Navegando por Autor "LUZ, Samuel Levi Freitas da"

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Acesso aberto (Open Access)
Migração em profundidade pré-empilhamento utilizando os atributos cinemáticos do empilhamento por superfície de reflexão comum
(Universidade Federal do Pará, 2007-11-12) LUZ, Samuel Levi Freitas da; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
The Common-Reflection-Surface (CRS) stack is a new seismic processing method for simulating zero-offset (ZO) and common-offset (CO) sections. It is based on a second-order hyperbolic paraxial approximation of reflection traveltimes in the vicinity of a central ray. For ZO section simulation the central ray is a normal ray, while for CO section simulation the central ray is a finite-offset ray. In addition to the ZO section, the CRS stack method also provides estimates of wavefield kinematic attributes useful for solving interval velocity inversion, geometrical spreading calculation, Fresnel zone estimate, and also diffraction events simulation. In this work, Its proposed a new strategy to do a pre-stack depth migration by using the CRS derived wavefield kinematic attributes, so-called CRS based pre-stack depth migration (CRS-PSDM) method. The CRS-PSDM method uses the CRS results (ZO section and kinematic attributes) to construct an optimized stack traveltime surface along which the amplitudes of the multi-coverage seismic data are to be summed and the result is put in a point of the migration target zone in depth. In the same sense as in Kirchhoff type pre-stack depth migration (K-PSDM), the CRSPSDM method needs a migration velocity model. Unlike the K-PSDM method, the CRS-PSDM needs only to calculate the zero-offset traveltimes, i.e, along only ray conecting the considered point in depth to a given coincident position of source-receptor at surface. The final result is a zero-offset time-to-depth converted seismic image of reflectors from pre-stack seismic data.
Acesso aberto (Open Access)
Migração em profundidade usando a solução numérica da equação da eiconal
(Universidade Federal do Pará, 2001-06-12) LUZ, Samuel Levi Freitas da; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
In the last years we have seen an increasing interest in seismic imaging algorithms in order to obtain better informations about the earth interior. The Kirchhoff migration method is very useful for determining the position of seismic reflectors, if is known the seismic wave velocity model and the traveltimes are well determined through the earth model. The traveltime calculation is a necessary step for stacking the seismic data by means of the Kirchhoff migration operator. In this work the traveltimes are obtained by solving the eiconal equation of the ray theory. At first, the theory of Kirchhoff migration is reviewed, by considering depth migration in heterogeneous media with arbitrary curved reflectors. Secondly, the numerical solution of the eiconal equation is presented for transmited, diffracted and head waves. There offer, the depth migration algorithm is presented, must makes use of traveltimes obtained by the eiconal equation. Finally, the developed migration algorithm is applied to synthetic models, providing a very good image resolution in comparison with the conventional ray tracing migration methods, even in the presence of random or coherent (multiple reflections) noise.