In the Brazilian off-shore scenario, one of the most used artificial oil-lifting techniques is the submergible centrifugal pump (“BCS”). One of its advantages is the great amount of fluid elevated from deep wells. Among the main limitations of the “BCS” is the quantity of free gas in the pump inlet, which varies with the reservoir characteristics. The performance of the “BCS” is seriously compromised when the system works with a big amount of free gas. As alternative solution for the separation of the produced free gas is the high-efficiency bottom-well gravitational gas separator for directional wells known as “inverted shroud”, which has the potential advantage of generating a stratified flow with enhancement of bubbles coalescence. Besides, a significant role of the inclination angle is expected as it is a determinant parameter in flow pattern transition. Analyzing the literature, one can see that studies on the effect of annular channel inclination on flow pattern transitions are scanty and that until now no model has been proposed to predict the separation efficiency in this specific kind of equipment. Therefore, the main goals of this research are the flow pattern observation and characterization in gas (compressed air)-liquid (tap water and mineral oil of 100 mPa.s and 860 kg/m3) annular-duct flow and the proposition of phenomenological flow-pattern transition models as a function of the flow rates and inclination angle. A glass inverted-shroud separator of reduced scale (75 mm i.d. and 10 m length) will be constructed for the data acquisition. The experimental facilities, including steel structure and instrumentation, will be basically the same available for the “Oleoduto Piloto do Laboratório de Engenharia Térmica e Fluidos (NETeF) da Escola de Engenharia de São Carlos (EESC - USP)”. Optical techniques, angle meter, flow meters, National Instruments data acquisition system and LabView software will be used in this project. The data will be treated, analyzed and plotted in a flow pattern map as a function of the air and water and air and oil flow rates and inclination angle. Finally, the predicted transition boundaries will be compared with those experimentally observed.
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