Alejandro Valenciano

Imaging of Primaries And Multiples Using a Dual-sensor Towed Streamer

Summary Multiple reflections are commonly treated as noise in oneway imaging methods. High effort is put into research and data processing worldwide in an effort to suppress this source of noise. In a new perspective multiples are treated as valuable imaging information. Based on dual-sensor towed streamer measurement, we decompose the wavefield and apply up/down imaging of primary and multiple reflections. This approach is tested using shallow water synthetic data and finally applied on dual-sensor field data.

Wave equation migration with attenuation and anisotropy compensation

We introduce a new viscoacoustic Wave Equation Migration (WEM) for media with attenuation. Our solution is based on a Fourier Finite-Difference (FFD) scheme for migration by wavefield continuation. Similarly to the acoustic solution, the viscoacoustic migration consists of three terms: a phase-shift extrapolation, a thin-lens correction, and a finite-differences operation. The viscoacoustic migration is also extended to account for anisotropy (VTI and TTI). The anisotropic effects are incorporated in the migration by using odd and even rational function terms in the finite differences solution. The dispersion relation, in presence of attenuation, includes both real and imaginary terms. While the real part controls the kinematics of the image, the imaginary part recovers the high vertical wave numbers in the seismic image; therefore improving resolution and amplitude balance. The implementation is stable, efficient, and very flexible. In absence of attenuation or anisotropy, the solution reduces to the familiar isotropic acoustic case. Results from synthetic example and two dual sensor field surveys from the North Sea and the Gulf of Mexico demonstrate the importance of incorporating the attenuation effects in isotropic and anisotropic migration algorithms.

Implicit Wave-equation Migration In TTI Media Using High Order Operators

This paper discusses high order implicit operators for migration by wavefield continuation in media with tilted transverse isotropy (TTI). The operators are built using Pade’s rational series expansion in the wave number domain, which translates to implicit finite-differences schemes in the space domain. They can be part of pure implicit finite-differences or mixed domain migration algorithms, e.g., Fourier finite-differences (FFD). Unlike the isotropic case, the TTI Pade’s expansion is formed by a combination of odd and even order polynomials. A third order approximation to the TTI dispersion relation is shown to be both accurate and efficient. Its numerical implementation requires a pentadiagonal solver instead of the conventional tridiagonal solver used with second and fourth order schemes.