基于数值模拟的X射线密度测井仪器源距设计  

A design of source spacing of the X-ray density logging tool based on numerical simulation

作　　者：武蕙琳 李雨莲 金亚 张琼 WU Huilin;LI Yulian;JIN Ya;ZHANG Qiong(School of Automation Engineering,University of Electronic Science and Technology,Chengdu 610000,China;China Oilfield Services Limited,Langfang 065000,China)

机构地区：[1]电子科技大学自动化工程学院,成都610000 [2]中海油田服务股份有限公司,廊坊065000

出　　处：《核技术》2022年第10期41-48,共8页Nuclear Techniques

基　　金：国家自然科学基金(No.52171253)资助。

摘　　要：随着环保及安全需求的提高,使用X射线源等可控源代替^(137)Cs等化学源的密度测井仪器研发成为新的发展趋势,但大部分适用于井下密度测量的X射线源强度相对γ源较弱。为克服上述挑战,基于现有的γ密度测井仪器基本架构研究了X射线密度测井仪器的探测器源距设计,通过蒙特卡罗软件Geant4模拟了偏心放置于井径为215.9 mm的淡水钻孔中的仪器模型,其地层密度变化范围为1.7-3.0 g∙cm^(−3)。根据密度测量灵敏度、探测效率和探测深度综合分析了探测器响应。最终成功设计了一款三探头X射线密度测井仪器,其中源距稍远的两个探测器主要收集地层信息,源距最短的探测器主要用于探测井壁以内环境。以上研究为X射线可控源在井下密度测量中的应用及相关仪器的设计提供了参考。[Background]In recent years,with increased awareness of environmental protection and safety,the development of nuclear logging tools using non-chemical sources such as X-ray instead of chemical sources like ^(137)Cs has become a new trend.However,X-ray source usually has a lower energy level compared to chemical source,therefore the measurement accuracy is hardly satisfying the demand of density logging tool.[Purpose]This study aims to investigates the detector spacing design of a X-ray source tool based on an existing multi-detector gamma density tool.[Methods]Based on a 215.9 mm diameter borehole filled with water where the logging tool was eccentrically placed in,Monte Carlo software Geant 4 was employed for the simulation of the X-ray density logging in the formation density range of 1.7-3.0 g∙cm^(−3).According to density sensitivity,detection efficiency and depth,a series of models of this logging tool with detector-to-source distance between 135 mm and 430 mm were simulated to analyze the detector responses.Finally,based on above data,the design of source spacing for detectors was determined for the X-ray density tool.[Results]The finalized tool includes three NaI detectors with detector-tosource distances of 160 mm,270 mm,and 344 mm,respectively.Simulation results show that the maximum wall detection depth reaches 120 mm with the vertical resolution of 344 mm,and the density measurement accuracy is 0.014 g∙cm^(−3).[Conclusions]The feasibility of developing a potential X-ray density logging tool is validated by this study,providing reference for future design of nonchemical source density logging tool.

关 键 词：X射线密度测井 蒙特卡罗 仪器设计 

分 类 号：P631.81[天文地球—地质矿产勘探]