| 题名 | 井下超声测流中噪声对时差估计的影响 |
| 作者 | 孙剑 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-26 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 井下 超声测流 时差估计 阈值法 互相关 双谱 |
| 其他题名 | Influence of Noise on the Time Delay Estimation in the Ultrasonic Flowmeter in the Oil Well |
| 学位专业 | 声学 |
| 中文摘要 | 准确测量井下不同地层的出液量对于油田生产有重要意义。因为井下流量测量不仅能保证油田开发产量和储量的精确评价，同时为油田后期驱油方案的制定提供参考数据。然而由于渤海等油田的原油粘度大，常规的机械式测流设备很难完成测量。 针对海上油气开发的复杂情况，配合海洋石油系统生产测井流量测量设备研制的需求，中国科学院声学研究所和中海油田服务有限股份公司合作启动了井下超声测流计的研发项目，目前已完成了实验室实验系统的研发、井下石油超声测流关键技术的专利申请和可用于石油现场作业的测量样机的研制等成果。本人在该项目中的主要工作是参加了仪器部分软硬件的研发，并独立完成了噪声对井下测流时差估计的影响的理论推导、数值仿真和实验分析。 本论文主要介绍井下测流的超声时差法，通过研究井下噪声的特点和影响，提高井下超声测流过程中时差估计的准确度和精度。由于时差估计是井下超声测流的关键，本文首先介绍时差估计的三种方法，即阈值法、互相关法和双谱法，并进行了比较。本文将双谱法时差估计引入到井下超声测流，根据井下测流信号和噪声的特点改进了双谱法时差估计的算法。其次，本文从理论上首次推导了噪声为加性不相关的高斯白噪声情况下，互相关函数的估计方差与信号功率、噪声功率之间的关系，推导互相关法时差估计的方差与信号自相关函数二次导数、噪声功率之间的关系。本文还通过数值仿真研究了阈值法、互相关法和双谱法三种时差估计方法的性能，得到了阈值法的最佳阈值选取范围。研究表明在噪声不相关条件下互相关时差估计方差最小，而噪声相关条件下双谱法时差估计准确度最高。本文的实验验证了部分理论结果。 |
| 英文摘要 | The flow rate of different reservoirs in the oil well is very important for the production of oil field not only because it provides precise evaluation of the oil production of the oil reserves, but also it is the base of the scheme establishment of oil production. However, general mechanical flowmeter can not be used due to the high viscosity of the oil in Bohai and other oilfields. To overcome the disadvantage of high viscosity and meet the demand of flowmeter for the production, a development project of ultrasonic flowmeter used in oil wells was conducted by the Institute of Acoustics, Chinese Academy of Science and China Oilfield Services Limited Co. The project has established a flow testing system in the laboratory and a flowmeter prototype which could be used in the oilfield, and a patent of the key technique of ultrasonic flowmeter is claimed. In the project, I have done some work on the development of the hardware and software, and studied the noise influence on the time delay estimation in the ultrasonic flowmeter in the oil well based on theoretical derivation, numerical simulation and experimental verification. This thesis focuses on the time delay estimation of ultrasonic flowmeter, with the purpose to increase the accuracy and the precision of the ultrasonic flowmeter. Firstly, three methods of time delay estimation, the threshold method, the cross-correlation method and the bispectrum method, are introduced and compared. An improved bispectrum method is used based on the properties of signal and noise in the oil well. Secondly, the relationship among the noise power, the signal power and the variation of the cross-correlation estimation in the presence of additive Gaussian white uncorrelated noise is studied theoretically, and a further theoretical derivation is introduced to reveal the relationship among the noise power, the second order derivative of the auto-correlation of the signal and the variation of the time estimation of the cross-correlation method. Thirdly, numerical simulation is carried out to find out the performance of three methods in presence of additive Gaussian bandwidth noise. From the simulation, the best threshold is obtained and it is shown that the cross-correlation method has the minimum variation when the noise is uncorrelated, and the bispectrum method has the highest accuracy if the noise is correlated. Finally, experiment has been carried out to verify some obtained results. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 85 |
| 内容类型 | 学位论文 |
| 源URL | [http://159.226.59.140/handle/311008/454]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 孙剑. 井下超声测流中噪声对时差估计的影响[D]. 声学研究所. 中国科学院声学研究所. 2009. |
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