能谱示踪注水剖面测井的物理基础和方法原理

Physics and Measuring Principle of Spectral Tracer Injection Profile Log

我国放射性同位素示踪注水剖面测井的年测井作业量超过１万井次，但因存在放射性示踪剂“沾污”等问题，使其测井资料中出现了相当多的假异常；现有的“沾污校正”法又因沾污类型需靠经验估计，导致相当大的不确定性。新的能谱示踪注水剖面测井法基本创新点是：（１）任一井段的放射性同位素示踪注水剖面测井曲线异常面积增量是由井筒各径向界面上的示踪剂对它分别贡献的“径向界面异常面积”之和所构成，引入“径向界面贡献率”来描述相应的贡献份额；（２）提出其物理基础——过油管伽马能谱探头测得的伽马能谱谱形会随示踪剂在井筒中的径向位置不同而发生明显变化；（３）导出了几种可以定量判断示踪剂在井筒中的径向位置和得到径向界面贡献率的谱分析方法。模型井实验结果证实此新方法可以为沾污的识别和校正提供客观的定量依据。此方法完全覆盖了现行放射性同位素示踪注水剖面测井法，不要求改变其示踪剂和施工工艺，有利于生产推广；但需要使用过油管伽马能谱测井仪及相应的地面仪器软硬件。它可能为大量存在的示踪剂沾污等问题提供一种解决办法。

The annual operation volume of radio isotope tracer injection profile log in China is more than 10000 trips. Because of the contamination of the radioactive tracer, there are many pseudo anomalies in the logging data. Since the estimation of the type of contamination is dependent on the analyst′s experience, the current contamination correction method often leads to considerable uncertainty. The new Spectral Tracer Injection Profile Log(STIP) is founded on the following new concepts: (1)The general response increment of a radio isotope tracer injection profile log at an injection interval is the sum of the various portions of response increment contributed by the individual tracer gathered on the corresponding annular boundaries of the same injection interval. “Annular boundary contribution rate” is used to describe the quantity of the corresponding portion. (2) Physics of STIP log is proposed, i.e. the form of gamma ray spectrum measured by the detector of a through tubing gamma spectroscopy tool varies distinctly as the tracer gathers on different annular boundary. (3) Several methods are deduced to analyze the spectrum so that the radial position of the tracer and the annular boundary contribution rate can be determined quantitatively. Experimental results in model well prove that STIP log can provide quantitative ground for the identification of contamination type and contamination correction, providing a solution for the current tracer contamination problem.