Migração FFD 3D em profundidade usando aproximação de Padé complexa
Fourier finite-difference (FFD) migration implementations use splitting techniques to accelerate performace and save computational cost. However, such techniques introduce numerical anisotropy which leads to mispositioning of dipping reflectors along directions not used for splitting the migratio...
| Autor principal: | CAMPOS, Itamara do Socorro da Silveira |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Pará
2014
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| Assuntos: | |
| Acesso em linha: |
http://repositorio.ufpa.br/jspui/handle/2011/5981 |
| Resumo: |
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Fourier finite-difference (FFD) migration implementations use splitting techniques to accelerate
performace and save computational cost. However, such techniques introduce numerical
anisotropy which leads to mispositioning of dipping reflectors along directions not used for
splitting the migration operator. We implement 3D FFD continuation migration without
splitting in the frequency-space domain using the complex Padé approximation and implicit
finite differences. This approach eliminates numerical anisotropy at the expense of a computationally
more intensive solution of a large banded linear system. Numerical experiments in
homogeneous and heterogeneous models show that splitting techniques produce noticiable positioning
erros for models with strong lateral velocity variation. We compare the performance
of the iterative stabilized biconjugate gradient (BICGSTAB) and the multifrontal massively
parallel direct solver (MUMPS). It turns out that the use of the complex Padé approximation
provides an effective preconditioner for the BICGSTAB, reducing the number of iterations
relative to the real Padé expansion. The iterative BICGSTAB method is more efficient than
the direct MUMPS method when solving for a single term in the Padé expansion. For wide
angle approximations more terms are required to represent the migration operator, in this
case direct methods are required. The algorithm is validated and the properties evaluated
computing the migration impulse response in the SEG/EAGE salt model. |