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Oil is the black blood that runs through the veins of the modern global energy system. While being the dominant source of energy, oil has also brought wealth and power to the western world. Future supply for oil is unsure or even expected to decrease due to limitations imposed by peak oil. Energy is fundamental to all parts of society. The enormous growth and development of society in the last two-hundred years has been driven by rapid increase in the extraction of fossil fuels. In the foresee-able future, the majority of energy will still come from fossil fuels. Consequently, reliable methods for forecasting their production, especially crude oil, are crucial. Forecasting crude oil production can be done in many different ways, but in order to provide realistic outlooks, one must be mindful of the physical laws that affect extraction of hydrocarbons from a reser-voir. Decline curve analysis is a long established tool for developing future outlooks for oil production from an individual well or an entire oilfield. Depletion has a fundamental role in the extraction of finite resources and is one of the driving mechanisms for oil flows within a reservoir. Depletion rate also can be connected to decline curves. Consequently, depletion analysis is a useful tool for analysis and forecasting crude oil production. Based on comprehensive databases with reserve and production data for hundreds of oil fields, it has been possible to identify typical behaviours and properties. Using a combination of depletion and decline rate analysis gives a better tool for describing future oil production on a field-by-field level. Reliable and reasonable forecasts are essential for planning and nec-essary in order to understand likely future world oil production.

This thesis analyses Turkey&rsquo / s energy policies and Turkey&rsquo / s foreign relations through the energy issues in the Eurasian region. In the first phase, the energy policies implemented by the state and free market orientation in Turkish energy sector will be discussed. The impacts of neo-liberal economic policies, regional organizations (the European Union and OECD), and global finance institutions (International Monetary Fund &ndash / the IMF and the World Bank &ndash / WB) on Turkish energy sub-sectors, particularly since the beginning of the 1980s, will be examined. In the second phase, Turkey&rsquo / s own autonomy and effectiveness within major energy pipeline projects in the Eurasian energy axis will be questioned in the post-Cold War period. Turkey&rsquo / s relations in the energy issues with the European Union, Middle East, Caucasus and Turkic States, Russia and the United States (US) will be discussed. Basic vulnerabilities in Turkish energy sector and possible acquisitions of Turkey through its international energy deals will be emphasized.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 4 uppsatser.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work seeks to analyze at different frequencies, the transmission of volatility in the prices of crude oil produced by OPEC members and other producing and exporting countries that are not part of this organization and to analyze the presence of structural breaks in dynamic correlation between crude oil spot and future prices. The Wavelets methodology employed aims to decompose the series to verify its behavior at different frequencies, revealing additional information or confirming trends. To check the transmission process of the volatility it is proposed the application of Granger Causality Test. This made it possible to understand the functioning of this important market and answer the following question: How behaves the volatility of oil prices when analyzed considering several time horizons in an analysis in the frequency domain? The analysis of volatility transmission shows a strong integration of the international oil market, the correlation structural breaks tests results shows that structural break point is not static for any analysis, it moves, depending the frequency scale and the time window. / Este trabalho busca analisar em diferentes frequências, o sentido e a transmissão da volatilidade nos preços do petróleo bruto produzido pelos países membros da OPEP (Organização dos Países Exportadores de Petróleo) e dos demais países produtores e exportadores que não fazem parte desta organização; bem como analisar a presença de quebras estruturais na correlação dinâmica entre os preços à vista e futuro do petróleo. A metodologia de Wavelets empregada tem por objetivo decompor as séries estudas a fim de verificar seu comportamento em diferentes frequências, revelando informações adicionais ou confirmando tendências observadas. Para a verificação do processo de transmissão da volatilidade foi proposta a utilização do método de Causalidade de Granger. Desta forma foi possível compreender o funcionamento deste importante mercado e responder a seguinte questão: Como se comporta a volatilidade do preço do petróleo quando se analisam variados horizontes de tempo em uma análise no domínio da frequência? A análise da transmissão da volatilidade aponta para uma forte integração do mercado internacional do petróleo, enquanto o resultado da análise das quebras na correlação mostra que o ponto de quebra estrutural não é estático para toda e qualquer análise, ele se move, dependendo da frequência e do horizonte temporal.

The objective of this research was to evaluate the forage yield and nutritive value of elephantgrass on conventional and organic systems. In the organic system, species with complementary growth periods were combined; elephantgrass was planted in lines 3m apart from each other; between the rows of elephantgrass, during the winter period, ryegrass was sown and in the summer period the development of species of spontaneous growth was allowed. In the conventional production, two pastures were studied, one with the same strategy of organic production, but with chemical fertilization and another with elephantgrass cultivated alone. 100 kg of N ha-1 were applied with mineral and organic fertilization (bovine manure and pig slurry) in conventional and organic systems, respectively. Holstein cows receiving 0.9% of body weight complementary concentrate feed were used in the evaluation. The experimental design was completely randomized, with three treatments (forage systems), three repetitions (paddocks) and with repeated measures in time (seasons). Forage mass parameters of pre and post grazing, botanical composition, forage production and nutritive value were evaluated. Forage samples were collected by hand-plucking technique for the determination of organic matter, crude protein and in situ digestibility of organic matter. During the experimental period (337 days) seven grazing cycles were performed. Forage production and stocking rate were 12548; 10270; 19168 kg ha-1 and 3.3; 2.1; 4.5 AU ha-1 dia-1, respectively, for the forage systems. Pastures mixed, on conventional and organic production, present best forage distribution throughout the seasons. Higher value of forage production was observed in elephantgrass cultivated alone, on conventional system. Better value of nutritional value parameters were observed in organic pasture. / O objetivo desta pesquisa foi avaliar a produção de forragem e o valor nutritivo do capim-elefante nos sistemas convencional e orgânico. No sistema orgânico, combinaram-se espécies com períodos de crescimento complementares; o capim-elefante foi plantado em linhas com 3m de distância uma da outra; entre as fileiras de capim-elefante, durante o período de inverno, foi semeado azevém e no período de verão permitiu-se o desenvolvimento de espécies de crescimento espontâneo. Na produção convencional, foram estudadas duas pastagens, uma com a mesma estratégia de produção orgânica, porém com adubação química e outra de capim-elefante sob cultivo singular. Foram aplicados 100 kg de N ha-1 com adubação mineral e orgânica (esterco de bovinos e dejetos de suínos) nos sistemas convencional e orgânico, respectivamente. Como animais experimentais foram utilizados vacas da raça Holandesa, recebendo alimentação complementar na forma de concentrado à razão de 0,9% do peso corporal. O delineamento experimental foi o inteiramente casualizado, com três tratamentos (sistemas forrageiros), três repetições (piquetes) e medidas repetidas no tempo (estações). Foram avaliados os parâmetros de massa de forragem pré e pós-pastejo, composição botânica, produção de forragem e valor nutritivo. Para a determinação de matéria orgânica, proteína bruta e digestibilidade in situ da matéria orgânica, foram coletadas manualmente amostras de forragem mediante técnica de simulação de pastejo. Durante o período experimental (337 dias) foram realizados sete ciclos de pastejo. A produção de forragem e a taxa de lotação foram de 12548; 10270; 19168 kg ha-1 e 3,3; 2,1; 4,5 UA ha-1 dia-1, para os sistemas forrageiros. Pastos com misturas forrageiras, sob produção convencional e orgânica, apresentam a melhor distribuição de forragem ao longo das estações. O maior valor de produção de forragem foi observado em pastagens cultivadas singularmente, no sistema convencional. Melhores parâmetros de valor nutricional foram observados em pastagens orgânicas.

Cette thèse analyse comment les fluctuations du prix du pétrole affectent les économies des pays exportateurs de produits de base. Plus précisément, l'objectif de cette thèse est d'étudier les impacts macroéconomiques, financiers et environnementaux des fluctuations des prix du pétrole, en accordant une attention particulière à l'hypothèse de la monnaie du pétrole. À cette fin, cette thèse se compose de trois chapitres. Les premier et deuxième chapitres portent sur le taux de change réel des devises de plusieurs pays exportateurs de pétrole. Le troisième chapitre explore les liens entre le prix des biocarburants et le compte courant des pays émergents et en développement exportant ou important des matières premières agricoles contrôlant l'effet non linéaire potentiel exercé par le prix du pétrole sur cette relation. Ces chapitres montrent que si le prix du pétrole a un effet macroéconomique sur les économies exportatrices de pétrole et les pays exportateurs de produits agricoles, son impact varie d'un pays à l'autre et il n'y a pas de règle unique pour décrire le fonctionnement de ces économies. / This thesis analyzes how fluctuations in the price of oil affect the economies of commodity exporting countries. More specifically, the aim of this thesis is to investigate the macroeconomic, financial and environmental impacts of oil price fluctuations, by paying particular attention to the oil currency hypothesis. To this end, this thesis is composed of three chapters. The first and second chapters deal with the real exchange rate of the currencies of several oil exporting countries. The third chapter explores the links between the price of biofuels and the current account of emerging and developing countries exporting or importing agricultural raw materials controlling for the potential nonlinear effect exerted by the price of oil on this relationship. Altogether these chapters show that while the price of oil has a macroeconomic effect on oil exporting and agricultural commodities exporting countries, its impact varies across countries and there is no one fits all rule.

L’amélioration de la récupération d’énergie dans les procédés industriels passe par une meilleure compréhension des phénomènes d’encrassement dans les échangeurs de chaleur. L’encrassement se caractérise par la formation de dépôts non désirés sur les surfaces d’échange de l’échangeur. Cette étude porte sur l’amélioration de l’efficacité énergétique des raffineries de pétrole par réduction de l’encrassement dans les échangeurs de chaleur du train de préchauffe.Pour cela, une boucle d’essai reproduisant les niveaux d’échange et les écoulements rencontrés en raffinerie a été employée pour tester un échangeur de type tubes et calandre. Les fluides traités sont du pétrole brut et de résidu de distillation atmosphérique (coupe lourde du pétrole) comme dans le procédé industriel. On s’intéresse à l’influence de la géométrie de l’échangeur. Des faisceaux de tubes avec des corrugations internes hélicoïdales et des ailettes externes sont successivement testés. Pour chacune des technologies, les paramètres opératoires optimums permettant de limiter la formation d’un dépôt encrassant sont identifiés sur une gamme de température de film et de cisaillement s’échelonnant respectivement de 230 à 300°C et de 1,3 à 8,8 N/m2. L’efficacité des tubes optimisés pour lutter contre l’encrassement est évaluée par comparaison avec l’encrassement obtenu sur le faisceau de tubes lisses pris comme référence. Les deux technologies se sont révélées efficaces pour réduire l’encrassement. Par rapport aux tubes lisses, l’encrassement a été réduit d’un ordre de grandeur à cisaillement et température de film équivalentes aussi bien avec les tubes structurés qu’ailetés.En parallèle, une simulation d’encrassement numérique (CFD) a été élaborée pour mieux comprendre le développement de l’encrassement dans l’échangeur équipé de tubes lisses. Les phénomènes dominants à l’origine de l’encrassement de l’échangeur ont été déterminés : la vitesse de formation du dépôt, peu affectée par les variations spatiales de la thermo-hydraulique, pilote l’encrassement. Les hétérogénéités d’encrassement sont causées par les disparités locales de la vitesse d’arrachement du dépôt qui varie en grande proportion mais dont l’influence sur la vitesse d’encrassement est faible. Elles sont dues à une inhomogénéité spatiale du cisaillement qui est la conséquence de l’établissement de l’écoulement dans les tubes. Une tentative d’amélioration de la précision de la prédiction de l’encrassement a été également entreprise en optimisant les paramètres d’un modèle d’encrassement existants et en tenant compte du vieillissement du dépôt. / Improving energy recovery in industrial processes requires a better understanding of fouling phenomena in heat exchangers. Fouling is the grow up of unwanted materials on heat transfer surfaces. This study focuses on improving the energy efficiency of petroleum refineries by reducing fouling in heat exchangers of the pre-heat train.For this purpose, a test rig reproducing thermal and flow characteristics encountered in the last heat exchanger of the pre-heat train was used to test a pilot-scale shell-and-tube heat exchanger. Fluids are the same as the ones processed in refineries: crude oil and atmospheric tower bottom, a heavy residue of oil. This study focuses on the influence of the heat exchanger geometry. Internally helically-finned tubes and externally low-finned tube bundles are successively tested. For each one, optimum operating parameters which reduce fouling are identified over a 230-300°C film temperature range and a 1.3-8.8 N/m2 wall shear stress range. The fouling mitigation efficiency of the enhanced tubes is compared with smooth tubes taken as a reference. Compared to smooth tubes, fouling on helically-finned and low-finned tubes is reduced by an order of magnitude when they are operated at equivalent wall shear stress and film temperature.In addition, a numerical (CFD) fouling simulation has been developed to provide a better understanding of the fouling in the heat exchanger with smooth tubes. Dominant phenomena driving fouling in the heat exchanger were determined. The deposition rate is weakly impacted by the spatial variations of the thermo-hydraulic and controls the overall fouling rate. Heterogeneities in fouling rate are caused by the local scattering in the removal rate, which varies in a broad range but whose impact on the overall fouling rate is low. The broad range of the shear stress is the consequence of the fluid flow entrance effects. An attempt to improve accuracy of the fouling model has been undertaken by optimizing the model parameters and by considering aging of the deposit.

Cette thèse porte sur l'utilisation de champs électriques pour faciliter l'élimination de l'eau coproduite avec le pétrole brut, sous la forme d'émulsions stables, lors des étapes d'extraction et de dessalement. Ce procédé, connu sous le nom d'électrocoalescence, s'appuie sur la capacité qu'ont les forces électrostatiques à promouvoir l'attraction et la coalescence de gouttelettes d'eau proches afin d'en augmenter la taille et ainsi d'en accélérer la sédimentation par gravité. Bien que les premières observations expérimentales datent déjà d'un siècle, de nombreuses zones d'ombres subsistent, notamment en ce qui concerne l'optimisation de l'efficacité des électrocoalesceurs de dernière génération. Dans ce contexte, une démarche, combinant simulation numérique multi-physique et expérimentation, a été mise en place pour étudier les phénomènes de mouvement, de déformation et d'instabilité d'interfaces eau-huile induit par la présence d'un champ électrique. La contribution la plus marquante concerne la modélisation et l'analyse de l'effet des forces électrostatiques sur le mécanisme d'amincissement du film d'huile séparant les gouttes. Les résultats numériques mettent en évidence la singularité du problème et l'inadaptabilité des modèles théoriques de lubrification classiquement adoptés pour représenter la coalescence dans les écoulements diphasiques. Une nouvelle expression asymptotique pour le calcul du temps de drainage entre les gouttelettes de l'émulsion est proposée et utilisée pour déduire un critère prédisant la probabilité d'électrocoalescence lors d'une collision dans un écoulement cisaillé. En parallèle, un dispositif sophistiqué, permettant de reproduire expérimentalement le phénomène et d'améliorer la représentativité du critère, a été construit. Enfin, en réponse à un point bloquant décelé lors de la phase de conception de ce dernier, une technique innovante d'injection à la demande de gouttes conductrices non chargées dans un liquide visqueux isolant, utilisant des impulsions électrostatiques, a été développé. / The present thesis deals with the electrostatically assisted removal of water coproduced with crude oil in the form of stable emulsions during recovery and desalting operations. This process, referred to as electrocoalescence, exploits the ability of electric forces to promote attraction and merging of adjacent water droplets to increase their size and related natural rate of sedimentation under gravity. Still, even one century after the first experimental observations, a lot of gray areas remain, particularly on the optimization of efficiency in state-of-the-art separators. To address this question, an approach combining multi-physics simulation and experiments has been used to investigate the phenomena of motion, deformation and instability of electrically influenced water-oil (droplets) interfaces. The main contribution concerns the modeling and analysis of the mechanism of oil film thinning between droplets approaching under the effect of electrostatic forces. Results from simulations highlight the strong singularity of the present problem and the inadequacy of existing theoretical lubrication models usually employed to represent coalescence events in two phase flows. For the small emulsified droplets, a new asymptotic expression for the drainage time is obtained and allows to deduce a criterion predicting the probability of electrocoalescence resulting from a shear flow induced collision. In parallel, a sophisticated setup, enabling to experimentally investigate the phenomenon and to improve the criterion relevance with regards to the actual processing conditions, has been assembled. At last and as an answer to an otherwise unfulfilled requirement defined in the design of the latter, an innovative actuation technique for the synchronous on-demand injection of two charge free conductive droplets in an insulating viscous liquid, relying on the application of a high electric field pulse, has been implemented.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Researches with the use of inoculants containing bacteria that promote plant growth have been increasing over the years, due to concerns about pollution and high costs of fertilizers. Therefore the objective of this research was to evaluate the forage yield, nutritive value, biological nitrogen fixation (BNF) and the N recovery of Coastcross-1 pastures inoculated with Azospirillum brasilense subjected to cut. The experimental design was randomized blocks with three replications, in a factorial scheme. The factors were the inoculation (without inoculation, inoculated just in the implantation and reinoculated in the second year), levels of nitrogen (0, 100 and 200 kg of N/ha/year) and periods of the years where cuts were made. Forage yield, daily accumulation rate, forage mass, botanical and structural pasture composition, crude protein content, in situ digestibility of organic matter and total digestible nutrients of Coastcross-1 were evaluated during two years. Forage yield without nitrogen fertilizer use in pastures was in the first year 9.1, 11.7 and 11.7 t of DM/ha, and in the second year 8.6, 11.2 and 11.5 t of DM/ha, to inoculation factor, respectively. The average Coastcross-1 contribution in pastures without nitrogen fertilization was 47.9, 58.5 and 62.7%, respectively to the inoculation. There was reduction in Coastcross-1 crude protein content when pasture fertilized with 200 kg of N/ha/year was inoculated. The forage yield and Coastcross-1 contribution rises with the inoculation without nitrogen fertilizers use; and reinoculation is not necessary. To evaluate BNF and the N recovery two treatments were considered for each variable. Evaluations were carried out during one year. To estimate the BNF the treatments were: Coastcross-1 inoculated and Coastcross-1 uninoculated, both without nitrogen fertilization. The biologically fixed nitrogen was 53.8 and 23.0 kg/ha/year for Coastcross-1 inoculated and uninoculated, respectively. In Coastcross-1 without nitrogen fertilization, inoculation elevates the BNF. To estimate the N recovery the treatments were: Coastcross-1 inoculated and Coastcross-1 uninoculated, both fertilized with 100 kg of N/ ha/year. Isotopic recovery of N was 16.5 and 13.7 kg/ha/year for Coastcross-1 inoculated and uninoculated, respectively. Inoculation increases recovery of N in Coastcross-1. The forage yield increase when don’t use nitrogen fertilizers with the inoculation is related to the increase of biological nitrogen fixation. / Pesquisas com o uso de inoculantes contendo bactérias promotoras do crescimento vegetal vêm aumentando ao longo dos anos, devido a preocupações com a poluição e o elevado custo dos fertilizantes. Desta forma, nesta pesquisa objetivou-se avaliar a produção de forragem, o valor nutritivo, a fixação biológica de nitrogênio (FBN) e a recuperação do nitrogênio (N) fertilizante em pastos de Coastcross-1, inoculados com Azospirillum brasilense e submetidos ao regime de corte. O delineamento experimental foi o de blocos ao acaso, com três repetições, em esquema fatorial. Os fatores foram o uso da inoculação (não inoculado, inoculado somente no plantio e reinoculado no segundo ano), doses de N (0, 100 e 200 kg de N/ha/ano) e os períodos do ano em que foram realizados cortes dos pastos. Avaliaram-se no decorrer de dois anos agrícolas a produção de forragem, a taxa de acúmulo de forragem, a massa de forragem, as composições botânica e estrutural do pasto, o teor de proteína bruta, a digestibilidade in situ da matéria orgânica e os nutrientes digestíveis totais da Coastcross-1. As produções de forragem, nos pastos sem aplicação de N, no primeiro ano, foram de 9,1; 11,7 e 11,7 t de MS/ha, e no segundo ano de 8,6; 11,2 e 11,5 t de MS/ha, para o fator inoculação, respectivamente. A participação média da Coastcross-1 nos pastos sem adubação nitrogenada foi de 47,9; 58,5 e 62,7%, respectivamente para o fator inoculação. Houve redução nos teores de proteína bruta da Coastcross-1, quando o pasto adubado com 200 kg de N/ha/ano foi inoculado. Há aumento na produção de forragem e na participação da Coastcross-1 com a inoculação na implantação dos pastos, quando não há aplicação de N, sendo que, a reinoculação não é necessária. Para a avaliação da FBN e da recuperação do N, foram considerados dois tratamentos para cada variável. As coletas foram realizadas durante um ano agrícola. Para a estimativa da FBN os tratamentos foram: a Coastcross-1 inoculada no plantio e a Coastcross-1 não inoculada, ambas sem adubação nitrogenada. O N biologicamente fixado foi de 53,8 e 23,0 kg/ha/ano para Coastcross-1 inoculada e não inoculada, respectivamente. A inoculação eleva a FBN na Coastcross-1 não submetida à adubação nitrogenada. Para a estimativa da recuperação do N aplicado os tratamentos foram: a Coastcross-1 inoculada no plantio e a Coastcross-1 não inoculada, ambas submetidas à adubação com 100 kg de N/ha/ano. A recuperação isotópica de N foi de 16,5 e 13,7 kg/ha/ano para Coastcross-1 inoculada e não inoculada, respectivamente. A inoculação aumenta a recuperação do N fertilizante aplicado pela Coastcross-1. A elevação da produção de forragem em pastos não submetidos à adubação nitrogenada causada pela inoculação tem relação com o aumento da FBN.