Research On Detection Method Of Oil Well Dynamic Fluid Level For The Complex Column Sound Field

The depth of the dynamic fluid level in an oil well is an important production parameter in the extraction of crude oil.Fast and accurate measurement of the dynamic liquid surface plays an important role in improving the efficiency of oilfield extraction and reducing energy consumption.The current echo measurement method has the defects of the fast decay rate of the acoustic wave,susceptible to noise interference,and difficulty to identify the echo signal,which is limited to achieve automatic measurement.The dynamic liquid level measurement method based on the principle of the tube and column sound field has the advantages of strong resistance to random noise and automatic measurement.However,as an emerging method,only the proof of principle has been completed at this stage,and there are still shortcomings such as insufficient measurement range,low measurement accuracy,and long measurement time.The main research contents of this thesis are as follows:1.Based on the research background and significance of oil well dynamic liquid level depth measurement,this thesis summarizes the advantages and disadvantages of current measurement methods and instruments.Simultaneously,focusing on the research status of dynamic liquid level measurement based on the principle of pipe string sound field,the deficiencies in the existing research are pointed out,and the main research contents of this thesis are given.2.This thesis introduces the rod pumping unit well system and analyzes in detail the influence of the structure of the oil casing ring air column,the internal environment of the oil well,and the rod pumping device on the measurement method based on the pipe string acoustic field model.On this basis,based on the measurement principle of the pipe string sound field model,a set of dynamic liquid level measurement devices that can be used in the oil field are designed and processed,and its broadband noise excitation method is improved to a low-frequency narrowband noise excitation method,which enhances the resonance intensity of the air column of the oil collar.The results show that the energy consumption during the excitation process was reduced by about one-third of the original.The performance of the measuring device was verified in subsequent experiments.3.The main components of the acoustic signal are analyzed,and the mathematical model is established.Aiming at the problem of the insufficient measuring range of the dynamic liquid surface depth,based on the improvement of the vibration method of the oil sleeve ring air column,an adaptive filter was designed through the Welch algorithm to reduce noise and then combined with the spectral kurtosis to automatically selected the resonance harmonic signal.Furthermore,a method based on multi-sensor signal fusion processing is proposed.Through the optimization of sensor data,the stability of dynamic liquid level measurement is improved.To solve the problem of insufficient accuracy in the measurement,the time-shift phase difference algorithm is applied to the accurate calculation of the number of resonance harmonic waves,which reduces the influence of spectrum leakage and the fence effect,thereby improving the measurement accuracy of the moving liquid level.4.By building a simulation experiment platform under the environment of uniform pipe string and complex pipe string,the actual test and analysis of the signal processing algorithm and the designed measuring device proposed in this thesis are carried out.The experimental results show that the improved dynamic liquid level measurement method can increase the measurement range of the simulated pipeline from 200 m to 1772 m.And through the discrete spectrum correction technology,the length measurement error of the1772 m pipeline was reduced from 1.62% to 0.61%,which realizes the accurate measurement of the complex shape of the long pipe.Moreover,the complex pipe string structure and the complex environment simulation experiment verified that the measurement algorithm still has better stability under the action of complex pipe string sound field.