Experimental investigate on the evolution of porosity structure in uranium-bearing sandstone cores within CO2+O2 in-situ leaching uranium mining
The evolution of porosity structure in uranium-bearing sandstone cores within CO2+O2 in-situ leaching uranium mining has a significant impact on the efficient leaching of uranium,and it has become a bottleneck in the development of in-situ uranium leaching technology.This study employed a custom-designed CO2+O2 in-situ leaching uranium test apparatus to simulate the in-situ uranium leaching process in a sandstone-type uranium deposit.Additionally,advanced equipment,including a high-pressure mer-cury porosimeter,CT scanner,and X-ray diffraction analyzer,was used to characterize the changes in porosity features of uranium-bearing sandstone core samples before and after experimentation.Further-more,3D digital core samples and their permeability models were created using Avizo software to ana-lyze the leachate fluid flow patterns.The research results indicate that after the experiments,the total po-rosity and connected porosity of the uranium-bearing sandstone core samples increased by 5.03％and 5.53％,respectively,compared to their pre-experiment state.The distribution range of layer-by-layer pore rates of the digital core samples was broader after the experiments,and the equivalent radius of pore throats and throat area experienced a significant increase.Additionally,the number of pores within the core samples decreased as the pore coordination number increased,but when the pore coordination num-ber was greater than or equal to 4,the number of pores after the experiments increased by a multiple,reaching a maximum of 21.63 times the pre-experiment levels.At this point,the core samples exhibited highly significant connected porosity,resulting in increased permeability.The interconnected pore net-work formed by large pore throats within the uranium-bearing sandstone core samples served as the pri-mary fluid flow pathways for the leachate,and the leachate flow velocity displayed a pattern of decrea-sing from large to small along the radial direction from the core center.These research findings provide significant insights into the analysis of solute migration and evolution in CO2+O2 in-situ leaching uranium processes,offering a meaningful reference for subsequent studies.
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