Quantifying the impact of mineralogical heterogeneity on reactive transport modeling of CO2 + O2 in-situ leaching of uranium

CO2 + O2in-situ leaching (ISL) of sandstone-type uranium ore represents the third generation of solution mining in China. In this study, reactive transport modeling of the interaction between hydrodynamic and geochemical reactions is performed to enable better prediction and regulation of the CO2 + O2in-situ leaching process of uranium. Geochemical reactions between mining solutions and rock, and the kinetic uranium dissolution controlled by O2 (aq) and bicarbonate (HCO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{ HCO}}_{3}^{ - }$$\end{document}) are considered in the CO2 + O2 ISL reactive transport model of a typical sandstone-hosted uranium ore deposit in northern China. The reactive leaching of uranium is most sensitive to the spatial distribution of the mineralogical properties of the uranium deposit. Stochastic geostatistical models are used to represent the uncertainty on the spatial distribution of mineral grades. A Monte Carlo analysis was also performed to simulate the uranium production variability over an entire set of geostatistical realizations. The ISL stochastic simulation performed with the selected geostatistical realizations approximates the uranium production variability well. The simulation results of the ISL reactive transport model show that the extent of the uranium plume is highly dependent on mineralogical heterogeneity. The uncertainty analysis suggests the effect of uranium grade heterogeneity was found to be important to improve the accurate capture of the uncertainty. This study provides guidance for the accurate simulation and dynamic regulation of the CO2 + O2 leaching process of uranium at the scale of large mining areas.