The viscous oil-water hydrodynamics in a microchannel and phase equilibria of heavy oil and carbon dioxide gas have been investigated in connection with the enhanced recovery of heavy oil from petroleum reservoirs. The oil-water flow was studied in a circular microchannel made of fused silica with an I.D. of 250 µm. The viscosity of the silicone oil (863 mPa.sec) was close to that of the gas-saturated heavy oil in reservoirs. The channel was always initially filled with the oil. Two different sets of experiments were conducted: continuous oil-water flow and immiscible displacement of oil by water. For the case of continuous water and oil injection, different types of liquid-liquid flow patterns were identified and a flow pattern map was developed based on Reynolds, Capillary and Weber numbers. Also, a simple correlation for pressure drop of the two phase system was developed. In the immiscible displacement experiments, the water initially formed a core-annular flow pattern, i.e. a water core surrounded by a viscous oil film. The initially symmetric flow became asymmetric with time as the water core shifted off centre and also the waves at the oil-water interface became asymmetric. A linear stability analysis for core-annular flow was also performed. A characteristic equation which predicts the growth rate of perturbations as a function of the core radius, Reynolds number, and viscosity and density ratios of the two phases was developed. Also, two micro cells for gas solubility measurements in oils were designed and constructed. The blind cell had an internal volume of less than 2 ml and the micro glass cell had a volume less than 100 µl. By minimizing the cell volume, measurements could be made more quickly. The CO2 solubility was determined in bitumen and ashphaltene-free bitumen samples to show that ashphaltene has a negligible effect on CO2 solubility.

The viscous oil-water hydrodynamics in a microchannel and phase equilibria of heavy oil and carbon dioxide gas have been investigated in connection with the enhanced recovery of heavy oil from petroleum reservoirs. The oil-water flow was studied in a circular microchannel made of fused silica with an I.D. of 250 µm. The viscosity of the silicone oil (863 mPa.sec) was close to that of the gas-saturated heavy oil in reservoirs. The channel was always initially filled with the oil. Two different sets of experiments were conducted: continuous oil-water flow and immiscible displacement of oil by water. For the case of continuous water and oil injection, different types of liquid-liquid flow patterns were identified and a flow pattern map was developed based on Reynolds, Capillary and Weber numbers. Also, a simple correlation for pressure drop of the two phase system was developed. In the immiscible displacement experiments, the water initially formed a core-annular flow pattern, i.e. a water core surrounded by a viscous oil film. The initially symmetric flow became asymmetric with time as the water core shifted off centre and also the waves at the oil-water interface became asymmetric. A linear stability analysis for core-annular flow was also performed. A characteristic equation which predicts the growth rate of perturbations as a function of the core radius, Reynolds number, and viscosity and density ratios of the two phases was developed. Also, two micro cells for gas solubility measurements in oils were designed and constructed. The blind cell had an internal volume of less than 2 ml and the micro glass cell had a volume less than 100 µl. By minimizing the cell volume, measurements could be made more quickly. The CO2 solubility was determined in bitumen and ashphaltene-free bitumen samples to show that ashphaltene has a negligible effect on CO2 solubility.

[pt] Sistemas de celulares de múltiplas camadas (hierarquizados) são úteis para acomodar densidade alta de tráfego mantendo a qualidade de serviço. Estes sistemas procuram agregar as vantagens dos sistemas micro e macrocelulares que são respectivamente: o aumento da capacidade do sistema e a carga de sinalização da rede. Neste trabalho são analisados aspectos de projeto e desempenho de estruturas hierarquizadas como: compartilhamento do espectro entre as camadas de micro- células e macro-células bem como o desempenho de diferentes estratégias de handoff entre essas camadas. Um outro objetivo do trabalho foi o desenvolvimento de uma ferramenta simples de simulação capaz de testar as diversas estratégias de handoff e o desempenho do sistema para diferentes soluções para a distribuição dos recursos de rádio entre camadas. / [en] Multilayer cell systems are useful to accommodate high traffic densities while still satisfying the QoS requirements. These systems combine the advantages of microcellular and macrocellular systems which are: the increase of system capacity and the reduction of the number of handoffs, hence decreasing the signaling load. This work address design aspects such as spectrum sharing between the macrocell and microcell layers and the performance of different handoff strategies considering both layers. Another goal of this work was the development of a simple, but realistic, simulation tool which will allow obtaining the radio resources management results here presented.

[pt] Este trabalho descreve uma ferramenta de simulação esenvolvida para analisar o gerenciamento dos recursos de rádio e parâmetros de QoS (Quality of Service) dos sistemas móveis celulares. Pela natureza de um sistema real de telefonia celular, é extremamente difícil que as variáveis de saída de um simulador sejam derivadas de um conjunto real de funções. Isso se deve à grande quantidade de parâmetros que devem ser considerados no comportamento da mobilidade, nas condições de tráfego, nas características geográficas e morfológicas da região, na modelagem complexa do canal rádio propagação móvel, entre outras. Visando a desenvolver uma ferramenta de simulação próxima da realidade, adotam-se modelos de propagação, de mobilidade e de tráfego que sejam satisfatoriamente adequados ao caso real. A contribuição deste trabalho é oferecer uma ferramenta de simulação flexível, aqui adequada ao sistema norte-americano TDMA (IS-136), que possibilite ao usuário, além de analisar a capacidade do sistema,também avaliar novos algoritmos de controle de potência, novas estratégias de handoff, novos esquemas de alocação de canal e modelos de propagação. A ferramenta será validada seguindo o processo de um projeto real de telefonia celular e ao final, será aplicada a um sistema celular com sobreposição macro-células/micro-células, analisando-se algumas estratégias de handoff dedicadas a esses sistemas. / [en] This work describes a simulation tool, which was developed to analyze the radio resources and QoS (Quality of Service) parameters in mobile systems. Because of the complex characteristics of an actual cellular network, it is extremely difficult having the outputs of the simulator being derived from a real set of functions, due to the large amount of parameters that have to be considered such as the mobility behavior, the traffic conditions, the geographic and morphologic characteristics of the region, the complex modeling of mobile radio propagation channel, and so on. In order to develop a simulation tool as near as possible to the reality, models that are satisfactorily adequate to the real case have been considered. So, propagation, mobility and traffic models were adapted from the IS-136 American system. The contribution of this work is to offer a flexible simulation tool that allows the user, in addition to analyzing the capacity of the system, to evaluate new algorithms of power control, handoff strategies, channel allocation schemes and propagation models. The tool will be validated following the process of a real project of cellular telephony and at the end, it will be applied to a cellular system with overlapped macro- cells/micro-cells, and some handoff strategies dedicated to those systems will be analyzed.