Orientador: Armando Zaupa Remacre / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-09T03:37:21Z (GMT). No. of bitstreams: 1 Sancevero_SergioSacani_D.pdf: 13993022 bytes, checksum: beb2507aee5ca130897dad57c706b2a9 (MD5) Previous issue date: 2007 / Resumo: O processo de caracterização de reservatórios é atualmente uma das etapas mais importantes na exploração, desenvolvimento e produção de um campo. Porém, para que esse processo seja realizado da melhor forma possível é preciso se ter o conhecimento de determinados métodos, que integram as diferentes informações disponíveis. Desse modo, o objetivo principal dessa tese é estudar de forma criteriosa e quantitativa o processo de caracterização de reservatórios do ponto de vista dos dados sísmicos, avaliando antigos e novos métodos, e definindo novas metodologias que possam ser aplicadas de maneira decisiva neste processo. Para que esses métodos pudessem ser avaliados de maneira conclusiva foi utilizado nesta tese um modelo sintético que reproduzisse minimamente algumas características cruciais de determinados reservatórios como a complexa distribuição dos corpos de areia e a presença de corpos com espessura subsísmica que levassem ao limite as técnicas de modelagem tradicionais, proporcionando avaliar novos métodos. Assim, para caracterizar essas complexas feições, foram utilizados nesta tese dois meios principais de interpretação, primeiro a inversão sísmica dando um caráter preditivo ao dado sísmico e por fim a análise multiatributos, dando um caráter classificatório. No caso da inversão sísmica foram utilizados três métodos de obtenção da impedância acústica. Entre eles, foi a inversão geoestatística que demonstrou ser a mais eficiente das técnicas no que diz respeito à caracterização de reservatórios com espessura subsísmica e complexa distribuição dos corpos de areia. No caso dos atributos, pôde-se demonstrar que é necessário que sejam tratados com uma abordagem multivariada para que seja aproveitada a correlação entre eles e que por meio de técnicas de classificação e modelagem possa se decidir os mais relevantes para o processo. Neste caso 3 métodos de análise multivariada foram apresentados e testados, sendo que dois deles (ICA e MAF) de maneira inédita e que produziram resultados superiores àqueles alcançados quando a tradicional técnica de PCA é aplicada. Assim, com o que foi apresentado, pode-se concluir que o processo de caracterização é um estágio crucial para o desenvolvimento dos campos, mas não é fácil de ser realizado, a menos que os métodos e as técnicas envolvidas sejam conhecidas de maneira profunda. Só assim, é possível extrair o máximo de informações do dado sísmico, caracterizando o reservatório de forma quantitativa e integrada, otimizando sua produção e reduzindo os riscos e custos com a sua explotação / Abstract: The reservoir characterization process can be considered curretly the most important stage in the exploration, development and production of the oil field. However, this process is only carried out in the best way if the geologists, geophisicist and engineering has the knowledge of some definitive methods and techniques that integrated all information available about the field. Thus, the aim of this thesis is to study in a criterious and quantitative way the reservoirscharacterization process, analyzing the seismic data,by the evaluation of classic and novel methods, to defining new methodlogies that can be applied in decisive way into this process. So, for these methods could be evaluated in a conclusive way, were used in this thesis asynthetic reference model that reproduced some critical features of determined reservoirs, as the complex distribution of sand bodies and the subseismic thickness. These characteristics pushing to the limit the traditional modelling techniques. In this thesis to characterizze the complex features present in the reference model we used two interpretation techniques, first we analyze the seismic inversion that give a preditive character to the seismic data and after we study the multiattribute analysis that give a classificatory caracter to the seismic interpretation. For the seismic inversion, the stochastic or geostatistical inversion, that demonstrated to be the most efficient technique to characterized the complex and the subseismic features present in the model. About the seismic attributes it could be demonstrated that even so in some cases they represent the features of the model, are necessary that they are dealt with a multivariate approach, to used the advantage of the correlation between them. For the seismic attribute analysis, 3 methods of multivariate statistics analysis were used, two of them (ICA and MAF) for the first time in the reservoir characterization processo With the results we can proved that these 2 new methods improved the process of multiattribute anlysis prducing superior results when compare with the results obtained by the application of traditional PCA technique. With it was presented, can be concluded that the reservoir characterization process is a crucial stage and have some difficults to be accomplishment, unless the methods and the involved techniques are known deeply. Thus it is possible to extract the maximum informations from the datasets, characterizing the reservoir in a quantitative and integrated environmental, optimizing its production and reducing the risks and the costs with its explotation / Doutorado / Administração e Politica de Recursos Minerais / Doutor em Ciências

South Africa, as one of the world’s largest gold producing countries, also generates large amounts of tailings. These tailings are disposed in tailings dams, which pose great threat to the environment in the case of failure, in particular, liquefaction. In order to evaluate the potential of liquefaction, the void ratio of the tailings is required and is often impossible to obtain. Seismic methods allow an indirect method to estimate void ratio of in situ deposits of which tailings are examples of. Currently, the use of seismic methods to estimate void ratio of tailings rely on shear wave velocity – void ratio relationships derived for sands. It is thus uncertain whether this relationship holds for gold tailings, which is classified as a sandy silt or silt. The measurement of shear wave velocity of tailings is done in the laboratory using a triaxial apparatus modified to accommodate bender element. Shear wave velocities are measured using wide square pulses and continuous sinusoidal waves. The results show that there is a near linear relationship between void ratio and shear wave velocity normalized against effective stress. The position of this relationship lies below the previously published results for sands. Shear wave velocity of gold tailings is more sensitive to changes in effective stress than changes in void ratio or over-consolidation ratio. Furthermore, using phase sensitive detection of continuous waves, we can conclude that shear wave velocity of gold tailings is also frequency dependent. / Dissertation (MEng)--University of Pretoria, 2006. / Civil Engineering / MEng / Unrestricted

The East African coastal basin of Tanzania, which is characterised by an extensional tectonic style, is located along the passive continental margin of the western Indian Ocean. The present study is concerned with the Mafia Island and the Mafia Channel which together form a subbasin within the north-south elongated coastal sedimentary basin of Tanzania. In the time interval from late Paleozoic to Recent, the passive margin of the region was subjected to a three-fold geological development, namely the Karoo rifting phase (1) which is characterised by extensional tectonics, the Gondwana break-up and opening of the Somali basin (2) which was contemporaneous with the movement of Madagascar off the east African coast in the Mesozoic, and the Cenozoic East African rift system (3). This structural framework made provision to the basin deposition history. The development started with the deposition of the continental, terrigenous, Karoo sequence in the Upper Permian to Lower Jurassic. The Karoo deposition was followed by a series of transgressions and regressions under full marine conditions which started in the Middle Jurassic and continued into the Tertiary. The deposits include marine marls, detrital limestones, fossiliferous shales and calcareous sandstones, reaching in places thicknesses of more than 4000 m of Mesozoic, and more than 6000 m of Cenozoic, sediments. Seismostratigraphic techniques applied in the Mafia Channel and Island identified five deposition sequences separated by regional unconformity surfaces i.e. sequence boundaries. Including the pre-Upper Cretaceous sequence they are; the Upper Cretaceous to Middle Eocene sequence (DS I), the Middle Eocene to Lower Miocene sequence (DS II), the Lower Miocene to Pliocene sequence (DS III), and the Pliocene to Recent sequence (DS IV). In the Mafia Channel up to 6000 m of sediments are present. Their ages range from Middle Eocene to Quaternary. The deposits start with marine shales which are overlain by carbonate rocks of Upper Eocene . These carbonates are in the present investigation regarded as the acoustic basement in the central and northern parts of the study area. On top of Upper Eocene carbonates, deltaic and shallow marine sediments are deposited. Southwards in the Channel, the sequences are located at shallower depths which makes it possible to trace also the Upper Cretaceous sequence with confidence. On the Mafia Island, the deposition on top of the Upper Cretaceous (Campanian) acoustic basement mainly includes deltaic sandstones, followed by intercalations of carbonate and argillaceous rocks. The structural framework reflects the different tectonic regimes which prevailed in the area. Above the acoustic basement structural elements of Mafia Channel and Island are interpreted as originating from the superimposition of the Cenozoic East African rifting event, and from the uplifts of the mainland coast and Mafia Island during Late Eocene time. As a result the central part collapsed and formed an asymmetric sag structure in the channel. These elements are seismically identified and subdivided as (from northwest to southeast), the Dar-es-Salaam Platform Offshore, the Central Mafia Channel and the Mafia Island Rise. These domains are separated by respective NE-SW major faults (MF1, MF2 and MF3) and can be demonstrated in the profiles which run in a NW-SE direction. With respect to petroleum potential, the Mafia Channel and Island indicate a considerable content. Three hydrocarbon plays are introduced, namely; 1) the Neocomian regressive sands of Songosongo play 2) the Upper Eocene limestone and 3) the Upper Oligocene turbidites.

Abstract The crustal and upper mantle structures of the Shield on the regional scale were investigated using the data of the POLENET/LAPNET passive seismic array and the previously published models of active and passive seismic experiments in the study area. This area is centred in northern Finland and it extends to surrounding areas in Sweden, Norway and northwestern Russia. The bedrock there is mostly of the Archaean origin and the lithosphere of the region was reworked by two orogenies during Palaeoproterozoic. One of the results of the thesis was a new map of the Moho depth of the study area, for which new estimates of the crustal thickness were obtained using receiver function method and complemented by published results of receiver function studies and controlled source seismic profiles. The map differs from the previously published maps in two locations, where we found significant deepening of the Moho. The 3D structure of the upper mantle was studied using teleseismic traveltime tomography method. The resulting model shows high seismic velocities below three cratonic units of the study area, which may correspond to non-reworked fragments of cratonic lithosphere and a low velocity anomaly separating these cratonic units from each other. The regional scale studies were complemented by two smaller scale studies in upper crust level using combined interpretation of seismic profiling and gravity data. These studies were centred on Archaean Kuhmo Greenstone Belt in eastern Finland and central Lapland in northern Finland located in the crust reworked during Palaeoproterozoic. Both areas are considered as prospective ones for mineral exploration. Both studies demonstrate the advantage of gravity data inversion in studying 3D density structure of geologically interesting formations, when the Bouguer anomaly data is combined with a priori information from petrophysical and seismic datasets.

The use of seismic methods in hard rock environments in Western Australia for mineral exploration is a new and burgeoning technology. Traditionally, mineral exploration has relied upon potential field methods and surface prospecting to reveal shallow targets for economic exploitation. These methods have been and will continue to be effective but lack lateral and depth resolution needed to image deeper mineral deposits for targeted mining. With global need for minerals, and gold in particular, increasing in demand, and with shallower targets harder to find, new methods to uncover deeper mineral reserves are needed. Seismic reflection imaging, hard rock borehole data analysis, seismic inversion and seismic attribute analysis all give the spatial and volumetric exploration techniques the mineral industry can use to reveal high value deeper mineral targets. / In 2002, two high resolution seismic lines, the East Victory and Intrepid, were acquired along with sonic logging, to assess the feasibility of seismic imaging and rock characterisation at the St. Ives gold camp in Western Australia. An innovative research project was undertaken combining seismic processing, rock characterization, reflection calibration, seismic inversion and seismic attribute analysis to show that volumetric predictions of rock type and gold-content may be viable in hard rock environments. Accurate seismic imaging and reflection identification proved to be challenging but achievable task in the all-out hard rock environment of the Yilgarn craton. Accurate results were confounded by crocked seismic line acquisition, low signal-to-noise ratio, regolith distortions, small elastic property variations in the rock, and a limited volume of sonic logging. Each of these challenges, however, did have a systematic solution which allowed for accurate results to be achieved. / Seismic imaging was successfully completed on both the East Victory and Intrepid data sets revealing complex structures in the Earth as shallow as 100 metres to as deep as 3000 metres. The successful imaging required homogenization of the regolith to eliminate regolith travel-time distortions and accurate constant velocity analysis for reflection focusing using migration. Verification of the high amplitude reflections within each image was achieved through integration of surface geological and underground mine data as well as calibration with log derived synthetic seismograms. The most accurate imaging results were ultimately achieved on the East Victory line which had good signal-to-noise ratio and close-to-straight data acquisition direction compared to the more crooked Intrepid seismic line. / The sonic logs from both the East Victory and Intrepid seismic lines were comprehensively analysed by re-sampling and separating the data based on rock type, structure type, alteration type, and Au assay. Cross plotting of the log data revealed statistically accurate separation between harder and softer rocks, as well as sheared and un-sheared rock, were possible based solely on compressional-wave, shear-wave, density, acoustic and elastic impedance. These results were used successfully to derive empirical relationships between seismic attributes and geology. Calibrations of the logs and seismic data provided proof that reflections, especially high-amplitude reflections, correlated well with certain rock properties as expected from the sonic data, including high gold content sheared zones. The correlation value, however, varied with signal-to-noise ratio and crookedness of the seismic line. Subsequent numerical modelling confirmed that separating soft from hard rocks can be based on both general reflectivity pattern and impedance contrasts. / Indeed impedance inversions on the calibrated seismic and sonic data produced reliable volumetric separations between harder rocks (basalt and dolerite) and softer rock (intermediate intrusive, mafic, and volcaniclastic). Acoustic impedance inversions produced the most statistically valid volumetric predictions with the simultaneous use of acoustic and elastic inversions producing stable separation of softer and harder rocks zones. Similarly, Lambda-Mu-Rho inversions showed good separations between softer and harder rock zones. With high gold content rock associated more with “softer” hard rocks and sheared zones, these volumetric inversion provide valuable information for targeted mining. The geostatistical method applied to attribute analysis, however, was highly ambiguous due to low correlations and thus produced overly generalized predictions. Overall reliability of the seismic inversion results were based on quality and quantity of sonic data leaving the East Victory data set, again with superior results as compared to the Intrepid data set. / In general, detailed processing and analysis of the 2D seismic data and the study of the relationship between the recorded wave-field and rock properties measured from borehole logs, core samples and open cut mining, revealed that positive correlations can be developed between the two. The results of rigorous research show that rock characterization using seismic methodology will greatly benefit the mineral industry.

Les voies ferrées, construites pour la plupart depuis plus d'une centaine d'années, sont des ouvrages vieillissants. Elles nécessitent une maintenance et un entretien accrus, ce qui constitue un enjeu technique et économique majeur pour les années à venir. Jusqu'à l'ouverture des marchés à la concurrence, la mise en œuvre des voies nouvelles était vérifiée empiriquement par la SNCF. Du fait de la mise en œuvre de la directive européenne 91/440/10, l'exploitant historique se tourne d'un objectif de moyen vers un objectif de résultat. Cela nécessite donc de disposer de méthodes d'auscultation non destructives, permettant de vérifier que le compactage du ballast est correctement réalisé, avant de faire circuler le trafic voyageurs, en vue de garantir un niveau de sécurité élevé. Cette première approche pourrait être poursuivie pour assurer une auscultation à grand rendement. Cependant, les méthodes existantes permettant d'obtenir l'état de compactage du ballast à la mise en œuvre sont ponctuelles et difficiles à mettre en place; elles ne répondent pas à la problématique de doublement de la maintenance des voies des prochaines années. L'étude de la propagation d'ondes vibratoires dans le ballast est une alternative à ces méthodes qui peut permettre de répondre à ces contraintes. Le ballast est un milieu discontinu complexe pour la compréhension des ondes car elles se propagent dans un chaînon de force. Il présente une grande difficulté dans la modélisation du fait de la taille élevée des éléments et doit être traité comme un milieu discret ne répondant pas à une mécanique élastique de milieu continu. Étant donné la difficulté de modéliser cette couche discrète, il convient de traiter le problème par l'expérimentation. L'objectif de cette thèse est donc d'orienter la recherche vers l'utilisation de la propagation des ondes vibratoires dans la structure de la voie. Ce mémoire est organisé comme suit :- un premier chapitre détaille la structure de la voie ferrée et le matériau granulaire qu'est le ballast, ainsi que les méthodes de diagnostic des voies ferrées existantes.- le deuxième chapitre décrit les différents types d'ondes vibratoires se propageant dans un milieu élastique homogène, puis dans le ballast, et étudie la réponse du ballast à travers celle de la traverse ferroviaire.- Ces deux chapitres, issus de l'état de l'art, permettent de définir dans le chapitre trois les expérimentations réalisées dans le cadre de ce travail sur une structure ferroviaire en vraie grandeur : mise en œuvre, instrumentation, résultats. Ce chapitre s'attache particulièrement à décrire la vitesse des ondes et leur amortissement dans le ballast, les courbes de dispersion mesurées.- Enfin, la propagation d'une onde vibratoire dans le ballast est étudiée dans le chapitre quatre par le biais d'une simulation numérique, avec la comparaison de deux modélisations discrète et continue avec l'expérimentation / Railways, most of them built for over one hundred years, are old structures. They require increasing maintenance, a major technical and economic challenge for the coming years. Until the opening of markets to competition, the implementation of new railroads was empirically controlled by SNCF. Because of the application of the European directive 91/440/10, the historical operator turns from a goal of means to a goal of results. This calls for non-destructive highly efficient auscultation methods to check the right compaction of the ballast. However, existing methods for obtain ballast compaction assessment during implementation stage are surface-limited and difficult to apply; they do not respond to the issue of the doubling of track maintenance. Thus the study of the propagation waves in the ballast is an alternative to these methods and may allow to answer these requirements. The ballast is a discontinuous medium, complex for the understanding of waves, as they propagate in a force link. Modelling ballast is especially difficult because of the large size of its components and because it should be treated as a discrete environment, not following the elastic mechanics of continuous media. Given the difficulty to model this discrete layer, it is necessary to undertake the problem with experimentation. The aim of this thesis is to focus on the use of the propagation of vibration waves in the railroad structure. This work is organized as follows : the first chapter details the structure of the railroad and the ballast as a granular material, and the existing assessment methods for railroad. The second chapter describes the different types of vibration waves that propagate, first, in an elastic homogeneous medium, second in the ballast, and presents the answer of ballast through the answer of the sleeper. The two previous chapters, derived from the state of the art, allow to define in chapter three the experiments implemented as part of this work on a full scale railroad structure : realization, instrumentation, results. This chapter especially endeavours to describe the waves celerity, their damping in ballast and the measured dispersion curves. Finally, the propagation of a vibration wave in the ballast is studied in chapter four and a numerical simulation, compares with a disctete model and a continuous model with experimental results

La caractérisation et le monitoring des ressources en eau souterraine et des processus d'écoulement et de transport associés reposent principalement sur la mise en place de forages (piézomètres). Mais la variété des échelles auxquelles se déroulent ces processus et leur variabilité dans l'espace et dans le temps limitent l'interprétation des observations hydrogéologiques. Dans un tel contexte, l'hydrogéophysique fait appel aux méthodes de prospection géophysique afin, notamment, d'améliorer la très faible résolution spatiale des données de forage et de limiter leur caractère destructif. Parmi les outils géophysiques appliqués à l'hydrogéologie, les méthodes sismiques sont régulièrement utilisées à différentes échelles. Mais la réponse sismique dans le contexte de la caractérisation des aquifères reste complexe. L'interprétation des vitesses estimées est souvent délicate à cause de leur variabilité en fonction de la lithologie de l'aquifère (paramètres mécaniques intrinsèques et géométrie des milieux poreux le constituant, influence du degré de saturation, etc). La perméabilité du milieu a également un effet sur la géométrie d'un réservoir hydrologique dont les contours peuvent varier en espace comme en temps, compliquant ainsi l'interprétation des données sismiques.Les géophysiciens cherchent à pallier ces limites, notamment à travers l'étude conjointe des vitesses (Vp et Vs) des ondes compression (P) et de cisaillement (S), dont l'évolution est par définition fortement découplée en présence de fluides. D'un point de vue théorique, cette approche se révèle appropriée à la caractérisation de certains aquifères, en particulier grâce à l'estimation des rapports Vp/Vs ou du coefficient de Poisson. L'évaluation de ces rapports peut être pratiquée de manière systématique grâce à la tomographie sismique en réfraction en utilisant parallèlement ondes P et S. Mais d'un point de vue pratique, la mesure de Vs reste délicate à mettre en oeuvre car les ondes S sont souvent difficiles à générer et à identifier sur les enregistrements sismiques. Une alternative est proposée par l’estimation indirecte de Vs à partir de l’inversion de la dispersion des ondes de surface, réalisée à partir de mesures de la vitesse des ondes de surface contenues dans les enregistrements sismiques classiques. Bien que généralement proposée pour la caractérisation de milieux 1D, la prospection par ondes de surface peut être déployée le long de sections linéaires dans le but de reconstruire un modèle 2D de distribution des Vs du sous-sol.Une méthodologie a été mise au point afin d'exploiter simultanément et de façon optimale les ondes P et les ondes de surface à partir des mêmes enregistrements sismiques. Lors de sa mise en oeuvre sur le terrain, cette acquisition « en ondes P » a été systématiquement suivie d'une acquisition « en ondes SH » afin de comparer les vitesses Vs obtenues par analyse de la dispersion des ondes de surface et par tomographie en ondes SH. L'utilisation de cette méthodologie dans différents contextes géologiques et hydrogéologiques a permis d'estimer les variations latérales et temporelles du rapport Vp/Vs, en bon accord avec les informations géologiques a priori et les données géophysiques et piézométriques existantes. L'utilisation de l'interférométrie laser a également permis de mettre ces techniques de traitement en application sur des modèles physiques parfaitement contrôlés afin d'étudier la propagation des ondes élastiques dans des « analogues » réalistes de milieux poreux partiellement saturés. / Characterisation and monitoring of groundwater resources and associated flow and transport processes mainly rely on the implementation of wells (piezometers). The interpretation of hydrogeological observations is however limited by the variety of scales at which these processes occur and by their variability in space and in time. In such a context, using geophysical methods often improves the very low spatial resolution of borehole data and limits their destructive nature. Among the geophysical tools applied to hydrogeology, seismic methods are commonly used at different scales. However, the seismic response in the context of aquifer characterisation remains complex. The interpretation of the estimated velocities is often difficult because of their variability depending on the aquifer lithology (intrinsic mechanical parameters and geometry of the constituting porous media, influence of the degree of saturation, etc). The permeability of the medium also affects the geometry of a hydrological reservoir whose contours may vary in space and in time, thus complicating the interpretation of seismic data. Geophysicists seek to overcome these limitations, especially through the joint study of compression (P-) and shear (S-) wave velocities (Vp and Vs), whose evolution is by definition highly decoupled in the presence of fluids. From a theoretical point of view, this approach proves suitable for the characterisation of aquifers, especially by estimating Vp/Vs or Poisson's ratio. The evaluation of these ratios can be systematically carried out with seismic refraction tomography using both P- and S-waves. However, retrieving Vs remains practically delicate because S-waves are usually difficult to generate and identify on seismic records. As an alternative, indirect estimation of Vs is commonly achieved thanks to surface-wave dispersion inversion, carried out from measurements of surface waves phase velocities contained in typical seismic records. Although it is usually proposed for the characterisation of 1D media, surface-wave prospecting can be deployed along linear sections in order to build 2D models of Vs distribution in the ground. A specific methodology has been developed for the combined and optimised exploitation of P- and surface waves present on single seismic records. When deployed on the field, this "P-wave" acquisition has been systematically followed by a "SH-wave" acquisition in order to compare Vs models obtained from surface-wave dispersion analysis and SH-wave refraction tomography. The use of this methodology in several geological and hydrogeological contexts allowed for estimating Vp/Vs ratio lateral and temporal variations in good agreement with a priori geological information and existing geophysical and piezometric data. Laser-based ultrasonic techniques were also proposed to put these processing techniques in practice on perfectly controlled physical models and study elastic wave propagation in partially saturated porous media.