砂岩型铀矿钻孔中放射性场特征和铀矿化关系研究及其应用

In the sandstone-type uranium prospecting and mining processes, the effective core recovery generally was not high, thus the results of the method which was to determine Ra-Rn balance coefficient by comparing the traditional ore section analysis results with the gamma logging interpretation results might have significant error, and thereby it would lead to false anomaly, leakage ledge, larger error of reserve calculation and other conditions. In this project, the sandstone-type uranium deposit in ili area, xinjiang province would be as the object, and the method of numerical simulation would be used to synthetically analyze the long-term observation data of radioactive geophysical logging, the chemical analysis data of radionuclide in borehole core samples, hydrological data and other relative data. The cause of Ra-Rn imbalance would be analyzed, and the correlativity between distribution characteristics of radioactive fields and uranium mineralization would be studied. On the basis of comparing the research results with those obtained by traditional method, the prospecting marks of uranium body presence around the well bore judged by the radioactivite geophysical well logging data would be concluded, the reasonable working methods of prospecting the sandstone-type uranium deposit body would be summarized, and the effective method of Ra-Rn balance coefficient calculation would be confirmed. The research results would do well the foundation work for more accurate reserve calculation. .This is an applied basic research that intercrosses the applied geophysics, nuclear technology application and mathematics, and its study achievements would have important application value to the promotion of search and exploration works to concealed sandstone-type uranium deposit.

砂岩型铀矿勘查及开采过程中，由于砂岩比较松散，有效的岩芯采取率很低，用传统的矿段分析结果与伽玛测井解释结果对比确定Ra-Rn平衡系数的方法，其结果误差较大，从而导致假异常、漏矿层、储量计算误差较大等情况。本项目拟以新疆伊犁地区砂岩型铀矿为研究对象，利用放射性地球物理测井长期观测资料、钻孔岩芯样品的放射性核素化学分析数据、地质及水文资料等，用数值模拟的方法进行综合分析，分析U-Ra和Ra-Rn不平衡的原因，研究放射性场分布特征与铀矿化之间的相关关系。在将这些研究结果与传统方法所得的结果进行对比的基础上，归纳用放射性地球物理测井资料判断井孔周围是否存在隐伏矿体的找矿标志；确定计算Ra-Rn平衡系数的有效方法，为更精确的储量计算做好前期的基础工作。.这是一项应用地球物理、核技术应用与计算数学相交叉的应用基础研究，其研究的预期成果对于推动砂岩型隐伏铀矿体的寻找及开采工作具有重要应用价值。

在铀矿勘查工作中，伽玛测井方法是确定铀矿体的空间位置、品位及厚度的重要技术手段。地浸砂岩型铀矿具有较高的孔隙度和水饱和度，该类型铀矿床往往表现出铀-镭及镭-氡不平衡现象，铀-镭和镭-氡平衡系数是地浸砂岩型铀矿勘查工作中的两个重要参数。及时开展钻孔中放射性场特征和铀矿化关系研究对指导砂岩型铀矿勘查评价、储量计算等具有重要的研究意义和应用价值。.本项目在吐哈盆地砂岩型铀矿研究区内选择具有代表性的含矿取芯钻孔，理清了镭-氡平衡主要影响因素及其平衡位移量，总结出钻探过程中铀矿层镭-氡平衡位移的研究方法和镭-氡平衡的分布规律。同时还研究了镭-氡平衡变化与放射性场特征之间的相互关系，总结出放射性场与铀矿化之间对应的规律，确定计算镭-氡平衡系数的有效方法。.在层状含矿层和覆盖层介质中，氡在向上、下覆盖层中迁移的量都很小，且氡在迁移过程中向上方不断积累。氡在给定矿化边界上的扩散长度很小，仅为20cm~30cm。钻孔中氡浓度时变曲线与实际伽马照射量率时变曲线具有很明显的一致性，可通过氡浓度随时间变化曲线来判断镭-氡之间是否达到平衡状态。.在砂岩型铀矿勘查中，利用镭线储量加权计算的铀-镭平衡系数对伽玛测井数据修正后更加接近实际结果，但成本较高；矿心分析与γ测井解释结果对比确定也可得出相应的镭-氡平衡系数，但计算结果受影响因素较多。两种修正方法在地浸砂岩型铀矿镭-氡平衡系数计算和研究中都非常重要，可以起到相互验证的作用。.通过对松辽盆地测井曲线的整体变化趋势和特征、曲线接触关系及各地层测井相研究和分析，厘定了松辽盆地西南部沉积相，为寻找河道砂体提供了可靠依据。γ测井照射量率均值增大，其均方差、变异系数也稳定增大，三者基本呈正相关，表明地层放射性元素含量增加，均匀富集、矿化，易形成品质较好的铀矿化体。基于对测井数据、地质条件及沉积相等资料的分析，在松辽盆地西南部圈定了5处有利于铀成矿远景区，为下一步的找矿工作提供依据。