Flow Rate Measurement of Oil–Gas–Water Three-Phase Slug Flow Using Pulse Wave Ultrasonic Doppler Technique

Oil-gas-water three-phase slug flow characterization and flowrate metering is an important issue highly related to the production safety and efficiency in petroleum industries. In this paper, to accurately measure the overall volume flowrate of horizontal oil-gas-water three-phase slug flow, a novel theoretical model was established and solved based on the flowing information acquired by a non-intrusive pulse wave ultrasonic Doppler (PWUD) system. Firstly, the frequency and amplitude of the echoes received by the PWUD sensor during the flow process were respectively used to construct the time-varying velocity profile and echo profile. Inspired by the significant differences in the echo profile appearances at different flow stages, the gas slug zone and liquid slug zone were distinguished by labeling the echo intensity time series within the lower part of the pipe with “0” and “1”. Based on the slug unit division result, the liquid film thickness, the gas fraction in the gas slug zone, and the velocities of liquid film and liquid slug were further calculated. The evolution trends of these flow parameters under different flow conditions were then analyzed. Finally, using the above acquired flow parameters, a closure model based on two sets of mass balance equations of different phases over a slug unit was established under reasonable assumptions for the overall volume flowrate estimation. The effectiveness of the model was verified through dynamic experiments. Compared with reference values, the mean absolute percentage error of the estimated overall volume flowrate is 2.71%.