3D characterization of porosity and minerals of low-permeability uranium-bearing sandstone based on multi-resolution ima
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3D characterization of porosity and minerals of low-permeability uranium-bearing sandstone based on multi-resolution image fusion Bing Sun1 • Shan-Shan Hou1 • Sheng Zeng2 Jing Zhang3
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Xin Bai2 • Shu-Wen Zhang2
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Received: 13 May 2020 / Revised: 3 September 2020 / Accepted: 9 September 2020 / Published online: 15 October 2020 China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd. 2020
Abstract In the process of in situ leaching of uranium, the microstructure controls and influences the flow distribution, percolation characteristics, and reaction mechanism of lixivium in the pores of reservoir rocks and directly affects the leaching of useful components. In this study, the pore throat, pore size distribution, and mineral composition of low-permeability uranium-bearing sandstone were quantitatively analyzed by high pressure mercury injection, nuclear magnetic resonance, X-ray diffraction, and wavelength-dispersive X-ray fluorescence. The distribution characteristics of pores and minerals in the samples were qualitatively analyzed using energy-dispersive scanning electron microscopy and multi-resolution CT images. Image registration with the landmarks algorithm provided by FEI Avizo was used to accurately match the CT images with different resolutions. The multi-scale and multi-mineral digital core model of low-permeability uranium-bearing sandstone is reconstructed through pore segmentation and mineral segmentation of fusion core scanning images. The results show that the pore structure of low-permeability uranium-bearing sandstone is complex and has
multi-scale and multi-crossing characteristics. The intergranular pores determine the main seepage channel in the pore space, and the secondary pores have poor connectivity with other pores. Pyrite and coffinite are isolated from the connected pores and surrounded by a large number of clay minerals and ankerite cements, which increases the difficulty of uranium leaching. Clays and a large amount of ankerite cement are filled in the primary and secondary pores and pore throats of the low-permeability uraniumbearing sandstone, which significantly reduces the porosity of the movable fluid and results in low overall permeability of the cores. The multi-scale and multi-mineral digital core proposed in this study provides a basis for characterizing macroscopic and microscopic pore-throat structures and mineral distributions of low-permeability uranium-bearing sandstone and can better understand the seepage characteristics. Keywords Low-permeability uranium-bearing sandstone Digital core Micro-CT SEM–EDS Image fusion
1 Introduction This work was supported by the National Natural Science Foundation of China (No. 11775107) and the Key Projects of Education Department of Hunan Province of China (No. 16A184). & Sheng Zeng [email protected] 1
School of Civil Engineering, University of South China, Hengyang 421001, China
2
School of
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