一种新的自然伽马测井仪死时间修正方法

A New Method for Dead Time Correction of Gamma Logging Instrument

死时间是决定伽马测井数据准确性的一个重要参数,传统的死时间修正方法存在测量条件较高,或测量步骤繁琐,或计算步骤复杂,或存在一定的安全隐患等不足。为降低测量条件、简化测量和计算步骤以及降低测量风险,提出一种新的死时间测量方法——“图解法”。从原理上详细论述了其可行性,并开展了相关实验以验证其可行性。使用2套伽马探测系统利用“图解法”获取的死时间对系列已知铀质量分数的饱和模型的计数率数据进行修正,对比修正前后计数率与铀质量分数的线性拟合优度以及“图解法”与“双源法”所得死时间值的大小。结果表明:2套伽马探测系统经“图解法”死时间修正前后计数率与铀质量分数的线性拟合优度分别为0.986和0.998以及0.98和0.998,说明“图解法”是有效的;“图解法”与“双源法”所得死时间值分别为0.902μs和0.941μs以及1.674μs和1.745μs,相对误差仅为-4.145%和-4.069%,说明“图解法”相对准确。因此,可将“图解法”作为伽马测井仪死时间修正方法应用于实际中。

Dead time is an important parameter to determine the accuracy of gamma logging data.The standard dead time corr-ection method has some shortcomings such as high measuring conditions,complicated measuring steps,complicated mathe-matical calculation or security risks.To reduce measurement conditions,simplify measurement and calculation steps,and re-duce measurement risk,a new method of dead time measurement with single point source as the measuring object is presented,it is named the"graphic method".its feasibility was discussed in detail from the principle,and related experiments were carried out to verify its feasibility.Two gamma measurement systems were used for testing.The dead time obtained by the"graphic method"was used to correct the counting rate data of a series of models of saturated uranium models with known content,Then the accuracy of the"graphic method"was verified by comparing the dead time values obtained by the"graphic method"and the"double source method".The experimental results showed that the linear fit of the counting rate and uranium content before and after the modification of the dead time by"graphic method"was 0.986 vs 0.998 and 0.98 vs 0.998,it verified the validity of the"graphic method".While the dead time obtained by"the graphic method"and"the double source method"was 0.902μs vs 0.941μs and 1.674μs vs 1.745μs,respectively,with a relative deviation of-4.145%and-4.069%,it verified the accuracy of the"graphic method".Therefore,the"graphic method"can be used as a method to correct the dead time of gamma logging instrument in practice.