Application Research Of Ultrasonic Frequency Difference Method In The Measurement Of Layered Flow Of Water Injection Well

With the development of oilfield development technology,stratified water injection technology is widely used in major oilfields because it can restore oil well pressure and improve oilfield recovery.The accurate measurement of water injection can effectively improve the efficiency of layered water injection,but the environmental factors such as down-hole temperature and pressure will affect the measurement of water injection.Therefore,in the process of layered water injection,it is particularly important to compensate for the influence of environmental factors on the measurement results and improve the measurement accuracy of the water injection.The research work of this paper mainly includes the following aspects:The traditional frequency difference measurement method treats the sound velocity of ultrasonic waves propagating in the fluid as a constant,ignoring the flow measurement error caused by environmental factors.In view of the above defects,the ultrasonic sound velocity is considered as a variable,and the influence of various environmental factors on the sound velocity and its influence on the measurement results of the ultrasonic echo signal and the water injection volume are analyzed.Curved surface fitting is performed on typical data by MATLAB,and a mathematical model of water injection volume error compensation by ultrasonic frequency difference method is established.Based on the frequency difference method,a correction method for water injection error considering the combined effects of formation temperature and down-hole pressure is proposed.Error analysis shows that the fitted surface is highly correlated with the data,the overall trend is consistent,and the fitting effect is good.For the processing method of ultrasonic echo signals,this article compares the Zoomfft algorithm and CZT algorithm.Compared with the amount of calculation and precision,the Zoomfft algorithm is finally adopted and applied to the actual signal processing.A water injection volume measurement system based on frequency difference method is designed.The hardware system includes transmission signal generation and amplification circuit,echo signal processing circuit,etc.The software system includes signal transmission module,ADacquisition module,signal processing module and so on.Finally,the water injection volume measurement system was tested at different temperatures and pressures.The test results show that the system has good stability and can effectively measure the water injection volume.Analyze and compare the results before and after using the mathematical model to compensate.On the basis of satisfying the water injection measurement,using the mathematical model to compensate the results can effectively reduce the impact of environmental factors on the measurement results and effectively improve the system measurement accuracy.