地层元素测井中探测器响应数值模拟研究

摘要

地层元素测井中常利用LaBr3、BGO等晶体探测器测量γ能谱确定元素和矿物含量，晶体探测器计数效率与能量分辨率等参数是决定能谱质量和元素含量计算精度的关键因素。本文通过对比研究LaBr3和BGO两种晶体探测器的能谱响应特性，利用蒙特卡罗方法建立了不同元素含量与种类的地层模型，模拟研究了两种晶体探测器的γ响应能谱，并利用最小二乘法计算了元素含量。结果表明：当地层矿物模型中元素种类较少时，两种晶体探测器测得的元素含量差异较小；当元素种类较多时，由于能谱中不同元素γ射线重叠及互相干扰，LaBr3晶体探测器测得的元素含量计算精度优于BGO晶体探测器，体现了在复杂地层岩性元素含量测量中，高能量分辨率晶体探测器的探测优势。%LaBr3 and BGO scintillators are often used for γ spectra detection to deter‐mine element and mineral content in formation element logging ,and the crystal scintilla‐tor counting efficiency and energy resolution are critical factors for the quality of meas‐uring spectrum and computational accuracy of element content .In this paper ,the detec‐tor spectrum response characteristics of LaBr3 and BGO scintillators were compared . The γ response spectra of the two kinds of scintillators were simulated under the forma‐tion condition with different kinds of elements and diverse contents by Monte Carlo method , and then the element content was calculated by least square processing method .The calculated results based on different scintillators have less diverse when the formation has the lesser kinds of elements .However ,when the formation has more kinds of elements , the γ ray peaks of different elements in the spectrum overlap and influence each other obviously .The more accurate results can be derived by LaBr3 detec‐tor than those by BGO detector .It reflects the element measurement advantage of high resolution scintillator in the formation with complex lithology .