井眼参数对瞬发裂变中子铀矿测井的影响机制及原位校正方法研究

Facing the major strategic requirement for uranium resources in China's national defense industry and nuclear energy development, revealing the influence of borehole parameters (composition and borehole diameter) on the accuracy of prompt fission neutron (PFN) uranium logging, and proposing an in-situ correction method to improve the accuracy of the uranium logging is a key issue that needs to be addressed urgently. Based on the previous research work, this project starts from the physical theory of the interaction between neutron and matter, derives the transport theory of the pulsed neutron source in dual media (borehole fluid, uranium proliferation medium) by the deterministic method in Fick's law and diffusion equation; transforms borehole parameters into physical parameters such as the neutron macroscopic absorption section and diffusion coefficient, clarifies the variation of double neutron field distribution with physical parameters, and reveals the influence mechanism of the borehole parameters for the accuracy in the PFN uranium logging. Simulation and experiment are applied to study the response laws of the gamma-ray generated by the neutron with borehole parameters, extract the borehole effective information in the gamma-ray time spectrum by using the time window and hydrogen peak energy window, and establish the obtaining method and the in-situ correcting model of the borehole parameters. Based on the above theoretical and experimental results, a new method of high-precision uranium logging with dual neutron and gamma-ray time spectrum will be proposed, which lays a theoretical and technical foundation for breaking through the new high-precision neutron logging equipment for uranium exploration in China.

面对我国国防和核能发展对铀资源的重大战略需求，针对井眼参数(干孔、井液、泥浆及井径)对瞬发裂变中子铀矿测井准确度的影响问题，建立一种适用于复杂测井环境的原位校正方法，达到提到铀矿定量准确度的目的。在前期研究工作基础上，本项目从中子与物质相互作用的物理基础出发，基于斐克定律和扩散方程，利用确定性方法阐明脉冲中子源在双介质(井液、铀增殖介质)中的输运理论；将井眼参数转化为中子物理学特征参数如宏观中子吸收截面、扩散系数等，研究双中子场(源中子、铀裂变瞬发中子)分布随上述特征参数的变化规律，揭示井眼参数对瞬发裂变铀矿测井准确度的影响机制。模拟与实验探究中子产生的伽马射线随井眼参数的响应规律，利用时间窗、氢峰能窗获取伽马时间谱中井眼信息，建立井眼特征参数的求取方法及原位校正模型。综上，提出一种融合双中子与伽马时间谱的高精度铀矿测井新方法，为突破我国铀矿勘查的新型高精度中子测井装备奠定理论和技术基础。

为满足我国国防军工和核能发展对铀资源的重大战略需求，建立高效、快速、准确的裂变中子铀矿测井装备，揭示井眼参数对瞬发裂变中子铀矿测井准确度的影响机制，建立一种更适用于复杂测井环境的井眼参数原位校正方法，提高铀矿测井准确度是刻不容缓需要解决的关键问题。在前期脉冲中子铀矿测井仪的研究基础上，本项目从中子与物质作用的物理基础出发，充分考虑脉冲中子源在井眼和地层的输运过程，推导了超热中子和热中子空间分布函数，建立了基于超热中子与热中子时间谱比值的铀定量理论；通过建立柱状测井模型，定义并推导了井眼中子物理学特征参数含氢系数的计算公式，模拟计算了干孔孔径、井眼水厚度、泥浆密度、PVC套管厚度等井眼参数变化对含氢系数影响规律，揭示了井眼中子物理学特征参数对铀矿测井准确度的影响机制；模拟与实验探究了中子与氢产生的俘获伽马射线随井眼参数的响应规律，利用时间窗、氢峰能窗获取伽马时间谱中含氢系数，提出了基于氢的俘获伽马时间谱的井眼参数原位修正方法；通过模型井的模拟及实验，分别对对干孔孔径、井眼水厚度、泥浆密度、PVC套管厚度等井眼参数的影响进行了修正，提高了铀矿测井准确度。本项目的顺利实施，为我国砂岩型铀矿的快速勘查技术与装备的研制奠定理论基础。