Dynamic liquid level detection method based on resonant frequency difference for oil wells

Abstract

The dynamic liquid level of an oil well can be used to determine the oil production strategies and analyze the reservoir performance. Therefore, it is important to measure the dynamic liquid level in an oil field. This paper proposes a novel dynamic liquid level measurement method for oil wells, where the resonant frequency difference (RFD) of the resonant acoustic signal in annular is used to calculate the dynamic liquid level. To solve the noise interference problem in the resonant acoustic signal, a spectral fast Fourier transform (FFT) method based on Welch power spectrum is proposed to obtain the RFD. First, the Welch power spectrum approach is employed to process the resonant acoustic signal, and a high-pass filter is designed to filter the inherent envelope of low frequency in the power spectrum. In particular, a clear and smooth power spectrum can be obtained by choosing a suitable window and a sectional length. Furthermore, the short-time Fourier transform method is used to extract the strongest energy spectrum of the power spectrum. Finally, the RFD of two adjacent resonant harmonics can be accurately obtained by using FFT for the strongest energy spectrum. Experimental results show the effectiveness of the proposed approach.

Robust Intelligent Monitoring and Measurement System toward Downhole Dynamic Liquid Level

“…The coupling wave is formed by a small portion of the reflected wave generated when the acoustic wave encounters the reflective interface created by the oil tube coupling. Assuming that the length of the oil tube is , and the travel path difference for the coupling wave echo is 2 , with the frequency of the coupling wave obtained through the Fourier transform being , the formula for the calculation of the propagation speed of sound waves in the oil well is as follows [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. …”

Measurement of sound velocity in oil wells based on fast adaptive median filtering

“…Figure 4 shows the sound velocity curve of six oil wells. According to equation (10), the range discrete coefficients of the sound velocity are shown in Table 1, where ν max , ν min , and ν mean are the maximum, minimum, and average value of the global data, respectively. The fitted parameter is shown as ν R .…”

“…That is very important for designing a reasonable oil extraction technology. Therefore, it is of great significance to accurately measure the dynamic liquid level, which is an effective way to realize oil well stabilization and improve oil recovery efficiency [7][8][9][10].…”

A Microwave Liquid Level Determination Method for Oil and Gas Pipelines

“…For these reasons, these acoustic methods, have continuously evolved and generally require advanced signal processing procedures for reliable data interpretation [6]- [15]. To overcome these issues the authors in [10] managed to improve the signal to noise ratio (SNR) by using some signal processing algorithms which included high-pass filtering and short-Fourier transforms applied to the reflected acoustic signals. However, when implementing these fiber-optics based sensor systems [14], [15], expensive cabling was required to be installed downhole which can further complicate the essential production measurements in practice.…”