• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 12
  • 11
  • 3
  • 3
  • Tagged with
  • 33
  • 9
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Synchrophasor Based Centralized Remote Synchroscope for Power System Restoration

Barik, Tapas Kumar January 2018 (has links)
The process of Synchronization between two buses in a power system plays a vital role, especially during blackstart or bulk power system restoration period. The synchronization process is primarily monitored in the presence of experienced personnel at the substation level, which might not control or even predict the after effects of synchronization as soon as the synchronizing breaker between the two buses respective to the two islands is closed. However, with the advent of phasor measurement units (PMUs) providing time synchronized synchrophasor data, synchroscope functionality can now be implemented at a centralized remote control platform, usually the control room of the specific utility. This thesis presents a technique along with the actual implementation of such a PMU Synchroscope analytic developed as a part of the Department of Energy sponsored open and Extensible Control and Analytics platform for synchrophasor data (openECA project). The challenges faced to realize this functionality at the centralized remote location along with methods to overcome these hurdles have been discussed in the document. Additional features in comparison to the conventional synchroscope device are also added to facilitate a smoother and successful synchronization, reducing error on behalf of the user /operator and thus, facilitating a faster power system restoration. / Master of Science / Successful and proper synchronization between different nodes of a power system is one of the most crucial stages of restoring power after a major wide area electricity outage. Improper synchronization may lead to additional system outages and might delay the restoration process. In this regards, it is desired to perform this vital task at the electric utility’s central remote control room. This thesis develops an application to perform the successful reconnection between two nodes of a system overcoming the various challenges and incorporating system delays. The application designed is based on real-time measurements and is integrated with an open source framework platform for ease of the user.
2

Development of a Three-Dimensional Mesh Generator With Analytical Mesh Sensitivities

Bam, Campbell A. January 2020 (has links)
Structural shape optimisation is a field that has been studied since early on in the development of finite element methods. The sub-fields of shape and topology optimisation are continuously growing in industry and aim to leverage the benefits of technologies such as 3D printing and additive manufacturing. These fields are also being used to optimise designs to improve quality and reduce cost. Gradient-based optimisation is well understood as an efficient method of obtaining solutions. In order to implement gradient-based optimisation methods in the context of structural shape optimisation, sensitivities describing the change of the domain stiffness are required. To obtain the stiffness sensitivities, mesh deformation sensitivities are required. In this study, a mesh generating method is developed that provides mesh deformation sensitivities. For shape optimisation it is advantageous to employ an optimisation algorithm that allows for the manipulation of CAD geometry. This means that the CAD geometry is finalised upon completion of the optimisation process. This, however, necessitates the calculation of accurate sensitivities associated with non-linear geometries, such as NURBS (those present in CAD), by the mesher. The meshing method developed in this study is analogous to a linear truss system. The system is solved for static equilibrium through a geometrically non-linear finite element analysis using Newton’s method. Sensitivities are made available by Newton’s method for use in generating mesh sensitivities for the system. It is important for the mesher to be able to accurately describe the geometrical domain which approximates the geometry being modelled. To do so, nodes on the boundary may not depart from the boundary. Instead of prescribing all boundary nodes, this mesher frees the boundary nodes to move University of Pretoria ii Department of Mechanical and Aeronautical Engineering along, but not away from the boundary. This is achieved using multipoint constraints since they allow for an analytical relationship between boundary node movement and the boundary. Two multipoint constraint (MPC) methods are investigated for boundary discretisation, namely, the Lagrangian and master-slave elimination methods (MSEM). The MSEM presents several difficulties in obtaining convergence on non-linear boundaries in general when compared to the Lagrangian method. The MSEM has reduced computational requirements for a single Newton step, especially when direct solvers are used. However, when indirect solvers are implemented the time difference between the two MPC methods reduces significantly. For a “medium” curvature geometry the Lagrangian implementation has only a 6% time penalty. The Lagrangian method is selected as the preferred MPC method for implementation in the mesher to avoid the convergence problems associated with the MSEM. This is justified on the basis of reliability outweighing the 6% time penalty for what is intended to be a tool in the shape optimisation process. Analytical sensitivities are obtained for the truss system in order to account for the MPC boundaries. The analytical mesh sensitivities are proven to be accurate through comparison with numerical sensitivities. The method is demonstrated to be able to accurately described the mesh deformation throughout the domain for both uniform and non-uniform meshes in the presence of non-linear boundaries. / Dissertation (MEng)--University of Pretoria, 2020. / Mechanical and Aeronautical Engineering / MEng (Mech) / Unrestricted
3

Chroniqueurs citadins et nouveaux pouvoirs en Émilie-Romagne (vers 1300 - vers 1500) / Power and City’s Chroniclers in Emilia-Romagna (ca.1300-ca.1500) / Cronisti cittadini e potere nell’Emilia-Romagna (c.1300-c.1500)

Bouchet, Serge 29 November 2011 (has links)
L’Émilie-Romagne, entre offensives seigneuriales et réaffirmation des prérogatives pontificales, connaît une abondante production historique citadine du XIVe siècle aux deux premières décennies du XVIe siècle. La transformation de l'écriture de l'histoire et la sensibilité des chroniqueurs sont analysées à partir de soixante-dix chroniques issues de Rimini, Césène, Forli, Bologne, Modène, Reggio Emilia et Ferrare.Après avoir présenté les auteurs, la forme des textes et leur évolution, l’étude expose les enjeux politiques des histoires des origines. L'espace est ensuite considéré afin de préciser le regard porté par ces chroniqueurs sur leur cité et, de là, sur l’espace régional et sur le monde. Les images ouvrent une autre dimension de la pensée des auteurs. Les messages des dessins insérés dans les manuscrits ainsi que l’iconographie des marges, la communication par l’image dans la ville et les icônes du pouvoir sont ainsi interprétés. L’analyse du discours tenu sur les hommes de pouvoir complète l’approche permettant d’appréhender les clichés, les critiques et les représentations des auteurs. Les manifestations du pouvoir viennent clore l’étude. L’évocation de la ville et de la société par les chroniqueurs écrivant entre la fin du XVe siècle et le XVIe siècle, est abordée pour finir. / From the 14th century to the first two decades of the 16th century, vast historical urban expansion took place in Emilia-Romagna, mainly due to offensives by lords and the reassertion of pontifical prerogatives. The aim of the paper is to analyze the evolution of the way history is told by chroniclers as well as their sensibilities. For this, we focused on seventy chronicles written in Rimini, Cesena, Forli, Bologna, Modena, Reggio-Emilia and Ferrara. First, the authors, the outline of the texts and their evolution are presented. Then the paper sheds light on the political stakes behind the original stories. Subsequently, the geographical location of the chroniclers is considered to analyze their points of view on their cities and, more widely, on the world. Images lead to other considerations: messages of the drawings inserted in the manuscripts, margin iconography, visual communication in the city, and icons of the power. Analysis of the descriptions of power holders gives an overview of the chroniclers’ criticisms and praises. Finally we reveal how the city and the societies in transformation are evoked in the 15th and 16th centuries. / L’Emilia Romagna, tra offensive delle signorie e riaffermazione delle prerogative pontifice, conosce una abbondante produzione storica cittadina dal XIV secolo fino ai primi due decenni del XVI secolo. La trasformazione della scrittura della storia e la sensibilità dei cronisti sono analizzati a partire dalle settanta cronache redatte a Rimini, a Cesena, Forlì, Bologna, Modena, Reggio Emilia e Ferrara. Dopo aver presentato gli autori, la forma dei testi e la loro evoluzione, lo studio espone le scommesse (o poste) politiche delle storie delle origini. Lo spazio è poi considerato per precisare lo sguardo che questi cronisti rivolgono alla loro città e, di qui, sullo spazio della loro regione e sul mondo. Le immagini autorizzano inoltre altre considerazioni. Vengono interpretati i messaggi veicolati dai disegni inseriti nei manoscritti, l’iconografia dei margini, la comunicazione attraverso l’immagine nella città e le icone del potere. L’analisi del discorso tenuto sugli uomini di potere completa l’approccio permettendo di cogliere critiche e lodi dei cronisti. Viene affrontata, poi, la rievocazione della città e di una società in trasformazione fatta dagli autori che scrivono tra la fine del XV e il XVI secolo.
4

Estimation methods for Asian Quanto Basket options

Adolfsson, David, Claesson, Tom January 2019 (has links)
All financial institutions that provide options to counterparties will in most cases get involved withMonte Carlo simulations. Options with a payoff function that depends on asset’s value at differenttime points over its lifespan are so called path dependent options. This path dependency impli-cates that there exists no parametric solution and the price must hence be estimated, it is hereMonte Carlo methods come into the picture. The problem though with this fundamental optionpricing method is the computational time. Prices fluctuate continuously on the open market withrespect to different risk factors and since it’s impossible to re-evaluate the option for all shifts dueto its computing intensive nature, estimations of the option price must be used. Estimating theprice from known points will of course never produce the same result as a full re-evaluation but anestimation method that produces reliable results and greatly reduces computing time is desirable.This thesis will evaluate different approaches and try to minimize the estimation error with respectto a certain number of risk factors.This is the background for our master thesis at Swedbank. The goal is to create multiple estima-tion methods and compare them to Swedbank’s current estimation model. By doing this we couldpotentially provide Swedbank with improvement ideas regarding some of its option products andrisk measurements. This thesis is primarily based on two estimation methods that estimate optionprices with respect to two variable risk factors, the value of the underlying assets and volatility.The first method is a grid that uses a second order Taylor expansion and the sensitivities delta,gamma and vega. The other method uses a grid of pre-simulated option prices for different shiftsin risk factors. The interpolation technique that is used in this method is calledPiecewise CubicHermiteinterpolation. The methods (or referred to as approaches in the report) are implementedto handle a relative change of 50 percent in the underlying asset’s index value, which is the firstrisk factor. Concerning the second risk factor, volatility, both methods estimate prices for a 50percent relative downward change and an upward change of 400 percent from the initial volatility.Should there emerge even more extreme market conditions both methods use linear extrapolationto estimate a new option price.
5

SENSIBILIDADES E PRÁTICAS NO ENSINO DE HISTÓRIA EM INHUMAS: 1996 - 2006

Souza, Eber Dornelas da Costa 12 March 2010 (has links)
Made available in DSpace on 2016-08-10T10:35:02Z (GMT). No. of bitstreams: 1 EBER DORNELAS DA COSTA SOUZA.pdf: 3429275 bytes, checksum: c71231f17c1f7aa6e50b7dc8dcce25a6 (MD5) Previous issue date: 2010-03-12 / This work analyses the sensitivities and practices in the teaching of History in Inhumas, Goiás. It reveals the feelings, emotions and sensations observed in teachers' practices. To understand how such sensitivities are represented in the teachers' personal life and work, the analysis is based on Cultural History works by various authors, especially Sandra Jatahy Pesavento. This research aims to identify insecurities, low self-esteem and lack of confidence on the part of History teachers. Based on the teachers' backgrounds, I investigate their reasons for seeking self-assertion throughout their lives and teaching practices. Therefore, I consider sensitivities as the basis for defining representations of a teacher's professional universe, which exerts direct and indirect influence on the way the legislation is applied. For this reason, it is important to identify the feelings and motivations of History teachers in order to comprehend representations and practices related to the teaching of History. / Esta dissertação tem como objeto de análise as Sensibilidades e Práticas no Ensino de História em Inhumas, Goiás, a partir de um olhar revelador sobre os sentimentos, às emoções e as sensações observadas na prática do profissional da educação. A análise busca fundamento baseados na História Cultural, por meio de diversos autores, em especial Sandra Jatahy Pesavento, para entender como estas sensibilidades são representadas na vida pessoal e no trabalho de cada um dos entrevistados. Na investigação realizada para este estudo, por meio de pesquisas e entrevistas, procura-se responder, fundamentalmente, à seguinte questão: como identificar à insegurança, a baixa estima dos professores, a falta de autoconfiança. Busca também a percepção de uma releitura sobre as sensibilidades e práticas efetivas dos professores de história. Após uma contextualização sobre a história de vida dos professores e uma reflexão sobre múltiplos caminhos, investigam-se as razões na busca pela auto-afirmação ao longo da vida e o caminho percorrido: professores de história. Portanto, pode-se considerar que as sensibilidades estão na base das representações sobre o mundo profissional dos professores e influenciam indireta e diretamente na forma como a legislação é aplicada. Por este motivo é importante identificar os sentimentos e motivações dos atores sociais envolvidos no ensino de história, para que se possa compreender as representações e práticas a ele relacionadas.
6

HISTÓRIA, LITERATURA E CRÍTICA LITERÁRIA GOIANA: SENSIBILIDADES REGIONAIS NA DÉCADA DE 1980. / History, literature and literary criticism Goias: regional sensibilities in the 1980.

Arima, Regina Oliveira Silva 06 September 2009 (has links)
Made available in DSpace on 2016-08-10T11:22:00Z (GMT). No. of bitstreams: 1 REGINA OLIVEIRA SILVA ARIMA.pdf: 899190 bytes, checksum: 6a2261208ec25490f6b9e6b6a3656216 (MD5) Previous issue date: 2009-09-06 / This work has a propose the redemption of regional sensibilities in the 1980s. The materiality of such feelings were found in the opinions and literary critics of the competition Exchange Publications "Hugo de Carvalho Ramos. Inside in of a thematic framework of cultural history sought to emphasize the dialogue between history and literature. It is emphasized in the text zoom in and out of such speeches, as well as its complementary relationship in the production of historical knowledge. The work also emphasizes the integration of literary criticism as a source for history, for it is pointed out some peculiarities that define its status as a stand-alone and text with specific aesthetic qualities. In addition, by working directly with literary texts we used the theory of reception as a way to explain how these texts have served as mediators between objective reality and the "world of the text" created by the fictional narrative. We made an overview of the Exchange Office, as well as some information about the writer Goias Hugo de Carvalho Ramos whose name was given to the stock as a way to honor the forerunner of regionalism in the state. Work verticalizes sensitivities as a representation of a specific temporality of history Goias. By focusing on emotions in relation to sensitive self and its reality, the sensitivities allow a form of knowledge of the world, making this a temporality disposed therefore to understand how men represented themselves and others. The texts (critical opinions) and (literary) were as marks of historicity, the reading of these sources could establish relations to reach another place where people expressed their feelings in many different ways. We decided to analyze literary works by dividing them according to genre (prose and poetry), then did the analysis of critical opinions. The reading of these sources revealed that nurture feelings relive a time unique, with remarkable presence of a regional identity with values and beliefs were associated with small-town atmosphere and simple country life. These specific situations have given their texts authors emphasize social and political critics. / Este trabalho tem como proposta o resgate das sensibilidades regionais na década de 1980. A materialidade de tais sentimentos foi encontrada nos pareceres críticos e obras literárias do concurso Bolsa de Publicações Hugo de Carvalho Ramos . Dentro de uma perspectiva temática da história cultural, procurou-se enfatizar o diálogo entre a história e a literatura. Ressaltam-se no texto as aproximações e distanciamentos de tais discursos, bem como sua relação de complementaridade na produção do conhecimento histórico. O trabalho destaca ainda a inserção da crítica literária como fonte para a história; pontuam-se, para isso, algumas singularidades que definem seu estatuto como um texto autônomo e com qualidades estéticas específicas. Além disso, por trabalhar diretamente com textos literários, utilizou-se a teoria da recepção como forma de esclarecer como esses textos serviram de mediadores entre a realidade objetiva e o mundo do texto criado pela narrativa de ficção. Procurou-se fazer um quadro geral da Bolsa de Publicações, bem como algumas informações a respeito do escritor goiano Hugo de Carvalho Ramos, cujo nome foi dado à bolsa, como forma de homenagear o precursor do regionalismo no Estado. O trabalho verticalizou as sensibilidades como representação de uma temporalidade específica da história goiana. Ao incidir sobre as emoções na relação do sensível do eu e sua realidade, as sensibilidades permitem uma forma de conhecimento do mundo, tornando presente uma temporalidade escoada, pois, permite entender como os homens representavam a si mesmos e aos outros. Os textos (pareceres críticos) e (obras literárias) apresentaram-se como marcas de historicidade, a leitura de tais fontes possibilitaram estabelecer relações para se alcançar um tempo em que as pessoas expressavam seus sentimentos das mais variadas formas. Optou-se por analisar as obras literárias dividindo-as de acordo com o gênero (prosa e poesia), em seguida procedeu-se à análise dos pareceres críticos. A leitura de tais fontes revelou sentimentos que oportunizaram reviver uma época singular, com presença marcante de uma identidade regional, cujos valores e crenças estavam associados ao ambiente interiorano e à vida simples do campo. Tais situações específicas proporcionaram aos autores enfatizarem em seus textos críticas políticas e sociais.
7

Melancolia e anticristo: sensibilidades contemporâneas e representação da loucura no cinema de Lars Von Trier

Kernicki, João Luís da Silva 17 November 2017 (has links)
Submitted by Eunice Novais (enovais@uepg.br) on 2018-02-28T19:57:01Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) João Luís da Silva Kernicki.pdf: 878145 bytes, checksum: a88dbbc5e35f66137c165fa7da7e2b96 (MD5) / Made available in DSpace on 2018-02-28T19:57:01Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) João Luís da Silva Kernicki.pdf: 878145 bytes, checksum: a88dbbc5e35f66137c165fa7da7e2b96 (MD5) Previous issue date: 2017-11-17 / Este trabalho realizado dentro do campo da historiografia, em sua abordagem multidisciplinar, que toma de empréstimo conceitos da psicanálise, filosofia e cinema, tem por objetivo abordar as relações entre história e cinema, questionando se há uma escrita fílmica da história e em que dimensão esse estudo pode contribuir para a historiografia quando se pensa em um filme não somente como uma fonte de dados visuais exploráveis pelo historiador, mas também situando o filme como um agente transformador da história, carregado de uma representação visual do sensível, e de um discurso que pode tanto ser atribuído à uma indústria cultural ou mais precisamente, a um cineasta problematizador. Investigando a filmografia de Lars Von Trier, usando o método da análise fílmica, exploraremos as peculiaridades das sensibilidades contemporâneas e o condicionamento sócio-histórico que estas sofrem, e como são representadas em sua obra. Trabalharemos com a questão da polissemia do termo loucura – seja aquela que passa pelo crivo do discurso moralizante, seja aquela enquadrada pelos termos da psicanálise - e com as diferentes representações que adquiriu ao longo do tempo até que se tornasse um objeto da medicina. Pontuaremos qual a especificidade do cinema de Lars Von Trier em relação ao mainstream, sua tentativa de purificação do cinema com o movimento Dogma 95 e como dentro de um movimento artístico este ganha destaque, seja pelos temas abordados, seja pela própria personalidade polêmica do autor. Por fim, investigaremos o sentir contemporâneo, situado naquilo que Bauman chamou de Modernidade Líquida, e como este sentir pode ser compreendido nas obras de Lars Von Trier, orientadas pelo conhecimento de um tempo trágico. . / This work carried out within the field of historiography, in its multidisciplinary approach, which borrows concepts from psychoanalysis, philosophy and cinema, aims to address the relations between history and cinema, questioning if there is a filmic writing of history and in what dimension this study may contribute to historiography when one thinks of a film not only as a source of visual data exploitable by the historian, but also situates the film as a transforming agent of history, loaded with a visual representation of the sensitive, and a discourse that can whether attributed to a cultural industry or, more precisely, to a problem-maker. Investigating Lars Von Trier's filmography, using the method of film analysis, we will explore the peculiarities of contemporary sensitivities and the socio-historical conditioning they suffer, and how they are represented in their work. We will deal with the question of the polysemy of the term madness - whether that which passes through the riddle of moralizing discourse, or that framed by the terms of psychoanalysis - and the different representations it acquired over time until it became an object of medicine. We will point out the specificity of Lars Von Trier's cinema in relation to the mainstream, his attempt to purify the cinema with the Dogma 95movement and, as part of an artistic movement, this is highlighted, both by the themes addressed and by the author's own controversial personality. Finally, we will investigate the contemporary feeling, situated in what Bauman called Liquid Modernity, and how this feeling can be understood in the works of Lars Von Trier, guided by the knowledge of a tragic time.
8

Entre verrinas e ditirambos: maternagem nos discursos normativos: São Paulo, 1925-1940

Colucci, Sandra Regina 18 February 2016 (has links)
Made available in DSpace on 2016-04-27T19:31:13Z (GMT). No. of bitstreams: 1 Sandra Regina Colucci.pdf: 8156122 bytes, checksum: 430c87a882f06ebdd6bc450c4429f603 (MD5) Previous issue date: 2016-02-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This research aimed to capture the constitution movement of different practices of mothering through fragments filtered by the hegemonic consciousness of documents, seeking historicizing the construction of the meanings assigned to it in his subjective process. The life of the city scaled the perspective of social history through different eyes, in the diversity of languages and the multiplicity of their code authorizes the analysis of the relationships established by different speeches that wove responsibility networks and guilt mothers front of child crime, forms of female labor, disease, death and food practices. In this sense, the theme of Between blame and praise: mothering in normative discourses" appears woven in the pursuit of building meanings to different feminine care practices with their children in ways of working, living, live, to have fun, to eat, to women's daily lives. Our goal was to analyze the discourses that allow heterogeneous seek the local knowledge, perception of other times / places in concurrency multidirectional experiences, in the seizure of tensions and confrontations inherent experiences, as well as on the construction of representations in its multiple interference the strategies of social groups, producing new study references that allow the expansion of women's studies / Esta pesquisa buscou captar o movimento de constituição de diferentes práticas de maternagem, através de fragmentos filtrados pela consciência hegemônica dos documentos, buscando historicizar a construção dos significados a ela atribuídos em seu processo de subjetivação. O cotidiano da cidade dimensionado na perspectiva da História Social através de olhares distintos, na diversidade de linguagens e na multiplicidade de seus códigos, autoriza a análise das relações estabelecidas por diferentes discursos que teceram redes de responsabilidade e culpa das mães frente à criminalidade infantil, formas de trabalho feminino, doenças, morte e práticas alimentares. Neste sentido, a temática de Entre verrinas e ditirambos: maternagem nos discursos normativos se apresenta tecida na busca da construção de significados atribuídos a diferentes práticas femininas de cuidados com os filhos, de modos de trabalhar, viver, morar, de se divertir, de se alimentar, ao cotidiano feminino. Nosso objetivo foi analisar os discursos que permitissem buscar o heterogêneo nos saberes locais, na percepção de outros tempos/espaços, na simultaneidade de vivências multidirecionais, na apreensão de tensões e confrontações inerentes às experiências, assim como sobre a construção das representações nas suas múltiplas interferências nas estratégias dos grupos sociais, produzindo novos referenciais de estudo que permitam a expansão dos estudos das mulheres
9

Multiscale-Streamline Inversion for High-Resolution Reservoir Models

Stenerud, Vegard January 2007 (has links)
<p>The topic of this thesis is streamline-based integration of dynamic data for porous media systems, particularly in petroleum reservoirs. In the petroleum industry the integration of dynamic data is usually referred to as history matching. The thesis starts out by giving an introduction to streamline-based history-matching methods. Implementations and extensions of two existing methods for streamline-based history matching are then presented.</p><p>The first method pursued is based on obtaining modifications for streamline-effective properties, which subsequently are propagated to the underlying simulation grid for further iterations. For this method, two improvements are proposed to the original existing method. First, the improved approach involves less approximations, enables matching of porosity, and can account for gravity. Second, a multiscale approach is applied for which the data integration is performed on a hierarchy of coarsened grids. The approach proved robust, and gave a faster and better match to the data.</p><p>The second method pursued is the so-called generalized travel-time inversion (GTTI) method, which earlier has proven very robust and efficient for history matching. The key to the efficiency of this method is the quasilinear convergence properties and the use of analytic streamline-based sensitivity coefficients. GTTI is applied together with an efficient multiscale-streamline simulator, where the pressure solver is based on a multiscale mixed finite-element method (MsMFEM). To make the history matching more efficient, a selective work-reduction strategy, based on the sensitivities provided by the inversion method, is proposed for the pressure solver. In addition, a method for improved mass conservation in streamline simulation is applied, which requires much fewer streamlines to obtain accurate production-response curves. For a reservoir model with more than one million grid blocks, 69 producers and 32 injectors, the data integration took less than twenty minutes on a standard desktop computer. Finally, we propose an extension of GTTI to fully unstructured grids, where we in particular address issues regarding regularization and computation of sensitivities on unstructured grids with large differences in cell sizes.</p> / Paper I reprinted with kind permission of Elsevier, sciencedirect.com
10

Multiscale-Streamline Inversion for High-Resolution Reservoir Models

Stenerud, Vegard January 2007 (has links)
The topic of this thesis is streamline-based integration of dynamic data for porous media systems, particularly in petroleum reservoirs. In the petroleum industry the integration of dynamic data is usually referred to as history matching. The thesis starts out by giving an introduction to streamline-based history-matching methods. Implementations and extensions of two existing methods for streamline-based history matching are then presented. The first method pursued is based on obtaining modifications for streamline-effective properties, which subsequently are propagated to the underlying simulation grid for further iterations. For this method, two improvements are proposed to the original existing method. First, the improved approach involves less approximations, enables matching of porosity, and can account for gravity. Second, a multiscale approach is applied for which the data integration is performed on a hierarchy of coarsened grids. The approach proved robust, and gave a faster and better match to the data. The second method pursued is the so-called generalized travel-time inversion (GTTI) method, which earlier has proven very robust and efficient for history matching. The key to the efficiency of this method is the quasilinear convergence properties and the use of analytic streamline-based sensitivity coefficients. GTTI is applied together with an efficient multiscale-streamline simulator, where the pressure solver is based on a multiscale mixed finite-element method (MsMFEM). To make the history matching more efficient, a selective work-reduction strategy, based on the sensitivities provided by the inversion method, is proposed for the pressure solver. In addition, a method for improved mass conservation in streamline simulation is applied, which requires much fewer streamlines to obtain accurate production-response curves. For a reservoir model with more than one million grid blocks, 69 producers and 32 injectors, the data integration took less than twenty minutes on a standard desktop computer. Finally, we propose an extension of GTTI to fully unstructured grids, where we in particular address issues regarding regularization and computation of sensitivities on unstructured grids with large differences in cell sizes. / Paper I reprinted with kind permission of Elsevier, sciencedirect.com

Page generated in 0.07 seconds