Numerical Simulation And Application Research Of Acoustic Wave Characteristics In Dynamic Liquid Level Measurement

In the actual oil and gas well production process,with the increase of the well depth,the error of the real-time measurement of the dynamic liquid surface depth increases,which makes it difficult to analyze and interpret the relevant parameters of the formation and formulate a reasonable production plan.In order to improve the accuracy of measuring the depth of the dynamic liquid surface,various methods of measuring the depth of the dynamic liquid surface have been proposed,and the existing measurement methods not only do not make an in-depth study on the generation mechanism of the measured object,that is,when the sound wave propagates in the annular space The generated echo characteristics are systematically studied,and the calculation method of the sound velocity of the oil jacket annulus is poor in noise resistance and stability.In this paper,a combination of numerical simulation and all-phase FFT method is used to conduct research from the accurate determination of the space velocity of the oil jacket ring and the determination of the position of the liquid surface wave.The thesis focuses on the following aspects:(1)The characteristics of reflection wave in the air of oil sheath ring are studied.Aiming at the problem that the location of the liquid surface wave is not easy to identify,based on the COMSOL finite element software,the oil jacket annulus acoustic wave propagation models of coupling,perforation,depression,and liquid surface are constructed respectively to study the excitation of signal sources with different polarities Time response characteristics and analysis of the factors affecting the reflected wave shape of the coupling.The results show that when the signal source polarity is positive(negative),the coupling reflection signal is positive(negative)and then negative(positive);the perforated reflection signal is negative(positive)and then positive(negative);the interface in the casing is corroded or depressed Under the circumstances,the reflected signal waveform is consistent with the perforated reflected signal waveform;the liquid surface reflected signal and the transmitted signal source have the same polarity.When the signal source is a positive and negative superimposed source,the response waveform is obtained by superimposing the response of the superimposed source's first peak polarity source and its opposite polarity source acting alone.The radius of the coupling and the space pressure of the oil jacket ring only affect the amplitude of the reflected wave,but have no effect on the shape of the coupled wave.With the continuous increase of the thickness of the coupling,the distance between the peak and peak of the reflected wave of the coupling becomes larger and larger,and the reflected wave Changes.The research results can provide strong support for the promotion and improvement of relevant theories,provide correct reference standards for the performance verification of echo processing methods,and provide an important theoretical basis for correctly identifying the position of the liquid surface echo.(2)A method for calculating the sound velocity between the annular gap of oil sleeve based on all-phase FFT was studied.Under the noise conditions,the traditional Fourier transform method(FFT)in the process of calculating the sound velocity of the oil jacket ring has poor noise resistance and poor stability,and a all-phase FFT based air velocity calculation of the oil jacket ring is studied.Method,all-phase Fourier transform is an improved method of Fourier transform,which can obtain more accurate frequency spectrum and phase spectrum.In this paper,the all-phase fast Fourier transform(apFFT)is used to obtain the frequency spectrum of the original coupling signal,and then the ring-shaped sound velocity is further calculated through the spectrum to obtain a more accurate sound velocity estimation.By using fast Fourier transform(FFT)and all-phase fast Fourier transform(apFFT)to obtain the spectrum of the analog coupling signals under different signal-to-noise ratios,it can be verified that apFFT has a strong ability to suppress spectrum leakage and resist Noise performance is better than FFT.Calculate the speed of sound according to the FFT spectrum and apFFT spectrum respectively and compare their accuracy.It can be verified that the speed of sound calculated by the apFFT spectrum has better stability and higher accuracy.Then use the above two methods to perform spectrum analysis and comparison on the measured coupling data of wells with different depths.It is verified that apFFT has a stronger ability to identify the peak position of the spectrum than FFT,so the accuracy of calculating the speed of sound according to the peak position will also be higher.The research results can provide a theoretical basis for the calculation of sound velocity and dynamic liquid surface depth.(3)The influence factors of sound wave propagation speed in the air of oil sheath ring are studied.In order to clarify the influence of temperature,medium density and pressure on the sound velocity,the theoretical derivation and the construction of the sound wave propagation model are used to study the results.The results show that sound velocity and pressure are positively correlated;the influence of medium density on the sound wave propagation velocity It can be attributed to the compressibility of the medium when it is disturbed by sound,which is inversely proportional to its compressibility;as the temperature increases,the speed of sound increases linearly.(4)The automatic identification and application of dynamic liquid surface reflection signal are studied.According to the waveform characteristics of the coupling wave and the liquid surface reflection wave obtained by the study,the corresponding reflection wave identification method is studied,so that the originally difficult to identify waveform can be clearly displayed,and it is applied to the liquid surface of the shallow well in the field depth calculation.