Faculdade de Geofísica - FAGEOF/IG

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

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Agora exibindo 1 - 4 de 4

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CRS seismic data imaging system: a case study for basib reevaluation
(2007-09) LEITE, Lourenildo Williame Barbosa; HEILMANN, Björn Zeno; GOMES, Anderson Batista
This paper summarizes practical results of a consistent attention to the seismic processing and interpretation of some land data lines from a set of the Tacutu graben (Brazil), where was applied the fundamental steps of the WIT imaging system grounded on the data-driven CRS (Common Reflection Surface) stack.As a major result, we expect to establish a work-flow for seismic reevaluation of sedimentary basins. Founded on the recovered wave front attributes of the CRS stack, a smooth macro-velocity model was obtained via tomographic inversion. Using this macro-model, pre- and post-stack depth migration was carried out. Besides that, other CRS-stack based processing techniques were performed in parallel as residual static correction and limited-aperture migration based on estimated projected Fresnel zone. A geological interpretation was attempted on the stacked and migrated sections. From visual details of the panels, we could interpret discontinuities, thinning, a principal faulted anticline where plays of horsts, grabens and rollovers are present. Also, part of the selected line needs more detailed processing to make better evident any present structures in the subsurface.
Acesso aberto (Open Access)
Deconvolução de processo sísmico não-estacionário
(2000-03) LEITE, Lourenildo Williame Barbosa; ROCHA, Marcus Pinto da Costa da
The present paper treats the application of the Kalman-Bucy filter (KBF), organized as a deconvolution (KBDF), for the extraction of the reflectivity function from seismic data. This means that the process is described as non-stationary, and corresponds to a generalization of the Wiener-Kolmogorov theory. The mathematical description of the KBF preserves its relationship to the Wiener-Hopf filter (WHF) that deals with the counterpart stationary stochastic process. The strategy to solve the problem is structured in parts: (a) The optimization criterion; (b) The a priori knowledge; (c) The algorithm; and (d) The quality. The a priori knowledge includes the convolutional model, and establishes statistics to its components (effective source wavelet, reflectivity function, and geological and local noises). To demonstrate the versatility, applicability and limitations of the method, we performed systematic deconvolution experiments under several situations of additive noise levels and effective source wavelet. First, we demonstrate the necessity of equalizer filters, and second that the spectral coherence factor is a good measure of the quality of the process. We also justify the present study for its application in real data, as exemplified.
Acesso aberto (Open Access)
Filtros ótimos: efeitos de janelas e de tipo de fase
(2003-06) LEITE, Lourenildo Williame Barbosa; ALVES, Fábio José da Costa
The central objective under investigation in this paper is the performance of WHL deconvolution operators for the compression of the seismic source-pulse under the conditions of non-minimum phase and density of events on the trace, as is the case supported for the real data and batch deconvolution. The method of attack to the constructed problems is centered on the information content of the autocorrelation function submitted to different conditions of: (a) the truncation and taper windows; (b) the characteristics of the operator phase (if minimum or non-minimum phase); (c) the measure of quality; (d) the whitening level; (e) the noise present and equalization; (f) the balancing of the trace; (g) the physical principles of wave propagation as expressed and limited by the convolutional model. Results can only be obtained numerically, and they are shown in the form of albums with increasing difficulties, and they demonstrate how the time windows on the autocorrelation serve to diagnostic and to improve the performance of the operators. We conclude that many questions still arise when deconvolution techniques are applied to seismic reflection data from sedimentary basins, and that the Goupillaud model is convenient for simulations through its simple and complete mathematical description.
Acesso aberto (Open Access)
Treatment of geophysical data as a non-stationary process
(2003) ROCHA, Marcus Pinto da Costa da; LEITE, Lourenildo Williame Barbosa
The Kalman-Bucy method is here analized and applied to the solution of a specific filtering problem to increase the signal message/noise ratio. The method is a time domain treatment of a geophysical process classified as stochastic non-stationary. The derivation of the estimator is based on the relationship between the Kalman-Bucy and Wiener approaches for linear systems. In the present work we emphasize the criterion used, the model with apriori information, the algorithm, and the quality as related to the results. The examples are for the ideal well-log response, and the results indicate that this method can be used on a variety of geophysical data treatments, and its study clearly offers a proper insight into modeling and processing of geophysical problems.

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Navegando Faculdade de Geofísica - FAGEOF/IG por Autor "LEITE, Lourenildo Williame Barbosa"