Phase fraction measurement of oil–gas–water three-phase flow with stratified gas by ultrasound technique

Abstract

Phase fraction is one of important indexes to characterize multiphase flow. In order to measure each phase fraction of oil–gas–water three-phase flow, liquid level height is detected by time-of-flight—TOF of reflected ultrasound at gas–liquid interface, while oil phase fraction in reflection path is calculated according to the ultrasound attenuation. By studying interactions between multiphase flow and the ultrasound propagation in certain flow patterns, a prediction model for phase fraction measurement of three-phase flow is proposed based on ultrasound transmission attenuation and reflection TOF in the process of horizontal flow with actual phase distributions. Simulation and experimental results under conditions of oil–water two-phase structure with stratified gas in a horizontal pipe show that the proposed method and the established model can accurately detect gas–liquid interface, so that measure oil, gas, water phase fraction. The mechanism prediction model and the measurement device effectively solve the nonlinear response of the ultrasonic measurement parameter, so that can estimate phase fractions of liquids and gas in two-phase as well as three-phase flows simultaneously, which extends the measurement range and the applicable scope of ultrasonic technique to multiphase flow.