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The material presented in this thesis falls into two main sections: 1. The determination of barium, strontium and calcium in oil-well waters (i) Determination of barium It is revealed that the addition of magnesium (5 g l-1) to samples for the determination of barium by d.c. plasma atomic emission spectrometry enhances the sensitivity of the analysis and dramatically reduces interference from calcium and strontium at both atomic and ionic emission wavelengths. (ii) Determination of strontium The determination of strontium in waters, was also subject to the interference of the concomitant elements like calcium, barium and magnesium. However, the addition of 3 g l-1 sodium with or without 5 g l-1 of magnesium eliminated all the interferences in the d.c. plasma and in the dinitrogen oxide-acetylene flame. (iii) Determination of calcium The determination of calcium in oil-well waters encountered some interference arising from the presence of sulfate. However, the effects of phosphate and sodium were also investigated in both air-acetylene and dinitrogen oxide-acetylene flames and in the direct current plasma. It was shown that the interference was reduced in the cool flame when 2 g l-1 of lanthanum was added. The absorbance of calcium was depressed by the presence of 2 g l-1 of sodium. The interferences from both sulfate and phosphate were eliminated when the hot flame or the d.c. plasma were used. 2. Slurry nebulization for soil, sediment and fertilizer samples A slurry atomisation direct current plasma (DCP) emission and flame atomic absorption and emission (FAAS and FAES) for the determination of alkaline earth elements and also of other minor and major elements in soils, marine sediments and fertilizer is reported. The results obtained by slurry nebulization, with lithium added as ionisation buffer, were compared with results obtained following fusion with LiBO2 at 950o for 10 minutes and dissolution of the residues in 4&'37 HNO3.

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Heat-integrated crude oil distillation systems – the atmospheric and vacuum distillation towers and associated heat recovery system – are energy and capital intensive. The structures of the distillation columns are very complex and the distillation columns interact strongly with the preheat train. There are many degrees of freedom in this system, most of which are interlinked with each other and cannot be considered separately. A systematic design approach is necessary to exploit these design issues for increasing the efficiency with which energy and capital are employed in the overall system. This thesis develops an optimisation-based methodology for the simultaneous design of crude oil distillation systems. Both new design and retrofit scenarios are considered. This design approach considers some significant design issues and generates design solutions that are realisable and industrially practicable. Robust and more accurate models have been developed to represent the distillation columns and heat exchanger networks (HENs) within an optimisation framework, compared with previous work. Facilitated by the decomposition approach (Liebmann, 1996), simplified models (Suphanit, 1999; Gadalla et al., 2003a; Rastogi, 2006), based on the Fenske-Underwood-Gilliland method, were developed previously to model the atmospheric distillation unit and the vacuum unit. This work extends and modifies these simplified models to account more accurately for the effect of pump-around location on the separation performance in atmospheric units. Moreover, the simplified model has been extended to consider an atmospheric distillation column with a pump-around located above the top side-stripper. This work also proposes a new methodology to incorporate product specifications following refining conventional in the simplified models. The proposed approach enables systematic identification of key components and associated recoveries to match specified boiling temperature profiles, as these are normally used as indicators of separation performance in the refining industry. The new simplified models are validated by comparison with rigorous simulation results of atmospheric distillation columns. Multi-segmented stream data are implemented in the design and analysis of heat exchanger networks, in which the thermal properties of streams are temperature dependent and cannot be assumed constant. Two existing promising HEN design approaches, the simulated annealing optimisation-based approach (Rodriguez, 2005)and the network pinch approach (Asante and Zhu, 1996), are modified and extended to apply to the HEN design with multi-segmented stream data. In the modified network pinch approach, the bottleneck of an existing HEN configuration is better overcome by varying stream split fractions and heat exchanger loads at the same time, rather than simply redistributing heat loads. The modified network pinch approach also combines structural modifications and cost optimisation in a single step to avoid missing cost-effective design solutions. An optimisation framework, applying a stochastic optimisation method – multiple simulated annealing runs – is developed to generate grassroots and retrofit designs of the heat-integrated crude oil distillation systems. The heat integration of the system is accounted for more accurately than previously by using multi-segmented stream data. Operating conditions and pump-around locations of distillation columns are optimised, together with structural options and continuous variables of heat exchanger networks as appropriate, in a single optimisation framework. The new degrees of freedom considered in this work include key components and associated recoveries (used in simplified models of distillation columns to express the separation of products) and operating pressures of distillation columns. The optimisation of key components and recoveries allow the systematic exploitation of product distributions and product slate in order to maximise net profit. Including operating pressures in the optimisation facilitates creation of heat recovery opportunities in configuration studies. Product specification constraints are imposed in the optimisation so that product quality is not compromised during design. A novel distillation configuration, with a liquid side-draw prefractionator column upstream of an atmospheric distillation column, is proposed in this work. The case study shows a very promising performance with respect to energy efficiency. Case studies illustrate the beneficial application of the proposed approach in both grassroots and retrofit design of crude oil distillation systems, with respect to energy demand and net profit improvement. Comparisons are made between different configurations, and results are given as proof of principle.

The main objective of this thesis was to study the effects of crude oil extracts on intertidal sediment communities. The approach was to focus on community structure and investigate the impact of a specific perturbation, crude oil extracts, relating to hypothetical oil spill situations. Both the impact of different disturbances on the same benthic community (i.e. with uniform structure) and the impact of the same disturbance on differently structured benthic communities were investigated. The effects on number of species, distribution of individuals between species and diversity were analysed, as well as recovery mode (trajectory of the system in time) and species arrival. The effects of different levels of a disturbance on an intertidal community were assessed, using water soluble fractions of crude oil (WSF) and two different concentrations of formaldehyde. The WSF had very little effect on community structure and recovery of the benthic community was prompt. The effects of the different concentrations of formaldehyde on the benthic community were indistinguishable: both concentrations had dramatic immediate effects. The relation between complexity and stability in benthic communities was evaluated by first setting-up two communities of different complexity using the equilibrium theory of island biogeography. After these different communities were established they were subjected to the effects of oil and dispersant. The impact of this perturbation on the two communities with different complexity was analysed both in terms of structure (as above) and functional level, through the analysis of oxygen uptake in the different communities. Although there was an indication that the oil had a depressing effect on the structure of both community types, it was not clear which species were most affected by the treatment. Individual comparisons between the two differently-structured treated communities and their controls were undertaken.

Computational Fluid Dynamics (CFD) is used in this study to assess the influence of temperature-dependent oil viscosity and density on the flow of oil up the well, and therefore the amount of insulation required. CFD is a difficult tool to apply to flows where the grid aspect ratio is as high as it needs to be to accommodate the full length of an oil well with a realistic number of grid points. Each model was therefore intensive in terms of computational effort and time. This study shows that by allowing oil viscosity and density to vary with temperature in a 2150 m vertical well with no insulation, the production output is significantly affected. The drop in production output is approximately 3% when oil viscosity varies with temperature, but when coupled with temperature-dependent density the loss in production increases to 22%. Ten CFD models, each with a different value of insulation heat transmission coefficient lying in the range 0.35 Wm^-2K^-1 to 16900 Wm^-2K^-1, are used to establish the temperature drop between riser inlet and outlet. The results obtained allow an operator to select an appropriate insulation based on the allowable temperature drop up the well, assuming all other properties are equal. The completion fluid region is situated outside the oil flow, tubing and insulation. The fluid is stationary which suggests that natural convection currents are present. Seven CFD models with annulus heights ranging from 1 m to 64 m are used to detect these currents, and assess the effectiveness of water as an insulating completion fluid. This thesis establishes that the natural convection currents do not split into multiple cells, but remain mono-cellular when the Grashof number is approximately 1x10⁸ and the Prandtl number is 2.3. This work also shows that heat loss due to natural convection from the completion fluid is an important contributory factor to the overall heat loss from a well, dependent on the well height.

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Made available in DSpace on 2018-08-01T21:36:53Z (GMT). No. of bitstreams: 1 tese_10765_Dissertação_final_Rayza.pdf: 2180620 bytes, checksum: 5e88e543a5adef7347618d2eef3cfb62 (MD5) Previous issue date: 2017-03-27 / A calibração multivariada associada à técnica de infravermelho é uma alternativa aos métodos tradicionais para determinação de parâmetros físico-químicos em petróleo. Entretanto, o modelo multivariado construído é aplicável somente para o instrumento no qual os espectros foram obtidos. A transferência de calibração de modelos multivariados é de fundamental importância para a indústria petrolífera, levando-se em conta que aumenta a aplicabilidade de modelos e permite estimar com rapidez e com poucos gastos diversas propriedades físico-químicas. Este trabalho foi dividido em duas seções: a primeira é dedicada à avaliação modelos de transferência entre dois instrumentos de infravermelho a região média (MIR) para modelos PLS (mínimos quadrados parciais) e OPLS (projeções ortogonais em estruturas latentes); e a segunda visa aplicar a transferência PDS (padronização direta por partes) a modelos PLS para predição de densidade API, TIAC (temperatura de início de aparecimento de cristais), NAT (número de acidez total) e NAN (número de acidez naftênica). Dentre os métodos quimiométricos SBC (correção de declive e viés), FR (recalibração total), DS (padronização direta) e PDS avaliados para previsão de densidade API, o modelo de transferência PDS aplicado ao modelo OPLS resultou na melhor capacidade preditiva (RMSEP de 1,48). A aplicação direta de PDS a um modelo PLS original conta com a vantagem de aproveitar modelos já consolidados, e os resultados da primeira seção indicam que isto é uma possibilidade. Na segunda seção, as propriedades API, TIAC, NAT e NAN foram modeladas e validadas por PLS para o instrumento primário. Espectros secundários, diferentes daqueles da primeira seção, passaram por uma interpolação polinomial a fim de igualar as variáveis às do instrumento primário, antes da aplicação da transferência PDS. Os espectros transferidos e processados por airPLS, técnica iterativa adaptativa, se tornaram indistiguíveis por PCA (análise por componentes principais) dos espectros primários. A técnica de PDS associada a modelos PLS mostrou-se promissora, especialmente sendo capaz de estimar com boa exatidão o valor da densidade API de amostras de petróleo classificadas como medianas.

Crude oil leakages often give rise to in situ contamination with both oil and salt. In this study, the biodegradation of model alkanes and of saturated hydrocarbons in whole crude oil by hydrocarbon-degrading bacteria was investigated at different salt (NaCl, KCl, Na2SO4) concentrations. Changes in cell surface hydrophobicity at different NaCl concentrations were also investigated. The results show that with increasing NaCl concentration, the lag phase for strain growth on hydrocarbons was prolonged; however, the total degradation efficiency was not influenced greatly. The formation of different sizes of cell aggregates at different salt concentrations indicated that salt could indirectly influence mass transfer of hydrocarbons from the medium to the interior of the cells. The results also showed that KCl had a less inhibitory effect on biodegradation than NaCl, and changes of Na2SO4 concentration did not greatly affect biodegradation. In addition, cell surface hydrophobicity increased with increasing NaCl concentration when the cultures were grown on hydrocarbons.