Measurement Of Oil-gas-water Three-phase Flow Using Distributed Differential Pressure And Conductance Sensors

Oil-gas-water flows with high water-cut and low flowrate are mainly remained in oil wells when entering mid-to-late stage of oil extraction.Limits are obvious for traditional flowmeters to measure multiphase flow with low flowrate.At present,collecting logging instruments with 20 mm ID are widely used in oil production measurement.Complex interactions in dispersed oil and gas phases and continuous water phase result in typical unsymmetrical distribution of flow structure and parameters,which is of great challenge for three-phase flow measurement.The present research has achieved the following innovative achievements:1.A distributed coaxial two-ring conductance sensor is designed to measure conductivity of oil-water in three phase flow by stimulating inner electrodes to decrease the radial depth of sensor detection field.Based on this,we propose a measurement system combined with both distributed differential pressure sensor and a symmetric distributed conductance sensor to explore the variation of Reynolds number in different flow patterns(bubble,churn and slug flow),which shows high accuracy in three phase flow gas holdup measurement.2.An inserted and distributed conductance sensor with asymmetrical electrodes is optimized in size to increase sensitivity using electromagnetic finite element analysis.Results show that the accuracy of water holdup and cross-correlation velocity is highly improved by distributed design,which makes flow structure insensitive to measurement results.3.A distributed multiple optical probe array sensor is designed to simultaneously acquire local gas holdup at 16 positions and image the gas holdup to uncover characteristics of gas distribution in different patterns.We find that local gas holdup in slug is affected by gas slug length while gas holdup in churn flow is affected by random bubble clusters.4.A combination of distributed differential pressure sensor and unsymmetrical conductance sensor is designed to extract individual phase holdup and velocity information.Then the drift-flux model of oil-gas-water three-phase flow is built and phase distribution coefficient in different flow patterns are optimized and fitted.This is proved to be an effective way to measure three phase parameters accurately.