge for current techniques. This paper presents a parametric level-set method for the reconstruction of salt-bodies in seismic full-waveform inversion. We split the subsurface model in two parts: a background velocity model and the salt body with known velocity but undetermined shape. The salt geometry is represented by a level-set function that evolves during the inversion. We choose radial basis functions to represent the level-set function, leading to an optimization problem with a modest number of parameters. A common problem with level-set methods is to fine tune the width of the level-set boundary for optimal sensitivity. We propose a robust algorithm that dynamically adapts the width of the level-set boundary to ensure faster convergence. Tests on a suite of idealized salt geometries show that the proposed method is stable against a modest amount of noise. We also extend the method to joint inversion of both the background velocity model and the salt-geometry.