S-3 aperture_distribution_v1_0_20210422_8.xlsx from Full-scale pore size distribution features of uranium-bearing sandstone in the northwest of Xinjiang, China

As an important nuclear fuel, uranium in sandstone uranium deposits is mainly extracted by <i>in situ</i> leaching. The porosity of sandstone is one of the important indexes determining <i>in situ</i> leaching efficiency. Moreover, the microscopic pore size distribution (PSD) of the uranium-bearing layer has an important effect on porosity. It is necessary to feature the pore structure by various techniques because of the different pore types and sizes in the uranium layer. In this paper, combined with nitrogen gas adsorption, nuclear magnetic resonance techniques and scanning electron microscopy, the full-scale PSD features of uranium-bearing sandstone in the northwest of Xinjiang are effectively characterized. The results show that pores structure of uranium-bearing sandstone include dissolution pores (<i>d </i>≤ 50 nm), intergranular pores (50 nm &lt; <i>d</i> ≤ 200 µm) and microfractures. Intergranular pores of 60 nm and 1 µm are the significant contributors to pore volume. The effects of the pore volume of two-pore types (dissolution pores and intergranular pores) on the porosity of uranium-bearing sandstone are analysed. The results show that intergranular pores have the greater influence on the porosity and are positively correlated to the porosity. Dissolution pores have little effect on the porosity, but it is one of the key factors for improving uranium recovery. Moreover, the greater the difference of PSD between sandstones, the stronger the interlayer heterogeneity of uranium-bearing sandstone. This kind of interlayer heterogeneity leads to the change of permeability in the horizontal direction of strata. It provides a basis for a reasonable setting of well type and well spacing parameters.

作为一类重要的核燃料，砂岩型铀矿床中的铀资源主要通过原地浸出（in situ leaching）法进行提取。砂岩孔隙度是决定原地浸出效率的核心指标之一，而含铀层的微观孔径分布（pore size distribution, PSD）对孔隙度具有显著影响。鉴于铀矿层内孔隙类型与尺寸分布存在显著差异，需通过多种技术手段对孔隙结构进行精准表征。本文结合氮气吸附法、核磁共振技术与扫描电子显微镜，对新疆西北部地区含铀砂岩的全尺度孔径分布特征开展了有效表征。研究结果显示，含铀砂岩的孔隙结构可分为溶蚀孔隙（粒径d ≤ 50 nm）、粒间孔隙（50 nm < d ≤ 200 μm）与微裂缝三类。其中，60 nm与1 μm级粒间孔隙对孔隙体积的贡献最为显著。本文分析了溶蚀孔隙与粒间孔隙两类孔隙的体积对含铀砂岩孔隙度的影响规律，结果表明：粒间孔隙对孔隙度的影响程度更大，且与孔隙度呈显著正相关关系；溶蚀孔隙对孔隙度的影响相对较小，但却是提升铀回收率的关键因素之一。此外，不同砂岩样品间的孔径分布差异越大，含铀砂岩的层间非均质性越强，此类层间非均质性会导致地层水平方向的渗透率发生变化，可为合理确定井型与井距参数提供科学依据。