Simulation Study Of Pseudo-slug Flow In Venturi And Research On Water Fraction Measurement By Microwave Resonant Cavity

The accurate measurement of the water fraction in the oil-gas-water mixture has important guiding significance for improving the efficiency of oil and gas field exploi-tation and realizing the stable and high production of oil and gas fields.This thesis studies the water fraction measurement method based on microwave resonator technol-ogy,aiming to find a non-invasive water fraction measurement sensor that is more prac-tical and reliable,and can adapt to a variety of complex working conditions.First,the principle of water fraction measurement using microwave resonator is given,and a new type of microwave resonant cavity sensor is designed.Using the finite element simulation method,the resonant frequency and S21 amplitude attenuation char-acteristics of the resonant cavity under different water fractions in the case of stratified flow and annular flow are explored.Both static experiment and simulation results show that the S21 amplitude attenuation at the second resonance mode TM₁₁₀ has a good monotonic relationship with the water fraction.Based on numerical simulation,a three-dimensional unsteady calculation method with periodic disturbance signal applied to the inlet was designed,and the complicated spatiotemporal evolution process of the flow field when pseudo-slug flow passed through Venturi was predicted.The fluctuation law of the differential pressure signal obtained by the simulation is in good agreement with the experiment.Measuring the water fraction of gas-water two-phase flow by using a precessing heterotype Venturi microwave sensor,and it is determined that the best resolution of the microwave S21 amplitude attenuation to the water fraction is in the range of 0～5%.Based on the dimensionless microwave amplitude attenuation signal,a gas-liquid two-phase flow volumetric water fraction model is established,and the average absolute error of the predicted value is 0.075%.Moreover,an over-reading prediction method of heterotype Venturi based on volumetric water fraction is proposed.The average rel-ative error of the model is 2.357%.The water fraction of the precessing oil-water two-phase flow is measured by the microwave resonator.A wide-range water cut（WLR=30～100%）prediction model based on the resonance frequency method and a high water cut（WLR=60～100%）pre-diction model based on the beat frequency amplitude method are established respec-tively.In order to verify the extrapolation of the latter,a vertical pipeline oil-water dy-namic test was carried out at the Daqing National Petroleum Large Flow Verification Station.The results show that the maximum error occurs under the condition of WLR=60%,and the prediction errors of the remaining data points are all within±3%.