脉冲中子衰减τ—Σ图的制作、分析与应用

The Creation,Analysis and Applications of τ– Σ Chart in the Pulsed Neutron Attenuation

针对利用脉冲中子衰减数据提取俘获截面会出现信息丢失、计算过程参数复杂变化的问题,提出一种新的分析和处理方法。基于Hough变换理论,脉冲中子衰减谱采用了非常规的ζ—θ方程变换并在Hough空间进行显示。根据脉冲中子衰减数据特征,需要采用Hough空间的图形增强模式进行处理,将Hough空间坐标轴进行转化,生成中子寿命—俘获截面图(τ—Σ图)。对中子寿命—俘获截面图的图形特征与物理意义的关系及其在数据处理过程中的优、缺点进行分析。处理了套后中子衰减饱和度仪器的实测资料,对比中子寿命—俘获截面图法与传统方法提取俘获截面的处理过程和曲线差别,结果表明,采用中子寿命—俘获截面图进行脉冲中子衰减测井资料处理,改进了俘获截面处理过程和结果,可以更有效地进行测井资料质量控制。该方法也可用于其他脉冲中子衰减仪器的资料处理。

Pulsed neutron attenuation logging data traditionally calculate capture cross section by slope change,and a new analysis and processing method is proposed to solve the problems of information loss and complex parameters setting.Traditional way displays the attenuation curves at time – counts figure,and based on the Hough transform theory,the logging data is now plotted at Hough space with ζ – θ equation,from where neutron life and capture cross section can be directly read.The graph need enhancement at Hough space because of pulsed neutron data feature,and the neutron lifetime – capture cross section chart(τ – Σ chart) is created after the coordinate axis of Hough space is scaled.This paper analyzed the relationship between the graphic features and the physical meaning on the τ – Σ chart,and its advantages and disadvantages in data processing.A field data of pulsed neutron instrument are processed,and the difference of results and processing steps between the traditional method and τ – Σ chart is analyzed.The results show that τ – Σ chart improved the processing algorithm and results,and the quality control of logging data by τ – Σchart can be more effective.Other pulsed neutron instruments also can apply this method in the data processing and logging data quality control.