蒙特卡罗模拟在放射性测井中的应用

Application of Monte Carlo simulation in nuclear well logging

蒙特卡罗模拟是放射性测井一种重要的数值模拟方法,利用通用程序MCNP可方便的建立地层模型,为放射性测井方法基础研究提供了简便有效的方法.借助于蒙特卡罗方法建立不同条件下计算模型,利用具体实例介绍了蒙特卡罗模拟在放射性测井中四大方面的应用:模拟不同条件下中子场及伽马场等核物理场分布,进而研究探测特性及测井响应,并可根据场分布特点形成不同测量方法;克服实体物理实验存在的困难,通过数值模拟方法开展对测井新方法的研究;可实现探测器类型和尺寸、源距及屏蔽体等仪器关键参数优化设计;通过模拟数据处理获得测井参数,建立与地质参数的响应关系,并研究各种影响因素的影响,形成数据处理方法.

Monte Carlo simulation is one of the most important numerical simulation methods in nuclear logging.Formation models can be built with MCNP special code,which provides a simple and effective approach to conduct fundamental study in nuclear logging.In this paper,Monte Carlo method is used to set up different simulation models under different situations,and the application of Monte Carlo method in nuclear well logging is demonstrated with simulation examples：distribution of nuclear physical field,including neutron and gamma field,can be simulated to study the investigation depth and logging response,and measurement methods can be built based on the distribution features of nuclear field;new logging method can be developed with numerical simulation, and physical experiments can be avoided to some extent; the tool parameters,including the type and size of detector,spacing,shielding and so on,can be optimally designed;the logging response can be established with the logging parameters,which are derived from the simulation data, and geological parameters,and data processing method can be got through the study of the effect of influential factors on logging response.