O presente trabalho faz uma análise estrutural estática dos enrijecedores à flexão - ou bend stiffeners - que consistem em componentes estruturais auxiliares utilizados em linhas flexíveis em suas conexões com unidades flutuantes em sistemas de produção de petróleo offshore. A configuração destes acessórios deve conferir à instalação uma variação gradual da rigidez à flexão próximo ao ponto de fixação da linha flexível à unidade flutuante, diminuindo sua curvatura e suavizando o campo de tensões, evitando assim que a linha ultrapasse a curvatura máxima estabelecida em projeto, além de garantir vida útil à fadiga igual ou maior que nas outras partes do sistema. Inicialmente é apresentado uma breve revisão bibliográfica de diversos autores, posteriormente é apresentada a tecnologia de fabricação de enrijecedores junto com os métodos de projeto. Um resumo dos materiais utilizados bem como as suas propriedades são descritas para uma melhor compreensão do problema. O entendimento da resposta mecânica vem se tornando cada vez mais importante visto o crescente número de enrijecedores em campo e as falhas que alguns apresentaram. Para tanto, desenvolvem-se neste trabalho modelos pelo método dos elementos finitos com diferentes níveis de hierarquia que representam o sistema linha flexível-enrijecedor para uma melhor percepção do comportamento mecânico dos enrijecedores. / The present work does a static structural analysis of bend stiffeners - which consist of auxiliary structural components used in flexible lines in their connections with floating units in offshore oil production systems. The configuration of these fittings should give the installation a gradual variation of the flexural stiffness near the point of attachment of the flexible line to the floating unit, reducing its curvature and smoothing the field of stresses, thus avoiding that the line exceeds the maximum curvature established in design, in addition to guaranteeing a fatigue life equal to or greater than in other parts of the system. Initially a brief bibliographical review of several authors is presented, later the technology of rigging is presented along with the design methods. A summary of the materials used as well as their properties are described for a better understanding of the problem. The understanding of the mechanical response has become increasingly important considering the increasing number of bend stiffeners in the field and the failures that some have presented. In order to do so, this work develops models by the finite element method with different levels of hierarchy that represent the flexible line-bend stiffener system for a better perception of the mechanical behavior of the bend stiffeners.

Dual Gradient Drilling (DGD) system is a promising technology that was developed to overcome the deep water drilling problems occurred due to narrow operating window between pore pressure and fracture pressure. In conventional drilling practice, single mud weight exists from drilling unit to TVD (True Vertical Depth) which creates big hydrostatic pressure in bottom hole ,moreover, minor changes in mud weight results a big pressure changes proportional to the length of hydrostatic column increase with water depth. On the other hand, DGD allows using two different mud weights to get same bottom hole pressure / low gradient drilling fluid from drilling unit to the sea floor and high gradient drilling fluid form the sea floor to TVD, to decrease the effect of water column on mud hydrostatic pressure in TVD. In this thesis, a conventionally drilled deepwater well was redesigned considering the DGD system and drilled virtually to determine the changes of cost of services and materials on total operation budget to prove the positive impact of system on total operation cost. This study not only proved the technical advantages of the DGD system, but also showed economical impact of the system on total drilling cost, by decreasing around 19%.

The thesis suppose to introduce the dimenisonal control surveyor’s role during manufacturing of the oil subsea structures, which are utilized for subsea pipeline systems assembly. The thesis contain the theory of oil production from the seabed, resources utilized for those purposes and describe the manufacturing process of the subsea equipment. The main focus of the work is in describing the methods (more detailed) applied during dimensional control, along with method of surveying, calculations and result presentations. The essential part is showing data processing of one representative structure, which the author processed himself during his particiaption on the project.

In the expansion of offshore sustainable energy systems, there is growing pressure on the environment and permit processes and the accumulation results in much higher total risk for accidents of future assets. Anticipating the problems at the design stage and improving verification is likely to increase energy development and reduce costs. This thesis explores offshore DST (Decision Support Tools) and risk verification of subsea cable assets.For subsea cables, a statistical method is proposed utilizing measurement data together with shipping traffic data (AIS) to estimate the environmental risk and risk of accidents of installed cable assets. This should partially solve issues of improving design using more data and surveys and utilizing mechanical and sensor-specific characteristics to improve the confidence and burial estimation, contrary to today’s methodology. The implication of the two studies of cable burial risk assessment techniques and verification shows how a developed methodology can solve issues for verifying the integrity of an installed asset. Putting our methodology into practice involves many challenges.  For the marine Decision Support Tool (DST) and sustainable energy development, to estimate potential savings if permit processes would be shorter and less burdensome without degrading the quality of the EIA (Environmental Impact Assessment). A method is proposed to model various scenarios of effective savings from the development of a DST to reduce costs spent on EIA permitting by the offshore energy developers. The study of the implication of the marine EIA DST shows a quantifiable estimate of the savings potential for permit processes for sustainable offshore development, and results indicate a need for optimization of DST development, which can be an essential factor in its implementation and success.

Infrastructure for electricity and telecommunication, such as subsea cables, are critical in modern society. Future estimates also indicate an increased demand. Subsea cables enable the use of offshore wind power farms, transnational energy distribution and global data transfer. It is therefore considered important for a continuous development toward a sustainable future. Consistently, long and seamless cables, with complex inner structure, are requested. This makes the manufacturing and recurrent storing process challenging. Present cable storage systems, namely carousels, are a vital part of the manufacturing.  In this case study, a present manufacturing system of subsea cables was presented, whereby a possible improvement for a more flexible manufacturing process was suggested. The work focused on developing a new turntable, which is a subsystem, within the main system, the carousel. A Systems Engineering approach was used in order to develop the manufacturing system. This development resulted in three conceptual turntable solutions with improved flexibility and resource efficiency. The solutions generated consist of a turntable with two independently rotatable compartments. Although the focus of this case study was to develop a solution toward the subsea power cable industry, it is possible to up- or downscale depending on the required weight capacity, area and number of compartments.

Hydrates, wax, and other fluids forms in cold subsea pipelines which restrict flow of petroleum products during operation. This thesis analyses the global buckling behaviour of subsea pipelines with Direct Electric Heating cables (DEH) through a combination of analytical and FEM simulations. A subsea pipeline with an attached DEH cable has limited impact on the pipelines initial global buckling behaviour. The DEH cable holds back and reduces the buckle size. Strap distance and cable rotational location has very limited impact on buckling behaviour. Analytical and FEM model has in places low convergence, this is likely due to limitations in the models. / Hydrater, vax, och andra fluider formas i kalla undervattensrörledningar som begränsar flödet av petroleumprodukter i drift. Detta examensarbete analyserar global buckling av undervattensrörledningar med Direct Electric Heating (DEH) kabel med en kombination av analytisk och FEM simuleringar. En undervattensrörledning med tillhörande DEH kabel har begränsad påverkan på en rörlednings initiala globala bucklingsbeteende. DEH kabeln håller tillbaka och reducerar bucklingsstorleken. Avstånd mellan remmar och kabelns läge har mycket begränsad påverkan på bucklingsbeteendet. Den analytiska och FEM‐modellen har i vissa fall låg konvergens, troligen på grund av begränsningar i modellerna.

[pt] Um sistema de produção e escoamento de petróleo, quando equipado com manifold submarino, viabiliza a produção conjunta de poços de diferentes capacidades de produção. O equilíbrio conseguido na produção desses poços se faz à custa do estrangulamento (choking) dos poços de mais alta capacidade de produção, de forma a propiciar um equilíbrio com aqueles de mais baixa capacidade de produção. Naturalmente as vazões atingidas nessa forma sinérgica são menores do que aquelas que seriam atingidas com a produção em separado desses poços mas, tais menores vazões são economicamente mais atraentes devido às economias atingidas nos custos de investimento (e.g., redução do comprimento total de linhas de produção e do número de risers) e das esperadas e normalmente ocorrentes reduções de custo operacional nesses sistemas. Entretanto, a partir da disponibilidade da tecnologia de bombeamento multifásico submarino, na qual se torna possível diretamente transferir energia à misturas multifásicas (óleo, gás e água) em produção, viabiliza-se o estabelecimento de um novo e mais atraente tipo de equilíbrio nesses sistemas. Tal novo equilíbrio, possível pelo uso de sistemas de bombeamento multifásico instalados em manifold submarinos de produção, deve propiciar níveis de produção governados inclusive pelos limites impostos pela engenharia de reservatórios e não mais tão somente pelas características físicas dos sistemas (seções de escoamento, distâncias, lâminas d`água, propriedades dos fluidos etc.). A esta forma inédita de obtenção de um novo e mais alto patamar de equilíbrio da produção, a literatura vem utilizando a denominação Estrangulamento Positivo (Positive Choking). Assim, baseados no aumento das vazões de produção - antecipação de produção - e no potencial aumento dos fatores de recuperação - maiores volumes produzidos - acredita-se ser tal técnica economicamente atraente quando aplicada em sistemas de produção ainda em implementação, ou mesmo, na implantação da mesma em sistemas já instalados. O propósito desta tese é o de contribuir na análise técnica e econômica da inédita aplicação de um sistema de bombeamento multifásico submarino num sistema de produção equipado com manifold. / [en] A subsea oil production system allows simultaneous production of several wells with different flow rates when the system has a subsea manifold. In order to balance the different flow rates, the higher production wells have their flow rates reduced via a choking system. As a result, the total flow is lower than the summmation of all individual well flow rates. But, this combined and lower production has a very attractive economics, as it requires lower capital expenditures, mainly due to the shorter overall length of flowlines and lower number of risers and, also due to the expected lower operational costs. Nowadays, however, with the availabity of the technology of subsea multiphase pumping system, which enables the transfer of energy to multiphase mixtures (oil, gas and water) under production, becomes possible to achieve an even higher and more attractive plateau in these petroleum production systems. This new equilibrium plateau, made possible by the technology of subsea multiphase pumping, will lead to production levels that will attempt to take benefit of all reservoir allowance and then extending the primary production limit imposed by the production system characteris tics (e.g., flowline length, water depth, produced fluid properties etc.). This novel scheme that allows obtaining a now and higher production level is being called in the literature as Positive Choking. Therefore, based on the resultant aspects of production flow rate increase - production anticipation - and on the potentially higher recovery factors - larger produced volumes - is what drives the belief that such technology can be economically attractive to new production systems being installed or even in those already in operation. The purpose of this work is to contribute in the technical and economical evaluation of Multiphase Pumping System application on a subsea production system equipped with a manifold.

Increasing worldwide demand for petroleum motivates greater efficiency, safety, and environmental responsibility in upstream oil and gas processes. The objective of this research is to improve these areas with advanced control methods. This work develops the integration of optimal control methods including model predictive control, moving horizon estimation, high fidelity simulators, and switched control techniques applied to subsea riser slugging and managed pressure drilling. A subsea riser slugging model predictive controller eliminates persistent offset and decreases settling time by 5% compared to a traditional PID controller. A sensitivity analysis shows the effect of riser base pressure sensor location on controller response. A review of current crude oil pipeline wax deposition prevention, monitoring, and remediation techniques is given. Also, industrially relevant control model parameter estimation techniques are reviewed and heuristics are developed for gain and time constant estimates for single input/single output systems. The analysis indicates that overestimated controller gain and underestimated controller time constant leads to better controller performance under model parameter uncertainty. An online method for giving statistical significance to control model parameter estimates is presented. Additionally, basic and advanced switched model predictive control schemes are presented. Both algorithms use control models of varying fidelity: a high fidelity process model, a reduced order nonlinear model, and a linear empirical model. The basic switched structure introduces a method for bumpless switching between control models in a predetermined switching order. The advanced switched controller builds on the basic controller; however, instead of a predetermined switching sequence, the advanced algorithm uses the linear empirical controller when possible. When controller performance becomes unacceptable, the algorithm implements the low order model to control the process while the high fidelity model generates simulated data which is used to estimate the empirical model parameters. Once this online model identification process is complete, the controller reinstates the empirical model to control the process. This control framework allows the more accurate, yet computationally expensive, predictive capabilities of the high fidelity simulator to be incorporated into the locally accurate linear empirical model while still maintaining convergence guarantees.

[pt] Linhas submarinas são utilizadas na produção e transporte de petróleo e seus derivados. Em ambas as situações, o controle da transferência de calor do fluido para o ambiente externo pode ser um fator determinante para o escoamento. No caso de produção em águas profundas, o fluido aquecido perde calor para a água do mar gelada. A perda de calor é controlada através do isolamento térmico, o qual é projetado para operações de escoamento em regime permanente. Durante eventuais paradas de operação, o fluido estagnado no interior da tubulação ao perder calor para o ambiente frio, pode atingir níveis críticos de temperatura, acarretando graves problemas, tais como formação de hidratos ou deposição de parafina nas paredes da tubulação, o que pode levar ao bloqueio da linha e interrupção de produção. No transporte de produtos, o reinício de bombeio de fluidos muitos viscosos também é um problema crítico, devido ao aumento significativo da viscosidade com a redução da temperatura. O presente trabalho apresenta uma análise da influência da capacidade térmica da parede do tubo e das camadas de revestimento no transiente térmico de linhas com muito isolamento. A perda de calor da linha para o ambiente é determinada resolvendo-se a equação transiente de condução de calor para as camadas de revestimento da tubulação, utilizando um modelo uni-dimensional na direção radial. O método de volumes finitos é empregado para resolver o escoamento transiente no interior da tubulação acoplado com o transiente térmico na parede da tubulação, a partir do instante em que uma válvula é fechada na extremidade da tubulação interrompendo o fluxo. Comparações com as previsões de softwares comerciais foram realizadas e suas limitações são discutidas. Resultados obtidos das simulações para o escoamento tanto de líquidos quanto de gases, considerando e desprezando a capacidade térmica, mostram que o efeito da mesma é relevante na determinação do tempo de resfriamento da linha e do fluido em seu interior. / [en] Subsea pipelines are employed not only for production but also for transportation. In both situations, warm oil loses heat to the cold sea water. The heat loss to the ambient is controlled by means of thermal insulation, which is designed for steady state operations. During shutdowns, the stagnant fluid in the pipeline loses heat to the cold surrounding, eventually reaching some critical temperature. As a result, several problems can occur, such as formation of hydrates or deposition of high molecular weight paraffins on the inner wall of the subsea line, which can lead to flow line blockage and production shutdown. Restart of very viscous fluid after shutdown is also critical, since viscosity increases significantly with the reduction of the temperature. This work presents an analysis of the influence of the pipe wall thermal capacitance on the transient behavior of heavily insulated lines. The heat loss from the pipeline is determined, by solving the transient heat conduction equation for the pipewall layers, utilizing a simple one-dimensional model in the radial direction. The finite volume method is employed to solve the transient flow inside the pipeline, from the time instant that a valve at the end point of the line is closed, coupled with the pipe wall thermal transient. Comparisons with the prediction of commercial softwares were performed and their limitations are addressed. Numerical results obtained for flows of both liquid and gases, considering and neglecting the thermal capacitance, revealed that accounting for the thermal capacity of the wall is relevant to the determination of cooldown times

Historicamente, o sistema para instalação de equipamentos de produção submarina de petróleo por meio de cabos guia, tem sua eficiência comprovada. Porém a grande maioria dos projetos das bases guia submarinas foi calculada por métodos analíticos, que embora permitam a obtenção de respostas exatas em todos os infinitos pontos de uma estrutura, não são aplicáveis a todos os casos. Isso motivou a aplicação do método dos elementos finitos (MEF) neste trabalho, que a partir do desenvolvimento de procedimentos aproximados, pode ser aplicado independentemente da forma da estrutura e das condições de carregamento. O estudo consiste da análise estrutural do modelo tridimensional da estrutura da base guia, modelado no software Autodesk Inventor e analisado no software ANSYS Workbench. O estudo traz uma pesquisa diagnóstica e utiliza abordagem quantitativa e exploratória. Diferentes modelos matemáticos foram gerados para obtenção dos resultados nos pontos mais críticos da estrutura, a fim de se determinar sua resistência aos esforços de instalação e operação aplicados, levando em consideração os critérios estabelecidos nas normas DNV No. 2.7-3, API 17D 1.ed. e a tensão equivalente de von-Mises. / Historically, the guideline system for installation of subsea oil production equipment has proven its efficiency. However the majority of the subsea guide base designs have been calculated by analytical methods, although they allow obtaining exact answers in all infinite points of a structure, they are not applicable to all cases. This motivated the application of the finite element analysis method (FEA) in this work, which from the development of approximate procedures can be applied regardless of the structure shape and loading conditions. This paper consists of a structural analysis of the guide base frame model, generated in Autodesk Inventor software and analyzed in ANSYS Workbench software. This study brings a diagnostic research using a quantitative and exploratory approach. Different mathematical models were generated to obtain the results at the most critical points of the structure in order to determine its resistance to the loads applied during installation and operation, taking into account the criteria laid down in DNV No. 2.7-3, API 17D 1st Ed. and the von-Mises equivalent stress.