Faculdade de Geofísica - FAGEOF/IG

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2544

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Acesso aberto (Open Access)
2-D ZO CRS stack by considering an acquisition line with smooth topography
(2005-03) OLIVA, Pedro Andrés Chira; CRUZ, João Carlos Ribeiro; CALLAPINO, German Garabito; HUBRAL, Peter; TYGEL, Martin
The land seismic data suffers from effects due to the near surface irregularities and the existence of topography. For obtaining a high resolution seismic image, these effects should be corrected by using seismic processing techniques, e.g. field and residual static corrections. The Common-Reflection-Surface (CRS) stack method is a new processing technique to simulate zero-offset (ZO) seismic sections from multi-coverage seismic data. It is based on a second-order hyperbolic paraxial traveltime approximation referred to a central normal ray. By considering a planar measurement surface, the CRS stacking operator is defined by means of three parameters, namely the emergence angle of the normal ray, the curvature of the normal incidence point (NIP) wave, and the curvature of the normal (N) wave. In this paper the 2-D ZO CRS stack method is modified in order to consider effects due to the smooth topography. By means of this new CRS formalism, we obtain a high resolution ZO seismic section, without applying static corrections. As by-products the 2-D ZO CRS stack method we estimate at each point of the ZO seismic section the three relevant parameters associated to the CRS stack process.
Acesso aberto (Open Access)
Migração (2,5-D) com amplitudes verdadeiras em meios com gradiente constante de velocidade
(2002-04) CASTILLO, Luis Antonio Lopes; CRUZ, João Carlos Ribeiro; CALLAPINO, German Garabito; URBAN, Jaime Antonio
The true-amplitude seismic migration, in time or depth, provides a measurement of the reflection coefficients of primary reflection events. These are constituted by P-P reflection of longitudinal waves at smooth reflectors. One of the mostly used method is the Kirchhoff migration, by which the seismic image is obtained by stacking the seismic wavefield using a diffraction surface, also called Huygens Surface. In order to obtain true amplitude migration, i.e. the removal of geometrical spreading, it is introduced a weight function in the migration operator. The weight function is determined by the asymptotic solution of the migration integral at stationary points. The ray tracing is a fundamental tool for determining the weight function and the traveltime, that increases the computational costs of the migration process in heterogeneous media. In this work it is presented a true-amplitude migration algorithm tailored for two-and-one-half dimensional model, i.e. when the velocity field varies only with two coordinates of the three dimensional Cartesian system. It is emphasized the special case of constant gradient velocity. As a second topic, this work concerns about recovering seismic attributes from pre-stack seismic data by applying the double diffraction stack inversion. The estimated parameter is the incidence angle at the reflector. Combining the estimated reflection coefficient and the incidence angle, it is possible to perform the so-called Amplitude versus Angle Analysis (AVA) on the interested reflector.

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Navegando Faculdade de Geofísica - FAGEOF/IG por Autor "CRUZ, João Carlos Ribeiro"