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Study of the effect of lateral inhomogeneities on the propagation of Rayleigh waves in an elastic mediumNasseri-Moghaddam, Ali January 2006 (has links)
The use of geophysical testing methods has considerable potential to be a cost effective and accurate technique to assess near-surface soil conditions. Multi channel analysis of surface waves (MASW) test is a geophysical non-intrusive test that uses the dispersive characteristic of Rayleigh waves to estimate low strain shear modulus and damping coefficient of near-surface soil. Also, this technique is used to detect underground voids. Recently, MASW technique has gained more attention, partly because of its ease of use and partly because of the significant improvements in data acquisition systems. The theories of MASW test consider the effect of horizontal soil layering, though the effect of lateral inhomogeneities (i. e. cavities and voids), inclined layering and inverse layering (i. e. a layered system in which the top layers are stiffer than the bottom ones) are not addressed properly in these theories. <br /><br /> The objective of this dissertation is to investigate the effect of lateral inhomogeneities on the propagation of Rayleigh waves in an elastic half-space excited by a transient loading. The results can be applied to locate underground cavities using MASW test and to improve the MASW analysis techniques. In lieu of theoretical solutions, two and three dimensional numerical models are constructed to simulate the MASW test. To assure the quality of the obtained data, numerical models are calibrated with Lamb solution. Voids with different sizes and embedment depths are inserted in the medium. Responses along the surface as well as inside the medium are recorded and analyzed in time, frequency, spatial and frequency-wave number domains. Different material types and sources are used to generalize the results. Afterwards, the combined effect of void and layered systems on the surface responses are studied. To verify the results, experimental field and laboratory data are presented and the trends are compared to the numerical results. <br /><br /> It is found that the void starts to vibrate in response to the Rayleigh wave excitation. Due to the vibration of the void energy partitioning occurs. Part of the incident energy is reflected in the form of Rayleigh wave. Another part is converted to body waves, and spread into the medium. The transferred part of the energy is attenuated and has smaller amplitudes. Finally, a part of energy is trapped in the void region and bounces back and forth between the void boundaries, until it damps. The trapped energy is associated to higher modes of Rayleigh waves and excited Lamb waves. The effect of trapped energy is seen as a region in the vicinity of the void with concentrated energy, in frequency domain. The extents of this region depends on the void size, and the frequency content of the incident energy. Thus, in some cases it is possible to correspond the size of the model to the extents of the region with energy concentration. <br /><br /> A new technique is proposed to determine the location of a void, and estimate its embedment depth. The technique is called Attenuation Analysis of Rayleigh Waves (AARW), and is based on the observed damping effect of the void on the surface responses. For verification, the results are compared to experimental field and laboratory data. The observations are in good agreement with the observed numerical results. Further, the AARW technique showed to be a promising tool for void detection.
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Determination Of The Dynamic Characteristics And Local Site Conditions Of The Plio-quarternary Sediments Situated Towards The North Of Ankara Through Surface Wave Testing MethodsEker, Mert Arif 01 August 2009 (has links) (PDF)
The purpose of this study is to assess the engineering geological and geotechnical characteristics and to perform seismic hazard studies of the Upper Pliocene to Quaternary (Plio-Quaternary) deposits located towards the north of Ankara through surface wave testing methods. Based on a general engineering geological and seismic site characterization studies, site classification systems are assigned in seismic hazard assessments. The objective of the research is to determine the regional and local seismic soil conditions (i.e., shear wave velocities, soil predominant periods and soil amplification factors) and to characterize the soil profile of the sites in this region by the help of surface geophysical methods. These studies have been supported by engineering geological and geotechnical field studies carried out prior to and during this study. By integrating these studies, local soil conditions and dynamic soil characteristics for the study area have been assessed by detailed soil characterization in the region. As a result, seismic hazard assessments have been performed for Ç / ubuk and its close vicinity with the aid of Geographical Information Systems (GIS) through establishing seismic characterization and local soil conditions of the area.
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Geoelectrical imaging for interpretation of geological conditions affecting quarry operationsMagnusson, Mimmi K. January 2008 (has links)
<p>Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping of the surface geology. However in Sweden the bedrock is often completely covered by Quaternary sediments making the prediction of subsurface geology quite difficult. Incorrect prediction of the rock-mass quality can lead to economic problems for the quarry. By performing geophysical measurements a more complete understanding of the subsurface geology can be determined. This study shows that by doing 2D-parallel data sampling a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Furthermore the electrical resistivity technique together with the induced polarization method proved to be very efficient in detecting fracture frequency, identification of major fracture zones, and variations in rock-mass quality all of which can affect the aggregate quality. With this technique not only the rock-mass quality is determined but also the thickness of the overburden. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits. </p>
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Modelo geológico 3D de reservatório carbonático albiano no sudoeste da Bacia de Campos (RJ) / 3D geological model of albian carbonate reservoir in the southwest of Campos Basin (RJ)Nascimento, Luana Fernandes do [UNESP] 21 October 2016 (has links)
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Previous issue date: 2016-10-21 / Outra / A área de estudo corresponde a um campo produtor de hidrocarbonetos situado no sudoeste da Bacia de Campos a 80 km da costa. Esta região produz hidrocarbonetos de diversos níveis estratigráficos, entre eles, os carbonatos do Albiano, foco deste estudo. O alto interesse econômico dos carbonatos no setor petrolífero mundial e a complexidade da sua análise nos dados geofísicos, justifica a importância desta pesquisa na definição de um método que auxilie na caracterização da distribuição regional da propriedade da rocha reservatório, neste caso, a porosidade. Neste contexto, este trabalho objetiva a determinação da heterogeneidade lateral e vertical das propriedades das rochas reservatórios, por meio da construção de um modelo geológico 3D de porosidade dos dois principais reservatórios identificados na Formação Quissamã (Grupo Macaé). Com esta finalidade, o método incluiu seis etapas principais: análise dos perfis geofísicos e correlação de poços, interpretação sísmica, conversão tempo x profundidade, análise de atributos sísmicos, análise geoestatística e modelagem geológica por meio da aplicação de Simulação Sequencial Gaussiana. Como níveis de referência, foram interpretados os intervalos estratigráficos correspondentes à Formação Outeiro e, na Formação Quissamã, os níveis Q1 e reservatórios R1 e R2 (principais produtores do campo). Estes níveis foram definidos com base na mudança do padrão geométrico dos perfis geofísicos de raio gama (RG), densidade (RHOB) e porosidade (Nphi). Os intervalos estudados estão distribuídos em um alto estrutural com eixo principal de direção NW-SE delimitado por falhas e pela própria geometria do banco carbonático. Na porção central do campo, este alto estrutural apresenta valores altos de porosidade (>21%), e se destacou no mapa de resistividade como portador de hidrocarbonetos nos reservatórios R1 e R2. Estas fácies carbonáticas variam para norte e nordeste da área com valores de porosidade mais baixos (<18%), representando a diminuição da qualidade dos reservatórios para estas regiões; esta observação, aliada à influência das falhas a sudoeste e nordeste do banco, permitiu classificar a trapa destes reservatórios como estrutural-estratigráfica. O sistema de falhas predominante na área de estudo corresponde ao NW-SE, que originou estruturas do tipo rollovers e horsts com potencial reservatório. Estas falhas abateram os blocos a sudeste e sul, que foram realçados nos mapas de atributos sísmicos como portadores de alta porosidade, comprovados por gráficos de correlação com coeficiente R2>0,65. Esta análise foi utilizada para determinar o modelo geológico 3D de porosidade, gerado por Simulação Sequencial Gaussiana. O resultado consistiu em uma representação coerente, com maior grau de certeza no alto estrutural central, que possui maior quantidade de dados de poços. Apesar das áreas a sudoeste e sul não apresentarem dados de poços, o método de Simulação Sequencial Gaussiana extrapolou altos valores de porosidade em 23% das 30 realizações geradas. / The study area is an ancient field and hydrocarbon producer, located in the southwest of the Campos Basin, in a water depth of approximately 100 m and 80 km distant from the coast. This region produces hydrocarbon from multiple stratigraphic layers, among them, there are the Albian carbonates, the focus of this research. The high economic interest in carbonates plays by the global oil industry and the complexity of their analysis in geophysical data, justifies the importance of this research to define a method, which determine the regional distribution of the property of the reservoir rock, in this case, the porosity. In this context, this study aims to determine the lateral and vertical heterogeneity of the properties of the reservoir rocks through the construction of a 3D geologic model of porosity from two main reservoirs in Quissamã formation (Macae Group). For this purpose, the method includes six major steps: analysis of well log and correlation of wells, seismic interpretation, conversion time vs. depth, analysis of seismic attributes, geostatistical analysis and geological modeling through the application of Gaussian simulation. The stratigraphic intervals such as Outeiro Formation and Quissamã Formation, which include level Q1, R1 and R2 reservoirs (main producers of the field) were interpreted as reference levels. These intervals were defined based on the change of the geometric standard of the geophysical profiles, as gamma ray (GR), density (RHOB) and porosity (Nphi). These levels are distributed in a carbonate bank with main axis in NW-SE direction, delimited by faults and its geometry. It was observed a structural high in the central portion of the field presenting high porosity values (> 21 %) that was highlighted in the resistivity maps as filled by oil in the reservoirs R1 and R2. These carbonate facies vary to the north and northeast of the area with lower values representing the decline in the quality of the reservoirs for these regions; this observation combined with the influence of the faults , in the southwest and northeast of the bank, allowed to classify the trap of these reservoirs as structural-stratigraphic. The predominant fault system in the study area corresponds to the NW-SE, which formed structures like rollovers and horsts with potential of being reservoir. These faults shot down the block to the southwest and south, which were highlighted in the maps of seismic attributes as having high porosity, supported by cross plots with correlation coefficient of R2> 0.65. This analysis was used to determine the 3D geologic model of porosity, generated by Gaussian simulation, most appropriate to the context of the geological area. The result was a coherent representation with greater certainty in the central structural high that presents a higher amount of well data. Despite the southwest and south areas do not present well data, the method was efficient in interpolate high values of porosity in 23% of 30 generated realizations. / PRH 05: 6000.0082154.13.4
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Identificação de areias siliciclásticas para a recuperação de praias em erosão através de métodos geofísicos acústicos / Sand search for beach nourisment by acoustic geophysical methodsNãnashaira Medeiros Siqueira 30 July 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Devido a sua grande extensão latitudinal, a costa brasileira é influenciada por diferentes regimes climáticos e oceanográficos. Adicionalmente, a distribuição da população brasileira é caracterizada por uma alta concentração nas capitais litorâneas. Todos esses fatores levam à construção de inúmeras estruturas de engenharia que podem de alguma forma impactar o transporte de sedimento e consequentemente o balanço sedimentar de algumas praias. Uma das formas mais eficientes de recuperar esse balanço sedimentar é a alimentação artificial de praias, com sedimentos provenientes da plataforma continental com características semelhantes. Os métodos geofísicos acústicos permitem mapear de forma eficiente o fundo e o subfundo marinho para a busca de áreas fontes para a lavra de forma eficiente. O objetivo deste estudo é a identificação de padrões geoacústicos a partir de analises quantitativas e qualitativas, para a caracterização de áreas fontes de areias siliciclásticas compatíveis com sedimentos de praias em erosão na cidade do Rio de Janeiro. O mapeamento foi realizado na plataforma continental interna do Rio de Janeiro, em área adjacente à praia de Itaipuaçu (Maricá, RJ). As análises evidenciaram depósitos, localizados entre 19 e 30 metros, de areias com granulometria, textura e selecionamento em condições ideias para a recomposição de praias do Rio de Janeiro. / The Brazilian coast is afected by different oceanographic characteristics, mainly due to its large latitudinal extention. Additionally, the distribution of the Brazilian population is characterized by a high concentration in the coastal capital. These facts generate a large number of coastal engineering structures that may impact the sediment transport and consequently the sediment balance in some beaches. All these factors impact some sand beaches and the best choice for its mitigation and recovering is the beach nourishment - with sediments from the continental shelf with similar characteristics. However to find a good place for dredging in the shelf, we need to use geophysical methods that allow to map the bottom and sub bottom environments more efficiently. The objective of this study is the identification of geoacoustics patterns, following qualitative and quantitative analyzes, for characterizing source areas of siliciclastic sands in ideal conditions for recovering eroded beaches in Rio de Janeiro. The mapping was done in the shelf in front of Itaipuaçu beach (Maricá, RJ). The quantitative results showed well sorted median sand placers seaward of the closure depth, located between 19 and 30 meters, ideal for Rios beaches recovering.
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InterSis : uma interface grafica para modelamento sismicoCalle Ochoa, Andres Eduardo 10 September 2003 (has links)
Orientadores: Martin Tygel, Rodrigo de Souza Portugal / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-03T20:40:40Z (GMT). No. of bitstreams: 1
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Previous issue date: 2003 / Resumo: o modelamento desempenha importante papel nos estudos de processamento e inversão de dados sísmicos. Muitos problemas complicados podem ser melhor atacados e entendidos quando os fenômenos de propagação de ondas envolvidos podem ser modelados, pelo menos em modelos geológicos mais simples. Tendo em vista ser o modelamento sísmico uma área de vasta aplicação e interesse, um grande número de pacotes computacionais existem capazes de oferecer sofisti-cadas capacitações para propósitos de modelagem. Esses pacotes são sujeitos entretanto, a severas limitações em sua utilização, não só devido aos seus altos custos, quanto também à inacessibi-lidade de seus códigos fonte. Por outro lado, as alternativas que existem, na forma de pacotes de uso livre, não representam substituição satisfatória. Isto porque os pacotes de modelamento disponíveis, geralmente desenvolvidos em ambientes científico-acadêmicos, não são suficiente-mente amigáveis e flexíveis, por exemplo na especificação de parâmetros de entrada, disposição gráfica de resultados, etc. o objetivo desta dissertação é investigar os principais problemas associados à construção de uma interface gráfica capaz de suportar uma variedade de programas de modelamento existentes e disponíveis como programas livres. Como resultado dessas investigações, é apresentada neste tra-balho a interface gráfica chamada InterSis. A interface InterSis foi construída de modo a aceitar, de forma simples e unificada, programas de modelamento destinados à propagação de ondas em meios 2D e 2.5D.InterSis foi desenvolvida utilizando os pacotes de domínio público GTK + (Graphical Tool/dt) e SU (Seismic Una). No seu presente estágio, InterSis é capaz de atuar como efetiva plataforma para os programas: (a) Seis88, um programa bem estabelecido de traçado de raios em mode-los elásticos e isotrópicos, desenvolvido por V. Cerveny e I. Psencík e (b) fd2d um programa de diferenças finitas para a equação de onda acústica, desenvolvido por 1. Costa. Como uma pro-priedade de particular interesse, InterSis utiliza a informação fomecida pelo programa Seis88 para computar os parâmetros do chamado método CRS (do Inglês Common-Reflection-Suiface). Desta forma, a interface proposta pode ser de valia nos estudos de imageamento e inversão que utilizam o método CRS. Vale notar que, devido à sua estrutura de caráter geral, InterSis pode ser bem adaptada a outros programas de modelamento / Abstract: Modelling plays an important role in seismie data processing and inversion. Several compli-cated problems can be better addressed and understood, when the wave propagation involved ean be modelled, at least in simple versions ofthe geological model. As a wide topie of application and interest, a number of commercial softwares exist that offer sophisticated capabilities for modelling purposes. These packages are subjected to a number of limitations on their use, not only of costs, but also because their source codes are not accessible. On the other hand, the few ahematives existo in the form of open packages do not represent an easy replacement. The available modelling codes, mainly developed within academie-scientific environments, are not friendly and flexible enough, e.g., in the specification of input parameters and display of resu1ts. The aim of this work is to investigate the main problems connected with the construction of a graphica1 interface that would be an useful support to a number of modelling programs available as open codes. As a result of the investigations, a graphical interface, ca1led InterSis, has been developed. InterSis ean accept and handle, in a simple and unified way,softwares that involves seismic modelling in 2D and 2.5D media. InterSis was developed using the public-domain softwares GTK + (Graphica/ Too/kit) and SU (Seismic Unix). In its present stage, it is able to be an effective platform for the following programs : (a) Seis88, a well-established ray-tracing program developed by v. Cerveny and I. PsenãK and (b) fd2d a finite-difference program for the acoustie wave equation developed by J. Costa. As a particular feature, InterSis uses the information provided by Seis88 to compute the parameters ofthe COmnJOlI-Rejlectioll-Surface (CRS) method. In this way, the proposed intedàce ean be useful to imaging and inversion studies based on the CRS method. It is to be noted that, due to its general s1ructure, InterSis can be well adapted to other modelling programs / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo
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Study of canopy variability and irrigable potential of rehabilitated and virgin mine lands by means of remote sensing and spatial analysisNarciso, Giovanni 01 August 2005 (has links)
Please read the abstract in the section 00front of this document / Dissertation (MSc (Agronomy))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted
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Aplicação de métodos geofísicos aplicados em pontos selecionados do Estuário do Rio Itanhaém / Application of the geophysical metods in selected places along Itanhaém River EstuaryVinhas, Maria Cecilia Sodero, 1968- 27 August 2018 (has links)
Orientador: Sueli Yoshinaga Pereira, Rodrigo de Souza Portugal / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-27T02:27:34Z (GMT). No. of bitstreams: 1
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Previous issue date: 2014 / Resumo: Essa pesquisa objetivou a aplicação e o entendimento da relação de três métodos geofísicos: eletrorresistividade, sísmica de refração e sismoelétrica; em pontos selecionados no Estuário do Rio Itanhaém e se eles podem ser validados pelas informações geológicas e hidrogeológicas da região. Os levantamentos foram realizados em duas etapas. A primeira etapa foi o de reconhecimento de campo, realizado no período de 21 a 26 de setembro/2009 que é considerado um período menos chuvoso. Os pontos escolhidos foram denominados de Ponto Praia, Ponto Chácara, Ponto Lixão e Ponto Country Club. A segunda etapa consistiu na coleta de dados propriamente dita nos pontos Chácara, Lixão e Country Club; o ponto Praia foi excluído por estar próximo às grandes torres de transmissão de energia, fazendo com que houvesse interferência nos dados. No ponto Lixão foi verificada a existência de gás metano, na superfície, através das bolhas de ar nas poças de água, no Ponto Country se localizava próximo a dois brejos e um pequeno córrego, e por fim o Ponto Chácara se localizava próximo ao Rio Branco, onde foi possível perceber a influência do aquífero livre na coleta dos dados. O período da segunda etapa dos levantamentos de dados ocorreu entre setembro de 2010 e agosto de 2011. Os levantamentos resultaram em um perfil vertical central, dos pontos selecionados, onde foram encontrados os seguintes materiais: areia, sedimentos arenosos, areia argilosa, argila seca, dois tipos de aquífero (de água doce e de água salobra), além de solos saturados e não saturados, e lixo. Em alguns levantamentos atingiram a rocha sã. Os levantamentos eletrorresistivos foram os que tiveram melhor resultado, os levantamentos de sísmica obtiveram uma camada apenas em quase todos os levantamentos, sendo que em um deles, o segundo campo do Ponto Country Club, se obteve mais de uma camada de material. Os levantamentos sismoelétricos não tiveram seus tratamentos finalizados, pois se percebeu que era necessária a utilização pré-amplificador; sua ausência no levantamento no campo, aliado a presença de linhas elétricas nos locais do levantamento, prejudicou nos resultados dos dados coletados, fato indicado pela presença das linhas harmônicas nos dados, e consequentemente não ter finalizado o algoritmo de tratamento desses dados / Abstract: This research intended the application and understanding about connexion among three geophysical methods: eletrical resistivity, refraction seismic and eletrical seismic; in selected places along Itanhaem River Estuary and if they can be accepted by geological and hydrogeological information of the region. The survey was accomplished in two phases. The first one was to recognize field of study, which was realized from 21st to 26th of September 2009, that is considered a less rainy season. The chosen sites were: Praia Point, Chácara Point, Lixão Point and Country Club Point. The second phase was the data collection, at these chosen sites, Chácara, Lixão and Country Club; The Praia Point was excluded because it was very near of large power transmission towers and it was causing interference in the collected information, at the Lixão Point was verified existence of methane, on the surface, through the air bubbles in puddles, in the case of Country Club Point was located near two swamps and a small stream, the Ranch Point was located near the river called Branco, and it was possible to realized the free influence of this aquifer in data collection. The second phase period of data collection, occurred between September 2010 and August 2011. The surveys resulted in a central vertical shape of the selected sites, where the following materials were found sand, sandy sediments, clayey sand, dry clay, two types of groundwater (freshwater and brackish water), and saturated and unsaturated soils and waste. In some surveys reached the bedrock. The electrical resistivity surveys were those who obtained better results, the seismic surveys obtained only a layer in almost all surveys, and in one of them, the second Country Club Point, got more than one layer of material. The electrical seismic surveys were not their treatments finalized, because it was realized the need to use a preamplifier; its absence in the field survey, combined with the presence of power lines in the survey sites, affected the collected data results, condition indicated by the presence of harmonic lines in the data, and consequently have not finalized these data processing algorithm / Doutorado / Geologia e Recursos Naturais / Doutora em Ciências
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Integração de dados sísmicos 3D e de perfis geofísicos de poços para a predição da porosidade de um reservatório carbonático da Bacia de Campos / Integration of 3D seismic data and geophysical well logs for porosity prediction of a carbonate reservoir in Campos BasinMori, Roberta Tomi, 1988- 04 September 2015 (has links)
Orientador: Emilson Pereira Leite / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Geociências / Made available in DSpace on 2018-08-27T16:08:56Z (GMT). No. of bitstreams: 1
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Previous issue date: 2015 / Resumo: Uma boa caracterização geológica dos reservatórios é de grande importância para a diminuição dos riscos da perfuração de um poço seco, assim como os custos de exploração e desenvolvimento de tal reservatório. No presente trabalho, buscou-se predizer os valores de porosidade de um reservatório através da integração de dados sísmicos 3D com perfis geofísicos de poços através de dois métodos: Regressão Linear Multiatributo e Redes Neurais Artificiais. O reservatório em questão é de constituição carbonática de origem Albiana, do final do Cretáceo Inferior. Na primeira etapa, foram traçados horizontes baseando-se em eventos sísmicos contínuos nas seções sísmicas, chamados superfícies cronoestratigráficas, no intervalo de profundidade que abrange o reservatório. Na segunda etapa, foram obtidos predições dos valores de porosidade do reservatório, assim como os respectivos modelos 3D, através dos dois métodos acima citados. Com a RLM, foram obtidos valores altos, baixos e intermediários de porosidade, variando desde 5% até 40%. Já com a RNA, tais valores variaram de 5% a 30%. Em ambos os métodos, os valores de porosidade apresentaram um crescimento da porção sudoeste em direção à porção nordeste, apresentando baixos valores nas profundidades referentes aos horizontes traçados. Picos com os valores máximos de porosidade foram observados em pontos dispersos por todo o volume 3D. Comparando-se os resultados obtidos pelos dois métodos, ficou evidente a maior eficácia da RNA, a qual apresentou correlação de 0,90 entre os valores reais e os valores preditos e erro de 2,86%, enquanto que os resultados obtidos através da RLM apresentou correlação de 0,55 e erro de 5,45%. Além disso, foi feita uma comparação com os aspectos geológicos do reservatório, na qual concluiu-se que as baixas porosidades da porção sudoeste se deve à presença de microporosidade e as altas porosidades da porção nordeste, à macroporosidade original das rochas. Concluiu-se também que as baixas porosidades encontradas nas regiões dos horizontes sísmicos estão relacionadas às diferentes texturas de rochas, já que as rochas presentes nessas regiões possuem maiores quantidades de matriz carbonática (packstones e wackestones) quando comparadas com as rochas das regiões entre os horizontes (grainstones) / Abstract: A good geological reservoirs characterization is very important for reducing the risk of drilling a dry hole as well as the costs for reservoir exploration and development. In this study, it was attempted to predict the porosity values of a reservoir through the integrations of 3D seismic data with geophysical well logs using two different methods: Multiattribute Linear Regression and Artificial Neural Networks. The studied reservoir has a carbonate composite, with the age of Albian, in late Early Cretaceous. On the first stage of the study, horizons have been traced based on continuous seismic events on seismic sections, in depths that cover the reservoir. On the second stage, it was obtained some predictions of reservoir porosity values, as well as their 3D models by the two methods that was already mentioned. High, low and intermediate porosity values have been obtained by the MLR, ranging from 5% to 40%. With the ANN, these values ranged from 5% to 30%. In both methods, the porosity values grew from south-west portion toward the northeast portion, with low values on the depths related to the horizons traced. We can observe maximum value peaks of porosity at points scattered throughout the 3D volume. A comparison of the results obtained by the two methods evidence the greater efficiency of the ANN, with a correlation of 0,90, between actual porosity and predicted values, and 2.86% of error, while the results obtained by the MLR showed a correlation of 0,55 and an error of 5.45%. Furthermore, we have made a comparison between the results obtained and the reservoir geological features, which allows us to conclude that the low porosity in the south-west portion is because of microporosity, while the high porosity in the northeast is because of the original macroporosity of the rocks. We also conclude that low porosity found on horizon surfaces are related to different rock textures, once the rocks on these horizon regions have more carbonatic matrix in their constitution (packstones and wackestones) than the rocks in the other regions between the horizons (grainstones) / Mestrado / Geologia e Recursos Naturais / Mestra em Geociências
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Geoelectrical imaging for interpretation of geological conditions affecting quarry operationsMagnusson, Mimmi K. January 2008 (has links)
Determination of the subsurface geology is very important for the rock quarry industry. This is primarily done by drilling and mapping of the surface geology. However in Sweden the bedrock is often completely covered by Quaternary sediments making the prediction of subsurface geology quite difficult. Incorrect prediction of the rock-mass quality can lead to economic problems for the quarry. By performing geophysical measurements a more complete understanding of the subsurface geology can be determined. This study shows that by doing 2D-parallel data sampling a 3D inversion of the dataset is possible, which greatly enhances the visualization of the subsurface. Furthermore the electrical resistivity technique together with the induced polarization method proved to be very efficient in detecting fracture frequency, identification of major fracture zones, and variations in rock-mass quality all of which can affect the aggregate quality. With this technique not only the rock-mass quality is determined but also the thickness of the overburden. Implementation of geophysics can be a valuable tool for the quarry industry, resulting in substantial economic benefits. / QC 20101118
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