井孔中的超声波传播特性研究及其应用

发布时间：2018-08-07 14:49

【摘要】：油田井固井后,水泥环将套管与地层紧紧粘接为一体,既起到保护套管不受腐蚀的作用又能保证油气井的正常生产。随着我国石油天然气开发技术的不断进步,地势形态日益复杂、钻采方式多样,油田固井技术的发展也突飞猛进,对固井质量的要求也越来越高。因此,在实际生产中,有效评价固井质量是至关重要的。固井质量的评价主要是水泥胶结质量的检测,由于界面发生应变或者水泥石本身密度等原因导致界面结构疏松,出现不同程度的缺陷。研究界面缺陷对固井质量的影响有助于在实际问题中更合理设计出检测方案和提高检测结果的准确性。声波测井是通过研究声波在井下岩层和介质中的传播特性,从而了解岩层的地质特性和判断固井质量的一种测井方法。基于井孔中的超声波传播特性及其在无损评价中的应用,本文的主要研究内容及结果如下:(1)研究了不同界面缺陷对套管井超声响应的影响。采用ANSYS有限元软件,分别建立了32组第一、第二界面不同缺陷尺寸模型,并对接收到的超声回波进行波形分析和频谱转化。结果表明:胶结良好情况下地层回波明显,随着缺陷的增大,回波逐渐减弱直至不明显;界面缺陷回波FFT峰值随着缺陷尺寸的增加先增大后减小,当缺陷增至一定程度后,能透过套管到达水泥层的能量大大减弱,频谱表现为自身固有频率。(2)研究了水泥环缺失范围对声场的影响以及缺失方位的判定。采用ANSYS有限元软件,建立了套管井胶结良好和沿x轴周向缺失不同范围水泥环有限元模型,对回波信号的套管波、首波幅度及对FFT变换峰值进行分析,结果表明:无缺陷模型首波幅度最小,但随着缺失角度的增大,首波幅度、不同方位回波FFT幅值都随之增大,到180°后幅度急剧减小并保持平稳;不同方位的缺陷有不同的敏感频率。(3)研究了不同椭圆形套管井声场的传播特征及时频分析。采用ANSYS有限元软件软件,分别建立不同椭圆形井场有限元模型,并通过FRFT对接收到的超声回波信号进行分析。结果表明:圆形井场分数阶傅里叶变换最优p值较大;随着椭圆度的增大,信号在分数阶域上的第一主峰值越来越大,但总体幅值比越来越小。通过本文的研究,对套管井结构进行超声波检测在理论和实践应用中都有一定的参考和指导意义。
[Abstract]:After cementing in oil field wells, the cement ring connects the casing and the formation tightly, which not only protects the casing from corrosion, but also ensures the normal production of oil and gas wells. With the continuous development of China's petroleum and natural gas development technology, the topography is increasingly complex and the drilling methods are varied, and the development of the cementing technology in the oil field is also advancing rapidly and cementing well. The quality requirements are getting higher and higher. Therefore, in actual production, it is very important to evaluate the cementing quality effectively. The evaluation of cementing quality is mainly the testing of cement cement quality. The interface structure is loose because of the interface strain or the density of cement stone itself. The effect of mass is helpful to the more reasonable design of the detection scheme and the accuracy of the detection results in practical problems. Acoustic logging is a well logging method to understand the geological characteristics of the rock layer and determine the quality of Cementing by studying the propagation characteristics of sound waves in the underground rock and medium. The main contents and results of this paper are as follows: (1) the effect of different interface defects on ultrasonic response of casing wells is studied. Using ANSYS finite element software, 32 groups of first and second interface defect size models are established respectively, and the ultrasonic echoes received are analyzed and frequency conversion. The results show that the echo of the formation is obvious under the condition of good cementation. With the increase of the defect, the echo gradually decreases until it is not obvious. The FFT peak of the interface defect echo increases first and then decreases with the increase of the defect size. When the defect increases to a certain extent, the energy to reach the cement layer through the casing is greatly weakened, and the frequency spectrum is its own natural frequency (2). The influence of the loss range of the cement ring on the acoustic field and the determination of the missing azimuth are studied. By using the ANSYS finite element software, a finite element model of cement ring with good cementation and the circumferential missing of X axis is established. The casing wave of the echo signal, the amplitude of the first wave and the peak value of the FFT transformation are analyzed. The results show that the head of the defect model is not the head of the defect model. The amplitude of the wave is the smallest, but with the increase of the missing angle, the amplitude of the first wave and the FFT amplitude of the different azimuth echoes all increase, and the amplitude decreases rapidly and keeps steady after 180 degrees. The defects in different azimuths have different sensitive frequencies. (3) the time frequency analysis of the propagation characteristics of the sound fields of different oval casing wells is studied. The software software of the finite element software is used for the analysis of the acoustic field of different oval casing wells. The finite element model of different elliptical wellfield is established, and the received ultrasonic echo signal is analyzed by FRFT. The result shows that the optimal p value of the fractional Fourier transform of the circular hole field is larger. With the increase of the ellipticity, the first peak value of the signal in the fractional domain is bigger and bigger, but the overall amplitude is smaller and smaller. Through this paper The ultrasonic testing of cased hole structure has certain reference and guiding significance in theory and practice application.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE256

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