脉冲中子全能谱测井闪烁探测器响应特性的蒙特卡罗模拟

利用蒙特卡罗方法模拟研究NaI和BGO晶体探测器对不同γ射线的响应。模拟结果表明，BGO晶体的光电峰和第一逃逸峰对计数贡献大，而NaI晶体的逃逸峰贡献大。对于井眼和地层流体分别为油和水砂岩地层，模拟改变NaI和BGO晶体探测器的直径和长度时的非弹性散射γ射线响应能谱，采用不同能窗处理方法对地层流体的分辨能力不同，选取光电峰和第一、第二逃逸峰对应的能量窗时，BGO晶体探测器比NaI晶体探测器测量的C/O（C与O的元素含量比）差值大，但受尺寸的影响不大；采用光电峰对应的能量窗时，BGO晶体探测器测量的C/O差值比NaI的大得多，且随尺寸的增加差值增大；能量道的漂移对C/O值影响较大，而能量分辨率对差值影响相对较小。

Monte-Carlo Simulation for Response Characteristic of Scintillator Detector in Pulsed Neutron Whole Energy Spectrum Logging

The response spectra of NaI and BGO detectors under the condition of different energy γ-rays were simulated by using Monte-Carlo method. It is concluded that the counting efficiency of photoelectric and the first escape peaks for BGO crystal is relatively higher, and that of the first and the second escape peaks for NaI crystal makes great contribution. Under the condition of the borehole and sandstone formation filling with oil and water, respectively, the ability is different when different energy windows are selected to distinguish formation by simulating the detector response spectrum of various diameters and length of NaI and BGO crystal. The C/O value difference of BGO crystal is higher than that of NaI crystal when the energy window includes photoelectric peak, the first and the second escape peaks, but it is less affected by the different sizes of detector crystal. Using photoelectric peak corresponding to the energy window, the C/O value difference of BGO crystal detector is much larger than that of NaI, but it increases with the crystal size increasing. The C/O value is greatly affected by energy drifting, while relatively a little by energy resolution.