| The dynamic liquid level depth of oil wells is an important parameter that has been closely monitored in the oil field industry.As a key indicator in the process of oil production,it directly reflects the liquid supply capacity of oil wells,and plays an important role in formulating a reasonable production plan for oil wells.When using the acoustic method to measure the dynamic fluid level depth,a series of interference will exist in the processing of the acoustic signal due to the complex conditions such as liquid level foam in the oil well annulus,wax formation in the pipe string,vibration and noise.As a result,the position of the coupling echo and liquid level echo is easily submerged in the noise and difficult to be identified,thus affecting the calculation of dynamic liquid level depth.With the gradual advancement of digital oilfield construction and efficiency enhancement measures,higher requirements have been proposed for the dynamic monitoring and application management of oil wells.Therefore,it is of important engineering significance to study a set of high-precision acoustic signal processing algorithms and design corresponding oil well dynamic level monitoring systems.This article focuses on the dynamic fluid level measurement technology based on the acoustic method,and carries out the following work around the downhole acoustic signal processing methods and software development:(1)The basic principle of using acoustic method to detect the dynamic fluid level depth of oil wells was explained,and the characteristics of the dynamic fluid level acoustic signal and interference were analyzed.Based on this,the need for acoustic signal processing was determined.(2)The basic principles and operating procedures of five acoustic signal denoising methods,including digital low-pass filtering,wavelet denoising,sparse decomposition,blind source separation,and spectral subtraction,were studied.The aim was to find a practical and feasible acoustic signal denoising methods.(3)Based on the acoustic data collected from the oilfield site,a simulation model of acoustic signal propagation in the wellbore was established using matlab.The advantages and disadvantages of three sound velocity algorithms,namely,short-term autocorrelation function,short-term average amplitude difference function,and Fourier transform,are analyzed through simulation.The effectiveness of three time algorithms,namely automatic identification method,wavelet singular value detection,and short-time amplitude-zero-crossing rate function,were also discussed.(4)A design scheme for the dynamic liquid level synthesis algorithm is proposed.Firstly,the Butterworth low-pass filter is used to filter out the coupling echo.Then,based on the periodic recognition feature of the short-time average amplitude difference function,it is utilized for estimating the sound speed.On this basis,the wavelet denoising and wavelet singular value detection methods are applied to determine the position of the dynamic liquid level,and thus obtain the time of sound wave travel.Finally,the depth of the oil well’s dynamic liquid level is calculated by using the sound speed and time.(5)According to the actual requirements of oil field data management,the specific scheme of data acquisition,processing,storage and management is further discussed,and a software system that can monitor the dynamic liquid level of oil wells in real time is developed.Field testing shows that the proposed algorithm can accurately obtain the depth of the downhole dynamic liquid level,with an absolute error controlled within 1 meter and an average relative error of around 0.1%.It can better meet the practical engineering requirements.The developed software system can achieve the reception,processing,and storage of data collected by the dynamic liquid level detector.It not only realizes the digital twinning of well site data,greatly improves visualization and humanization,but also achieves unified management of oil well data.The system provides a feasible solution for dynamic liquid level depth detection,promotes the digital construction of the oilfield,and has certain practical value and promotional value. |
