| 仵杰,王轲,刘彦萍,高建申.基于全相位FFT的油套环空中声速计算方法[J].声学技术,2021,40(2):246~253 |
| 基于全相位FFT的油套环空中声速计算方法 |
| Acoustic velocity calculation method of oil tubing casing annulus based on all-phase FFT |
| 投稿时间：2019-11-06 修订日期：2019-12-25 |
| DOI：10.16300/j.cnki.1000-3630.2021.02.016 |
| 中文关键词: 接箍反射信号 声速 快速傅里叶变换(FFT) 全相位快速傅里叶变换(apFFT) |
| 英文关键词: coupling reflection signal acoustic velocity fast Fourier transform (FFT) all-phase fast Fourier transform (apFFT) |
| 基金项目:国家自然科学基金青年科学基金项目（41704106）；陕西省自然科学基础研究计划项目（2018JQ4045）；陕西省教育厅专项科研计划项目（19JK0665）资助 |
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| 中文摘要: |
| 油套环空中会产生各种噪声，使测得的接箍反射信号非常复杂，环隙中真实的声速则很难计算准确，可通过对原始接箍数据进行傅里叶变换的方法对声速进行估计，但是存在不可忽视的误差。全相位傅里叶变换是傅里叶变换的一种改进方法，能够获得更加准确的频率谱与相位谱。文章采用全相位快速傅里叶变换（all-phase Fast Fourier Transform，apFFT）得到原始接箍信号的频谱，然后通过该频谱进一步计算环隙声速，可得到更加准确的声速估计。通过对不同信噪比下的模拟接箍信号采用快速傅里叶变换（Fast Fourier Transform，FFT）和全相位快速傅里叶变换（apFFT）得到其频谱，可以验证apFFT具有很强的抑制频谱泄漏的能力，且抗噪性能比FFT更好。根据FFT谱和apFFT谱分别计算出声速并对比其精度，可以验证通过apFFT谱计算出的声速稳定性更好、精度更高。然后采用上述两种方法对不同深度井的实测接箍数据进行频谱分析与对比，验证了apFFT较之于FFT对谱峰位置的辨识能力更强，根据谱峰位置计算声速的准确性也将更高。 |
| 英文摘要: |
| The tube-casing annulus generates various noises, which makes the measured coupling reflection signal very complex. The real acoustic velocity in annulus is difficult to calculate accurately. It can be calculated by Fourier transform of the original coupling data, but there are errors that cannot be ignored. The all-phase Fourier transform is an improved method of the Fourier transform to obtain a more accurate frequency spectrum and phase spectrum. In this paper, the spectrum of the original coupling signal is obtained by using the all-phase fast Fourier transform (apFFT), and then the acoustic velocity in annulus is further calculated by the spectrum. So, more accurate acoustic velocity estimation can be obtained. By using FFT and apFFT to obtain the spectrums of the simulated coupling signals under different signal-to-noise ratios (SNRs), it can be seen that apFFT has superior ability to suppress spectral leakage and better anti-noise capability than FFT. Then, according to the FFT spectrum and the apFFT spectrum, the acoustic velocity is calculated and the accuracy is compared respectively, it is verified that the acoustic velocity calculated by the apFFT spectrum is more stable and accurate. The above two methods are applied to analyzing and comparing the spectrums of the measured coupling data in different depth wells. It is shown that apFFT has better identification ability to peak positions than FFT, and so the accuracy of calculating acoustic velocity according to peak position will be higher. |
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