核磁共振测井受激回波校正方法研究

核磁共振测井中,受激回波导致CPMG序列中前2个回波与期望值存在较大差异,严重影响仪器信噪比和储层评价效果.为进一步改善核磁共振测井仪性能,通过探究受激回波产生机理,揭示其对CPMG回波串作用规律,提出了受激回波的校正方法.同时针对仪器负载不同,相同发射功率产生射频场强度各异的特性,建立受激回波校正系数与射频场强的数学关系,在不同应用环境中实现对CPMG测量结果的校正.实验表明,在信噪比较低的应用环境中,采用传统的舍去前2个回波的方法误差达24.58%,而该文设计的校正算法误差仅为4.9%....

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Bibliographic Details
Published in波谱学杂志 Vol. 30; no. 1; pp. 103 - 112
Main Author 宋公仆 范伟 张嘉伟 薛志波 吴磊
Format Journal Article
LanguageChinese
Published 中海油田服务股份有限公司油田技术研究院,北京,101149%北京理工大学化工与环境学院,北京,100081 2013
Subjects
CPMG脉冲序列
受激回波
射频场强
核磁共振测井
核磁共振测井
CPMG脉冲序列
射频场强
受激回波
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Summary:核磁共振测井中,受激回波导致CPMG序列中前2个回波与期望值存在较大差异,严重影响仪器信噪比和储层评价效果.为进一步改善核磁共振测井仪性能,通过探究受激回波产生机理,揭示其对CPMG回波串作用规律,提出了受激回波的校正方法.同时针对仪器负载不同,相同发射功率产生射频场强度各异的特性,建立受激回波校正系数与射频场强的数学关系,在不同应用环境中实现对CPMG测量结果的校正.实验表明,在信噪比较低的应用环境中,采用传统的舍去前2个回波的方法误差达24.58%,而该文设计的校正算法误差仅为4.9%.
Bibliography:SONG Gong-pu, FAN Wei, ZHANG Jia-wei, XUE Zhi-bo, WU Lei （1. Well Tech R＆D Institutes, China OilaCield Service Limited, Beijing 101149, China; 2. School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081, China）
The CPMG sequence is the most widely used pulse sequence in NMR logging. However, the formation Of stimulated echo will distort the first two echoes acquired with the CPMG sequence, affecting the signal-to-noise ratio （SNR） of logging tools and the outcome of reservoir evaluation. To improve the performance of NMR logging tools, a correction method for stimulated echo was proposed, based on theoretical studies on the how the stimulated echoes are formed and what are their effects on CPMG acquisi- tion. Because the radio frequency （RF） field generated by a RF pulse might vary by the load, a relationship between stimulated echo correction coefficient and the RF field was established to calibrate the CPMG measurement made under different environment. With real logging
ISSN:1000-4556