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  • 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.
131

Avaliação da vulnerabilidade natural à contaminação do solo e aqüífero do reservatório Batatã - São Luís (MA) /

Pereira, Ediléa Dutra. January 2006 (has links)
Orientador: José Eduardo Zaine / Banca: Antonio Roberto Saad / Banca: Edson Gomes de Oliveira / Banca: José Luiz Albuquerque Filho / Banca: Fábio Augusto Vieira Reis / Resumo: O mapeamento geológico-geotécnico em áreas urbanas foi utilizado na análise das características do meio físico e processos geológicos, avaliando suas limitações e potencialidades como subsídio à gestão e ao planejamento municipal. A Bacia do Rio Bacanga, localizada na Ilha do Maranhão, no município de São Luis-Maranhão (Brasil), apresenta uma área de 106 km2 que através dos tempos vem passando por um dinâmico processo de ocupação de forma não planejadas, provocando diversos impactos ambientais como assoreamento dos mangues, desmatamentos, aterramentos, impermeabilizações do solo, erosão, contaminação da água, inundações e outros. Os recursos hídricos genuinamente luduvicense são estratégicos para a Ilha oceânica, como reservas que precisam ser preservadas por se tratar de um ecossistema frágil. O estudo foi realizado através do método do detalhamento progressivo (análise do geral para o particular) para determinação e avaliação de áreas vulneráveis a contaminação do solo e da água no Reservatório Batatã. Na etapa geral do método foi elaborado o mapa geológico-geotécnico na escala 1:20.000 onde foram individualizada 6 unidades no terreno. Na etapa de semi-detalhe a pesquisa se direcionou para o estudo da vulnerabilidade natural à contaminação do solo e aqüífero do Reservatório Batatã e entorno. Nesta etapa, os estudos enfocaram uma área de 6,6 km2, para a qual foram geradas cartas na escala de 1:10.000: de declividade, de profundidade do nível de água subterrânea, de superfície potenciométrica do aqüífero livre Barreiras, de material inconsolidado e de uso e ocupação do solo. Nesta etapa, utilizou-se o método de avaliação da vulnerabilidade natural GOD utilizando-se as informações das cartas de unidades de material inconsolidado e da profundidade do nível de água subterrânea sendo gerado o mapa de vulnerabilidade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The geological-geotechnical mapping in urban areas was used in the analysis of the environment characteristics and geological processes, evaluating its limitations and potentialities as subsidy to the municipal management and planning. The Basin of the river Bacanga is located in the Maranhão lsland, in the city of São Luis - Maranhão (northeast of Brazil) and presents an area of 106 km2. lt has been passing through a dynamic process of non-planned human occupation which has caused many impacts as mangroves landfill environmental in region, deforestation, ground waterproofing, erosion, water contamination, flooding and others. Local water resources constitute a fragile ecosystem but a strategic one for such an oceanic island. Therefore, it must be preserved. The study was done through the method of the gradual detailing (it analyzes first the general aspects and afterwards the specific ones) for determination in the Batatã Reservoir. On Lhe first and most general step, a 1:20.000 scale geologic-geotechnical map was made, on where six land units were set up. The semi-detailed step studied the natural vulnerability to ground and aquifer contaminaton of the Batatã Reservoir and its surroundings. Such stage focused a 6.6 km2 area for which 1:10.000 scale charts were generated: declivity, underground water level depth, potentiometric surface, unconsolidated material and ground occupation. At this phase, the GOD natural vulnerability evaluation approach was used, and then information from the land unit charts of unconsolidated material and underground water level depth was utilized, resulting a map of natural vulnerability concerned to the contamination of ground and aquifer. The map of ground occupation was overlapped on the natural vulnerability map, resulting a map of natural vulnerability and potential contamination of the ground and aquifer of the Batatã Reservoir... (Complete abstract, click electronic address below) / Doutor
132

Evolução da capacidade de regularização do sistema hidrelétrico brasileiro. / Evolution of storage capacity in the brazilian hydropower system.

Filipe Antonio Marques Falcetta 20 August 2015 (has links)
No Brasil, cerca de dois terços da capacidade total instalada de geração de energia elétrica e, em média nos últimos quinze anos, aproximadamente 90% da geração efetiva provêm das hidrelétricas. Este sistema inclui 170 usinas hidrelétricas de médio e grande porte existentes ou previstas até 2023, aproximadamente dois terços delas com capacidade de regularizar vazões e todas operando de maneira interligada. Restrições ambientais, técnicas, sociais e econômicas tem dificultado cada vez mais a implantação de empreendimentos hidráulicos contendo reservatórios de grande porte, tornando a maioria dos novos empreendimentos a fio d´água. Para compreender melhor o processo, este trabalho apresenta um levantamento da evolução anual da capacidade instalada e de armazenamento do sistema desde 1950 até a expansão prevista nos próximos 8 anos, em 2023. Os dados da década de 2000 e a previsão até 2023 de forma ainda mais acentuada indicam uma redução continua e significativa da capacidade relativa de regularização, com impacto direto nas decisões de operação e de expansão do sistema térmico complementar. A fim de avaliar as possíveis consequências da redução da capacidade de regularização, simulações foram realizadas no modelo HIDROTERM (ZAMBON et al. 2012); os resultados apontam para uma necessidade de ser complementar continuamente a energia hídrica, não só em períodos hidrologicamente desfavoráveis. / In Brazil, about two-thirds of electricity installed capacity and over the last fifteen years, on average 90% of energy consumed has come from hydropower generation. The hydro system includes 170 medium and large hydropower plants in integrated operation today or planned to be operational by the end of 2023, about two-thirds of them have large storage capacities to regulate flows. Environmental, technical, social and economic constraints have made it increasingly difficult to project and build new reservoirs with large storage capacities. As a result, newly built hydropower plants are mostly the run-of-river type. To better understand the process, this paper presents a historical survey of the installed capacity of hydropower and storage capacity of the system since 1950 and extends to the planned expansion over the next eight years, through 2023. Data from 2000 and projections through 2023 indicate a significant reduction of relative regulating capacity, which has a direct impact on decisions regarding operation and expansion of the complementary thermal system. In order to assess the possible consequences of the reduction in regulating capacity, simulations were performed on HIDROTERM model (ZAMBON et al. 2012); the simulation results point to a continuous need for complementing the hydropower generation, not only on hydrologically unfavorable years.
133

Quantifying the role of microporosity in fluid flow within carbonate reservoirs

Harland, Sophie Rebekah January 2016 (has links)
Micropores can constitute up to 100% of the total porosity within carbonate hosted hydrocarbon reservoirs, usually existing within micritic fabrics. There is, however, only a rudimentary understanding of the contribution that these pores make to reservoir performance and hydrocarbon recovery. To further our understanding, a flexible, object-based algorithm has been developed to produce 3D computational representations of end-point micritic fabrics. By methodically altering model parameters, the state-space of microporous carbonates is explored. Flow properties are quantified using lattice-Boltzmann and network modelling methods. In purely micritic fabrics, it has been observed that average pore radius has a positive correlation with single-phase permeability and results in decreasing residual oil saturations under both water-wet and 50% fractionally oil-wet states. Similarly, permeability increases by an order of magnitude (from 0.6md to 7.5md) within fabrics of varying total matrix porosity (from 18% to 35%) due to increasing pore size, but this has minimal effect on multi-phase flow. Increased pore size due to micrite rounding notably increases permeability in comparison to original rhombic fabrics with the same porosity, but again, multi-phase flow properties are unaffected. The wetting state of these fabrics, however, can strongly influence multi-phase flow; residual oil saturations vary from 30% for a water-wet state and up to 50% for an 80% oil wet fraction. flow when directly connected. Otherwise, micropores control single-phase permeability magnitude. Importantly in these fabrics, recovery is dependent on both wetting scenario and pore-network homogeneity; under water-wet imbibition, increasing proportions of microporosity yield lower residual oil saturations. Finally, in grain-based fabrics where mesopores form an independently connected pore network, micropores do not affect permeability, even when they constitute up to 50% of the total porosity. Through examination of these three styles of microporous carbonates, it is apparent that micropores can have a significant impact on flow and sweep characteristics in such fabrics.
134

Spatiotemporal distribution and shoaling behaviour of fish (Časoprostorová distribuce a hejnové chování ryb)

SAJDLOVÁ, Zuzana January 2018 (has links)
The dissertation thesis is focused on pelagic fish distribution in the large freshwater bodies and the main factors affecting it. Paper 1 describes fish behaviour in a mouth of a midwater trawl during different day time periods as fish activity may importantly affect abundance estimates of the sampled fish stock. Acoustically recorded avoidance behaviour in a vertical direction is described. The second part of the thesis refers to the diel distribution and behaviour of the pelagic fry communities with a particular focus on the vertically migrating bathypelagic percid fry that occupy open water during early ontogeny. Paper 2 shows that the vertically migrating community can create a dominant part of fry assemblages in the reservoir, which is in contrast to many previous observations of an usually prevailing non-migrating epipelagic community. At their day refuge, bathypelagic percid fry (BPF) created dense shoals whose physical parameters are described. Paper 3 for the first time demonstrates that vertical shifts of BPF were under direct light control, hence were not a genetically fixed behaviour. A unique large-scale field experiment with the simultaneously operating up-looking and down looking transducers was carried out under artificially controlled light regime. Moreover effect of predation as the main ultimate cause of vertical shifts is discussed. The introductory part of the thesis opens with the current possibilities of assessing distribution and behaviour of fish in the open water. Benefits of shoaling/schooling behaviour during defence against predators, foraging and learning abilities of fish are mentioned and some implications of fish behaviour on the fish capture process are pointed out. The second chapter deals with the diel shifts between habitats that belong among the most common activities of fish. However, distribution of fish varies also over the long temporal scale and currently has been strongly affected by changing climate. Therefore, the main affects of climate change on the world´s fish populations are introduced using examples from both freshwater and marine environment.
135

Air Pressures Over Reservoir, Canal, and Water Catchment Surfaces Exposed to Wind

Dedrick, Allen Ray 01 May 1973 (has links)
Surface air pressure differentials that occur over reservoirs, canals, and water-catchment aprons in high-wind conditions were determined by the use of models in a wind tunnel. Such information was needed concerning the magnitude and location of destructive wind forces on water barriers constructed of exposed flexible membrane liners. Rigid models, without a membrane, were used to measure airpressure differentials. Air-pressure differentials were dependent on geometric configuration and were independent of viccous forces above the critical Reynolds number which was determined experimentally. The geometric factors studied with respect to reservoirs and canals included approach slope, approach slope length, leeward slope, and breadth-depth ratio. Those pertaining to water-catchment aprons included breadth-berm height ratio and berm shape. On the leeward slope of reservoirs, favorable (positive) differential pressures were more apt to occur as the approach and leeward slopes decreased (became less steep), but extreme adverse (negative) pressures occurred under the same conditions near the top edge of the slope. As the leeward slope increased the pressure coefficient values were essentially constant over the entire surface. On the reservoir bottom, adverse pressures did not exist when approach and leeward slopes were at the minimum evaluated (1:4). When the leeward and approach slopes increased the average pressure on the bottom became less favorable. The most adverse pressure coefficients generally occurred at the toe of the leeward slope, while maximum favorable pressures on the reservoir bottom generally occurred at the toe of the downwind slope. In most instances, the pressure on the downwind slope was favorable; however, adverse pressures were recorded near the top edge of the slope. These adverse or negative pressure conditions were more apt to occur as the breadth-depth ratio increased and the leeward slope decreased. Average pressure values on the interior surface of canals were generally less adverse than for reservoirs. Similar to the reservoirs, the most adverse pressures on the leeward slope of the canals were found immediately over the upper edge of the slope. Extreme adverse pressures on the canal bottom were associated with long and steep approach slope conditions. One exception was the occurrence of the most favorable pressure over the canal bottom when the approach slope was short but still steep. In addition to measurement of adverse pressures near the top edge of the downwind slope, adverse pressures were found near the toe of the slope in some instances. The portion of the downwind slope under an adverse pressure influence decreased as the breadth-depth ratio increased. Generally, pressures over a canal were more responsive to the approach slope and approach slope height than to leeward slope arid breadth-depth ratio. For a reservoir, however, pressures were responsive to all geometric factors, depending on which section of the reservoir was being considered. Pressure distributions over water-catchment aprons were independent of breadth-berm height ratios of 50 or greater. Negative pressures were lower over gradual sloped catchment berms by a factor of three than over sine-shaped berms. Each berm shape, on the leeward side of the upwind berm, had a pressure distribution associated with it that was the same as far as shape but was different in magnitude depending on the shape of the windward side of the berm. Pressures were less adverse on the leeward side of the berm, if the windward side were gradually sloped. Pressures were near zero to slightly favorable over a large portion of the water-catchment apron between the berm toes. This near stable favorable condition might change significantly, if site conditions were to change.
136

Surface mixers for destratification and management of Anabaena circinalis / by David Milton Lewis.

Lewis, David M. January 2004 (has links)
"March 2004" / Bibliography: leaves 221-234. / xxiv, 249 leaves : ill. (some col.), maps, photos (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This research is part of the SA Water and Cooperative Centre for Water Quality and Treatment project entitled Destratification for control of phyloplankton. The major objective of this project was to assess a novel method of destratification and control of cyanobacteria, in particular Anabaena circinalis Rabenh. ex Born. et Flah, with the use of raft-mounted mechanical surface mixers with draft-tubes. / Thesis (Ph.D.)--University of Adelaide, School of Civil and Environmental Engineering, 2004
137

Oil recovery by spontaneous imbibition for a wide range of viscosity ratios

Fischer, Herbert. January 2006 (has links)
Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on Dec. 20, 2007). Includes bibliographical references (p. 208-216).
138

Application of a statistical zonation technique to Granny Creek field in West Virginia

Kristamsetty, Venkata. January 2006 (has links)
Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xx, 159 p. : ill. (some col.), map. Includes abstract. Includes bibliographical references (p. 64-65).
139

A new method for the rapid calculation of finely-gridded reservoir simulation pressures /

Hardy, Benjamin Arik, January 2005 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Chemical Engineering, 2005. / Includes bibliographical references (p. 159-161).
140

A model for matrix acidizing of long horizontal well in carbonate reservoirs

Mishra, Varun 02 June 2009 (has links)
Horizontal wells are drilled to achieve improved reservoir coverage, high production rates, and to overcome water coning problems, etc. Many of these wells often produce at rates much below the expected production rates. Low productivity of horizontal wells is attributed to various factors such as drilling induced formation damage, high completion skins, and variable formation properties along the length of the wellbore as in the case of heterogeneous carbonate reservoirs. Matrix acidizing is used to overcome the formation damage by injecting the acid into the carbonate rock to improve well performance. Designing the matrix acidizing treatments for horizontal wells is a challenging task because of the complex process. The estimation of acid distribution along wellbore is required to analyze that the zones needing stimulation are receiving enough acid. It is even more important in cases where the reservoir properties are varying along the length of the wellbore. A model is developed in this study to simulate the placement of injected acid in a long horizontal well and to predict the subsequent effect of the acid in creating wormholes, overcoming damage effects, and stimulating productivity. The model tracks the interface between the acid and the completion fluid in the wellbore, models transient flow in the reservoir during acid injection, considers frictional effects in the tubulars, and predicts the depth of penetration of acid as a function of the acid volume and injection rate at all locations along the completion. A computer program is developed implementing the developed model. The program is used to simulate hypothetical examples of acid placement in a long horizontal section. A real field example of using the model to history match actual treatment data from a North Sea chalk well is demonstrated. The model will help to optimize acid stimulation in horizontal wells.

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