Quando ocorrem solicitações dinâmicas nos solos, torna-se indispensável a determinação do módulo de cisalhamento máximo (Go) para elaboração de projetos de Engenharia Geotécnica. Este parâmetro pode ser determinado a partir da velocidade de propagação das ondas S (Vs). Em campo, os ensaios mais empregadas para determinação de Vs são o cross-hole e o down-hole. O down-hole tem sido bastante empregado com a incorporação de geofones em ponteiras de piezocone. Esse ensaio tem se mostrado uma maneira rápida, econômica e muito confiável para determinação de Go, apresentando resultados consistentes com os obtidos no ensaio cross-hole. O objetivo deste trabalho é o desenvolvimento de um sistema para realização do ensaio sísmico down-hole e sua implantação. Inúmeros ensaios foram realizados no campus da Universidade Estadual Paulista, em Bauru/SP a fim de testar os procedimentos para execução do ensaio, os equipamentos utilizados e as técnicas de interpretação, onde se observou que a manutenção do eixo de vibração dos geofones paralelo a direção de aplicação do golpe foi o fator que mais influenciou na qualidade dos sinais. Para analisar a resposta dos geofones instalados na ponteira desenvolvida, realizaram-se ensaios em laboratório, onde se verificou que os geofones apresentavam resposta idêntica ao dos acelerômetro de referência. Por fim, foram realizados ensaios em três campos experimentais no interior do Estado de São Paulo, onde estão disponíveis resultados de ensaios cross-hole e ensaios down-hole realizados com equipamentos comerciais. Os resultados obtidos com o sistema desenvolvido nestes campos permitiram validar o sistema desenvolvido. / In the design stages of geotechnical engineering of a given project, it is imperative to ascertain the maximum shear modulus (Go) of those soils experiencing dynamic loads. One common method to determine Go is to measure shear wave velocity. Most field experiments are the cross-hole and down-hole tests to determine the velocity of shear waves. The downhole test has been widely used in conjunction with geophones placed behind the tip of piezocones. The down-hole test has proven to be a fast, economic, and very reliable method to determine Go, it has produced data consistent with results obtained in cross-hole tests. The objective of this work is to present a comprehensive system for the down-hole test, which includes its implementation, execution, and the interpretation of data collected. Several tests were performed at the campus of Universidade Estadual Paulista, UNESP, in Bauru, S.P. The objective of those experiments was to test the execution procedures and method of interpretation. It was observed the quality of the results obtained was chiefly dependent on maintaining the axis of vibration of the geophones parallel to the direction of application of the original blow. The analysis of the response by the geophones installed at the tip of the cone included experiments performed at the laboratory, where it was observed that the geophones responded identically to those accelerometers used as reference. Further, downhole experiments using system proposed here were performed in three experimental research sites of the state of São Paulo. The objective was to compare results to the data available in literature, which were obtained using commercial SCPT equipment and cross-hole tests. The down-hole testswere performed within the guidelines of the system proposed here and the results of the experiment served to corroborate the suitability of the developed system.

Quando ocorrem solicitações dinâmicas nos solos, torna-se indispensável a determinação do módulo de cisalhamento máximo (Go) para elaboração de projetos de Engenharia Geotécnica. Este parâmetro pode ser determinado a partir da velocidade de propagação das ondas S (Vs). Em campo, os ensaios mais empregadas para determinação de Vs são o cross-hole e o down-hole. O down-hole tem sido bastante empregado com a incorporação de geofones em ponteiras de piezocone. Esse ensaio tem se mostrado uma maneira rápida, econômica e muito confiável para determinação de Go, apresentando resultados consistentes com os obtidos no ensaio cross-hole. O objetivo deste trabalho é o desenvolvimento de um sistema para realização do ensaio sísmico down-hole e sua implantação. Inúmeros ensaios foram realizados no campus da Universidade Estadual Paulista, em Bauru/SP a fim de testar os procedimentos para execução do ensaio, os equipamentos utilizados e as técnicas de interpretação, onde se observou que a manutenção do eixo de vibração dos geofones paralelo a direção de aplicação do golpe foi o fator que mais influenciou na qualidade dos sinais. Para analisar a resposta dos geofones instalados na ponteira desenvolvida, realizaram-se ensaios em laboratório, onde se verificou que os geofones apresentavam resposta idêntica ao dos acelerômetro de referência. Por fim, foram realizados ensaios em três campos experimentais no interior do Estado de São Paulo, onde estão disponíveis resultados de ensaios cross-hole e ensaios down-hole realizados com equipamentos comerciais. Os resultados obtidos com o sistema desenvolvido nestes campos permitiram validar o sistema desenvolvido. / In the design stages of geotechnical engineering of a given project, it is imperative to ascertain the maximum shear modulus (Go) of those soils experiencing dynamic loads. One common method to determine Go is to measure shear wave velocity. Most field experiments are the cross-hole and down-hole tests to determine the velocity of shear waves. The downhole test has been widely used in conjunction with geophones placed behind the tip of piezocones. The down-hole test has proven to be a fast, economic, and very reliable method to determine Go, it has produced data consistent with results obtained in cross-hole tests. The objective of this work is to present a comprehensive system for the down-hole test, which includes its implementation, execution, and the interpretation of data collected. Several tests were performed at the campus of Universidade Estadual Paulista, UNESP, in Bauru, S.P. The objective of those experiments was to test the execution procedures and method of interpretation. It was observed the quality of the results obtained was chiefly dependent on maintaining the axis of vibration of the geophones parallel to the direction of application of the original blow. The analysis of the response by the geophones installed at the tip of the cone included experiments performed at the laboratory, where it was observed that the geophones responded identically to those accelerometers used as reference. Further, downhole experiments using system proposed here were performed in three experimental research sites of the state of São Paulo. The objective was to compare results to the data available in literature, which were obtained using commercial SCPT equipment and cross-hole tests. The down-hole testswere performed within the guidelines of the system proposed here and the results of the experiment served to corroborate the suitability of the developed system.

This thesis utilizes several geophysical methods to study the Siljan Ring impact structure, focusing on the western part of the structure. This thesis, and the three papers upon which it is based, reports on attempts to delineate the Paleozoic rocks at depth within the annular ring graben and characterize their structure. In addition, the nature of the basement, which underlies these sedimentary rocks is investigated. Papers I and III focus on analysis of the down-hole logging and borehole core data. As well as the acquisition, processing and interpretation of 2D high-resolution reflection seismic data from the Mora area. The borehole log responses were compared with the core lithology from the Mora 001 borehole and information from two other cores (Mora VM 2 and Mora MV 3) in order to interpret the logs. The logs reveal significant changes in the lithology between boreholes, indicating a very high level of structural complexity, which is attributed to impact tectonics. In addition, the log data revealed a high sonic velocity contrast between the Silurian and Ordovician successions and a higher apparent temperature gradient than in the northern part of the structure. The interpretation of the high-resolution 2D seismic data suggest that the Mora area has been significantly affected by the impact. Several potential faults were identified in the area and interpreted to be post depositional and related to the impact. In paper II, a 2D seismic profile from the Orsa area (12 km) located in the northwestern part of the Siljan Ring was re-processed. To compliment this seismic line, first break traveltime tomography results, vintage seismic OPAB profiles, new and pre-existing gravity data, aeromagnetic data and the bedrock geological map were used to present a geological model along the Orsa profile. Reprocessing of the seismic data resulted in improved stacked and migrated sections and better imaging of the top of the crystalline basement than the original processing. Integrated interpretation of the seismic profiles suggests that the area has been significantly affected by faulting and that the depth to the basement varies greatly along the different profiles.

The need for energy and the associated economic benefits from the oil and gas deposits found mainly in the Niger Delta region of Nigeria necessitated the exploration and exploitation activities being carried out by the oil and gas Companies. However, these exploration and exploitation activities due to their unpredictable nature have a huge potential for environmental pollution as been experienced in the form of oil spills, gas flaring, irresponsible disposal of waste and several other activities that have resulted in the environmental degradation of the Niger Delta region. In the light of these, the Federal Government of Nigeria having experienced the consequences of pollution of the environment during the Koko Toxic Waste Dump incident in the then Bendel State in 1987 established a regulatory body tasked with the responsibility of harmonizing the economic interest from the oil and gas exploration and exploitation activities with the sustainability of the natural environment by developing well structured and articulated policies aimed at guiding the operations of the oil and gas operators, track their compliance and administer appropriate punitive measures for non compliance. However, this research work which is aimed at evaluating the impact of the environmental protection policies in upstream oil and gas activities in the Niger Delta region, involved the use of questionnaires and interviews. These questionnaires were completed by the management and staff of three major oil and gas companies operating within the area, the Department of Petroleum Resources and members of the Host communities. The interview was carried out to provide relevant feedback on their assessment of the impact made by the environmental protection policies on the upstream oil and gas activities in their operational areas/host communities. The study however concluded that “Although there is a regulatory body tasked with the responsibility to develop, implement and track compliance of the environmental protection policies in the upstream oil industry, the body is ineffective and as such the impact of the environmental protection policies is inadequate. Appropriate informed recommendations on the improvement strategies to the identified gaps that resulted in the unfavorable conditions were also provided. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011

The need for energy and the associated economic benefits from the oil and gas deposits found mainly in the Niger Delta region of Nigeria necessitated the exploration and exploitation activities being carried out by the oil and gas Companies. However, these exploration and exploitation activities due to their unpredictable nature have a huge potential for environmental pollution as been experienced in the form of oil spills, gas flaring, irresponsible disposal of waste and several other activities that have resulted in the environmental degradation of the Niger Delta region. In the light of these, the Federal Government of Nigeria having experienced the consequences of pollution of the environment during the Koko Toxic Waste Dump incident in the then Bendel State in 1987 established a regulatory body tasked with the responsibility of harmonizing the economic interest from the oil and gas exploration and exploitation activities with the sustainability of the natural environment by developing well structured and articulated policies aimed at guiding the operations of the oil and gas operators, track their compliance and administer appropriate punitive measures for non compliance. However, this research work which is aimed at evaluating the impact of the environmental protection policies in upstream oil and gas activities in the Niger Delta region, involved the use of questionnaires and interviews. These questionnaires were completed by the management and staff of three major oil and gas companies operating within the area, the Department of Petroleum Resources and members of the Host communities. The interview was carried out to provide relevant feedback on their assessment of the impact made by the environmental protection policies on the upstream oil and gas activities in their operational areas/host communities. The study however concluded that “Although there is a regulatory body tasked with the responsibility to develop, implement and track compliance of the environmental protection policies in the upstream oil industry, the body is ineffective and as such the impact of the environmental protection policies is inadequate. Appropriate informed recommendations on the improvement strategies to the identified gaps that resulted in the unfavorable conditions were also provided. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2011

Cette thèse s’inscrit dans le domaine de la modélisation des circuits analogiques et mixtes.Le travail part d’une problématique industrielle concernant les circuits électroniques utilisés dansles systèmes de forage pétrolier pour des besoins d’instrumentation et mesures. Ce travail de recherche concerne les circuits du front-end analogique que nous trouvons dans cette application industrielle. Nous examinons et nous essayons de trouver des modèles pour décrire l’effet des hautes températures sur les circuits électroniques dans un forage pétrolier. Ces circuits font partie des circuits industriels conventionnels. Ils ont généralement une température maximale de fonctionnement qui ne dépasse pas 125°C. Même si la température modifie le comportement de ces circuits, il existe des techniques d’adaptation qui permettent de compenser l’effet de la température sur ces circuits. Cependant, pour bien réussir la phase de la conception, il faut d’abord bien caractériser le comportement des différents circuits industriels utilisés en haute température. Il faut également trouver des modèles exacts qui décrivent le comportement de ces circuits en haute température. Or nous savons que la majorité des circuits industriels analogiques et mixtes sont décrits par des modèles de type SPICE. Par un choix de l’entreprise Schlumberger, notre partenaire industriel qui a financé ce travail, nous nous sommes intéressés dans notre étude à un composantspécifique présent dans la majorité des circuits analogiques et mixtes d’instrumentation :l’amplificateur opérationnel (l’AOP).Le travail commence par une étude des spécifications du circuit ainsi que le modèle SPICE.Une étude de la structure de ce modèle et sa simulation ont montré la non-précision du modèle audelàde 125°C. L’étude de validité du modèle a concerné le paramètre de la tension de décalage etle paramètre taux de rejection du mode commun. Nous avons interprété la différence des résultatsentre les mesures et la simulation de la tension de décalage. Nous avons constaté la limitation quereprésente l’approche structurelle par modélisation SPICE. Pour cette raison, nous avonssélectionné l’approche de modélisation comportementale pour les différents avantages qu’elleprésente. Ces avantages répondent à nos besoins et conviennent les mesures qui ont été effectuées.Nous avons sélectionné le langage VHDL-AMS et l’environnement Cadence ADVanceMS. Pourdéveloppé les modèles, nous avons alors énuméré les différents paramètres de performance d’unAOP. Nous avons validé la représentation de chaque paramètre par un circuit de test approprié.Dans un deuxième temps, nous avons approximé la variation de ces paramètres en température pardes équations polynomiales et exponentielles pour développer le modèle précis en HT. Le modèlea été validé par un circuit de test similaire au circuit expérimental. De bons résultats ont ététrouvés. L’erreur moyenne entre simulation VHDL-AMS et mesures n’a pas dépassé 3,11%. Dansle denier chapitre, nous avons simulé des circuits d’une chaine d’instrumentation. Nous avonssimulé l’effet de la température sur un capteur piézo-résistif (pont de Wheatstone). Trois architectures d’un amplificateur d’instrumentation ont été également modélisées e en se basant surle modèle VHD-AMS de l’AOP. / This work is dealing with the modelling of analogue and mixed signal circuits. Moreprecisely, we focus on modelling the circuits of an analogue front-end which is used in down-holedrilling industry for instrumentation and measurement purposes. This research had as a goal tomodel the temperature increasing effect in the behaviour of each circuit of the considered frontend.The studied circuits belong to the family of “conventional” circuits. Most of these circuitsoperate in a temperature which does not exceed 125°C. Even if the behaviour of the circuit changesdue to an increasing of the temperature, there are some well-know techniques that enable thecompensation of such effects. However, in order to obtain a precise simulation in the design phase,it is very important to have accurate models that describe the temperature increasing effect. Asmost of the commercial circuits models are written in SPICE, it is necessary first to review theaccuracy of SPICE models in high temperature (HT). This work focus on a specific circuit: theoperational amplifier (opamp). This device is present in many instrumentation circuits. Obtainingan accurate op-amp model in HT will help us develop accurate models of these circuits byconsidering their architectural description which is based on the opamp model.The work starts with the study of the structure of the SPICE model of the considered opamp.This study enables us to confirm the non-validity of the SPICE model in HT. The validity studyconsists in comparing the SPCE simulation results of two parameters (the voltage offset and thecommon mode rejection ratio) to measurement results. Moreover, we present an interpretation tothe difference that was observed in this comparison. After comparing different modellingapproaches, we select the behavioural modelling one. The VHDL-AMS was used to develop thenew precise opamp model in HT. The simulation is performance in Cadence/ADVanceMSenvironment. The representation of each opamp parameter is validated by a specific circuit. Thismodel is developed in two steps. In the first step, we develop an opamp model in which there is noconsideration of the temperature effect. In the second step, dependence of each parameter to thetemperature is described by a polynomial or exponential function. This function is the result of thefitting process of the measurement results. These equations are inserted in the VHDL-AMS model.All parameters are again validated in each temperature. The test-circuit is the same circuit used inthe experimental test of the opamp parameters. The average error between measurement andsimulation does not exceed 3.11%. In the last chapter, we simulate some circuits of the theanalogue front-end of an acquisition system. We simulate for example the effect of the temperatureeffect on the accuracy of a Wheatstone bridge. Three architecture of an instrumentation amplifierwere also modelled and simulated in different temperature of [20°C, 220°C] in the basis of thedeveloped opamp model.