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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.
1

Factors affecting injection well performance and fracture growth in waterflooded reservoirs

Hwang, Jongsoo 10 February 2015 (has links)
Waterflooding involves the injection of water to displace oil from oil and gas reservoirs. Well over 80% of oil reservoirs will undergo waterflooding at some point in their life. It is, therefore, important to understand some key aspects of this process that have hitherto not been well studied. This dissertation investigates the following aspects of waterflooding: (i) the filtration of solids and oil-in-water emulsions in fractured and unfractured injection wells, (ii) the generation and filtration of oil-in-water (O/W) emulsion droplets in the near-well region or in the fracture, (iii) the height-growth and containment of injection-induced fractures, and (iv) the stress reorientation induced by water injection when waterflooding reservoirs. These aspects are investigated as separate physical phenomena, but their impacts are integrated using the platform of a comprehensive waterflooding injection well model. The first phenomenon investigated is filtration in frac-packed injectors. During long-term water injection, solid particles in the injection water may deposit in the proppant pack of frac-packed injectors. Researchers have not fully understood whether particles will travel without plugging the frac-packs or deposit in the near-well area under the high-velocity flow conditions in the proppants. Filtration behavior under frac-pack flow conditions is the most important factor that determines overall injector performance. In this dissertation the filtration of injected solids under these conditions was experimentally studied, and the effect of frac-pack filtration on the injector performance was predicted. The flow of dilute oil droplets in a porous medium under near-well conditions was experimentally investigated. When the porous medium has a residual oil saturation, oil droplets can be generated by viscous forces overcoming entrapping capillary forces. The generated oil droplets will subsequently participate in filtration processes along with injected oil droplets. If this occurs in the near-injector area, the injectivity can severely decline and this may require expensive remediation processes. In this study, prediction of O/W emulsion flow was improved by experimental observations of the rates of generation and filtration of oil droplets. In a larger scale problem, a 3-dimensional model of water-injection-induced fracture was developed to predict the fracture height growth. If a fracture breaches the bounding layers, the sweep efficiency can be significantly impaired and it could have severe environmental consequences (such as contamination of shallower aquifers or the seabed). During long-term water injection, fracture growth can only be simulated properly when the filtration near fractures, thermo-elastic stress changes and reservoir fluid flow behavior are all concurrently calculated. Based on this new model, the impact of reservoir stress conditions, mechanical properties, and injection-water quality on fracture growth was studied. On a reservoir-scale, the stress reorientation caused by injection-production activities during waterflooding was investigated. A new finite-volume multi-phase reservoir simulation with poro- and thermo-elasticity was developed. This model was applied to various waterflooding well patterns, such as five-, nine-spot, line-drive and horizontal well pairs, and the critical geomechanical responses by injection-production activities during waterflooding operations were analyzed. The model can be used to predict the direction of induced fractures, design infill well locations and configurations and optimize the reservoir sweep. Through the use of both experimental observations and numerical models this work has elucidated various physical phenomena affecting fracture growth and injection-well performance. The findings in this dissertation provide critical data and models that help us to more confidently specify injection water quality, the design of pumping and water treatment facilities, and the optimization of well planning. The models developed in this work can be used to substantially improve the predictions of injection well performance and improve reservoir oil recovery by waterflooding. / text
2

Investigation to enhance the performance of evaporative spray cooling within Tair cycle refrigeration and air conditioning systems

Hamlin, Stephen January 2000 (has links)
No description available.
3

Modeling and Analysis of Reservoir Response to Stimulation by Water Injection

Ge, Jun 2009 December 1900 (has links)
The distributions of pore pressure and stresses around a fracture are of interest in conventional hydraulic fracturing operations, fracturing during water-flooding of petroleum reservoirs, shale gas, and injection/extraction operations in a geothermal reservoir. During the operations, the pore pressure will increase with fluid injection into the fracture and leak off to surround the formation. The pore pressure increase will induce the stress variations around the fracture surface. This can cause the slip of weakness planes in the formation and cause the variation of the permeability in the reservoir. Therefore, the investigation on the pore pressure and stress variations around a hydraulic fracture in petroleum and geothermal reservoirs has practical applications. The stress and pore pressure fields around a fracture are affected by: poroelastic, thermoelastic phenomena as well as by fracture opening under the combined action of applied pressure and in-situ stress. In our study, we built up two models. One is a model (WFPSD model) of water-flood induced fracturing from a single well in an infinite reservoir. WFPSD model calculates the length of a water flood fracture and the extent of the cooled and flooded zones. The second model (FracJStim model) calculates the stress and pore pressure distribution around a fracture of a given length under the action of applied internal pressure and in-situ stresses as well as their variation due to cooling and pore pressure changes. In our FracJStim model, the Structural Permeability Diagram is used to estimate the required additional pore pressure to reactivate the joints in the rock formations of the reservoir. By estimating the failed reservoir volume and comparing with the actual stimulated reservoir volume, the enhanced reservoir permeability in the stimulated zone can be estimated. In our research, the traditional two dimensional hydraulic fracturing propagation models are reviewed, the propagation and recession of a poroelastic PKN hydraulic fracturing model are studied, and the pore pressure and stress distributions around a hydraulically induced fracture are calculated and plotted at a specific time. The pore pressure and stress distributions are used to estimate the failure potentials of the joints in rock formations around the hydraulic fracture. The joint slips and rock failure result in permeability change which can be calculated under certain conditions. As a case study and verification step, the failure of rock mass around a hydraulic fracture for the stimulation of Barnett Shale is considered. With the simulations using our models, the pore pressure and poro-induced stresses around a hydraulic fracture are elliptically distributed near the fracture. From the case study on Barnett Shale, the required additional pore pressure is about 0.06 psi/ft. With the given treatment pressure, the enhanced permeability after the stimulation of hydraulic fracture is calculated and plotted. And the results can be verified by previous work by Palmer, Moschovidis and Cameron in 2007.
4

NAPL Recovery Using CO<sub>2</sub>-Supersaturated Water Injection: Distribution of the CO<sub>2</sub> Gas Phase

Doughty, Cynthia January 2006 (has links)
Gas inFusion? is a novel remedial technology that dissolves CO<sub>2</sub> into water under pressure for NAPL recovery. As the supersaturated liquid flows through the porous medium gas evolution occurs in situ as the system returns to thermodynamic equilibrium. The evolution of gas bubbles leads to NAPL recovery by two mechanisms: 1) volatilization and 2) mobilization by the NAPL spreading in a film around the rising bubbles. Laboratory experiments by Li demonstrated that injecting the supersaturated water into a porous medium minimized the buoyancy driven flow of gas and the fingering phenomena that limit typical gas sparging. The distribution of carbon dioxide at partial pressures (p<sub>CO2</sub>) above the applicable hydrostatic pressure and the evolved gas phase were determined in two field experiments conducted in the relatively homogeneous fine to medium sand at CFB Borden. First, CO<sub>2</sub>-supersaturated water was injected into a single point located approximately 4 metres below ground surface. Then this injection was repeated with pumping of two nearby wells to see if the lateral distribution of CO<sub>2</sub> gas could be controlled hydraulically. Groundwater monitoring of p<sub>CO2</sub> above the hydrostatic pressure and geophysical surveys (neutron measurements, surface ground penetrating radar (GPR), and cross-borehole GPR) to find zones of induced gas content were supported by hydraulic monitoring and physical observations of gas bubble distribution at the water table. <br /><br /> Based on the results of these tests, enhanced CO<sub>2</sub> levels above the hydrostatic pressure were observed up to 5. 5-7. 0 m from the injection point and the gas phase up to ~5. 3 m. It was not possible to determine the impact hydraulic control had on the lateral distribution of CO<sub>2</sub> due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO<sub>2</sub> gas pockets forming below low permeability layers, as evidenced by surface GPR, permeameter tests, and grain size analyses. These gas pockets accumulated until sufficient pressure built up to overcome the displacement pressure of these lower permeability layers. At this point there is evidence of CO<sub>2</sub> breakthrough in the cross-borehole GPR data and physical observations of gas bubbles at the water table. These observations are consistent with previous investigations, which indicate that although the Borden aquifer is homogeneous, distinct horizontal layering is present with sufficient variations in permeability/displacement pressure to trap and cause some lateral spreading of a gas phase. The evidence of channeling and the impact of heterogeneities on gas distribution are consistent with air sparging studies.
5

NAPL Recovery Using CO<sub>2</sub>-Supersaturated Water Injection: Distribution of the CO<sub>2</sub> Gas Phase

Doughty, Cynthia January 2006 (has links)
Gas inFusion? is a novel remedial technology that dissolves CO<sub>2</sub> into water under pressure for NAPL recovery. As the supersaturated liquid flows through the porous medium gas evolution occurs in situ as the system returns to thermodynamic equilibrium. The evolution of gas bubbles leads to NAPL recovery by two mechanisms: 1) volatilization and 2) mobilization by the NAPL spreading in a film around the rising bubbles. Laboratory experiments by Li demonstrated that injecting the supersaturated water into a porous medium minimized the buoyancy driven flow of gas and the fingering phenomena that limit typical gas sparging. The distribution of carbon dioxide at partial pressures (p<sub>CO2</sub>) above the applicable hydrostatic pressure and the evolved gas phase were determined in two field experiments conducted in the relatively homogeneous fine to medium sand at CFB Borden. First, CO<sub>2</sub>-supersaturated water was injected into a single point located approximately 4 metres below ground surface. Then this injection was repeated with pumping of two nearby wells to see if the lateral distribution of CO<sub>2</sub> gas could be controlled hydraulically. Groundwater monitoring of p<sub>CO2</sub> above the hydrostatic pressure and geophysical surveys (neutron measurements, surface ground penetrating radar (GPR), and cross-borehole GPR) to find zones of induced gas content were supported by hydraulic monitoring and physical observations of gas bubble distribution at the water table. <br /><br /> Based on the results of these tests, enhanced CO<sub>2</sub> levels above the hydrostatic pressure were observed up to 5. 5-7. 0 m from the injection point and the gas phase up to ~5. 3 m. It was not possible to determine the impact hydraulic control had on the lateral distribution of CO<sub>2</sub> due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO<sub>2</sub> gas pockets forming below low permeability layers, as evidenced by surface GPR, permeameter tests, and grain size analyses. These gas pockets accumulated until sufficient pressure built up to overcome the displacement pressure of these lower permeability layers. At this point there is evidence of CO<sub>2</sub> breakthrough in the cross-borehole GPR data and physical observations of gas bubbles at the water table. These observations are consistent with previous investigations, which indicate that although the Borden aquifer is homogeneous, distinct horizontal layering is present with sufficient variations in permeability/displacement pressure to trap and cause some lateral spreading of a gas phase. The evidence of channeling and the impact of heterogeneities on gas distribution are consistent with air sparging studies.
6

[en] ANALYTICAL STUDY OF THE INJECTIVITY LOSS OF ROCKS / [pt] VERIFICAÇÃO DE MODELOS ANALÍTICOS PARA A PERDA DE INJETIVIDADE DE ROCHAS

URSULA EL-AMME DE ALMEIDA 29 October 2002 (has links)
[pt] Este trabalho trata do problema de entupimento de rochas provocado pela injeção de água contendo partículas sólidas. O efeito da redução de permeabilidade e conseqüente perda de injetividade da rocha é analisada através da interpretação de ensaios unidimensionais de fluxo obtidos da literatura e simulados por um programa computacional desenvolvido nesta dissertação. O programa baseia-se no modelo de Pang e Sharma (1994) de perda de injetividade, escolhido dentre um conjunto de modelos pesquisados, e contempla o processo de entupimento devido à formação de camada de filtro interno e/ou externo, onde é introduzido o conceito de tempo de transição. Nesta formulação utilizam-se também dois importantes parâmetros: lambda , definido como coeficiente de filtração, e beta , fator de dano, podendo estes ser determinados por ensaios ou por correlações empíricas. Uma nova teoria de Bredrikovetsky (2001) que sugere o cálculo de ambos parâmetros por dados de pressão também é empregada. Com o objetivo de validar o modelo e o programa, apresenta-se um estudo paramétrico cujas informações podem ser utilizadas na previsão do comportamento de poços injetores. / [en] This work deals with the impairment of rocks subjected to the injection of water with solid particles in suspension. The effect of the permeability reduction and consequent loss in rock injectivity is analyzed by the interpretation of core flow tests, previously reported, and simulated by using a computational program developed for this research. The program is based on the Pang and Sharmas model (1994) for the prediction of injectivity decline, chosen amongst a set of existing models, and contemplates the process of impairment due the formation of an external and/or an internal filter cake, where the concept of transition time is introduced. The formulation also uses two important parameters: lambda, defined as filtration coefficient, and beta, damage factor, which can be determined by test data or empirical correlations. A new theory of Bredrikovetsky (2001) that suggests the calculation of both parameters for pressure data is used. With the objective to validate the model and the program, a parametric study is presented whose information can be used in the prediction of the behavior of the injection wells.
7

Expanding operation ranges using active flow control in Francis turbines / Lastområdesutvidgning med aktiv flödeskontroll i Francisturbiner

Adolfsson, Sebastian January 2014 (has links)
This report contains an investigation of fluid injection techniques used in the purpose of reducing deleterious flow effects occurring in the draft tube of Francis turbines when operating outside nominal load. There is a focus on implement ability at Jämtkrafts hydroelectric power plants and two power plants were investigated, located in series with each other named Lövhöjden and Ålviken. The only profitable scenario found with some degree of certainty was an increase in the operating range upwards to allow overload operation. Findings show that both air and water can be introduced in various locations to improve hydraulic efficiency around the turbine parts as well as reduce pressure pulsations in harmful operating regions. Investments in such systems have proven useful and profitable at several facilities with poorly adapted operating conditions. But due to losses in efficiency when operating injection systems, it turns out unprofitable in situations where it does not improve the operating range in a way that is resulting in increased annual or peak production.
8

[en] ANALYSIS OF RESERVOIR ROCKS PLUGGING DURING WATER INJECTION OPERATIONS / [pt] ANÁLISE DO ENTUPIMENTO DE ROCHAS RESERVATÓRIO DURANTE OPERAÇÕES DE INJEÇÃO DE ÁGUA

RODRIGO ALVES SPAGNOLO 19 December 2001 (has links)
[pt] O presente trabalho apresenta um estudo paramétrico de alguns fatores intervenientes no processo de entupimento de formações rochosas por sólidos em suspensão, sob injeção de água. Primeiramente se fez uma revisão das formulações mais comumente utilizadas em se tratando de modelos de redução de permeabilidade na literatura técnica especializada. Em seguida, a partir de dois simuladores numéricos, executou- se vários casos de injeção de água,e tais resultados foram comparados entre si e comentários foram feitos a respeito da validade das informações por eles fornecidas. Uma campanha de ensaios foi executada de forma a avaliar alguns parâmetros intervenientes na retenção de partículas em suspensão quando injetadas em um meio poroso, como a rocha. Inicialmente foi feita uma revisão bibliográfica sobre ensaios de injeção já realizados em diversos centros de pesquisas do mundo. Os resultados desses experimentos de injeção, conjugados a análises complementares de microscopia eletrônica, fornecem informações bastantes úteis para determinados aspectos a serem considerados na execução de injeção de água produzida em poços offshore. / [en] The present work presents a parametric study of some intervening factors in the blockage process of rocky formations for solids in suspension, under injection of water.Firstly it was made a review in the specialized technical literature on the formulations more commonly used for modelling the permeability reduction. Next, using two numeric simulators, several examples of water injection were executed, and the results were compared amongst each other. A series of laboratory tests was performed in order to evaluate some intervening parameters in the retention of particles in suspension when injected in a porous medium. Initially it was made a bibliographical review on injection tests carried out in several research centers of the world. The results of the injection experiments, with associated analyses of electronic microscopy, were able to supply useful information for certain aspects to be considered when injecting produced water in offshore wells.
9

Contribution to the understanding of filtration and pressure drop phenomena in wall-flow DPFs

Angiolini, Emanuele 01 September 2017 (has links)
From the last decades of the 20th century, internal combustion engines have undergone a continuous improvement process aimed to the increase of their efficiency and decrease of the pollutants emissions. The reduction of the availability of fossil fuel and the increase of human-made pollution observed in the last decades is leading worldwide to more stringent emission standards that make the engine manufacturers to constantly look for fuel consumption and emission reductions while keeping engine performance. To comply with current and incoming emission regulations, the exhaust line of internal combustion engines has been gradually complicated by the presence of aftertreatment systems. Among them, the particulate filter is the device in charge of abating the emission of soot in the atmosphere. Concerning compression ignition engines, diesel particulate filters (DPF) were first commercially utilized in significant numbers in passenger car and heavy-duty engines since the beginning of the 21st century. Euro 6 emission standards limits the emitted particulate matter from direct injection engines, thus extending the use of particulate filters also to direct injection gasoline engines. A deep knowledge of the phenomena happening inside the DPF is required for the correct understanding of the behaviour of this system and its interaction with the engine. The precise knowledge of the filtration and pressure drop processes is mandatory for the design of the particulate filter and is also essential to wisely think up and analyse solutions aimed to limit the negative impact of the filter on the fuel consumption maintaining its capability of retaining soot particles. Thus, the present work pretends to provide a contribution to the understanding of these phenomena in wall-flow DPFs. The problem has been faced on a computational and experimental basis. A notable part of the work was dedicated to the development and validation of a one-dimensional DPF filtration model to be coupled with the existing pressure drop model. The model was implemented in OpenWAM¿, the open-source gas dynamics software for internal combustion engines and components computation developed at CMT - Motores Térmicos. The developed computational tool was applied to the assessment of the aftertreatment (DOC&DPF) volume downsizing potential in post- and pre-turbo aftertreatment configuration. The study is completed with experimental analysis to support theoretical insights discussing how the soot deposition profile and the particulate layer properties impact on the DPF pressure drop. / Desde las últimas décadas del siglo XX, se ha producido un proceso de mejora continua de los motores de combustión interna alternativos con el fin de aumentar su eficiencia y reducir las emisiones contaminantes. La reducción de la disponibilidad de combustibles fósiles y el incremento de la polución de origen antropogénico observados en las ultimas décadas ha provocado el progresivo endurecimiento de las normativas anticontaminación a nivel mundial obligando a los fabricantes de motores a buscar la reducción continua del consumo de combustible y emisiones, manteniendo las prestaciones del motor. El cumplimiento de las actuales y futuras normativas anticontaminación requiere de la instalación de diversos sistemas de postratamiento de gases en la línea de escape de los motores de combustión interna alternativos, aumentando su complejidad. Entre estos sistemas, el filtro de partículas es el equipo encargado de la reducción de la emisión de hollín a la atmósfera. Con respeto a los motores de encendido por compresión, los filtros de partículas diésel se implementaron por primera vez de forma masiva en vehículos de pasajeros y vehículos pesados a principio del siglo XXI. La normativa anti contaminación Euro 6 limita las emisiones de partículas de los motores de inyección directa, extendiendo el uso de filtros de partículas a los motores de inyección directa de gasolina. Es necesario tener un conocimiento profundo de los fenómenos que tienen lugar en el DPF para comprender el comportamiento de este sistema y su interacción con el motor. El conocimiento de los procesos de filtrado y perdida de presión es vital para el diseño del filtro de partículas y resulta esencial para encontrar y analizar soluciones que ayuden a limitar el impacto negativo del DPF sobre el consumo de combustible sin perder la capacidad de retener partículas de hollín. En este contexto, este trabajo pretende aportar una contribucción a la comprensión de estos fenómenos en filtros de partículas de flujo de pared. Esta tarea se ha planteado desde un punto de vista computacional y experimental. Parte importante de este trabajo ha consistido en el desarrollo y validación de un modelo de filtrado unidimensional de DPF que se ha acoplado con el modelo de caida de presión ya existente. El modelo se ha implementado en OpenWAM¿, el software de libre acceso para el cálculo fluidodinámico de motores de combustión interna y sus componentes desarrollado en CMT - Motores Térmicos. La herramienta computacional desarrollada se ha aplicado a la evaluación del potencial de reducción de volumen de sistemas de postratamiento (DOC&DPF) en configuraciones post- y pre-turbo. Este estudio se ha completado con un análisis experimental para dar respaldo a los conceptos teóricos empleados discutiendo como el perfil de deposición del hollín y las propiedades de la capa de partículas afectan a la perdida de presión del DPF. / Des les últimes dècades del segle XX, s'ha produït un procés de millora contínua dels motors de combustió interna alternatius amb l'objectiu d'augmentar la seua eficiència i reduir les emissions contaminants. La reducció de la disponibilitat de combustibles fòssils i l'increment de la polució d'origen antropòlogic observats en les últimes dècades ha provocat que les normatives anticontaminació s'han fet més rígides a nivell mundial, obligant als fabricants de motors a buscar la reducció contínua del consum de combustibles i emissions, mantenint les prestacions dels motors. El cumpliment de les normes anticontaminació actuals i futures, requereixen de l'instalació de diversos sistemes de post-tractament de gasos a l'eixida dels motors de combustió interna alternatius, llavors augmentant la complexitat. Entre aquestos sistemes, el filtre de partícules es l'equip encarregat de la reducció de les partícules de sutge a l'atmosfera. Respecte als motors d'encès per compressió, els filtres de partícules van instalar-se de manera massiva als vehicles de passatgers i vehicles pesats al principi del segle XXI. La normativa anti contaminació Euro 6 limita les emissions de partícules dels motors d'inyecció directa, estenent l'ús del filtre de partícules als motors d'injecció directa de gasolina. És necessari tindre un coneixement dels fenòmens que tenen lloc al DPF per a comprendre el comportament del sistema i la seua interacció amb el motor. El coneixement dels processos de filtrat i la pèrdua de pressió és vital per al diseny del filtre de partícules i resulta essencial per a trobar i analitzar les solucions que ajuden a limitar l'impacte negatiu del DPF sobre el consum de combustible sense perdre la capacitat de retenir partícules de sutge. En aquest context, el projecte pretén aportar una contribució a la comprensió d'aquestos fenòmens en els filtres de partícules de flux de paret. Aquesta feina s'ha plantejat des d'un punt de vista computacional i experimental. Part important d'aquest treball ha consistit en el desenvolupament i validació d'un model de filtrat unidimensional de DPF que s'ha acoplat a un model de pèrdua de pressió existent. El model s'ha implementat en OpenWAM¿, el software de lliure accés per al cálcul fluidodinámic de motors de combustió interna i els seus components desenvolupats al CMT - Motores Térmicos. La ferramenta computacional desenvolupada s'ha aplicat a la evaluació del potencial de reducció del volum de sistemes de post tractament (DOC&DPF) en les configuracions post- i pre-turbo. Aquest estudi s'ha completat amb una anàlisi experimental per a donar suport als concepts teòrics emprats discutint com el perfil de la disposició de sutge i les propietats de la capa de partícules que afecten a la pèrdua de pressió del DPF. / Angiolini, E. (2017). Contribution to the understanding of filtration and pressure drop phenomena in wall-flow DPFs [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86157 / TESIS
10

Design and Optimization of a Plug-In Hybrid Electric Vehicle Powertrain for Reduced Energy Consumption

Oakley, Jared Tyler 11 August 2017 (has links)
Mississippi State University was selected for participation in the EcoCAR 3 Advance Vehicle Technology Competition. The team designed its architecture around the use of two UQM electric motors, and a Weber MPE 850cc turbocharged engine. To combine the three inputs into a singular output a custom gearbox was designed with seven helical gears. The gears were designed to handle the high torque and speeds the vehicle would experience. The use of this custom gearbox allows for a variety of control strategies. By optimizing the torque supplied by each motor, the overall energy consumption of the vehicle could be reduced. Additionally, studies were completed on the engine to understand the effects of injecting water into the engine’s intake manifold at 25% pedal request from 2000-3500 rpm. Overall, every speed showed an optimum at 20% water to fuel ratio, which obtained reductions in brake specific fuel consumption of up to 9.4%.

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