裂缝型铀矿环境中子测井数值模拟

Numerical Simulation of Neutron Logging in Fracture Uranium Environment

在铀矿地球物理勘探领域,裂缝型铀矿一直是重要的勘探对象之一。通过野外勘探发现,裂缝型铀矿多为黄铁矿、方解石及有机质矿物裂缝中的沥青铀矿以及少量的硅铀、钛铀矿。同时,裂缝结构的存在对测井结果会产生影响,为了准确识别裂缝型铀矿分布状态、分析铀矿含量,对裂缝型铀矿的中子测井响应规律进行研究是十分必要的。基于变化角度裂缝理论,模拟了孔-裂缝介质环境下的铀矿赋存状态,并通过设定不同裂缝参数得到相应的测井响应数据。通过分析结果发现,垂直角度裂缝环境下的热中子密度分布最大值小于水平裂缝环境;垂直角度裂缝环境中的热中子计数明显多于水平角度裂缝环境;裂缝数密度递增前提下,垂直角度裂缝环境下的中子计数值下降幅度明显大于水平裂缝环境。水平角度裂缝环境对热中子的俘获作用更加明显;中子在垂直角度裂缝环境下对裂缝数密度的变化更加敏感。

In the field of uranium geophysical exploration, fissured uranium deposits have always been one of the important exploration objects. Through field exploration, it is found that the main forms of fracture uranium include: uranium stone in pyrite, calcite and organic matter;a small amount of silicon uranium ore, titanium uranium ore. At the same time, the existence of the fracture structure will affect the result of the log, in order to accurately identify fracture distribution status, analysis of uranium content, research the neutron log response law of fracture uranium is necessary. Based on the theory of variation angle fractures, the state of uranium deposit in the pore-fracture medium insimulated, and the logging response data are obtained by setting different fracture parameters. The results show that the maximum thermal neutron density in vertical fracture environment is smaller than that in horizontal environment. The thermal neutron count in the vertical fracture environment is more than the horizontal environment. When the fracture number density increases, the value of neutron number in the vertical crack environment decreases more obviously. By summarizing the experimental results, it is found that the capture effect of thermal neutron in horizontal angle crack environment is more obvious;neutron is more sensitive to fracture number density in vertical angle crack environment.