电磁法水下管道埋深检测及防腐层缺陷定位技术研究

发布时间：2018-04-09 15:57

本文选题：水下管道　切入点：电磁法　出处：《西南石油大学》2015年硕士论文

【摘要】：随着我国油气输送管道规模的不断扩大,水下管道在长输油气管道工程中所占比例不断增大,已成为油气管道的重要环节。为保证管道运行安全,需定期对水下管道进行检测。但随着水平定向钻等新铺管技术的广泛应用,管道埋深不断增大,现有埋深计算方法、检测措施等存在埋深检测范围不足、精度不高、防腐层缺陷检测困难等诸多问题,水下管道检测已成为管道检测工作者而临的新难题和新挑战。针对现有问题,本文通过理论与实验相结合,对水下管道埋深计算方法、检测措施和防腐层缺陷定位方法进行研究,分析检测回路和频率对埋深检测结果的影响,提高埋深检测范围和精度,为现场检测提供技术支持。本论文所做工作如下： (1)通过分析管道电磁场信号随检测深度的变化规律,提出了水下管道埋深动态计算新方法：利用指数函数、Logistic函数和Lognormal函数模型对校准点处管道电磁场信号进行数据拟合,并用拟合度最高的函数对各测试点的信号值进行插值,计算出水下管道检测深度。通过与原有计算方法相比和现场应用,新的动态计算方法计算精度更高,具有可行性。 (2)通过分析水下管道埋深检测影响因素,提出检测回路及频率选用原则：埋深检测应采用“电缆回路”,减小检测回路电阻,提高管道周围信号强度；针对不同检测深度应采用不同检测频率：当检测深度在0～10m范围内,可采用1kHz、2kHz、8kHz或33kHz；当检测深度在10～20m范围内,采用512Hz或1kHz；当检测深度在20～40m范围内,采用512Hz；当检测大管径、防腐层电阻率低、土壤电阻率大的管道时,应较低的检测频率。 (3)通过分析防腐层缺陷处管道电磁场信号衰减规律,得出了水下管道防腐层缺陷定位方法：在水下管道防腐层缺陷检测过程中,采用“管地回路”和“密间隔”检测方式,沿管道方向间隔1-2m密集取点,测量管道正上方管道磁场强度,绘制管道磁场强度衰减曲线,判断其是否存在异常衰减区域,从而实现防腐层缺陷的识别与定位。 (4)将埋深动态计算新方法与防腐层缺陷定位方法应用于现场检测,结果表明：采用上述方法得出的管道埋深及防腐层缺陷位置与开挖验证结果吻合,能够满足现场检测要求,具有良好的工程应用效果。
[Abstract]:With the continuous expansion of the scale of oil and gas pipeline in China, the proportion of underwater pipeline in long oil and gas pipeline project is increasing, which has become an important part of oil and gas pipeline.In order to ensure the safety of pipeline operation, it is necessary to inspect the underwater pipeline regularly.However, with the wide application of new pipe laying technology, such as horizontal directional drill, the buried depth of pipeline is increasing continuously. There are many problems such as insufficient range of depth detection, low precision, difficulty in detecting defects of anticorrosive coating, and so on.Underwater pipeline detection has become a new problem and challenge for pipeline inspection workers.Aiming at the existing problems, this paper, by combining theory with experiment, studies the calculation method of buried depth of underwater pipeline, the detection measures and the defect location method of anticorrosion coating, and analyzes the influence of detection circuit and frequency on the result of buried depth detection.To improve the range and accuracy of buried depth detection, provide technical support for field detection.The work of this thesis is as follows:1) based on the analysis of the variation of the electromagnetic field signal with the detection depth, a new method of dynamic calculation of the buried depth of the underwater pipeline is proposed. The data of the pipeline electromagnetic field signal at the calibration point are fitted by the exponential function logistic function and the Lognormal function model.The highest fitting function is used to interpolate the signal values of each test point, and the detection depth of underwater pipeline is calculated.Compared with the original calculation method and the field application, the new dynamic calculation method is more accurate and feasible.2) by analyzing the influencing factors of underwater pipeline buried depth detection, the principles of detecting loop and frequency selection are put forward: the "cable circuit" should be used in the buried depth detection, the resistance of the detection loop should be reduced, and the signal intensity around the pipeline should be improved;Different detection frequencies should be used for different detection depths: when the detection depth is in the range of 0 ~ 10 m, 1 kHz or 33 kHz can be used; when the detection depth is in the range of 10 ~ 20 m, 512Hz or 1 kHz is used; when the detection depth is in the range of 20 ~ 40 m, 512 Hz is used; and when the diameter of a large pipe is measured,The detection frequency of pipeline with low resistivity and high soil resistivity should be lower.3) by analyzing the attenuation law of electromagnetic field signal of pipeline at the defect of anticorrosive coating, the defect location method of underwater pipeline anticorrosive coating is obtained. In the process of detecting the defect of anticorrosion layer of underwater pipeline, "pipe and ground loop" and "dense interval" are used to detect the defect.The magnetic field intensity of the pipeline is measured and the attenuation curve of the magnetic field intensity of the pipeline is plotted to determine whether there is an abnormal attenuation area so as to identify and locate the defects of the anticorrosive coating.4) the new method of dynamic calculation of buried depth and the method of defect location of anticorrosive coating are applied to the field detection. The results show that the buried depth and the defect location of anticorrosive coating obtained by the above method are consistent with the results of excavation verification, and can meet the requirements of field detection.It has good engineering application effect.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE973.6;TE988.2

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