Analysis of the elemental spectral characteristics of single elemental capture spectrum log using Monte-Carlo simulation*
Lan Chang-Lin, Zhan Xu-Wen, Wu Hong-Liang, Zhang Yi , Liu Tong, Feng Zhou, and Lv Tao
1. School of Nuclear Science and Technology, Lanzhou University, Gansu 730000, China.
2. Research Institute of Petroleum Exploration and Development, Beijing 100083, China.
摘要 为了使用简易的方法获取可靠的单元素伽马能谱，本文针对元素俘获能谱测井仪器单元素中子伽马能谱的获取进行了仿真模拟计算，包括中子源的选择、地层模型的设计以及探测器的布置。采用Monte Carlo 方法中具有代表性的MCNP（MonteCarlo N-Particle Transport Code System）程序模拟了Am-Be 中子源产生的中子经过慢化后与地层元素发生热中子俘获反应的中子和光子的输运过程，记录了元素的特征γ射线和伽马能谱，获得的了十种元素的中子俘获伽马能谱。经过对比分析，模拟计算结果与斯伦贝谢公司公布的单元素标准γ能谱在特征峰位位置及谱形变化方面具有很好的一致性，且主要特征峰位所在的位置与国际原子能机构核数据中心数据一致，用实际测量谱验证表明了利用该方法获得的中子伽马能谱具有较强的实用性，对于元素俘获能谱测井数据处理的深化研究具有一定的实用价值，同时也为其他类型元素测井仪器数据处理提供了重要的借鉴意义。
Abstract：
In this study, the gamma-ray spectrum of single elemental capture spectrum log was simulated. By numerical simulation we obtain a single-element neutron capture gamma spectrum. The neutron and photon transportable processes were simulated using the Monte Carlo N-Particle Transport Code System (MCNP), where an Am–Be neutron source generated the neutrons and thermal neutron capture reactions with the stratigraphic elements. The characteristic gamma rays and the standard gamma spectra were recorded, from analyzing of the characteristic spectra analysis we obtain the ten elements in the stratum, such as Si, Ca, Fe, S, Ti, Al, K, Na, Cl, and Ba. Comparing with single elemental capture gamma spectrum of Schlumberger, the simulated characteristic peak and the spectral change results are in good agreement with Schlumberger. The characteristic peak positions observed also consistent with the data obtained from the National Nuclear Data Center of the International Atomic Energy Agency. The neutron gamma spectrum results calculated using this simple method have practical applications. They also serve as an reference for data processing using other types of element logging tools.
. Analysis of the elemental spectral characteristics of single elemental capture spectrum log using Monte-Carlo simulation*[J]. APPLIED GEOPHYSICS, 2019, 16(3): 321-326.
2019, Vol. 16 
