Method for numerical simulation of reactive transport during CO2+O2 in-situ leaching of uranium at sandstone-type uranium deposit

A method for numerical simulation of reactive transport during CO2+O2 in-situ leaching of uranium at a sandstone-type uranium deposit, said method comprising the following steps:

• (1) collecting basic data of a mining area of the sandstone-type uranium deposit, said basic data including relative plane positions of injection and production wells in the mining area, a distance between injection and production wells of the mining area, injection and production rates, groundwater level monitoring data, and hydro-chemical analysis data of leaching solution and leachate;
• (2) constructing a hydrodynamic model of CO2+O2 in-situ leaching of uranium based on the basic data collected in step (1) in combination with hydrogeological conditions of the mining area including the type, lithology and thickness of an ore-bearing aquifer, the depth of a groundwater level, the depth and thickness of an ore body, the condition of groundwater recharge based on the fundamental principle of conservation of mass and energy, and Darcy's law;
• (3) determining initial conditions, boundary conditions, hydraulic parameters, and a source-sink term of the hydrodynamic model, and performing spatial mesh dissection and temporal discretization;
• (4) solving the hydrodynamic model to obtain a distribution of temporal and spatial flow velocity vectors and a pressure distribution within a simulated domain;
• (5) establishing a reactive solute transport model of CO2+O2 in-situ leaching of uranium based on the results of the hydrodynamic model in step (4) according to processes of component solute transport and chemical reactions in a system of in-situ leaching of uranium;
• (6) determining a network of geochemical reactions and processes of equilibrium reactions and dynamic reactions of the reactive solute transport model;
• (7) determining initial concentrations of simulated components in the reactive solute transport model, the composition of minerals involved in simulation, minerals produced by reactions and volume fractions thereof, and parameters for calculation of reaction dynamic rates of the minerals involved in simulation;
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• (8) solving the reactive solute transport model to obtain trends of variation in leaching concentration of dissolved uranium U (VI), pH and mineral content in the system of in-situ leaching of uranium, thereby completing the numerical simulation of reactive transport during CO2+O2 in-situ leaching of uranium.