Navegando por Assunto "Sistemas de imageamento em sismologia"

Agora exibindo 1 - 5 de 5

Acesso aberto (Open Access)
Avaliação de algoritmos para conversão de modelos de velocidade de tempo para profundidade
(Universidade Federal do Pará, 2013-03-26) VALENTE, Leandro da Silva Sadala; COSTA, Jessé Carvalho; http://lattes.cnpq.br/7294174204296739
Even today, time migration is the imaging process substantially employed in the oil industry. Such popularity is due to its high degree of efficiency and robustness, and its ability to focus reflectors in various geological environments. However, in areas of high geological complexity, time migration fails so that depth migration and a depth velocity field are indispensable. This field is usually obtained through tomographic iterative processes starting from an initial velocity field. The conversion of velocity fields from time to depth is a quick way of obtaining a geologically more consistent initial velocity field for such processes. Some algorithms for time-to-depth conversion based on newly developed image-ray tracing are reviewed and an alternative algorithm based on propagation of the image-wavefront is proposed. The algorithms are applied to two-dimensional synthetic data and evaluated according to their efficiency and accuracy, highlighting their advantages, disadvantages and limitations in obtaining depth velocity fields.
Acesso aberto (Open Access)
Joining diffraction filter and residual diffraction moveout to constructo a velocity model in the depth and time domains: application to a Viking Graben data set
(Universidade Federal do Pará, 2014-08-14) COLLAZOS GONZALEZ, Jaime Andres; FIGUEIREDO, José Jadsom Sampaio de; http://lattes.cnpq.br/1610827269025210
Diffracted seismic waves are generated by unsmooth structures in the subsurface with a size on the order of seismic wavelengths. Because the incident wave field can be significantly affected by these discontinuities, many important properties of the seismic events can be used to improve the velocity model building. In this thesis, we propose a practical approach to construct velocity models in the time and depth domains using diffractions. This methodology applies the plane wave destruction (PWD) filter jointly with the residual diffraction moveout (RDM) method to construct velocity models in time and depth domains. Our method does not depend on any requirements except for identifiable diffractions filtered from reflection events and an arbitrary initial velocity model as input. The post-stack migrated images (in the time and depth domains) are compared with the mi- grated images derived from conventional seismic processing steps. In both cases, we used post-stack Kirchhoff Migration. Beyond the to the need to identify and select the diffraction events in the post-stack migrated sections in the depth domain, the method has a very low computational cost of processing time. To reach an acceptable velocity model was less compared with conventional processing. The applicability of our methodology was verified using a real Viking Graben seismic dataset.
Acesso aberto (Open Access)
NIP-tomografia usando método CRS e dados sísmicos marinhos
(Universidade Federal do Pará, 2013) AFONSO, João Batista Rodrigues; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work consisted on the application of techniques for processing, inversion and imaging of the Marmousoft synthetic data, and of the Jequitinhonha real data obtained on the eastern Atlantic continental shelf of the State of Bahia. The convencional NMO and CRS stack methods, and NIP-tomographic inversion were applied to the mentioned data. The NMO stack served to produce RMS and interval velocity distribution maps on the semblance domain. The CRS stack of both data we used for picking of re ection events to obtain the wave eld parameters that served to constrain the model as input for the NIP-tomographic inversion. The inversion characterizes as resulting in a smooth velocity model. Kirchhoff depth migration was used for verifying the obtained velocity models. We critically analyzed the applied techniques, and compared the CRS and the NMO stacks. The evolution of the visual quality of the obtained CRS and NMO sections were analyzed as measured by event continuity trace-by-trace and the signal/noise ratio. The di erences and improvements on the velocity model obtained by NIP-tomographic were also analyzed. The Kirchhoff prestack depth migration was applied aiming at geological interpretations, and to point out for better conditions of processing and imaging.
Acesso aberto (Open Access)
Processamento e imageamento sísmico usando o CRS
(Universidade Federal do Pará, 2014-02-04) PENA, Felipe Astur Valdes; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work aimed at the application of the common-reflection-surface stack methods (CRSconventional), of the CRS-partial method, and of the NIP-tomography inversion method, to generate seismic data images for the interpretation related to geologically complex areas. The constructed model, and named Duveneck-Astur, was used to simulate a geological ambient formed by layers limited by smooth surface reflector interfaces, but that the paraxial ray theory was attended, differently from other synthetic common models where the presence of geological faults, and of high horizontal and vertical gradients exist, like in the Marmousi and the Sigsbee models, among others. To analyze comparatively the resolution of the applied methods, two tests were performed with the synthetic data. One test consisted of decimated data with random muting of traces in the CMP families, and another test with addition of noise. It was computer analyzed the behavior of the different stack methods to obtain a depth velocity distribution by NIP-tomography inversion, that uses the kinematic wavefield attribute constraints to estimate a velocity model consistent with the data. NIP-tomography results were mutually compared, and also to the velocity model obtained from semblance velocity analysis. The velocity distribution were used in the PSPI migration to verify consistency in the results.
Acesso aberto (Open Access)
Processamento, inversão e imageamento de dados sísmicos marinhos
(Universidade Federal do Pará, 2012) SILVA, Douglas Augusto Barbosa da; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617
This work was there on the study and processing, inversion and imaging in time and in depthof Marmousi seismic data, and of the real Jequitinhonha obtained in the Bahia state Brazilian atlantic oriental continental platform. Were applied the NMO and CRS stack methods andthe niptomographic inversion technique of the cinematic attributes of the wave field. Withthe NMO stack was obtained a velocity distribution map throughout the velocity analysis onthe semblance coherence map and straight afterward the stacked and migrated sections in thedomain of the time and depth. The stack method of the common reflection surface (CRS)was applied with the crsstack-511 program to obtain the stacked and migrated sections inthe time domain and to extract the field wave parameters throughout the coherence analysis and of the redundancy obtained on the seismic data of multi-device. The niptomographicinversion phenomena of reflection took place throughout the aplication of the niptomo program,which is an implementation of the inversion method of the cinematic attributes ofthe NIP hypothetic wave, extracted straight from the CRS stack, to obtain an smoothedvelocity model, and subsequently, a migrated section in depth. The migrated sections areof the Kirchhoff kind. The techniques used follow a pre-determined and realized flowchartfollowing a file “makefile”, that works as an stage organizer. These stages were realized in theLinux desktop and in the Seismic Uni*x system of the Center for Wave Phenomena (CWP)of Colorado School of Mines. The results of the three techniques were compared with theaim of illustrating the evolution of the visual quality of the reluctant sections throughout theevents continuity trace-by-trace and the signal/noise relation, to analyze differences and improvementsin the migrated sections expecting a better geologic interpretation and organizebetter terms of processing and imaging, trying to aid possible well succeed drillings.