Teses em Geofísica (Doutorado) - CPGF/IG
URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2357
O Doutorado 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 Teses em Geofísica (Doutorado) - CPGF/IG por Assunto "Amazônia brasileira"
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Item Acesso aberto (Open Access) Atenuação de múltiplas pelo método WHLP-CRS(Universidade Federal do Pará, 2003-01-28) ALVES, Fábio José da Costa; LEITE, Lourenildo Williame Barbosa; http://lattes.cnpq.br/8588738536047617In the sedimentary basins of the Amazon region, the generation and accumulation of hydrocarbons is related to the presence of diabase sills. These rocks present a great impedance contrast to the host rocks what turns to cause the generation of internal and external multiples with similar amplitudes the primary events. These multiples can predominate over the information originated at the deeper interfaces, making more difficult the processing, interpretation and imaging of the seismic section. In the present research work, we conducted de multiple attenuation in synthetic commonsource (CS) seismic sections by combining the Wiener-Hopf-Levinson for prediction (WHLP) and the common-reflection-surface-stack (CRS) methods. We denominated this new combination under the name and label of WHLP-CRS method. The deconvolution operator is calculated from the real amplitudes of the seismic section trace-by-trace, and this strategy represents efficiency in the process of multiples attenuation. Multiples identification is carried out in the zero-offset (ZO) section simulated by the CRS-stack applying the periodicity criteria between the primary and its repeated multiples. The wavefront attributes, obtained by the CRS-stack, are employed to move the shifting windows in the timespace domain, and these windows are used to calculate the WHLP-CRS operator for the multiple attenuation carried out in the CS sections. The development of the present research had several intentions as: (first) avoid the inconveniencies of the processed ZO section; (second) design and apply operators in the CS configuration; (third) extend the WHL method to curved interface; (fourth) use the good results obtained in the new CRS-stack technology whose application extends to migration, tomography, inversion and AVO.Item Acesso aberto (Open Access) Geotermia rasa em Belém(Universidade Federal do Pará, 1987-12-15) ARAÚJO, Rutênio Luiz Castro de; SOUZA, José Ricardo Santos de; http://lattes.cnpq.br/2797414407717271A detailed study of shallow geothermics was carried out at depth intervals of 0.02 to 210.0 m, in the metropolitan área of the city of Belém-Brazil. The temperature measurements were performed by using mercury and thermistor thermometers, while the thermal conductivity measurements were made on core samples obtained from boreholes, by using a needle type apparatus. The incident solar radiation flux was recorded by a Robitzech type actinography. The average geothermal gradient obtained for the metropolitan area of the city of Belém was of 0.0254 ± 0.0007 °C.m-1. The average value of the thermal conductivity of the core samples collected in this region was of 1.66 ± 0.52 W.m-1.°C-1. On the other hand the average geothermal flux observed within the studied region was of about 42.16 ± 1.14 mW.m-2. At 1.0 m depth one observes changes of the temperature values with time which can not be neglected. These changes are directly related to the incident solar radiation flux variations at the surface. The largest increment of this flux observed from one day to the other was about 30 W.m-2, which corresponded to a temperature increment of the order of 0.22 °C at 1.0 m depth. The temperature profiles obtained in this work, presented drifts in alternating directions during the one-year cycle of observations. The shallow geothermal profiles are characterized by a zone of vanishing heat flux, so called “elbow zone”, past which the temperature increases with depth. The depth of the elbow zone is mainly influenced by the heat flux generated by the incident solar radiation on the surface of the area under study. A numerical model of the thermal structure evolution in time, was developed for the 0.02 to 10.0 m depth zone. The results generated from this model of heat transfer by conduction were compared with those obtained from the field work data. One observes good agreement between the two sets of data. However the numerical adjustment representation is closer to the field data in the period of September to February. The model developed can be used for of profile drifts geothermal forecasts, as long as one knows a priori the corresponding values of the monthly averages of the soil temperatures at the surface, the regional geothermal gradient and one given geothermal profile. This work demonstrates that the incident solar radiation flux at the surface is the main source of influence on the shallow geothermal profiles. The maximum depth of such influence depends mainly on the magnitude of such flux, on the degree of protection of the surface from the direct incidence of solar radiation and the lithology of the site under study.