Flow patterns in inclined gas-liquid annular duct flow

Abstract

The submergible centrifugal pump (SCP) is one of the most common artificial lifting techniques employed in the Brazilian offshore scenario. However, free gas in the suction of the SCP is one of the most important limitations in the design of the pumping system. Gas-liquid flow in annular-ducts is found in the petroleum industry associated with gravitational gas separators that are applied with the SCP technique for oil production in directional wells. The main goal of this study is to investigate the behavior, i.e., flow patterns and maps, of gas-liquid flow in an annular duct at several inclinations in a setup with dimensions which are closer to real offshore application. High-speed video recording together with an objective technique based on the time-frequency pressure-signature analysis were applied for the flow pattern characterization. The experimental data were collected in the apparatus consisted of an inclinable test section, 0 to 90 degrees, with inner and outer diameters of 75 mm and 111 mm, respectively, hence the annular channel possessing an 18 mm gap. The total length of the test section was of 10.5 m. Air, water and oil at near atmospheric pressure constituted the gas and liquid phases. The air, water and oil superficial velocities were in the range of 0.02–30 m/s, 0.02–5 m/s and 0.005–0.5 m/s, respectively. Comparisons between data and flow pattern maps available in the literature for annular duct allowed the discrimination of regions and flow situations for which improvements of the transition modelling are required.