Broadband least-squares wave-equation migration

Abstract

We introduce an effective iterative Least-Squares Wave-Equation Migration (LS-WEM) solution for broadband imaging. Least-Squares Migration (LSM) solutions are designed to produce images of the subsurface corrected for wavefield distortions caused by acquisition and propagation effects. They implicitly solve for the earth reflectivity by means of data residual reduction in an iterative fashion, which usually demands intensive computation. The LS-WEM is implemented using a visco-acoustic anisotropic one-way wave-equation wavefield propagator that is able to fully utilize both the broader seismic bandwidth and the high-resolution velocity information from Full Waveform Inversion (FWI). Our implementation combines the one-way extrapolator with fast linear inversion solvers into an efficient migration inversion system. Application to the 2D Sigsbee2b synthetic model improves the sub-salt illumination by balancing the image amplitudes and reducing the effects of the shadow zones, enhances temporal resolution by broadening the frequency spectrum, balances the wavenumber content and improves images of faults and dipping salt flanks. In addition, LS-WEM converges rapidly to the true solution, reducing the data residuals by 90% in only four iterations. Application to real 3D datasets from the Gulf of Mexico and the North Sea demonstrates high-resolution imaging with reduced acquisition footprint effects, improved spatial frequency content, and better structural imaging at all depths.

High-resolution Seismic imaging in the Santos Basin, Brazil and its impact on Salt Mechanics

“…Current imaging technologies (RTM, Kirchhoff Migration) provide a level of seismic resolution that suits the industry's expectation for capturing hydrocarbon reservoirs and outlining prospects. To obtain further resolution an iterative Least-squares migration approach was utilized to correct for acquisition effects, limited aperture and variable illumination (Korsmo & Valenciano 2018, Lu et al 2017. In this particular approach, the difference between the observed data and the synthetic data, modeled using a migrated stack and a velocity model, is minimized in a Least-squares sense to update the image.…”

One‐way waveform inversion: Real marine data application

“…Therefore, within the scale separation approach, the one-way wave equation is better appropriated to establish a strict separation in an arbitrary model. The adaptation of the one-way wave equation in the context of the reflection waves modelling or inversion has been proposed in different works (see Dong et al, 2018;Hua-Min et al, 2014;Lu et al, 2017;P. Shen & Calandra, 2005) This paper describes the extension of the OWI method in anisotropic media using a high-order Fourier finite difference one-way propagator (Hua et al, 2013).…”