多孔隙度变化倾角裂缝型砂岩铀矿超热中子运移模拟

Simulation of epithermal neutron migration in fractured sandstone-hosted uranium deposits with variable porosities and dip angles

铀矿作为重要的清洁能源一直备受地质勘探领域的关注,然而,其中的裂缝型砂岩铀矿(孔、裂隙型铀矿)因其结构复杂一直是勘查工作的难点。因此,为了对此类型铀矿进行定量分析,有必要对铀矿赋存状态、含量与地质结构(孔、裂隙)参数的响应关系进行研究。通过瞬发中子测井技术和指向概率模拟算法可以对孔、裂缝型砂岩铀矿中的中子运移情况进行模拟,基于理想模型将研究重点集中于裂缝结构对中子测井结果的影响,包括:裂隙孔隙度对超热中子运移的影响作用随着孔隙度的升高而显著提高,同时使测井响应敏感度大幅提升;近似垂直裂隙环境下,超热中子聚集峰呈现多点分布状态;高裂缝倾角环境对中子能量和时间谱峰值的衰减作用最为严重,并且中子时间谱峰值存在随孔隙度增大向低裂缝倾角度区间移动的现象;不同裂缝倾角环境下,孔隙度与超热中子计数比存在一定的特征线性关系,可以辅助修正特定角度裂隙环境中的铀含量范围。以上结论可以为裂缝砂岩铀矿、复杂环境铀矿勘探工作提供理论参考依据并提高铀矿定量准确性。

Uranium ores,as a significant clean energy source,have been highly anticipated in the field of geological exploration.How-ever,fractured sandstone-hosted uranium deposits(pore-fissure type uranium deposits)face challenges in exploration because of their complex structures.Therefore,to quantify such uranium deposits,it is necessary to investigate the response relationships between the occurrence state and content of uranium and the parameters of geological structures(pores and fissures).This study simulated the neu-tron migration in the pore-fissure type sandstone-hosted uranium deposits using the prompt neutron log technology and the directive probability simulation algorithm.Through an ideal model,this study focused on the effects of fracture structures on neutron logs.The results are as follows:(1)The effects of fissure porosity on epithermal neutron migration intensified significantly with an increase in porosity,accompanied by substantially enhanced log response sensitivity;(2)The epithermal neutron accumulation peaks exhibit a multi-point distribution in a nearly vertical fissure environment;(3)The fracture environment with high dip angles manifested the most significant attenuation effect on the neutron energy and time spectrum peaks,and the neutron time spectrum peaks tended to move to the low-dip-angle interval with an increase in porosity;(4)In the fracture environment with variable dip angles,there was a linear re-lationship between the porosity and the epithermal neutron count ratio,which can assist in correcting the uranium content range in frac-ture environments at specific angles.The above results can provide a theoretical reference for the exploration of fractured sandstone-hos-ted uranium deposits and other uranium deposits in a complex environment and improve the quantitative accuracy of uranium deposits.