Downhole Flow Measurement By Ultrasonic Frequency Difference Method

The optimal combination mining of each reservoir in the process of crude oil production is the important content of the intelligent well,and it is also the key to improve the recovery rate,which puts forward pressing demand for the stratified test of the downhole flow.The biggest difference between downhole and ground measurement is the limited volume,so the test system needs to consider the harsh environment such as high temperature and high pressure.Taking the ultrasonic frequency difference method in the downhole flow measurement system as the research object,the liquid characteristic analysis,the ultrasonic sensor,the downhole test circuit,the ground transmission and the software development have been carried out.According to the complex conditions of the underground and ultrasonic attenuation characteristics,the related analysis is carried out theoretically.The ultrasonic attenuation of oil,gas and water ratio in tubing is simulated with COMSOL software,which provides technical basis for accurate measurement of flow.In the light of the distribution rule of liquid and the structure of pipe string,the size and installation mode of the sensor are determined,and the working frequency is optimized,and the sensor is trial-produced.On the basis of the characteristics of high temperature resistance and limited volume,the electronic devices used in downhole measurement are selected and screened,the related circuits have been developed,and a fully functional downhole measurement system has been formed.In order to improve the accuracy of the downhole flow measurement,the high speed and high temperature CPU is used to carry out the spectral thinning of the measured data.Through the contrast of various thinning methods,the ZOOM FFT thinning method is optimized,and the related mixing and filtering circuits are debugged,thus the measurement system can be adapted to the measurement demand of low production oil layer.Combined with the transmission system underground,the ground software is developed by LABVIEW,which realizes the receiving,real-time display and storage of downhole data.A complete measurement system has been formed after the above components are assembled,and related simulation tests have been carried out to confirm the validity of the system.The experimental results show that the downhole flow measurement system with ultrasonic frequency difference method works well,which provides the basis for the realization of the intelligent well system and the measurement of the downhole flow.In the light of the demand of production,the measuring system can be applied in underground?...