Dissertações em Geofísica (Mestrado) - CPGF/IG
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4993
O Mestrado Acadêmico pertente a o Programa de Pós-Graduação em Geofísica (CPGF) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).
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Navegando Dissertações em Geofísica (Mestrado) - CPGF/IG por Linha de Pesquisa "SÍSMICA APLICADA À EXPLORAÇÃO E CARACTERIZAÇÃO DE RESERVATÓRIOS"
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Item Acesso aberto (Open Access) Caracterização de hidratos de gás a partir de dados geofísicos da região da Bacia Tumbes-Progresso (Peru)(Universidade Federal do Pará, 2014-02-25) TEJADA SOTO, Zoraida Roxana; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660Gas hydrate is known as a potential source of hydrocarbon energy. However, the detection of exploitation of this resource is still inexpressive. This is due to two factors: the diculty of detecting pro table areas of gas hydrates and due to the high risk involved in exploration. In this study, an analysis is presented to detect possible areas of gas hydrate ocurrence in a region of Tumbes-Progresso Basin, using geophysical data: magnetic, gravity, seismic and borehole (well data). It presents three approaches to demarcate the possible zones of hydrate: First, magnetic and gravity anomalies analyzed with respect to the geology and the study area that was chosen. It was subsequently made a seismic imaging the region of interest and the gas hydrates has been identied based on the presence identication of BSR (Bottom Simulating Refletor), This reflector correspond to a limit between gas hydrate and free gas zone. BSR potential was applied the AVO analysis (Amplitude Versus Oset). Finally, in the third approach, well data are evaluated, calculating the porosity and saturation of the rock in the gas hydrate stability zone. According to the analysis presented, It was veried the occurrence of gas hydrate in the study area.Item Acesso aberto (Open Access) Determinação de modelo de velocidades para a migração em profundidade de dados sísmicos 2-D da Bacia do Jequitinhonha(Universidade Federal do Pará, 2013-12-13) OLIVEIRA, Lelis Araújo de; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660The migration time domain is quite employed by the oil industry for its low computational requirements, however in areas where the velocity field has great lateral variation as result of the environment is complex subsurface structures, such as faults, salt domes, etc.., this technique becomes inefficient in the characterization of geological features. Although the computational cost is high, migration in the field of depth, proves more effective than time migration to deal with these structures. However for a section in depth there is a need for a velocity model in depth with some degree of precision. In this paper, two methodologies for time to depth conversion for obtaining the velocity model in depth to two real 2-D marine lines Jequitinhonha Basin are applied. The accuracy of the models generated were analyzed from migrated seismic sections obtained by means of these velocityes.Item Acesso aberto (Open Access) Implementações alternativas de tomografia do tempo de trânsito utilizando a equação da onda(Universidade Federal do Pará, 2014-04-23) CARDOSO FILHO, Josafat Lopes; COSTA, Jessé Carvalho; http://lattes.cnpq.br/7294174204296739Wave equation tomography is a robust methodology for velocity analysis when strong velocity variations occurs. This approach has been successfully applied for reservoir monitoring and characterization using crosswell data. The choice of the objective functions, preconditioners and regularizing functionals controls the robustness, eciency and the quality of the velocity reconstruction. This dissertation investigates each of these design parameters and its consequences for the performance of the wave equation tomography using synthetic crosswell data generated from smoothly and strongly heterogeneous velocity models. Two proposals for the objective functions are used in this work; the first is sensitive to phase dierences and the other is proposal to be less sensitive to the source pulse. Both do not require velocity picking performed well in the numerical experiments. A preconditioning strategy adapted from the imaging processing literature produced a noticiable improvement the convergence rate of the algorithm by eliminating artifacts caused by limited aperture, random noise and artifacts produced by sources and receivers. A regularizing functional penalizing deviations from velocity information available near the wells additionally contributes to recover a velocity tomogram with higher resolution and consistent with the synthetic model. Wave equation tomography is a robust methodology for velocity analysis when strong velocity variations occurs.Item 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/1610827269025210Diffracted 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.Item Acesso aberto (Open Access) Utilização de múltiplas de superfície livre no imageamento sísmico(Universidade Federal do Pará, 2014-08-29) SANTOS, Isis Tourinho dos; GOMES, Ellen de Nazaré Souza; http://lattes.cnpq.br/1134403454849660Conventional seismic processing treats multiple reflections as noise, removing them from the imaging process. However, multiple reflections have different propagation wave paths from primary reflections and thus can be used to illuminate areas not illuminated by primary reflections. Consequently, migration of multiples can arise as possibility of imaging of complex structures in the subsurface. In this context, this work shows a abstract about the most relevant approaches from the imaging using multiples. In addition, this work shows results with free-surface multiples used in seismic imaging by reverse time migration.