Optimum Design Of Fiber Optic Probe Sensor Structure For Measurement Of Gas Holdup In Oil-Gas-Water Three-Phase Flow

The accurate measurement of the gas holdup parameters of the underground three-phase flow is of great significance to optimize the production.In view of the poor measurement environment and the complexity of fluid flow,the traditional method of measuring the hold rate is poor.With the rise and development of optical fiber sensing technology,the use of fiber optic probe sensor for downhole gas holding capacity measurement.In order to improve the reliability and sensitivity of the fiber probe sensor to measure the gas holding rate,the fiber optic probe sensor is optimized.In order to solve the problem that the single fiber probe can only measure the local hold rate,this paper designs the array fiber probe and is optimized.Firstly,for the underground oil-gas-water three-phase flow gas holdup is difficult to accurately measure the problem.Fiber optic probe sensor is mainly composed of transmission optical path and probe sensitive head.The optimization of the material and shape of the sensitive head is achieved from the aspects of the intensity distribution of the back light and the power of the backlight.The tip angle of the sensitive head is optimized from both the piercing ability and the back light power.Aiming at the problem of low transmission efficiency of traditional coupled optical path,an optical fiber optical path is proposed.According to the size of the fiber diameter,16 optical fiber optical paths are designed and the optical path is optimized.Secondly,aiming at the problem that the single-fiber probe sensor can only measure the local hold rate around it..The distribution of gas distribution under different total flow was analyzed by Fluent simulation.Based on Zemax,a probe piercing bubble model was established.The variation of the response characteristics of the probe was analyzed by simulation.Based on this,an array of fiber optic probes is proposed and six structures are designed.The structure of the array is optimized by obtaining the gas-phase information capability from the probe and the effect of the interference on the fluid.Finally,a single fiber probe sensor,an array fiber optic probe sensor and a gas holdup logging tool are developed based on the optimized parameters.The fiber probe was subjected to an oil contamination test to verify the feasibility of the fiber optic probe used to measure the three-phase flow.The three-phase flow simulation experiment was carried out by means of gas-holding logging tool.The accuracy of the gas-holding logging tool was verified by comparing the gas-holding rate and the real gas-bearing rate.