Orientador: Osvair Vidal Trevisan / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-21T20:38:31Z (GMT). No. of bitstreams: 1 MedeirosJunior_Flavio_M.pdf: 5849713 bytes, checksum: d198866e74ce5c49813b449117b5005b (MD5) Previous issue date: 1996 / Resumo: As operações de Acidificação de Matriz são usadas com freqüência para remoção do dano à formação causado por partículas sólidas de minerais que obstruem parcialmente o espaço poroso nas proximidades do poço. A cinética da reação química entre o ácido e os minerais da rocha é bastante sensível à temperatura na qual a reação se desenvolve. A temperatura do ácido na zona injetora depende dos fenômenos de transferência de calor que ocorrem no interior da coluna de injeção e no reservatório submetido à injeção do ácido. Normalmente utiliza-se pequenos volumes de ácidos bombeados com vazões médias e altas tendo como conseqüência pequenos períodos de injeção. O modelo proposto para o cálculo da temperatura na coluna considera os termos de acumulação de calor no interior da coluna e no anular, além da hipótese de poço com raio finito, importantes para soluções de curto tempo. No reservatório são consideradas as perdas para a formação vizinha e analisada a influência do calor gerado pela reação química no comportamento da temperatura do ácido. As hipóteses de condução de calor desprezível na direção do fluxo de fluido, equilíbrio térmico instantâneo, gradiente geotérmico linear e condução de calor unidimensional na formação também são utilizadas. A solução para temperatura do ácido na zona. injetora é apresentada no espaço de Laplace considerando o acoplamento da solução para temperatura na coluna à solução para a temperatura no reservatório através do teorema da convolução. A inversão numérica das funções no espaço de Laplace é feita com o algoritmo de Stehfest. Os resultados obtidos indicam que a temperatura do ácido na zona injetara é bastante sensível à vazão do ácido injetado e aos volumes deslocados a frente do tratamento, podendo atingir valores significativamente inferiores à temperatura do reservatório no decorrer da operação / Abstract: Matrix Acidization is frequently used to remove formation damage from pore plugging caused by deposition of small mineral particles. The kinetics of the chemical reactions between acid and minerais is very sensitive to fluid temperature. The temperature of the acid at the injection zone depth depends on the heat transfer that occurs as the acid travels through the injection column and on the heat exchange with the reservoir rock and fluids. The volume of injected acid is usually small and the injection time is short, compared to other thermal injection operations. Two heat transfer models are proposed: one to calculate the temperature profile along the injection column and other to calculate the temperature distribution within the reservoir. The model proposed here for the heat transfer along the column incorporates heat accumulation (in the fluid and at the annulus) to the heat exchange between the wellbore and the semi-infinite surroundings. For the heat transfer in the reservoir, the modei accounts for the conductive losses to the neighboring formation, the heat generation from the chemical reactions and heat transported by the injected fluid. The eventual temperature distribution for the acid in the reservoir is obtained after coupling of the solution for the column problem and the solution for the reservoir problem. Both problems were solved by Laplace transforms and the final solution is obtained using the convolution theorem. Stehfest's algorithm is used to invert the solution to real domain. Results for typical operational parameters show that the acid temperature is very sensitive to the injection flow rate and to the fluid volumes injected during the pre-treatment. The acid temperature can be significantly lower than the reservoir temperature along the operation / Mestrado / Mestre em Engenharia de Petróleo

Orientador: Paulo Roberto Ribeiro / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T14:14:36Z (GMT). No. of bitstreams: 1 LimaNeto_EpaminondasGonzaga_M.pdf: 3589611 bytes, checksum: e5bb12837c541392cc224ea75b48dc4b (MD5) Previous issue date: 2014 / Resumo: O cenário das perfurações de poços de petróleo vem mudando ao longo do tempo. Tanto pela necessidade do suprimento da demanda crescente por petróleo e gás quanto pela queda na produção de campos maduros, a perfuração de poços tem se deparado com ambientes mais agressivos a cada dia: maiores temperaturas, maiores pressões, maior afastamento em relação à costa e ambientes quimicamente mais hostis. A presença considerável de dióxido de carbono - CO2 - nos reservatórios aponta para uma maior preocupação na perfuração de poços em tais formações uma vez que, se esse componente adentra ao poço numa situação de kick, sua interação com a lama de perfuração pode alterar características importantes desse fluido, tais como: densidade, viscosidade e acidez. Este trabalho tem por objetivo investigar o comportamento PVT de sistemas contendo CO2 e líquidos com composição similar aos fluidos de perfuração à base de óleo: n-parafina pura e emulsão inversa. Foram realizados um estudo experimental de tais sistemas, uma simulação computacional, uma análise estatística dos dados obtidos para esse sistema com o intuito de avaliar as melhores correlações matemáticas para representação dos dados experimentais e aplicações de tais correlações em exemplos de controle de poço. Os resultados experimentais mostram que a simulação consegue reproduzir bem os dados experimentais (desvios de até 16%), apenas subestimando-os em frações molares de CO2 mais elevadas. Comparando os dados para o CO2, obtidos neste trabalho, com dados para o metano, obtidos da literatura, observa-se que o sistema contendo CO2 apresenta, dentre outras características, maior fator de formação de volume e solubilidade até 15 vezes maior que o sistema contendo metano. Por fim, ao examinar os exemplos de controle de poço, percebe-se que quanto maior é o teor de CO2 no sistema, maior é o valor do pit gain, tornando a presença de CO2 no sistema favorável à detecção do kick / Abstract: The scenario of oil and gas well drilling has been changing over the years. Not only because the need of supplying the increasing demand for petroleum and gas but also due to the decrease on the production of mature fields, well drilling has been constantly facing aggressive environments: higher temperatures, higher pressures, higher offshore distances and hazardous chemical environments. The presence of carbon dioxide - CO2 - on reservoirs leads to a concern on well drilling in these formations because the entrance of this gas into the well, in a kick situation, and its interaction with the drilling fluid can change important characteristics of this fluid such as: density, viscosity and acidity. This work aims to evaluate the PVT behavior of the systems containing CO2 and liquids similar to the ones used as base for oil-based drilling fluids: n-paraffin and inverse emulsion. An experimental study of these systems, a computational simulation, a statistical analysis of the data acquired aiming to evaluate the best mathematical correlations to represent these data and applications of these correlations were carried out. The experimental results show that the simulation can reproduce satisfactorily the experimental data (deviations up to 16%), only underestimating them at higher CO2 molar fractions. When comparing the data for CO2, obtained in this work, and the ones for methane, obtained from literature, it is possible to notice that the system containing CO2 has, among other characteristics, higher oil volume formation factor and solubility 15 times greater than the system containing methane. Finally, by examining well control examples, one can notice that the pit gain assumes higher values as the CO2 content increases making the presence of CO2 in the system favorable to kick detection / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Orientador: Denis Jose Schiozer / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica, Instituto de Geociencias / Made available in DSpace on 2018-08-04T14:56:10Z (GMT). No. of bitstreams: 1 Xavier_AlexandreMonticuco_M.pdf: 1314652 bytes, checksum: f1d19635e80ee2c542dd65483505cb25 (MD5) Previous issue date: 2004 / Resumo: A capacidade de lidar com incertezas pode ser um fator decisivo para viabilizar projetos de avaliação e desenvolvimento de campos de petróleo. Um critério econômico utilizado em processos de tomada de decisões é o valor da informação (VDI) que envolve a quantificação das incertezas, a avaliação econômica de diversos cenários de desenvolvimento e a quantificação dos benefícios que dados adicionais podem trazer ao processo. O cálculo do VDI pode ser complexo e demorado, principalmente nas fases de avaliação e desenvolvimento, em que uma modelagem detalhada do problema pode ser necessária. Nessas fases, a quantificação do VDI, assim como o de adicionar flexibilidade ao processo (valor da flexibilização - VDF), deve levar em conta os benefícios que podem ser extraídos do processo através da aplicação de estratégias de produção mais adequadas para os vários cenários possíveis. A quantificação do VDI e VDF, portanto, exige que a estratégia de produção seja determinada para cada cenário possível. Como isso geralmente não é viável, devido ao grande esforço que seria exigido, existem simplificações possíveis, como a determinação de modelos geológicos representativos (MGR) que podem fornecer a incerteza agregada dos atributos geológicos. Dessa forma, o objetivo deste trabalho é desenvolver e aplicar uma metodologia de cálculo do VDI durante as fases de avaliação e desenvolvimento de campos de petróleo com aplicação para casos simples e complexos, considerando diferentes números de parâmetros analisados. Esta etapa é realizada através da aplicação da metodologia em três exemplos, sendo dois casos teóricos, visando expor o conceito do VDI e VDF, e um caso real complexo, visando o cálculo do VDI para um caso utilizando a simplificação do processo. Os resultados indicam que a precisão do cálculo do VDI depende do número de MGR e a melhor forma de avaliação é através da aplicação das melhores estratégias em todos os cenários. Uma boa aproximação do VDI pode ser obtida pelo procedimento de inclusão gradativa de MGR até a estabilização dos resultados. Outra simplificação possível é usar também os MGR para representar a árvore no cálculo do VDI, mas com prejuízo de precisão nos resultados / Abstract: The capacity to deal with uncertainties is responsible for the economic viability of petroleum fields. The Value of Information (VOI) is an economic criterion used in decisionmaking process. It involves the quantification of uncertainties and the economic evaluation of various development scenarios. The quantification of the value of the information (VOI) and flexibility (VOF) can be highly complex and time-consuming, mainly in the appraisal and development phases when a detailed modeling of the problem may be necessary. The quantification of the value of information and of flexibility must take into account the benefits that can be extracted of the process. In these phases, these benefits result from a specific production strategy applied to several possible scenarios after the acquisition of the information. Therefore, the quantification of the VOI and VOF demand that the production strategy be determined to each possible scenario. This is not usually viable because a great effort would be needed; to circumvent this problem, there are some alternatives, such as the determination of geologic representative models (GRM) that can represent the uncertainty of the geologic attributes. The objective of this work is to develop and apply a methodology that can calculate the value of information during the appraisal and development phases in petroleum fields which can be applied to simple and complex cases, considering the number of analyzed parameters. This stage is realized through the application of the methodology to three examples; two theoretical models showing the concept of the value of information and, one real and complex case that demands a detailed analysis of the process. The results show that the quality of the results depends on the number of GRM and the best quantification technique is to apply the best production strategy to all possible scenarios. It is shown in this work that a good approximation of the VOI can be obtained by a dynamic procedure including new GRM until a stabilization of the results. The GRM can be used also to represent the decision tree but with some deterioration of the results / Mestrado / Mestre em Ciências e Engenharia de Petróleo

Orientador: Celso Kazuyuki Morooka / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-22T07:36:07Z (GMT). No. of bitstreams: 1 Filardo_JuarezGuaraci_M.pdf: 9792292 bytes, checksum: fc41bb8bdaac74a7d5124bbc10c3f37b (MD5) Previous issue date: 2012 / Resumo: Este trabalho apresenta a solução para o problema das empresas de petróleo em determinar os quantitativos ótimos de recursos materiais a serem adquiridos para a construção dos poços de petróleo num ambiente de risco, assegurando o cumprimento das metas plurianuais da empresa. Para isto foi necessário gerar vários cenários de demanda pelos materiais através da simulação estocástica do portfólio, pesquisar os mais variados modelos de inventário para entender o dinamismo existente no processo de levantamento de demanda dos materiais até o seu emprego nos poços, possibilitar representar estes fluxos matematicamente por uma função objetivo com termos de receita e de custos destoando dos processos usuais de tomada de decisão que consideram apenas os custos de aquisição; otimizar a função objetivo característica de cada cenário através do método dos algoritmos genéticos para permitir uma flexibilização no uso de modelos mais complexos de representação da demanda, e no final obter uma função multivariada conjunta construída com o auxílio do método das cópulas a qual o tomador de decisão fará o seu julgamento. O processo acima permitiu construir uma metodologia cuja robustez foi testada para um caso prático de definição do quantitativo ótimo de revestimentos de perfuração a ser adquirido para um portfólio de poços constituído por 596 poços marítimos brasileiros em atividades de perfuração, completação, e restauração, e 60 sondas de perfuração com trabalhos simultâneos, intervalo de planejamento de um ano e poços possuindo as mesmas características de projeto do pré-sal. A decisão sobre o quantitativo ideal conforme o risco da empresa foi conseguido facilmente analisando-se as curvas de nível da função multivariada conjunta, que para o caso prático do pré-sal e considerando confiança nos dados de 73%, o quantitativo de revestimento ótimo foi de 140.000 m, caso fosse analisado sem considerar os riscos o quantitativo seria de 145.000 m, indicando que o tomador de decisão tradicional foi conservador e tenderia encarecer o processo. Outra conclusão importante foi que os pontos ótimos situaram-se num intervalo de tempo anterior ao do final do planejamento indicando ter sido vantajoso admitir a falta do revestimento e não construir o poço a partir deste ponto, o que possibilitou também verificar o quão consistente foi o sequenciamento dos poços do portfólio / Abstract: This thesis presents a solution for the problem of oil companies to determine the optimal quantity of material resources to be acquired for the construction of oil wells in a risky environment and assuring the company multiannual goals. In order to achieve that it was necessary to generate various scenarios of materials demand by stochastic simulation of the portfolio, researching the most varied inventory models to understand the existing dynamics in the process of raising materials demand up to their use in the wells, and make possible the representation of these flows mathematically by an objective function in terms of revenue and costs, diverging from the usual decision making processes that consider only the acquisition costs . The characteristic objective function of each scene was optimized by the genetic algorithms method to allow greater flexibility in the use of more complex models to represent the demand by the end of the process is obtained a joint multivariate function built with the aid of the method of copulas and whose decision maker will make their judgment. The above process allowed us to provide a methodology whose robustness has been tested for a practical case of defining the optimum quantity of drilling casings to be acquired for a wells portfolio, consisting of 596 wells in Brazilian offshore drilling, completion, and restore and 60 drilling rigs with simultaneous work, one year for range of planning and wells having the same design features of the sub-salt environment. The decision about the ideal amount considering the company's risk was easily accomplished by analyzing the joint multivariate function contour, to the studied practical case and considering 73% of confidence in the data, the optimum quantity was 140,000 m, if analyzed without considering the risks the quantity would be 145,000 m, indicating that the decision maker was traditionally conservative and would tend to become the process more expensive. Another important conclusion was that the optimal points were located in a time prior to the end of the plan, indicating it was advantageous to allow the lack of the casing and not to build the well from that point, it also allowed to check how consistent the wells portfolio scheduling was / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Hydraulic fracturing is essential for producing gas and oil at an economic rate from low permeability sands. Most fracturing treatments use water and polymers with a gelling agent as a fracturing fluid. The water is held in the small pore spaces by capillary pressure and is not recovered when drawdown pressures are low. The un-recovered water leaves a water saturated zone around the fracture face that stops the flow of gas into the fracture. This is a particularly acute problem in low permeability formations where capillary pressures are high. Depletion (lower reservoir pressures) causes a limitation on the drawdown pressure that can be applied. A hydraulic fracturing process can be energized by the addition of a compressible, sometimes soluble, gas phase into the treatment fluid. When the well is produced, the energized fluid expands and gas comes out of solution. Energizing the fluid creates high gas saturation in the invaded zone, thereby facilitating gas flowback. A new compositional hydraulic fracturing model has been created (EFRAC). This is the first model to include changes in composition, temperature, and phase behavior of the fluid inside the fracture. An equation of state is used to evaluate the phase behavior of the fluid. These compositional effects are coupled with the fluid rheology, proppant transport, and mechanics of fracture growth to create a general model for fracture creation when energized fluids are used. In addition to the fracture propagation model, we have also introduced another new model for hydraulically fractured well productivity. This is the first and only model that takes into account both finite fracture conductivity and damage in the invaded zone in a simple analytical way. EFRAC was successfully used to simulate several fracture treatments in a gas field in South Texas. Based on production estimates, energized fluids may be required when drawdown pressures are smaller than the capillary forces in the formation. For this field, the minimum CO2 gas quality (volume % of gas) recommended is 30% for moderate differences between fracture and reservoir pressures (2900 psi reservoir, 5300 psi fracture). The minimum quality is reduced to 20% when the difference between pressures is larger, resulting in additional gas expansion in the invaded zone. Inlet fluid temperature, flowrate, and base viscosity did not have a large impact on fracture production. Finally, every stage of the fracturing treatment should be energized with a gas component to ensure high gas saturation in the invaded zone. A second, more general, sensitivity study was conducted. Simulations show that CO2 outperforms N2 as a fluid component because it has higher solubility in water at fracturing temperatures and pressures. In fact, all gas components with higher solubility in water will increase the fluid’s ability to reduce damage in the invaded zone. Adding methanol to the fracturing solution can increase the solubility of CO2. N2 should only be used if the gas leaks-off either during the creation of the fracture or during closure, resulting in gas going into the invaded zone. Experimental data is needed to determine if the gas phase leaks-off during the creation of the fracture. Simulations show that the bubbles in a fluid traveling across the face of a porous medium are not likely to attach to the surface of the rock, the filter cake, or penetrate far into the porous medium. In summary, this research has created the first compositional fracturing simulator, a useful tool to aid in energized fracture design. We have made several important and original conclusions about the best practices when using energized fluids in tight gas sands. The models and tools presented here may be used in the future to predict behavior of any multi-phase or multi-component fracturing fluid system. / text

Lors du forage des puits d'hydrocarbure, une pâte de ciment est coulée dans l'espace annulaire entre le cuvelage en acier et les formations géologiques traversées. Pompée à l'état liquide, cette pâte de ciment fait sa prise le long du puits sous différentes conditions de température et de pression. La gaine de ciment ainsi mise en place a pour principales fonctions de promouvoir l'étanchéité pour protéger le casing contre la corrosion, de fournir le support mécanique pour assurer la stabilité du puits et d'isoler les différents fluides dans les couches traversées. Au cours de sa vie dans le puits, depuis le forage à la complétion et de la production à l'abandon, la gaine de ciment est soumise à différentes sollicitations mécaniques et thermiques qui peuvent l'endommager et altérer ses principales fonctions. La réponse de la pâte de ciment soumis à ces sollicitations dépend non seulement des conditions d'hydratation mais aussi de l'histoire des chargements précédemment appliqués. La prédiction du comportement de la gaine de ciment doit donc se faire à l'aide d'une modélisation numérique qui nécessite une loi de comportement pour la pâte de ciment. Le but de cette thèse est d'établir une loi de comportement de la pâte de ciment en cours d'hydratation pendant le jeune-âge (les 144 premières heures). Pour ce faire, des essais calorimétriques, de mesures de vitesse des ondes et des essais œdométriques ont été réalisés sur une pâte de ciment pétrolier classe G (w/c = 0,44) en cours de prise. Les conditions d'hydratation explorées vont de 7 à 30°C pour les températures et de 0,3 à 45MPa pour les pressions. Les résultats expérimentaux ont montré que les déformations volumiques de la pâte de ciment dues à son hydratation (retrait macroscopique) sont considérablement influencées par la contrainte sous laquelle la pâte de ciment s'hydrate. Plus la contrainte d'hydratation est élevée, plus élevé est le retrait macroscopique à 144 heures. Inversement, les déformations irréversibles dues à un cycle de chargement mécanique à cet âge sont moins importantes pour les contraintes plus élevées. Les résultats ont également montrés qu'au cours de la prise du ciment, il existe un temps critique à partir duquel l'application des cycles de chargement mécanique crée des déformations résiduelles dans la pâte de ciment. Ce temps critique arrive à un degré d'hydratation relativement constant, compris entre 0,18 et 0,20. Le modèle « Boundary Nucleation and Growth » a été utilisé pour étudier la dépendance de ce temps critique à la pression et à la température. Pour la modélisation du retrait macroscopique et de la réponse contrainte – déformation de la pâte de ciment, un modèle élasto-plastique chemo-poro-mécanique couplé, prenant en compte la désaturation du milieu, a été développé. Ce modèle utilise une surface de charge fermée de type Cam-Clay et une loi plastique associée. La loi d'écrouissage dépend des déformations volumiques plastiques et du degré d'hydratation. Les paramètres du modèle ont été évalués pour simuler le retrait macroscopique de la pâte de ciment hydratée sous différentes contraintes et températures. A un degré d'hydratation donnée, le modèle permet également de simuler la réponse contrainte-déformation due à un chargement mécanique / When drilling oil & gas well, cement slurry is pumped between the casing and the rock formation. This cement slurry sets at different conditions of temperature and pressure. The role of this cement sheath is to provide zonal isolation of different fluid along the well, to protect the casing against corrosion and to provide mechanical support. During the life of the well, from drilling to completion, production and P&A (plug and abandonment), the cement sheath is submitted to various mechanical and thermal loading that can potentially damage its properties and alter its performance. The behavior of cement paste submitted to theses solicitations depends both on the hydration condition and the loadings previously applied on the cement paste. The prediction of cement sheath behavior should be done by numerical modeling, which needs a constitutive law for cement paste. The purpose of the present work is to establish a constitutive law of cement paste during its hydration at early age (first 144 hours). The approach is based on combined calorimetric, wave velocities and oedometric tests on an oil-well class G cement paste with water-to-cement ratio equals 0.44. The hydration conditions explored are 7 to 30°C for temperature and 0.3 to 45MPa for pressure. The experimental results showed that the volumetric strain due to cement hydration (macroscopic shrinkage) depends considerably on the hydration pressure. At 144 hours of hydration, the macroscopic shrinkage increases with the hydration pressure increase. But, the residual strain due to application of mechanical cycle at this age is less for cement hydrated under higher pressure. The experimental results revealed that during the hydration there is a critical time after which, the application of mechanical loading can potentially induce residual strain in cement paste. This time is reached at constant hydration degree between 0.18 and 0.20. The Boundary Nucleation and Growth model was used to model the pressure and temperature dependence of this critical time. A coupled elasto-plastic chemo-poro-mechanical model is developed to simulate the macroscopic shrinkage of cement paste hydrated at different conditions of temperature and pressure. A modified Cam-Clay type yield surface with associate flow rule is used. The hardening law depends both on the degree of hydration and on the plastic volumetric strain. At constant degree of hydration, the developed model permits to simulate the stress – strain behavior of cement paste due to the mechanical loading

[pt] Um dos principais objetivos da engenharia de petróleo é desenvolver e aplicar técnicas capazes de aumentar a produtividade de poços de petróleo, incluindo a estimulação da formação através de operações que aumentem a permeabilidade da rocha-reservatório e facilitem o escoamento do fluido. Dentre as técnicas de estimulação, a mais utilizada é o fraturamento hidráulico, a qual tem viabilizado a exploração em cerca de 40 por cento dos poços produtores de petróleo em todo o mundo. Durante o fraturamento hidráulico, um material granular conhecido como material de sustentação ou propante, é injetado nas fraturas recém-criadas com o objetivo de mantê-las abertas e garantir-lhes condições de alta permeabilidade. A produção de material de sustentação (proppant flowback) é termo usado para descrever o refluxo do propante para o interior do poço, juntamente com o hidrocarboneto produzido. O controle do fluxo de propante representa um grave desafio para a indústria de petróleo, pois pode causar graves problemas operacionais e de segurança, relacionados com o desgaste dos equipamentos de produção, problemas econômicos associados ao custo de limpeza, paralisação das operações e intervenção no tratamento da fratura, problemas ambientais relacionados com a disposição de sólidos impregnados por hidrocarbonetos, etc. Neste contexto, a presente dissertação apresenta um estudo detalhado dos principais tipos de propante e de suas propriedades, bem como descreve os mecanismos que influem no refluxo do material de sustentação da fratura e analisa os principais modelos apresentados na literatura para previsão deste fenômeno. Uma retroanálise considerando os dados de campo em 22 poços da Petrobrás, localizados em Sergipe, permite uma comparação da eficiência entre quatro dos modelos, desenvolvidos com base em resultados de ensaios de laboratório, indicando suas vantagens e desvantagens para aplicação na prática da engenharia. / [en] One of the main objectives of petroleum engineering is to develop and to apply techniques aiming the productivity increase of oil fields, including the stimulation of the rock through operations that increase the permeability of the oil reservoir and makes the flow of the fluid toward the well more efficient. Among the stimulation techniques, the most used is the hydraulic fracturing, carried out in about 40 percent of the producing oil wells around the world. During hydraulic fracturing, a granular material known as proppant, is injected into the just created fractures with the objective to keep them open and in order to guarantee the designed conditions of high permeability. Proppant flowback is the technical terminology employed to describe the flow of proppant from the fracture to the interior of the oil well, together with the produced hydrocarbon. An efficient and reliable control of this problem is still a major challenge to the oil industry, given the serious operational and security problems that it may cause, including costs of interrupted operations, cleaning measures, environmental contamination risks associated with the disposal of residues impregnated by oil, etc. In this context, the present thesis presents a detailed description on the main proppant materials and their engineering properties and available treatments, as well as on the physical mechanisms that control the flowback phenomenon. Several simple models published in the literature, that permit the forecast of proppant flowback in a fast and easy way, are also presented and discussed. Finally, a back-analysis considering the actual conditions in 22 Petrobras oil wells located in Sergipe was also carried out, what permitted a comparison among the results calculated according 4 prediction models, putting in evidence their advantages, shortcomings and adequacy as a design or control tool in the design and exploration of oil fields stimulated by hydraulic fracturing.

[pt] A viabilidade da exploração de um campo petrolífero está associada às características produtivas da formação, obtidas mediante o desenvolvimento e a aplicação de técnicas capazes de aumentar a economicidade dos poços. A técnica de estimulação mais utilizada atualmente é o fraturamento hidráulico, que tem como uma das etapas principais a injeção de um material granular, denominado de propante, para a manutenção da abertura da fratura. Tal técnica tem como obstáculo o refluxo do propante para o interior do poço (proppant flowback), ocasionando diversos problemas que podem levar à interrupção da produção do mesmo. Alguns modelos teóricos e empíricos foram desenvolvidos para a previsão desse fenômeno, mas os mecanismos que o governam não são ainda claramente explicados. Alguns fatores que influenciam na produção de propante são largura da fratura, tensão de fechamento, gradiente hidráulico e características do propante. O refluxo de propante não é considerado nos procedimentos atuais de projeto de fraturamento hidráulico. Nessa dissertação de mestrado foi desenvolvida uma ferramenta computacional com uma arquitetura orientada a objeto, em linguagem de programação Java, para a análise de estabilidade do propante no interior da fratura com base em modelos empíricos e teóricos. Além disso, foi investigada a influência da inclusão de restrições no projeto de fraturamento de modo a prevenir o fenômeno. Busca-se, desse modo, a obtenção de melhores projetos de fraturamento hidráulicos com prevenção do refluxo de propante, garantindo a produtividade do poço e prolongando sua vida útil. / [en] The viability of the exploration of an oil field is associated with the productive characteristics of the formation, guaranteed by means of the development and application of techniques capable of increasing the productivity and the economy of the oil fields. The currently most used stimulation technique is hydraulic fracturing, by which one of the main stages is the injection of a granular material called proppant to keep the fracture open and enhance fracture permeability. This technique presents as a drawback the phenomenon known as proppant flowback. The proppant is carried to the inside of the well causing many problems which can lead to production interruption. Some empirical and theoretical models for its prediction have been developed, however the mechanisms that govern it are still not clearly explained. Parameters that are related to proppant flowback are fracture width, closure pressure, drag force and proppant characteristics. Proppant flowback prediction is not included in today s procedures of the hydraulic fracturing project. In the present work a computational tool for proppant stability analysis was developed based on empirical and theoretical prediction models. This tool has an object oriented architecture written in Java language. The influence of the introduction of restrictions to prevent proppant production in the hydraulic fracture design procedure was also investigated. In this way, it is aimed to obtain hydraulic fracturing projects by which proppant flowback is prevented in field situations assuring well productivity and extending its activity period.

Lors du forage des puits d'hydrocarbure, une pâte de ciment est coulée dans l'espace annulaire entre le cuvelage en acier et les formations géologiques traversées. Pompée à l'état liquide, cette pâte de ciment fait sa prise le long du puits sous différentes conditions de température et de pression. La gaine de ciment ainsi mise en place a pour principales fonctions de promouvoir l'étanchéité pour protéger le casing contre la corrosion, de fournir le support mécanique pour assurer la stabilité du puits et d'isoler les différents fluides dans les couches traversées. Au cours de sa vie dans le puits, depuis le forage à la complétion et de la production à l'abandon, la gaine de ciment est soumise à différentes sollicitations mécaniques et thermiques qui peuvent l'endommager et altérer ses principales fonctions. La réponse de la pâte de ciment soumis à ces sollicitations dépend non seulement des conditions d'hydratation mais aussi de l'histoire des chargements précédemment appliqués. La prédiction du comportement de la gaine de ciment doit donc se faire à l'aide d'une modélisation numérique qui nécessite une loi de comportement pour la pâte de ciment. Le but de cette thèse est d'établir une loi de comportement de la pâte de ciment en cours d'hydratation pendant le jeune-âge (les 144 premières heures). Pour ce faire, des essais calorimétriques, de mesures de vitesse des ondes et des essais œdométriques ont été réalisés sur une pâte de ciment pétrolier classe G (w/c = 0,44) en cours de prise. Les conditions d'hydratation explorées vont de 7 à 30°C pour les températures et de 0,3 à 45MPa pour les pressions. Les résultats expérimentaux ont montré que les déformations volumiques de la pâte de ciment dues à son hydratation (retrait macroscopique) sont considérablement influencées par la contrainte sous laquelle la pâte de ciment s'hydrate. Plus la contrainte d'hydratation est élevée, plus élevé est le retrait macroscopique à 144 heures. Inversement, les déformations irréversibles dues à un cycle de chargement mécanique à cet âge sont moins importantes pour les contraintes plus élevées. Les résultats ont également montrés qu'au cours de la prise du ciment, il existe un temps critique à partir duquel l'application des cycles de chargement mécanique crée des déformations résiduelles dans la pâte de ciment. Ce temps critique arrive à un degré d'hydratation relativement constant, compris entre 0,18 et 0,20. Le modèle « Boundary Nucleation and Growth » a été utilisé pour étudier la dépendance de ce temps critique à la pression et à la température. Pour la modélisation du retrait macroscopique et de la réponse contrainte – déformation de la pâte de ciment, un modèle élasto-plastique chemo-poro-mécanique couplé, prenant en compte la désaturation du milieu, a été développé. Ce modèle utilise une surface de charge fermée de type Cam-Clay et une loi plastique associée. La loi d'écrouissage dépend des déformations volumiques plastiques et du degré d'hydratation. Les paramètres du modèle ont été évalués pour simuler le retrait macroscopique de la pâte de ciment hydratée sous différentes contraintes et températures. A un degré d'hydratation donnée, le modèle permet également de simuler la réponse contrainte-déformation due à un chargement mécanique / When drilling oil & gas well, cement slurry is pumped between the casing and the rock formation. This cement slurry sets at different conditions of temperature and pressure. The role of this cement sheath is to provide zonal isolation of different fluid along the well, to protect the casing against corrosion and to provide mechanical support. During the life of the well, from drilling to completion, production and P&A (plug and abandonment), the cement sheath is submitted to various mechanical and thermal loading that can potentially damage its properties and alter its performance. The behavior of cement paste submitted to theses solicitations depends both on the hydration condition and the loadings previously applied on the cement paste. The prediction of cement sheath behavior should be done by numerical modeling, which needs a constitutive law for cement paste. The purpose of the present work is to establish a constitutive law of cement paste during its hydration at early age (first 144 hours). The approach is based on combined calorimetric, wave velocities and oedometric tests on an oil-well class G cement paste with water-to-cement ratio equals 0.44. The hydration conditions explored are 7 to 30°C for temperature and 0.3 to 45MPa for pressure. The experimental results showed that the volumetric strain due to cement hydration (macroscopic shrinkage) depends considerably on the hydration pressure. At 144 hours of hydration, the macroscopic shrinkage increases with the hydration pressure increase. But, the residual strain due to application of mechanical cycle at this age is less for cement hydrated under higher pressure. The experimental results revealed that during the hydration there is a critical time after which, the application of mechanical loading can potentially induce residual strain in cement paste. This time is reached at constant hydration degree between 0.18 and 0.20. The Boundary Nucleation and Growth model was used to model the pressure and temperature dependence of this critical time. A coupled elasto-plastic chemo-poro-mechanical model is developed to simulate the macroscopic shrinkage of cement paste hydrated at different conditions of temperature and pressure. A modified Cam-Clay type yield surface with associate flow rule is used. The hardening law depends both on the degree of hydration and on the plastic volumetric strain. At constant degree of hydration, the developed model permits to simulate the stress – strain behavior of cement paste due to the mechanical loading

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-04T19:50:45Z No. of bitstreams: 1 IVNA DANIELE SOUZA PEREIRA - DISSERTAÇÃO PPG-CEMat 2014..pdf: 2113912 bytes, checksum: e7cd84f19623986d5ca5b0df7875190e (MD5) / Made available in DSpace on 2018-04-04T19:50:45Z (GMT). No. of bitstreams: 1 IVNA DANIELE SOUZA PEREIRA - DISSERTAÇÃO PPG-CEMat 2014..pdf: 2113912 bytes, checksum: e7cd84f19623986d5ca5b0df7875190e (MD5) Previous issue date: 2014-08-29 / Capes / No Estado da Paraíba há grandes ocorrências de minerais não metálicos principalmente de argilas bentoniticas, ball clays, caulins, feldspatos, quartzo, calcários e micas. Recentemente foram descobertos novos depósitos de argilas no município de Sossego, propiciando assim, uma expectativa de ampliação de insumos minerais na região. Assim, este trabalho tem por objetivo caracterizar física, mineralógica e tecnologicamente argilas esmectíticas do Município de Sossego, PB, Brasil, para uso em fluidos de perfuração. Para tanto, as argilas foram beneficiadas e caracterizadas através das seguintes técnicas: granulometria a laser (AG), difração de raios-X (DRX), análise química (EDX), capacidade de troca de cátions (CTC), análise termogravimétrica(TG) e térmica diferencial (DTA). Em seguida as argilas foram transformadas em sódicas por meio de tratamento com carbonato de sódio (Na2CO3), hexametafosfato de sódio (NaPO3)6 nos teores: 75, 100, 125 e 150meq/100g de argila seca, além de serem ativadas com a combinações de (Na2CO3) e óxido de magnésio (MgO), em seguida realizou-se o estudo do comportamento reológico das dispersões no intuito de determinar viscosidade aparente (VA), viscosidade plástica (VP), volume de filtrado e pH. Os resultados mostraram que as argilas estudadas eram constituídas de esmectítica, caulinita e quartzo, apresentando teores de MgO e CaO, evidenciando que são bentonitas policatiônicas. Com relação ao uso das argilas como agente viscosificante para fluidos de perfuração, observou-se que as amostras de AM2 ativadas com Na2CO3 atenderam parcialmente as especificações necessária para uso em fluidos de perfuração base água. Já as amostra ativadas com (NaPO3)6 não desenvolveram melhoria nas suas característica reológicas, logo seu uso como fluido de perfuração não é viável. A combinação de Na2CO3 e de MgO produziu um melhoramento nas propriedades dos fluidos produzidos, demonstrando ser aplicável na perfuração de poços. / In Paraíba's large occurrences of non-metallic minerals mainly of bentonite clays, ball clays, kaolin, feldspar, quartz, limestone and mica. Recently discovered new deposits of clays in the city of Sossego, providing an expected expansion of mineral inputs in the region. This work aims to characterize physical, mineralogical and technologically smectite clays Municipality Sossego, PB, Brazil, for use in drilling fluids. For both, the clays were processed and characterized by the following techniques: laser granulometry (AG), X-ray diffraction (XRD), chemical analysis (EDX), cation exchange capacity (CEC), thermogravimetric analysis (TG) and differential thermal analysis (DTA). The clays were then transformed into sodic by treatment with sodium carbonate (Na2CO3), sodium hexametaphosphate (NaPO3) 6 in levels: 75, 100, 125 and 150meq / 100g of dry clay, and being activated with combinations (Na2CO3) and magnesium oxide (MgO), then held up the study of the rheological behavior of the dispersions in order to determine apparent viscosity (VA), plastic viscosity (PV), filtrate volume and pH. The results showed that the clays of smectite were formed, kaolinite and quartz, with MgO and CaO contents, showing that bentonites are polycationic. Regarding the use of clays as viscosity agent for drilling fluids, it was observed that the samples activated with Na2CO3 AM2 partially met the necessary for use in water based drilling fluids specifications. As for the sample activated to (NaPO3)6 did not develop improvement in rheological characteristic, then its use as drilling fluid is not feasible. The combination of Na2CO3 and MgO produced an improvement in the properties of the produced fluids, proving to be applicable in drilling wells Keywords: bentonite, rheology, characterization, drilling fluids.