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10th International Congress of the Brazilian Geophysical Society
- Conference date: 19 Nov 2007 - 23 Nov 2007
- Location: Rio de Janeiro, Brazil
- Published: 19 November 2007
81 - 100 of 484 results
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Pre-drill pore pressure study for a high temperature well in the Gulf of Mexico using reprocessed fit-for-purpose seismic velocities
Predrill formation pressure predictions are essential forwell planning and for optimizing drilling decisions. In this case study, a predrill model for an exploration well in the Gulf of Mexico is described. The interval velocities obtained from the available stacking velocities were reprocessed based on a method that maximizes the stacking power of spatially continuous events in prestack gathers. The reprocessing resulted in a fit-for-purpose velocity model appropriate for pore pressure prediction. Calibration of the velocity-to-pore pressure transform was performed with existing well log data from offset wells. Because of large-scale major faulting and possible pressure compartments, only offset wells in geologically comparable locations, e.g., same major fault block, were
used for transform calibration. Also the influence of overpressure on flow focusing (centroid-effect) was estimated for three sand horizons in the area.
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3D opacity in volume rendering of seismic data
It is presented a technique called 3D opacity for the volume rendering of seismic data. The technique employs a transfer function composed of three attributes. It not only improves the image quality, but also takes advantage of the Graphics Processor Unit and thus speeds up the rendering process. Two applications are considered in order to validate the proposed technique.
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Sondagens TDEM no Sítio Controlado de Geofísica Rasa do IAG-USP: Resultados Preliminares
Authors Thiago Gomes dos Santos and Jorge Luís PorsaniIn this Work are presented preliminary results of electromagnetic soundings in the time-domain - TDEM acquired in the area where the Controlled Site of Shallow Geophysics of the IAG/USP is installed. The objective is to map the geoelectrical stratigraphy of the sediments of the sedimentary basin of São Paulo with emphasis in the studies of groundwater. Although preliminary, the results of TDEM soundings are satisfactory and show a good agreement with the stratigraphy of the sedimentary basin of São Paulo. Other soundings will be acquired aiming to obtain the geoelectrical stratigraphy of some places inside the campus of USP. With the resulted futures of this research, one expects to show the applicabilities of TDEM method in the urban environment emphasizing the groundwater studies in sedimentary basins.
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Interpretación volumétrica de ambientes sedimentarios en al Campo Socororo - Venezuela
More LessUtilizando datos sísmicos 3D experimentales del Campo Socororo, se pretende determinar si es posible la visualización de paleo-ambientes sedimentarios utilizando técnicas de opacidad y transparencia, en conjunto con el software Earthcube de Landmark Graphics, donado a través del Grant Program al Laboratorio de Integración de datos sísmicos y geológicos (Lisg) en la Universidad Estadual Paulista en Rio Claro – São Paulo-Brasil. El objetivo de conocer los paleoambientes, es determinar indirectamente la distribución de cuerpos de arena con capacidad de almacenar hidrocarburo. El estudio se concentra sobre los niveles tradicionalmente productores como son las formaciones Oficina y Merecure, en el Área Mayor Socororo. Con el conocimiento de la distribución espacial de las áreas potencialmente productoras será disminuido de una forma eficiente el riesgo exploratorio.
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Detecting of unstructured traps using the Prony technology
Authors Georgy Mitrofanov and Viatcheslav PriimenkoWe discuss some current results concerned to the processing and interpretation of surface seismic data using the Prony filtration method. It is the new method in the characterization of oil/gas fields. In particular the Prony filtration method can be applied to detecting of fracture zones and zones with high permeability, which can be connected with fluids reservoirs and traps of unstructured forms. Possibilities of this approach are demonstrated on real seismic data and results of monitor wells, drilled using the information obtained by the Prony method only.
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Redes neurais artificiais para mapeamento do potencial mineral de Cu-Au na Província Mineral de Carajás, norte do Brasil
Authors Emilson Pereira Leite and Carlos Roberto de Souza FilhoThis work presents an application of a Radial Basis Function Neural Network (RBFNN) and a Probabilistic Neural Network (PNN) to map the potential for Cu-Au mineralizations in the Carajás Mineral Province, northern Brazil. Geophysical gamma-spectrometric and magnetic data and proximity to faults/lithological contacts values were used as evidential maps to derive input feature vectors. A set of feature vectors representing known mineralized locations was used as a training data set. The networks were created based on the training data set and the whole data set was classified using these networks. Ternary maps showing high, moderate and low favorability sectors were generated for the study area. Results from the RBFNN method shows that 10% of the study area has a great potential to contain some type of Cu-Au mineralization, whereas the high favorability area mapped by the PNN method represents 15,3% of the study area. Although the RBFNN method was more efficient in narrowing the search area for Cu-Au
mineralizations, the classification values obtained from the PNN method showed a well defined threshold that delimitates non-favorable areas.
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Análise exploratória integrada da porção noroeste da Bacia do Espírito Santo Mar
Baseado no sucesso exploratório das descobertas dos campos de Peroá e Cangoá, o presente estudo visa a caracterização do potencial petrolífero da região centro-oeste da Bacia do Espírito Santo Mar. O objetivo foi alcançado utilizando-se a interpretação de dados sísmicos integrados com mapas de atributos sísmicos, técnicas de balanceamento de seção geológica e modelagem do sistema petrolífero. Verificou-se a presença de um sistema compressivo formado provavelmente pelo levantamento dos Abrolhos, configurando armadilhas no Cretáceo, as quais seriam capazes de conter hidrocarbonetos. Como resultado da análise dos sucessos e insucessos dos poços perfurados na região, interpretou-se que o sucesso exploratório está associado à presença de armadilhas estruturais em associação com fácies favoráveis à ocorrência de hidrocarbonetos. Os mapas de atributos sísmicos integrados com informações de poços permitiram a correlação das anomalias de amplitude com as características das rochas.
O balanceamento e a retrodeformação da seção geológica indicaram que a rocha geradora começou a gerar hidrocarbonetos a partir de uma espessura de soterramento superior a 4.000 metros, espessura esta atingida no Oligoceno com a associação de sedimentação e encurtamento da seção de aproximadamente 19 km nesta época. O encurtamento total da seção atingiu 29,48 km, ou 26,2%. Finalmente, com a modelagem do sistema petrolífero concluiu-se que nos atuais horizontes portadores de hidrocarbonetos (Oligoceno e Eoceno Superior), o volume de reservas na área estudada poderia ser dobrado, em relação ao volume de gás contido nos campos de Peroá e Cangoá, alcançando entre os dois níveis estratigráficos volumes de até 33,6 bilhões de metros cúbicos de gás. Por sua vez, para outros horizontes estratigráficos foram calculados volumes adicionais de 12,7 bilhões de metros cúbicos de gás no Cretáceo Superior e 35,5 bilhões de metros cúbicos de gás no Albiano-Cenomaniano.
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Geophysical and geological evidence of Precambrian evaporites within western São Francisco basin – A working hypothesis for gas and oil exploration to unveil an Earth´s secret of central Brazil
Authors E.M. Meister, M.C. Lobianco and J.M. TravassosGeological and geophysical evidence is presented for the highly probable local presence of evaporites within the Precambrian São Francisco basin of Brazil. This working hypothesis has obvious implications both for the exploration of gas and oil, and for more general scientific and macroeconomic questions.
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Application of 3D Reverse Time Migration
Authors P.A. Farmer and I.F. JonesFollowing completion of model building, amplitude preserving 3D depth migration is usually performed using a Kirchhoff scheme for modest structural problems with steep dips. For structures where multi-valued ray-paths exist (e.g. complex salt bodies), we generally use a oneway Wavefield Extrapolation (WE) algorithm instead. However, more recently, full two-way solutions of the wave equation, such as Reverse Time Migration (RTM) have become commercially available:- these are suited for highly complex environments, where both steep dips and multi-pathing are an issue. Standard shot-based one-way WE preSDM techniques image the subsurface by extrapolating the source and receiver wave-fields for each shot. The imaging condition is invoked by cross correlating these two wave-fields at each depth level, and then summing the contributions from all shots in the aperture to form the image. One of the assumptions made in using this technique is that the wave-fields travel along the direction of extrapolation only
in one direction: downwards for the source wave-field, and upwards for the receiver or scattered wave-field. In practice, each of these wave-fields will generally travel both up and down when the velocity model is complex, when turning (diving) raypaths are involved, or when multiples are being generated. In addition, approximations in the extrapolation techniques usually limit the dips present in the final image to less than seventy degrees. Steeper dips, and turning rays are usually imaged using Kirchhoff techniques, but these fail to deliver acceptable images once we have a multi-pathing problem. One technique which can address all these issues is migration using the two-way wave equation. Here we have used an RTM algorithm to achieve this. RTM properly propagatesthe wave-field through velocity structures of arbitrary complexity, correctly imaging dips greater than 90 degrees. It even has the potential to image with internal multiples when the boundaries responsible for the multiple are present in the model. We will show examples of RTM from the North Sea andthe Gulf of Mexico to demonstrate the the potential benefit of migrating with the full acoustic two-way wave equation
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Neo-morfotectônica e diapirismo de lama na região de Cartagena, Colômbia
More LessExpõem-se as feições morfo-estruturais na sísmica e no campo, que revelam atividade tectônica recente e atual na região costeira norte da Colômbia. O diapirismo de lama e os recifes de coral quaternários soerguidos até 200 msnm são as mais chamativas
evidências. A partir de informações geofísicas geradas nos últimos 25 anos e indicadores cinemáticos coletados recentemente, discute-se sobre o arcabouço estrutural que relaciona os domos com o tectonismo local e regional.
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Caracterização geofísica da estrutura de Piratiniga - SP (Brasil)
More LessThe Piratininga Structure, located within coordinates 22°30'S and 49°10'W, is a possible meteorite impact crater of complex nature and Cretaceous age. The structure is in advanced stage of erosion, show 12 km in diameter and topographical gradients of up to 130 m between the rim and its center. The available geophysical data for this structure comprise airborne magnetics and seismic profile data, which were processed and interpreted together with the SRTM-derived (Shuttle Radar Topographic Mission) digital elevation model (DEM). The results allowed the recognition of the structure in subsurface and unraveled geophysical features that are akin to those observed in proven impact craters worldwide. Among the features revealed by the magnetic products there is a peak of high intensity located in the center of the structure, enclosed by magnetic anomalies with lower values. In the seismic profile, the following features were distinguished: (i) distinct normal faults with fault plane plunging to the interior of the structure e forming terraces; (ii) interruption of key stratigraphic layers; and (iii) verticalization of the sedimentary bedding around the center of the structure, possibly as a result of central uplift. The structure of Piratininga, however, cannot be considered an impact crater based only in subsurface structures. This requires finding typical shock features such as impact breccias, shatter cones, planar deformation features (PDFs) in quartz and feldspars, etc. Quartz grains derived from samples collected in the center of the structure were investigated in this work and although planar features have been identified, will be still necessary to demonstrate its origin by shock (e.g., evidence of shock melts along these planes).
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Fault identification using competitive learning
Authors Marcos Machado and Marcelo GattassManual fault mapping from 3D seismic data is a timeconsuming task. A plethora of seismic attributes have been proposed to enhance the discontinuity measures associated with the faults. However, some features in the attribute data make extraction of the fault surfaces as separate objects difficult. This paper proposes the use of competitive learning algorithms to tackle this problem and analyzes two different approaches. In the first approach, the Growing Neural Gas algorithm is used to transform the fault attribute volume in a graph, reducing drastically the number of samples to be considered in a surface modeling stage. The graph so obtained is then submitted to a pruning strategy in order to identify the main fault surfaces. In the second approach, the Neural Mesh algorithm is used to generate a fault surface triangulation.
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Aeromagnetometria e Deconvolução De Euler Apilcada à Interpretação Estrutural Do Sistema De Cisalhamento Porangatu, Brasil Central
High resolution aeromagnetic airborne survey is used to determinate the tectonic framework from the Porangatu region, NW Goiás. We recognized different crustal blocks and large lineaments that are interpreted as a system of strike slip shear zones. Euler deconvolution method is a potencial tool to define the geometry of these structures in deep.
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Algumas Reflexões sobre a tecnologia da exploração de petróleo abaixo do sal – exemplo da Bacia de Santos
More LessÉ amplamente conhecido que as características físicas apresentadas por níveis evaporíticos - incluindo os domos de sal - nas bacias petrolíferas, são um complicador natural no processo exploratório. Desde os primeiros fracassos, na década de 80, quando os exploracionistas de petróleo procuravam plays adjacentes às camada de sal com base unicamente em dados sísmicos bidimensionais, estão sendo desenvolvidas novas tecnologias tanto na área de processamento do dado sísmico quanto na área de interpretação. Este artigo, além de apresentar a história que conduz ao sucesso no play exploratório subsal, apresenta um exercício de modelagem em duas dimensões do sistema petrolífero abaixo do sal na Bacia de Santos. Desde os primórdios do sucesso exploratório relacionado à descoberta de petróleo no Campo de Cascade, nos Estados Unidos, localizado em águas ultraprofundas, o risco exploratorio neste tipo de play tem diminuído de 64% para 40%, utilizando-se técnicas de migração em profundidade pré e pós-stack. A exploração de acumulações situadas abaixo do sal envolve alguns métodos tradicionais, entre eles a interpretação do dado sísmico em tempo, com o objetivo de controlar o modelo de velocidades utilizado no processo de migração em profundidade pré e pós- empilhamento da seção sísmica (pre and post- stack depth migration). Como resultado, aplicando um processo exploratório integrado com todas as fases do tratamento do dado (processamento, interpretação e modelagem do sistema petrolífero), especificamente orientado para a exploração associada com a presença de sal, o risco exploratório pode diminuir para níveis inferiores a 40%. Finalmente, deve-se esclarecer que os resultados obtidos na modelagem do sistema petrolífero destes níveis subsal são meramente indicativos das áreas com maior probabilidade de conter hidrocarbonetos, sendo que estes níveis não têm reservas reportadas que sirvam de calibração para nossos modelos.
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Deconvolução iterativa tipo Wiener-Levinson
Authors Paulo E. M. de Melo and Milton J. PorsaniThe importance of the seismic resolution, and of the quality of the seismic images to the industry of petroleum, has motivated the development of new filtering techniques for processing of the seismic reflection data. In this paper we present a new filtering method to improve the resolution of the seismic sections. Unlike the conventional Wiener-Levinson approach which uses causal filter and L2 norm, the proposed method is iterative and uses causal and anticausal filters, combined with variable norm. Numerical results using synthetic seismic data demonstrates its ability to overcome some limitations of the conventional Wiener-Levinson method, providing good results even when the wavelet is not minimum-phase or the reflectivity series is not a random process. Numerical examples using poststack marine seismic reflection data, demonstrates the efficacy of the new iterative wavelet deconvolution method.
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Caminhamento Elétrico Multieletrodo Aplicado ao Mapeamento de Áreas de Risco em Travessias de Dutos: Estudos de Casos
The results of electrical multielectrode WENNER array in geophysical survey are geoelectrical sections marked by resistivity contrasts in different geological units, as well as the mapping of the bedrock, rock blocks, boulders and fractured zones. Different resistivity values are associated to the inhomogeneous and anisotropic layers related to different geological domains, due to its own geoelectrical characteristics. This geophysical technique was used to reduce the drilling risk for pipeline location below crossing rivers, where geological information is important and difficult to obtain. This paper presents three case histories in which this electrical method was used successfully showing how it should be extended to similar applications.
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Interpretação de Dados de GPR com Base na Hierarquização de Superfícies Limitantes e na Adaptação de Critérios Sismoestratigráficos
More LessThe goal of this research is to propose an interpretation methodology of GPR data able to perform this task at least for siliciclastic deposits. In order to do so, the proposed GPR interpretation method is based both on seismostratigraphic concepts and on the bounding surface hierarchy tool from Miall (1988). As consequence of this joint use, the results of GPR interpretation can be associated to the sedimentary facies in a genetic context, so that it is possible to: (i) individualize radar facies and correlate them to the sedimentary facies by using depositional models; (ii) characterize a given depositional system, and (iii) determine its stratigraphic framework highligthing how it evolved through geologic time. To illustrate its use the proposed methodology was applied in a GPR data set from Galos area which is part of the Galinhos spit, located in Rio Grande do Norte state, Northeastern Brazil.
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Simulações Numéricas GPR 2D para Caracterizar Vazamentos de Óleo Provenientes de Cabos Elétricos de Alta Tensão Instalados no Subsolo
More LessThis work shows results about GPR numeric simulation to locate electric cables in the subsoil and to characterize the contamination plume from the oil used in high-voltage electric cables. The models simulate electric cables of low, mean and high-voltage installed in the subsoil of SãoPaulo city, Brazil. 200MHz GPR profile over targets installed in test site of the IAG/USP present good agreement with the numeric simulation results for the same targets. The results can be used in the viability studies of the GPR method in mapping interferences in the subsoil and in environment contamination characterization.
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Correção topográfica em dados de GPR 3D
Authors Fábio José Miranda and Guilherme Pena CastilhoAtalmente, aina não é comum a aplicação de correção topográfica em dados de GPR Tridimensional, o que dificulta a integração dos dados com outros em que foi realizada tal correção e a integração com informações de investigações diretas, não retratando as possíveis variações topográficas do terreno onde se realizou a investigação. Este trabalho traz algumas informações sobre a estrutura de um arquivo de GPR3D e GPR2D no formato seg-y e as modificações que são verificadas quando aplica-se a correção topográfica, demonstrando a importância dessa correção para que o trabalho do inérprete seja mais preciso.
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Investigações GPR no Sítio Arqueológico Lapa do Santo-MG: Resultados Preliminares
Authors Guilherme de Matos Jangelme, Jorge Luís Porsani and Renato KipnisIn this article we present preliminary results of 2D and 3D GPR survey carried out at the archaeological site Lapa do Santo. This cave is found within the Lagoa Santa karstic region, Matosinhos, Minas Gerais. 44 GPR profiles were acquired with 200 and 400 MHz antennas focusing on three mains objectives: (1) to characterize stratigraphic layer; (2) to identify geological and archaeological anomalies; and (3) to identify potential areas for archaeological excavations. Data obtained with the 400 MHz antenna indicate two anomalous hyperbolic reflections that suggest potential archaeological targets. These results are very encouraging and will be used to guide future excavations at the site. The results also indicate the importance of geophysical survey as a tool for assisting with the paleoanthropological project being coordinated by Prof. Walter Neves (IB-USP).
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