Measurement On Water Holdup Of Oil-water Two-phase Flow Using High Frequency Sensor

Oil-water two-phase flow widely exists in nature and industrial production.Oilfields in China have entered into a stage characterized by high water-cut.Oil reservoirs with low permeability and low fluid productivity are commonly encountered because of the large amount of formation water and long-term water injection exploitation.Realizing water holdup measurement is of great significance to comprehensively understand the production characteristics of oil-water flows and optimize the production profile well logging technology under the condition of low velocity and high water-cut.However,due to the severe slippage effect and mutual interactions between two phases,the distribution of phases presents non-uniform and the flow structures are extremely complex.Moreover,the oil droplets become pretty small with the increasing flow rate and water-cut in oil-in-water two-phase flow.Therefore,the water holdup measurement in dynamic monitoring of oil wells is a great challenge.For the traditional conductance and capacitance method exist limitation in capturing high diversity size of the dispersed phase when water is the continuous phase,a high frequency sensor measurement method is proposed in this paper.Firstly,the sensitivity field of sensor is simulated and optimized,and the optimal sensor geometry size is determined according to the average sensitivity and sensitivity uniformity error index.In the present study,a novel method designated as high frequency sensor is proposed to overcome the problem that the traditional conductance and capacitance sensor have low resolution in water holdup measurement.Firstly,the effects of water holdup on amplitude-frequency characteristics and phase-frequency characteristics are investigated with finite element method(FEM),then the optimal working frequency is determined.Afterwards,the relationship between the phase output and the water holdup are obtained using FEM.The measurement system is designed and an experiment of vertical upward oil-water two-phase flow with low velocity and high water-cut is implemented.Finally,based on the drift-flux model,a high accuracy of water cut prediction is achieved which verifies the high-resolution measurement characteristics in high water-cut.In order to improve the stability of high frequency sensor measurement and realize high-resolution and stable measurement of water holdup of high water-cut oil-water two-phase flow,based on the arc-to-wall high frequency sensor,this chapter improves the polar plate form,and proposes a staggered double helix high-frequency sensor for measuring water holdup.Compared with the arc-to-wall sensor structure,the experimental results show that the staggered double helix high frequency sensor can effectively reduce the limitations of the sensor in different directions,realize the steady measurement of water holdup in different flow patterns,and improve the resolution of water holdup measurement to a certain extent.On this basis,in view of the low resolution of water holdup measurement under the condition of high salinity of water continuous phase,a dual-frequency method for water holdup measurement under high frequency was proposed.In order to analyze flow regime instability using high frequency sensor measurement signals,the Multiscale Fractional order Weighted Permutation Entropy(WFMPE)in four typical non-linear systems are investigated,and it is applied to the analysis and measurement of oil-water two-phase flow regime with high water content obtained from the application of arc-to-wall high frequency sensor measurement signals.The results show that the high-frequency sensor signal is sensitive to the flow state changes in the oil-water two-phase flow structure fluid,and shows excellent flow pattern resolution ability,and achieves good results in the analysis of instability of oilwater two-phase flow pattern.