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9th International Congress of the Brazilian Geophysical Society
- Conference date: 11 Sep 2005 - 14 Sep 2005
- Location: Salvador, Bahia, Brazil
- Published: 11 September 2005
201 - 250 of 462 results
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An application example of shallow seismic reflection technique for geologicalgeotechnical mapping in the urban area of the city of São Paulo, Brazil
Authors Oleg Bokhonok, Renato Luiz Prado and Liliana Alcazar DiogoWe evaluate the potential of shallow seismic reflection for a geological and geotechnical research in noisy urban environments with a paved surface. The field tests were made at the Sedimentary Basin of São Paulo, in the urban area of the city of São Paulo. It was verified that a sledgehammer and 100 Hz geophones provide the most suitable equipment. An interpretation of the CMP section, interpolated by the well information, demonstrated a high potential for mapping geological structures with numerous details and good continuity. The information obtained from the final seismic section revealed various sediment strata of the São Paulo Basin and several bedrock structures. The results characterize the shallow seismic reflection method as a flexible tool that can be adapted to the objectives of the proposed research. The latter can be accomplished by defining appropriate acquisition parameters as well as through perceptive processing.
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Modelo geométrico estrutural a partir de interpretações em seções sísmicas de alta resolução
Outline the 3D geometry of the structural model from high resolution seismic faults interpretation was the main objective of this work. The analysis of a seismic array of lines, acquired transversally to the predominant structural trend, resulted in interpretation of various fault segments. After coherence tracking of this alone segments along the seismic sections, some fault planes came out. Those planes were converted to pillars in order to interpolate surfaces for constructing the structural model skeleton. The resulted 3D grid was stuffed with faults heterogeneity preserving the interpretation and preparing the model for horizons insertions and 3D integration.
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LEVANTAMENTO GEOFÍSICO EM CORDÕES ARENOSOS, ZONA COSTEIRA DA BAÍA DE SEPETIBA, ITAGUAÍ – R J: RESULTADOS PRELIMINARES
It is presented in this paper the results of a geophysical research based on electrical resistivity applied to Holocene deposits, located at the inner part of the Sepetiba bay, at the Itaguaí county, state of Rio de Janeiro. Interpretation of the data showed results that nicely match with the conventional models of such architectural depositional element, that will be integrated to the geological model of a wider area that is under investigation. The results of this investigation has also served to test the resistivity equipment that is being developed by the Geophysical Laboratory of the Federal University of Rio de Janeiro.
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Processamento sísmico de reflexão rasa em rochas fraturadas do Grupo Itararé
Authors R. Brunetta, M.K. Bartoszeck, M. K., J.N. Lonardelli, J. N., A. Rigoti, S.P. Rostirolla, S. P., C.J. Appi and C. J. BolsistaHigh resolution seismic was used to study rocks of the Itararé Group for fracturing reservoir caracterization. The area of the studies is next to Ponta Grossa city (PR), where are exposed rocks like sandstones, basal shales, diamictic and conglomerates. The seismic processing has become a great challenge because there is no good evident reflector in shot window. In the attempt of identifying these reflectors, traditional techniques of seismic processing, like Predictive Deconvolution that comes to be used with relative success at the area in studies, even not be usually applied in shallow seismic.
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Aplicação de tomografia elétrica na detecção de tambores plásticos na área do Sítio Controlado de Geofísica Rasa do IAG/USP
O resumo mostra resultados de tomografia elétrica 2D realizada sobre tambores plásticos enterrados na área do Sítio Controlado de Geofísica Rasa do IAG/USP. A metodologia aplicada teve como objetivo identificar o padrão das anomalias elétricas dos tambores plásticos utilizando o arranjo dipolo-dipolo com espaçamento entre os dipolos de 1 metro. Os resultados mostraram que os parâmetros de campo utilizados permitiram somente identificar a posição horizontal dos tambores. Os alvos apresentaram anomalias de alta resistividade e baixo valor de cargabilidade.
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Prospecção arqueológica por métodos geofísicos no Sudeste do Pará: O caso do Sítio Domingos, Canaã dos Carajás
More LessMagnetic, resistivity, and ground penetrating radar (GPR) measurements were carried out on an archaeological site under investigation to find remains buried by ancient people that could have lived in the area. Archaeological excavation on places indicated by magnetic anomalies revealed concentration of ceramic fragments and intact pottery. The correlation between resistivity measurements and the soil profile described in the area suggest the 1810 to 2560 Ohm.m range as the most representative for the archaeological occupation layer. GPR images showed anomalous features correlating to several magnetic anomalies. Those features, however, are not very conclusive to represent the searched remains. Because of that, GPR is not recommended to be the main tool for archaeological prospecting in the area.
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Caracterização do Solo para Uso em Agricultura de Precisão através de Métodos Elétricos e Eletromagnéticos (GPR): Resultados Preliminares
More LessIn this work, the Ground Penetrating Radar-GPR and Continuous electric profile-VERIS methods had been used to characterize the structures of the soil for use in precision agriculture. The studies were carried out in a pilot area closed for soy plantation located in Farroupilha farm, Mato Grosso state, Brazil. GPR Profiles allowed characterizing the subsurface until 12 m depth. The main images structures were: the soil thickness, a lateritic layer with iron oxide and the water table top. The electric conductivity mapping obtained with VERIS profiles showed that the conductivity varies laterally and it is heterogeneous for all the pilot area until 1 m of depth. The results had shown a good correlation between the reflections zones from GPR profiles and the electric conductivity anomalies zones. In regions where the conductivity is highest, there is absence of GPR reflections. On the other hand, where the conductivity is lowest occur good penetration of the radar and the reflectors are stronger.
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Utilização de Metodologias Geofísicas na Identificação de Manilhas de Concreto Instaladas no Sítio Controlado de Geofísica Rasa do IAG/USP
Authors Welitom Rodrigues Borges and Jorge Luís PorsaniThis work presents some results obtained with the Ground Penetrating Radar (GPR), electric, and inductive electromagnetic (EM38) methods applied to identify concrete tubes installed in Shallow Geophysical Test Site SCGR – IAG/USP. The results showed that the GPR is the most effective method for concrete tubes identification, and that objects buried in soils with electric resistivity lower than 200 ohm.m were not identified by other methods.
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Metodologia geofísica aplicada ao salvamento arqueológico de área adjacente a mineroduto no nordeste do Pará
More LessMagnetic, total count gamma cintilometry, and ground penetrating radar measurements were carried out on two archaeological sites located adjacent to the place where a miner duct will be buried. The aim of the measurements was to indicate the optimal areas for archaeological excavation to find subsurface remains related to ancient communities that lived in the sites. Magnetic measurements showed anomalies that lead to the discovery of a large amount of ceramic fragments and
other remains. Cintilometry allowed discriminating argillaceous from sandy soil, an important result since sandy soil can be correlated to the archaeological layer, where remains are normally found.
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Seismic Inversion by Principal Components Analysis and Neural Networks
Authors Oswaldo Ludwig Júnior and Wilson M. FigueiróThis paper describes how Artificial Neural Networks can be employed to solve seismic inverse problems. The main objective is to obtain one-dimensional Earth velocity models from seismic waveform data. Precedent works are discussed and a new approach is suggested. It means, the Principal Component Analysis is adopted to avoid redundant information that is originated due to the Common Middle Point gather. A secondary objective is to reduce the total number of network parameters and increase the generalization skill on the neural network.
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Aplicação do WTdecon - deconvolução colorida implementada por Transformada Wavelet
Authors Evaldo C Mundim, Heron A. Schots, João M. de Araújo and Deilson M. TavaresThis paper presents the application of WTdecon, a new seismic deconvolution technique applied to deep water seismic data in Campos Basin, Brazil. WTdecon deconvolution doesn’t rely on the white reflectivity hypothesis, instead associates the reflectivity series to major fluctuations on the trace amplitude spectrum. The seismic wavelet is the smoothest component being obtained by Wavelet Transform decomposition of the seismic amplitude spectrum. Given that, the deconvolution is implemented in a deterministic way.
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Direct hydrocarbon detection experiment in Potiguar Basin
From March to May 2004 PETROBRAS performed an experimental geophysical survey in Potiguar basin, Brazil. For the first time, in a Brazilian sedimentary basin, the technology named “Hydrocarbon Micro-Tremor Analysis” (+\0$6
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Aplicação da decomposição espectral em campo cretáceo da bacia de campos, análise e comparação de metodologias
The Spectral decomposition has been used widely in a on seismic interpretation. Because of this, many companies developed themselves algorithms for application of the spectral decomposition technique. This work shows the applications and results of four metodologies based on spectral decomposition, that is the technique proposed initially by Partyka et al. (1999) . These metodologies were applied on oilfield placed in the continental margin of the Campos basin, offshore Brazil.
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PROCESSAMENTO E INTERPRETAÇÃO DE DADOS AEROGEOFÍSICOS DA PORÇÃO CENTRO-OESTE DO DOMÍNIO CEARÁ CENTRAL, NW PROVÍNCIA BORBOREMA
This paper reports the processing and interpretation of the airborne geophysical data (MAGNETIC and GAMAESPECTROMETRY) from the Itatira Project (1977). The aerogeophysical themes can be used on the characterization of the tectonic framework of the Ceará central region. The data processing was able to distinguish the inner differentiation of the Santa Quitéria migmatitic complex and the distinct nappe systems in the Ceará supracrustal sequence. Granites bodies and faults are well recognized in the airborne products.
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Estimación de espesores reales de las principales unidades tectono-estratigráficas Mesozoicas-Cenozoicas en la Plataforma Deltana, Cuenca Oriental de Venezuela
Authors R. Karla and M.I. JácomeSix tectono-stratigraphic units have been regionally defined in an area of 12.321 Km2 located towards the marine extension of the eastern Venezuelan basin (i.e. the Deltaic Platform of the Orinoco River). The tectono-stratigraphic units studied are: 1) Cretaceous-Paleogene; 2) Lower Miocene; 3) Middle Miocene; 4) Upper Miocene and 5) Pliocene. Decompacted isopach maps have been generated to determine the original thickness and regional 3D distribution of these tectono-stratigraphic units in the area, and to relate these units to tectonism and sediment supply. The descompacted isopach maps have been produced using thirteen regional 2D seismic reflection profiles previously interpreted and published. The seismic profiles are more than 1500 km long and have been digitised and converted to depth.
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Development of a digital proton magnetometer: an efficient algorithm model to determine the Larmor precession frequency
Authors André Wiermann and Luiz C. C. BenyosefThis paper presents results from a algorithm model proposed to estimate the central value for small measurement data sets. The algorithm was derived to achievea computationally efficient method to estimate the Larmor precession magnetometer that is being developed at the Observatorio Nacional (Wiermann & Benyosef, 2004). An additional comparison is shown between the proposed algorithm and a technique called meadian that combines mean and median procedures and it is based on statistical bootstrapping.
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Simulação sísmica entre poços e tratamento tomográfico dos dados visando a caracterização geológica – geotécnica rasa
More LessA tomografia sísmica é uma ferramenta muito importante para imagear diferenças de propriedades físicas em subsuperfície. Uma boa distribuição dos raios é um fator muito importante para o sucesso dessa inversão. Um dos algoritmos mais conhecidos em tomografia é o SIRT.
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AEROGEOFÍSICA APLICADA COMO FERRAMENTA DE SUPORTE AO MAPEAMENTO GEOLÓGICO NA REGIÃO DE NOVA XAVANTINA – MT, BRASIL CENTRAL
The present paper aim shows the processing of the aerogeophysical data from the Barreiro Project (1976), generating themes than can be used as a tool to suporte geologic mapping in the region of Nova Xavantina-MT, Central Brazil. They include K, U and Th channels images, and a color composition RGB (K:Th:U). Also, anomalous magnetic field transformed products, as the analytical signal amplitude and inclination (zero order), and total horizontal gradient amplitude (first order). Magnetic themes reflect the main structural trends (E-W e NE-SW) in the area. We found a good correlation between the known geologic units and gamma ray spectrometry products. But, more detailed domains were identified in the processed data that need to be checked in a future the fieldwork.
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PROCESSAMENTO E INTERPRETAÇÃO DE DADOS AEROGEOFÍSICOS DA REGIÃO DE PORANGATU – GO, BRASIL CENTRAL
This paper aim shows the processing and interpretation of the aerogeophysical data from the PGBC (1975/1976), generating themes than can be used as a tool to suporte geologic mapping in the region of Porangatu (GO), Central Brazil. They include K, U and Th channels images, and a color composition RGB (K:Th:U). Also, anomalous magnetic field transformed products, as the analytical signal amplitude and inclination (zero order). The aerogeophysical themes can be used on the characterization of the tectonic framework and litologic differentiation.
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Condutividade térmica a partir de perfilagem geofísica de poço
More LessIn this paper, using self-similar mixture laws, we developed a set of analytical expressions to derive, explicitly, the thermal conductivity of granular sedimentary rocks, from measurements of the true electrical conductivity and porosity obtained from geophysical well logging. The developed equations were tested with well log data from oil fields in Reconcavo basin, and the averaged results are comparable to sample laboratory measurements made by Carvalho (1981).
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Tomografia ultrasônica em testemunhos: simulação de inclusões e interlaminados
Authors Michelli Silva de Oliveira and José Agnelo SoaresThis work presents a simulation study for ultrasonic tomography in cores. More specifically, the capacity of this technique to image inclusions and interlaminated units is investigated. Tomograms representing internal P wave velocities of virtual cores are obtained. These virtual cores are defined in terms of initial velocity models that have zones of high or low wave velocity. The ultrasonic tomography technique is based on ray tracing through an arbitrary grid of cells with constant velocities. Tomograms are obtained as a result of a data inversion algorithm that, in this work, uses alternatively, the algebraic reconstruction technique (ART) or the piecewise polynomial truncated singular values decomposition (PP-TSVD) one. Five different initial models, representing reasonable geological cores, were tested. All results were considered acceptable, but for strong contrasts of velocity the inversion algorithms do not work so perfectly, what is believed due to the using of straight ray paths.
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Análise Petrofísica do “Arenito Namorado” na Porção Sudeste do Campo de Namorado - Bacia de Campos, Brasil
More LessBrazil fossil energy requirements are increasing along last years, and Brazil’s reserves are going to decrease after 2006, in order to have a minimum impact over Brazil’s fossil energy consumes, it will necessary found new reservoirs or re-explorer ancients reservoirs with new technologies.
Namorado´s field is a re-exploration area, but it’s difficult for university’s researches found data like petrophysics characteristics in the field, for this motive this study calculated shale volume, total sand, net to gross o the petroliferous sand, porosity, water saturation, over seven reservoirs identified in a stratigraphic cross-section.
This project was development with a software “Geographix” (Prizm) of Landmark Graphics, and it was used wire log like as Gamma Ray, Density, Neutron and Induction dual laterolog.
The reservoir level was denominated as “Arenito de Namorado”, this level represents a turbidite reservoir and dated as Cretaceous, with a poor lateral continuity. Between the seven levels reservoir here interpreted, the superior level (F) and de inferior level (A) show the most interest for re-exploration with a low percentage of shale volume (less than 15%).
Water saturation was calculated in 3.5% for the deeper reservoir (A)_less than their maximum value calculate in 16%, and over 16% for the rest of reservoirs; for the porosity is observe a minimum value of 10% and the calculus for the different reservoirs are over 15%, this facts let us to thing that the “Arenito de Namorado” deeper level (level A) has conditions for re-exploration.
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Um fluxo de trabalho para modelagem de eletrofácies com entrelaçamento de técnicas de classificação supervisionada e não-supervisionada
More LessThis paper presents a workflow to build logfacies models which is based on the interlaced application of non-supervised and supervised statistical techniques. The workflow allows answering, in an interactive manner, some basic issues which appear in any logfacies modeling program: How many facies may be recognized? Which is the best log suite to be used in? How the generated logfacies correlate with the original lithofacies? Due to the interactive process between supervised and non-supervised techniques, the proposed workflow is biased to produce a fewer number of logfacies than the number of original lithofacies, but those logfacies tend to correspond to, in a physical properties sense, those most representative lithofacies. A main feature of this workflow is the adoption of the logfacies column provided by a non-supervised classification algorithm as the input column of facies for a supervised classification procedure. This feature warrants that the recognized logfacies suite is the best possible, in terms of log physical properties and lithofacies reproduction. Finally, it is shown a real case were this workflow was applied successfully.
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Projeto e construção de um tomógrafo ultrasônico para testemunhos
More LessThis paper presents the development of a novel petrophysical equipment, the ultrasonic tomograph for well cores, which may be used for several petrophysical analysis, as inhomogeneous composition, patch saturation or internal distribution of stress in rock samples. Initially, a brief introduction to seismic transmission tomography is done in order to drive the understanding of this imaging technique as a whole. Some particularities about well core tomography are discussed, as the number of piezoelectric transducers to be distributed around the core section, the grid of cells used for velocity determination, the algorithm used for data inversion, and the simplification of considering straight ray tracing. Details about the project of this equipment, which at the moment of writing of this paper was yet under construction, are presented. Finally, the effect of stresses on rock velocities is investigated and the results indicate the ultrasonic tomography of orientated cores as a very promising technique for determination of direction and magnitude of in situ stress.
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Quantificação da anisotropia sísmica de folhelhos antes, durante e após a geração de hidrocarbonetos
More LessShales represent an important parameter in the discovery of oil accumulation. They are however a lithological type not often studied in terms of the relationships between the petrophysical properties and the velocity of seismic waves. The main objective of this work is to understand the influence of the hydrocarbon generation process in the seismic velocities (shale anisotropy). The elastic velocities have been measured in samples plugged in directions parallel and perpendicular to the bedding and, whenever possible, 45 degrees to the bedding. The anisotropy simulation of hydrocarbon generation process was made using the combination of Thomsen’s petrophysical model and the effective media theory. The combined analysis of anisotropy and mineral composition indicates a more significant contribution of the expansive clay minerals in the anisotropy values. The simulation of the presence of gas inside of organic matter affects in a substantial way the spread of the P wave, which has its velocity reduced when going through organic matter with gas. Therefore, although anisotropies observed in the shales samples studied are not strongly related with the contents of organic matter in the low and high degrees of thermal maturity samples, the simulation of the hydrocarbon generation process indicates that, during the generation process, the contribution of organic matter is as relevant as the presence of oriented clay minerals.
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Computing Resistivity Anisotropy and Structural Dip Using Multi-component Induction Data
Authors Berthold Kriegshäuser, Bill Corley, Michael Rabinovich and Lev TabarovskyA multi-component induction tool like the 3DEXSM provides all the data necessary to derive formationresistivity parallel and perpendicular to bedding. It hasbeen shown in the past that the resistivity perpendicularto bedding can be extremely important to detect andquantify hydrocarbons in so-called low-resistivity pay zones. However, in order to accurately derive formation resistivities at any relative dip from the 3DEX data, the formation dip and azimuth needs to be known. Until recently, this information needed to be provided as a priori information, either from surface seismic data, and/or derived from borehole imaging analysis. In this paper we discuss a new method that utilizes all 3DEX data to derive not only formation resistivities parallel and perpendicular to bedding but also formation dip and azimuth. The 3DEX tool is comprised of three mutually orthogonal transmitter-receiver pairs that allow measurement of the full magnetic field matrix at multiple frequencies. Using a rapid two-step least-square optimization scheme we first derive at every logging depth formation dip and azimuth; then we compute formation resistivities parallel and perpendicular to bedding. We first validated our algorithm with synthetic examples, and then, we applied this enhanced processing to many field data sets, for example, to data acquired offshore Brazil. The generally good agreement between the computed formation dips and azimuths from 3DEX data and those obtained from borehole imaging data confirm the strength and efficacy of this new processing algorithm.
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Simulação do perfil sônico para poços do campo de Namorado utilizando lógica fuzzy
More LessNowadays the offshore industry depends on deepwater exploration that represents costs around thousand million dollars. New techniques of optimization are very welcome to save time and money for petroleum companies.
In this work we will show a new technique using fuzzy systems with real data from an offshore Brazilian field, called Namorado field.
Using this new technique we may simulate the sonic log in wells where we don´t have these data. For this purpose we need other types of log data, like resistivity, gamma ray and sonic log from neighborhood wells.
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Intervalos de variação da velocidade cisalhante no arenito Namorado a partir de um modelo para meios efetivos
More LessIn this paper, shear-wave velocity (VS) intervals were estimated for 32 Namorado sandstone’s samples using Hashin & Shtrikman’s (HS) bounds. In order to achieve this purpose, we assumed the Namorado sandstone as a rock composite with 40% quartz, 25% feldspar, 20% oil, 10% clay and 5% brine. The upper and lower HS bounds resulted from this hypothesis remained in the following intervals: 22.15 and 6.26 GPa for bulk modulus (K), and 17.82 and 2.66 GPa for shear modulus (μ). Moreover, distinct values for the Possion coefficient (ν) were assumed (0.30, 0.25, 0.20, 0.15 and 0.10). The availability of P-wave sonic (DT) and density (RHOB) logs allowed calibration of K and μ for each assumed value of ν, as a function of compressional velocity (VP) and bulk density (ρ). Therefore, a linear relationship between K and μ could be calculated for each ν used, as well as constant VP/VS values (1.8709 for ν = 0.30, 1.7319 for ν = 0.25, 1.6329 for ν = 0.20, 1.5584 for ν = 0.15 and 1.4999 for ν = 0.10). As a result, an interval containing probable VS values could be estimated for each value observed of VP.
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The use of well logs in logfacies modeling – example in the Namorado Field, Campos Basin, Brazil
Authors Camila Faria de Albuquerque, José Agnelo Soares and Claudio BettiniOne of the most important stages for oilfield development is the reservoir modeling, which can be performed in many ways. In this study, we decided to use facies modeling based on well logs, owing to their availability in the petroleum industry. We have used the statistical software Enterprise Guide 2.0, with a specific tool developed for logfacies modeling. The logfacies modeling used here includes a sequence of stages: calibration, validation and application of a discriminant function, which can be linear or quadratic. The data were previously treated with discriminant and cluster analyzes. This study describes an example of the application of this technique to the Namorado Field, Campos Basin, Brazil, showing the modeling stages and the results for two wells.
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PROCINT_LOG: “Software” Acadêmico para Processamento e Análise de Perfis Convencionais de Poço
More LessPROCINT_LOG is a free GUI academic software that runs under MATLAB and is useful for simplified conventional oil and gas well logs analysis. It works through two distinct modes: (1) direct petrophysical parameters inclusion from both field copies and digital
files and (2) by reading digital file and performing the calculations along chosen intervals. The software load ASCII and LAS format files and identifies the logs available, supplying both a header file with additional information about the well and a matrix with the depth in the first column and logs in the remain columns. The last can be loaded by PROCINT_LOG and checked out for unusual highly noisy and/or spurious data, allowing an efficient data control. Furthermore, each one of the proposed processing modes fits well to any chosen processing sequence, allowing the log interpreter to drive your own perspectives into log analysis. To provide a little of perspective, fundamental well-logging principles are stressed by informative icons that can be searched at any time the interpreter need. Calculations such as invasioncorrected resistivity, shale volume, and Archie, Dual Water and Simandoux methods for water saturation computations and three types of water resistivity computations are viable. One complete example is performed on both synthetic and real data and results are checked against visual analysis to show the usefulness, rapidness and accuracy of PROCINT_LOG in performing accurate logs analysis.
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Projeto RADAM-D - conversão e disponibilização em meio digital das imagens originais geradas pelos projetos RADAM e RADAMBRASIL
The RADAM Project (for Radar Amazon), organized in October 1970, was a Brazilian government decision to undertake a reconnaissance survey of the Amazon region and the adjacent Brazilian Northeast. The major objective was to collect information on mineral resources, soils, vegetation and land use. In June 1971, the first flights took place. In July 1975, the program was expanded to the hole country and had its name changed to RADAMBRASIL. The remote-sensing platform was a twin-jet Caravelle flying at an altitude of 12 km with a speed of approximately 690 km/h. On board was the side-looking radar Goodyear Mapping System 1000 (GEMS). The generated data are stored at CPRM-Geological Survey of Brazil. This RADAM-D Project deals with the preservation of original SLAR image negatives and diafilms through data scanning and digitization. The project works with the inventary of available material, organization of radar strips, high resolution image scanning, composition of final images and its publication.
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Variações da metodologia de micronivelamento de Minty em dados aerogeofísicos no domínio do espaço
Authors Mariana V. Maziviero, Rodrigo S. Portugal and Adalene M. SilvaO método de Minty (1991) vem sendo utilizado extensivamente para micronivelamento de dados aerogeofísicos no domínio do espaço, 1-D. No entanto, este método possui algumas limitações, que motivou a remodelagem desta rotina utilizando diferentes filtros. Estes filtros foram testado exaustivamente em um levantamento aerogeofísico a fim de verificar as características dos resultados finais (dado micronivelado) e possibilitando uma comparação entre eles.
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O efeito de adjacência em imagens de satélite numa atmosfera Rayleigh: uma aplicação no estado da Paraíba
More LessThe analysis of the influence of atmospheric effects in remote sensing are based on the principle that the imaged surface is uniform. This assumption has been a great problem in the case of low reflectance surfaces such as water surfaces (water reservoirs, lakes), for which the background influence is very important. The atmospheric correction method used here is based on the optical properties of the atmosphere. A background function is used to evaluate the percentage of the background contribution. In order to evaluate the adjacency effect on Landsat-5 images, several areas of different sizes were selected over the water reservoir of São Gonçalo, located in the interior region of Paraíba state. The adjacency effect is clearly seen in the selected areas.
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CAMPO DE ANOMALÍAS CORTICALES DEL SATÉLITE MAGSAT OBTENIDO POR CALIBRACIÓN CON DATOS DE SUPERFICIE CON APLICACIONES AL CAMPO DE ANOMALÍAS DE LA RED GEOMAGNÉTICA DEL BRASIL
Authors Jaime R, Añazco P and Luiz Muniz Barreto y Ronaldo M. De CarvalhoIn this work a crustal anomaly field of total intensity (F) at Earth’s surface level for the Brazilian territory is derived. The starting point was the crustal anomaly field obtained from Magsat data, to the average height of the satellite (350 km), by a calibration process, with surface profile anomalies and done by bands. This calibration is an alternative to the continuation methods. The anomaly field of the geomagnetic network, analyzed according to this calibrated field, displays an intense spurious negative
anomaly of approximately 150 nT, in the southern region of the country, that covers the states of São Paulo and Paraná. It has an orientation almost NE and a length of 7 degrees approximately. This effect seems to be produced by the insufficient removal of South Atlantic Magnetic Anomaly (SAMA), when the main field of the data is removed with the reference model IGRF of order and degree equal to 10. This problem should be present in every geomagnetic database, for this area, where the main field was removed with that reference model.
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Controle da Escala na Estacionaridade de Perfis de Poço (Scale dependence of well log stationarity)
Authors Adalberto da Silva and Armando Zaupa RemacreUpscaling (or downscaling) is a fundamental procedure to reservoir management in order to integrate scattered and linear high vertical resolution well logging data with volumetrically widespread but low vertical resolution seismic data. Analysis of the log signal behaviour must precede the interpreter’s decision on filtering denoising and scale transference methods. As a rule, well logging data is assumed as a stochastic, non-stationary realization and this assumption conditions the filtering method choice. In this paper, we analyse a set of four curves from seven vertical wells at Namorado Field, Campos Basin, Brazil using Fourier, wavelet filtering and variogram analysis to investigate the scale dependence of the geophysical signal, exploring the different filter responses to stationary and non-stationary signals. Using a 10 meter cutting wavelength that corresponds to the parasequence scale of the Namorado field turbidite system, the Fourier filtered signal preserves much more the variance than its wavelet filtered analogue. This indicates a strong stationary content of the geophysical signal at this scale level and suggests a decoupling of the signal in components at reservoir level: a medium to high energy / large scale stationary component and its fine scale non-stationary counterpart. This result poses some important constraints on the well logging data filtering strategy choice and its use in scale transference.
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Results from new technology and workflows for fast track reservoir characterisation of a Palaeocene deep marine turbidite field
Authors Martyn Millwood Hargrave, Rod Christiansen and Henry MorrisThe Brenda field in UK North Sea Block 15/25b (see Figure 1) has undergone very rapid exploration and appraisal in 2004 and is now poised to move into development and production phases over the next 18 months.
Over 12 “cluster” penetrations of the Palaeocene Upper Balmoral reservoir have been drilled and a substantial amount of reservoir data has been collected. The objective of the project required fast assimilation and integration into operations to ensure that each well was targeted and optimally drilled with the benefit of the enhanced understanding of the previous data collected.
We describe the combination of rock physics driven seismic interpretation of attributes, and new technology for “inversion of inversion” for reservoir characterisation used to fast track the Brenda field previously considered non economic.
The Brenda net oil reservoir varies from 15m- 30m in thickness trapped by a combination of structural and stratigraphic elements and our understanding of the relative importance of the two major controls and modifiers such as hydrostatic gradients is still evolving.
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Construction and validation of an integrated 3D geomodel for reservoir characterization – case study, offshore Angola
Authors Antonio Kaschaka and Idima PimentaWM field, offshore Angola produces significant quantities of oil from sandstones of the Upper Cretaceous Vermelha Formation. This sequence of mixed carbonate and interbedded siliciclastic sediments was deposited as a transgressive-regressive barrier island system. Approximately 97,5 m of conventional whole core was examined in order to define depositional facies and understand their relationships. Three principal facies were recognized: (1) inner shelf to shoreface sediments characterized by bioturbated, argillaceous, dolomitic siltstones, very fine-grained sandstones, and silty/sandy dolowackestones; (2) beach/barrier bar complex ranging from well-sorted, very fine-to fine-grained to poorly sorted, very fine-to very coarse-grained subarkoses and arkoses commonly containing planar cross-lamination; and (3) lagoon and tidal-flat sediments composed primarily of argillaceous dolomudstones and wackestones punctuated by dolomitic sandstones.
This integrated study used geophysical, geologic, and engineering data simultaneously to guarantee the accuracy in the models to be used for simulation purposes on a well by well basis, for matching the past dynamic performance, and to investigate the future reservoir management strategies such as remaining hydrocarbon reserves estimates, better understanding of water conformance, and to minimize the risks on implementing new production wells.
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Incorporating Seismic Constraints into High-Resolution Geologic Models
More LessWell data alone cannot accurately recover the requested property variations, because of their sparse lateral distribution and their large spacing, compared to the size of the lateral heterogeneities to be modeled. On the opposite and despite its poor vertical resolution, seismic data provide valuable information to overcome such a limitation as it benefits from the highest lateral density of information. Accurate descriptions of the lateral variation of reservoir heterogeneities is a critical issue when generating reservoir models dedicated to history matching and sub-sequent production forecasts.
This paper describes one of the workflow that has been successfully applied on a turbidite field in Angola, which allows (1) extracting reliable constraints from post-stack seismic amplitudes and (2) incorporating them into high-resolution geological models.
Relevant constraints are generated using seismic reservoir characterization techniques, based on seismic inversion followed by seismic facies analysis and generation of net-to-gross maps. Then, for geological modeling, we chose a pluri-gaussian modeling technique, which provides the requested level of flexibility for mixing the obtained map with well data and thus solving the downscaling issues.
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Saturating pore fluid Bayes Indicator for reservoir mapping
More LessA seismic-based reservoir properties estimation is implemented and tested in this work. The main goal in this work is to map oil saturated sands based on a sandshale oil field system. We consider petrophysical measurements as source of information to construct a conditional probability density function (PDF) for water saturated sand and a conditional PDF for oil saturated sand. Using these PDFs’ and seismic attributes from a reservoir cell, we compute the probability for water saturation given the attributes and the probability for oil saturation given the attributes. From these probabilities and following a Bayesian criterion we create an indicator for saturating fluid to this cell and the associated Bayes error. We analyze each reservoir cell to create a map for oil saturated indicator, water saturated indicator and the associated uncertainty. Several seismic attributes are analyzed in this work and using the maximum entropy measured from these PDFs’ we decide the most informative attributes and attribute pair to reduce uncertainty. In the current time, the methodology was successful tested in well log data. Our next step is to test the methodology with seismic attributes and apply the methodology in a real situation.
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Reservoir characterization using high frequency seismic data in Roncador, Campos Basin
Based on a detailed mapping of surfaces and faults (accomplished with high resolution seismic) and the use of seismic attributes, geological models are constantly updated, to better estimate reservoirs spatial distribution and their petrophysical properties at Roncador (Campos Basin). Such models are used in fluid flow simulations. The results present significant improvements on detailing the characteristics and properties of reservoirs compared to conventional seismic data. Also, a brief discussion about resolution and detection is included.
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A Bayesian approach for lithofacies identification and classification
Authors Igor L. S. Braga and Luiz Geraldo LouresThis work introduces a methodology for lithofacies identification and classification following the probabilistic theory of pattern recognition. This methodology applies the Expectation Maximization algorithm to identify lithofacies in the learning stage. This unsupervised learning process is applied to well log data to identify lithofacies. Uncertainty analysis is performed to predict the classification success and the Bayesian decision theory is applied to classify new incoming data. This methodology was tested in well log data. The results achieved are interesting enough to extend the methodology to seismic resolution to classify lithofacies in the inter-well zone using seismic attributes.
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Vertical Seismic Facies Detection Through Unsupervised 3D Voxel Based Seismic Facies Classification Applied to a Turbidite Field in Campos Basin, Brazil
Authors Marcílio C. Matos, Paulo L.M. Osório and Paulo R.S. JohannWe propose to use the 3D voxel based unsupervised seismic facies classification to identify vertical facies variations within a turbidite reservoir. The technique was applied to a real data from a deep water field in the Campos basin, Brazil, and the results were compared with other classical facies analysis method, with similar results.
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Sensitivity Analysis in Various Inversion Schemes for evaluating Saturation and Pressure changes in the Context of 4D seismic studies
More LessHere, a sensitivity analysis on saturation (ΔS) and pressure (ΔP) variations due to uncertainties in the input parameters of several inversion schemes is presented. In this sense, input parameters can be classified with respect to how their uncertainties impact the value of estimated inverted parameters, all of which depend on reservoir thickness, or stage of production, and the particular inversion scheme considered. In this sense, the possibility of diminishing uncertainties in the predicted values of ΔS and ΔP is tied to the feasibility for discrimination of the critical input parameters, as sources of uncertainty for the inverted indicators (ΔS and ΔP). This way, it would be possible to concentrate efforts in obtaining reliably the important inputs for inversion.
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INTEGRATION OF TECHNOLOGIES FOR IMPROVED RESERVOIR RECOVERY
More LessThere are several options in the industry today when considering the technologies to be used in a seismic program. Consideration must be made when designing the survey, the acquisition technique to be used and what technologies to apply that ultimately result in improved recovery from the objective(s). These technologies include not only the traditional towed streamer arrays, ocean bottom cable systems and ocean bottom autonomous nodes, but also as to what type of seismic source, sensors, source/receiver positioning techniques, quality control processes and methodologies and even the personnel assisting with the survey operations. Attention to these details must start in the initial planning stages and be implemented during the survey acquisition and data processing, through product deliveries. These processes will involve several disciplines within and outside the geophysical community. Integrated discussions are ongoing, which will in due course, improve probabilities for improved recovery.
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Interpretação Inteligente de Perfis de Produção
More LessProduction Logging can be interpreted in intermittent wells using the intelligent analysis program presents in this work, called PAINTWELL, which permits to use of same string configuration than a conventional Production Loggging. This program can be performed in layered reservoir, determining the flowrate and type of the fluid for each production zone. The use of Artificial Neural Network as integrated part of this analysis program, provides a powerful tool to describe how downhole logging and advances in computer processing and interpretation data could spearhead the transformation that can take place in production logging with use of this new technique. This methodology should aid the production and reservoir engineering to solve recovery problems during the well life. The results of the production log using the PAINTWELL method is very similar to measurements using test separator in production facilities for each single perforated interval. This program was applied successfully for an typical intermittent well on Maracaibo Lake basin, in Venezuela, which produces oil with high water cut using a gas-lift completion system.
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High resolution 4D-friendly analysis: application to gas-oil contact monitoring at Troll West
Authors Alexandre Bertrand, Sean McQuaid, Roman Bobolecki, Sture Leiknes and Hans Egil RoA new workflow automatically providing high-resolution 4D-friendly attributes is applied to the Troll West Gas Province datasets (offshore Norway) to monitor the movement of the gas-oil contact. It consists in generating attributes of velocity and amplitude changes using enhanced resolution imaging and morphing. Morphing is used to remove velocity or noise-induced traveltime differences between the vintages, resulting in a 4Dfriendly difference which reflects more genuine changes of amplitude. These attributes are used to train a neural network scheme for estimation of gas-saturation changes and quantification of the gas-oil contact movement. The analysis shows coning along the tracks of a number of multilateral wells and identifies undrained volumes for infill drilling.
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Steam injection monitoring with high resolution time lapse seismic
Authors Marco Schinelli, Selma Sacramento and Odilon KellerThe challenge to produce parafinic oil from shallow sandstone reservoir in the Fazenda Alvorada onshore field, located Northeast of Reconcavo Basin, led to the option of using steam injection as a secondary recovery process. In 1994, a project was designed to introduce the 4D seismic technology in Petrobras and at the same time to evaluate the efficiency of that recovery process. Petrobras opted by monitor the injection using for the first time high resolution time lapse seismic. Geophones with 60 Hz resonance were used instead of conventional 10 Hz in the sucessive acquisitions. Circumstantial reasons led to almost 5 years interval between the successive surveys what increased the difficulties to the project. This work will focus on some aspects related with acquisition, processing and interpretation of that 4D project.
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Improving 4D Seismic Data Interpretation using Geostatistical Filtering
More Less4D Seismic is becoming a conventional tool for hydrocarbon reservoirs monitoring and management, especially for heavy oil bearing fields (Calvert, 2005). In this case, 4D, or time-lapse seismic, can be used to detect important reservoir properties variations imposed by thermal enhanced oil recovery processes. This work aims at identifying remaining noise, invariant common features and time-dependent variations in oil reservoirs from post-stack amplitude time-lapse data. It involves a geostatistical multivariate technique called factorial co-kriging, an extension of the factorial kriging (FK) technique proposed by Matheron (1982). It is based on the decomposition of spatial correlations to identify redundant structures at various scales. Three seismic surveys, with different acquisition parameters, were acquired at the same site in different calendar times to monitor the progress of injected steam fronts into a heavy-oil reservoir. These seismic volumes were then carefully processed to minimize their discrepancies. Factorial co kriging revealed possible common geological structures, 4D effects and remaining noise, and it seems to be an efficient method for extracting common regional trends from several repeated seismic datasets.
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Time-Lapse Feasibility Analysis for a Brazilian Offshore Field: Target on Saturation and Pressure Changes Interpretation
Time-lapse feasibility study is not only the first step to validate a 4D campaign; it is also an essential tool for the interpretation of the acquired seismic volumes. In this paper we present a practical example of feasibility study for a Brazilian offshore reservoir to illustrate the main issues and benefits of feasibility analysis. Our goal is to emphasize which information may be accessed with the feasibility analysis, as well as the uncertainties and nonuniqueness in time-lapse feasibility and interpretation.
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ATUM Field: 4D QUALIFICATION OF 2 SEISMIC VINTAGES USING GEOSTATISTICS
Authors L. Sandjivy, C. Magneron, C. Formento and Odilon Keller4D spatial diagnostic and geostatistical filtering (factorial kriging) were applied to the 1987 and 2003 seismic vintages acquired on the PETROBRAS RN Atum field. The goal was to evaluate the suitability of these seismic data to highlight 4D production effects. A spatial analysis (controlled by frequency power spectrum) and factorial kriging were used to quantify and suppress the noises and acquisition artefacts in both data sets in order to improve the 4D repeatability. After spatial filtering, the measured coherency (both vertically and spatially) between the two cubes was largely improved but major amplitudes differences still remained due to the different acquisition parameters: streamer in 1987 and ocean bottom cable conventional in 2003. Consequently, the data were not qualified as such for a further 4D study: Instead, dedicated spatial filters controlled by geophysical frequency spectrum were derived to enable comparison and further amplitude equalization of the data sets. The filtered results are currently being used to increase the confidence level on structural interpretation of both seismic data sets.
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