Made available in DSpace on 2014-12-17T14:08:35Z (GMT). No. of bitstreams: 1 KeilaRSpdf.pdf: 4445609 bytes, checksum: 3395044458045d549e1940f35912e4a6 (MD5) Previous issue date: 2009-07-31 / Petr?leo Brasileiro SA - PETROBRAS / Due to reservoirs complexity and significantly large reserves, heavy oil recovery has become one of the major oil industry challenges. Thus, thermal methods have been widely used as a strategic method to improve heavy oil recovery. These methods improve oil displacement through viscosity reduction, enabling oil production in fields which are not considered commercial by conventional recovery methods. Among the thermal processes, steam flooding is the most used today. One consequence in this process is gravity segregation, given by difference between reservoir and injected fluids density. This phenomenon may be influenced by the presence of reservoir heterogeneities. Since most of the studies are carried out in homogeneous reservoirs, more detailed studies of heterogeneities effects in the reservoirs during steam flooding are necessary, since most oil reservoirs are heterogeneous. This paper presents a study of reservoir heterogeneities and their influence in gravity segregation during steam flooding process. In this study some heterogeneous reservoirs with physical characteristics similar those found in the Brazilian Northeast Basin were analyzed. To carry out the simulations, it was used the commercial simulator STARS by CMG (Computer Modeling Group) - version 2007.11. Heterogeneities were modeled with lower permeability layers. Results showed that the presence of low permeability barriers can improve the oil recovery, and reduce the effects of gravity segregation, depending on the location of heterogeneities. The presence of these barriers have also increased the recovered fraction even with the reduction of injected steam rate / Devido a complexidade dos reservat?rios e as reservas significativamente grandes, a recupera??o de ?leos pesados tem se tornado um dos grandes desafios da ind?stria petrol?fera. Os processos de recupera??o t?rmica t?m sido largamente empregados como um m?todo estrat?gico para melhorar a recupera??o de ?leo pesado. Estes melhoram o escoamento de ?leos atrav?s da redu??o da viscosidade, viabilizando a produ??o de petr?leo em campos considerados n?o comerciais pelos m?todos convencionais de recupera??o. Entre os m?todos t?rmicos, a inje??o de vapor ? o mais utilizado atualmente. Uma consequ?ncia inerente a este processo ? a segrega??o gravitacional, dada pela diferen?a de densidades dos fluidos do reservat?rio e o injetado. Este fen?meno ? fortemente influenciado pela presen?a de heterogeneidades. Como a maior parte dos estudos ? realizada em reservat?rios homog?neos, necessita-se de um estudo mais detalhado dos efeitos das heterogeneidades nos reservat?rios durante a inje??o de vapor, j? que a maioria dos reservat?rios de petr?leo s?o heterog?neos. Este trabalho apresenta um estudo da influ?ncia da presen?a de heterogeneidades na segrega??o gravitacional durante o processo de inje??o cont?nua de vapor. Os modelos estudados representam reservat?rios heterog?neos com caracter?sticas similares ?s encontradas no Nordeste brasileiro. Para a realiza??o das simula??es, foi utilizado o simulador comercial STARS (Steam, Thermal, and Advanced Processes Reservoir Simulator) do grupo CMG (Computer Modelling Group) vers?o 2007.11. As heterogeneidades foram modeladas como camadas de baixa permeabilidade. Os resultados mostraram que a presen?a de barreiras de baixa permeabilidade pode melhorar a recupera??o de ?leo, al?m de reduzir os efeitos da segrega??o gravitacional, dependendo da localiza??o da heterogeneidade. A presen?a dessas barreiras tamb?m permitiu o aumento da fra??o recuperada mesmo com a redu??o da vaz?o de inje??o do vapor

Made available in DSpace on 2014-12-17T14:57:51Z (GMT). No. of bitstreams: 1 SidneyOL.pdf: 4301786 bytes, checksum: 9f7a7a0d30a925198ccebaa046c885a4 (MD5) Previous issue date: 2009-02-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work proposes a computational methodology to solve problems of optimization in structural design. The application develops, implements and integrates methods for structural analysis, geometric modeling, design sensitivity analysis and optimization. So, the optimum design problem is particularized for plane stress case, with the objective to minimize the structural mass subject to a stress criterion. Notice that, these constraints must be evaluated at a series of discrete points, whose distribution should be dense enough in order to minimize the chance of any significant constraint violation between specified points. Therefore, the local stress constraints are transformed into a global stress measure reducing the computational cost in deriving the optimal shape design. The problem is approximated by Finite Element Method using Lagrangian triangular elements with six nodes, and use a automatic mesh generation with a mesh quality criterion of geometric element. The geometric modeling, i.e., the contour is defined by parametric curves of type B-splines, these curves hold suitable characteristics to implement the Shape Optimization Method, that uses the key points like design variables to determine the solution of minimum problem. A reliable tool for design sensitivity analysis is a prerequisite for performing interactive structural design, synthesis and optimization. General expressions for design sensitivity analysis are derived with respect to key points of B-splines. The method of design sensitivity analysis used is the adjoin approach and the analytical method. The formulation of the optimization problem applies the Augmented Lagrangian Method, which convert an optimization problem constrained problem in an unconstrained. The solution of the Augmented Lagrangian function is achieved by determining the analysis of sensitivity. Therefore, the optimization problem reduces to the solution of a sequence of problems with lateral limits constraints, which is solved by the Memoryless Quasi-Newton Method It is demonstrated by several examples that this new approach of analytical design sensitivity analysis of integrated shape design optimization with a global stress criterion purpose is computationally efficient / Neste trabalho prop?e-se uma metodologia computacional para resolver problemas de Otimiza??o de Forma para projeto estrutural. A aplica??o ? particularizada para problemas bidimensionais em estado plano de tens?es, de modo a minimizar a massa atendendo um crit?rio de tens?o. Para atender ao crit?rio param?trico de tens?es ? proposto um crit?rio global de tens?o de von Mises, dessa maneira, amplia-se o crit?rio local de tens?es sobre o dom?nio, visando ? obten??o de programas mais seguros. O problema ? aproximado pelo M?todo dos Elementos Finitos utilizando elementos triangulares da base Lagrangiana padr?o com seis n?s, tendo uma estrat?gia de gera??o autom?tica de malhas baseada em um crit?rio geom?trico do elemento. O modelo geom?trico do contorno material ? definido por curvas param?tricas B-splines. Estas curvas possuem caracter?sticas vantajosas para implementa??o do processo de otimiza??o de forma, que se utiliza dos pontos-chave para determinar o m?nimo do problema. A formula??o do problema de otimiza??o faz uso do M?todo Lagrangiano Aumentado, que transforma o problema de otimiza??o com restri??o, em problema irrestrito. A solu??o da fun??o Lagrangiana Aumentada ? alcan?ada pela determina??o da an?lise das sensibilidades anal?ticas em rela??o aos pontos-chave da curva B-spline. Como conseq??ncia, o problema de otimiza??o reduz-se ? solu??o de uma seq??ncia de problemas de limites laterais do tipo caixa, o qual ? resolvido por um m?todo de proje??o de segunda ordem que usa o m?todo de Quase-Newton projetado sem mem?ria. S?o demonstrados v?rios exemplos para o M?todo de Otimiza??o de Forma integrado a An?lise da Sensibilidade Anal?tica sob o crit?rio global de tens?o de von Mises

Made available in DSpace on 2014-12-17T15:26:38Z (GMT). No. of bitstreams: 1 MarconioSS_DISSERT.pdf: 828358 bytes, checksum: d4bc4c24d61f5cdfad5c76519c34784e (MD5) Previous issue date: 2010-06-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work we studied the asymptotic unbiasedness, the strong and the uniform strong consistencies of a class of kernel estimators fn as an estimator of the density function f taking values on a k-dimensional sphere / Nesse trabalho estudamos o n?o-v?cio assint?tico, a consist?ncia forte e a consist?ncia uniformemente forte de um estimador do tipo n?cleo, que como a maioria dos estimadores ? constru?do com base em n observa??es i.i.d. X1,..., Xn de X, para a densidade f(x) de um vetor aleat?rio X que assume valores em uma esfera unit?ria k-dimensional