Gas-liquid flow in annular geometries is the one of the most frequently encountered flow conditions in petroleum industry, either during drilling operations if aerated fluids are used, or production stages, if the produced fluid is under bubble point pressure. With the increase in the interest in horizontal / extended reach wells, understanding the flow behavior of gas-liquid mixtures in horizontal wells is essential for better pressure control downhole. Although two-phase fluid flow is studied intensively for circular pipes, there exists a lack of information about aerated fluid flow behavior inside annular geometries, both theoretically and experimentally. Existing two-phase fluid flow models available in the literature developed for circular pipes are performing poorly for annular geometries. Using hydraulic diameter definitions or effective diameter terms simply give inaccurate results for both flow pattern estimations and friction pressure loss determination. This study aims to identify the flow patterns of gasified fluids, and to determine frictional pressure losses for two phase flow through horizontal eccentric annular geometry. In order to develop the liquid holdup, Digital Image Processing Techniques have been used. Friction pressure losses are determined by applying two different methods; i) Modifying Lockhart-Martinelli parameter, and ii) Modifying Beggs and Brill’s method, originally developed for circular pipes. Experiments have been conducted at Middle East Technical University (METU) Multiphase Flow Loop using air-water mixtures with various in-situ flow velocities. A digital camera is used for recording each test dynamically for the identification of flow patterns and the measurement of liquid holdup. Friction pressure losses are recorded during each test. The comparison of modified models with experimental data indicates that liquid holdup and friction pressure losses can be estimated with a reasonable accuracy. The information obtained from this study is critical, since very limited information is available in the literature for modeling two-phase flow behavior.

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