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

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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.

Gas inFusion? is a novel remedial technology that dissolves CO₂ 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_CO2) 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, CO₂-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 CO₂ gas could be controlled hydraulically. Groundwater monitoring of p_CO2 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 CO₂ 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 CO₂ due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO₂ 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 CO₂ 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.

Gas inFusion? is a novel remedial technology that dissolves CO₂ 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_CO2) 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, CO₂-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 CO₂ gas could be controlled hydraulically. Groundwater monitoring of p_CO2 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 CO₂ 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 CO₂ due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO₂ 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 CO₂ 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.

[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.

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.

[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.

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%.

[pt] Os testes de formação são uma operação realizada com o objetivo de identificar os fluidos, determinar os parâmetros de reservatório associados à produtividade e avaliar a extensão da jazida. Para executar o teste, o poço é completado temporariamente para permitir a produção dos fluidos de forma segura, e o intervalo a ser testado é isolado e um diferencial de pressão entre a formação e o interior do poço é estabelecido, forçando os fluidos da formação a serem produzidos. A busca por uma forma de substituir os testes de produção tradicionais, evitando a queima de gás natural e o aumento da segurança operacional, somada ao fato de completações de poços injetores de água na zona produtora de óleo ser uma prática comum do desenvolvimento de campos marítimos, levaram os testes de injetividade a ter um importante papel no gerenciamento dos reservatórios desses campos. Embora os métodos de análise de fluxo monofásico com pequena compressibilidade sejam bem documentados na literatura, soluções bifásicas e métodos de análise ainda precisam ser desenvolvidos. Nessa dissertação, é proposta a modelagem do problema de testes de injetividade com vazão variável, utilizando soluções analíticas aproximadas. / [en] The pressure response during a well test provides information on well productivity and reservoir performance. To replace traditional production tests, avoiding the gas flaring and increasing operational safety, the injectivity test began to play an important role in the management of the reservoirs in these fields. Although analytical models are able to describe injection and falloff periods, variable rate models still need to be developed. This work attempts to present a variable rate approximate solution for pressure response in a water injection well. The accuracy of the proposed solution was assessed by comparison with a numerical simulator. The suggested model was also used to determine the reservoir equivalent permeability.