脉冲中子地层元素测井仪优化设计中的蒙特卡罗模拟研究

采用蒙特卡罗方法研究了脉冲中子地层元素测井仪闪烁晶体材料、井眼屏蔽体厚度、硼套表面密度等设计参数对仪器测井响应的影响。结果表明：LaBr₃晶体的测井响应特性优于BGO晶体；高矿化度盐水对测量结果影响很大，井眼屏蔽体厚度为1.2 cm时，可屏蔽60%以上井眼γ射线；硼套中¹⁰B表面密度达到0.065 g/cm²时，可消除仪器外壳材料产生的俘获γ本底；俘获能谱的探测深度随孔隙度的增加而减小，非弹性散射能谱对不同孔隙度地层的探测深度基本一致，约为14 cm。

Study of Monte Carlo Simulation on Optimally Designing Pulsing Neutron Formation Element Logging Tool

The effects of design parameters such as the scintillation crystal materials, the thickness of borehole shield and the surface density of boron sleeve on the logging response of the formation element logging tool were studied by using Monte Carlo meth-od.The results show that LaBr3 detector has outstanding performance in logging response compared with BGO detector.Salt water with high salinity affects ultimately the measurement of the element concentrations.The borehole shield thickness of 1.2 cm can shield more than 60% γ-ray from borehole.1 0 B surface density of 0.065 g/cm2 can eliminate the capture γ background from tool material.With the increase of formation porosity,the investigation depth of capture spectrum decreases.The investigation depth of inelastic spectrum is about 14 cm,which is almost identical among the formations with different porosities.