Hydrodynamic Justification of the Effectiveness of Horizontal Wells for In-Situ Uranium Leaching in Low-Permeability Formations

In-situ leaching (ISL) is the dominant method of uranium production from sandstone-hosted deposits, since its efficiency falls sharply in low-permeability ore horizons, where vertical wells create a narrow zone of hydraulic influence. This study quantifies how far a horizontal well can restore the productivity of such blocks and identifies the mechanism responsible for the gain. Steady-state Darcy flow was computed for a vertical well (Dupuit–Thiem) and for a 150 m J-shaped horizontal well (Joshi) using the parameters of Section 6–7 of the Budenovskoye deposit, Kazakhstan: kh = 1.0 mD, h = 8.0 m, kz/kx = 0.1. The vertical-well solution was calibrated against measured field flow rates from the same section. The horizontal configuration raises productivity from 0.32 to 1.95 m³/day (a factor of 6.1), expands the swept pore volume by a factor of 2.9, and lowers the Darcy velocity at the sandface by a factor of 3.1. Assuming the same characteristic transport length and reaction parameters, the lower sandface Darcy velocity increases the relative Damköhler number by a factor of 3.1, indicating a greater potential for reaction during fluid residence. The effect on uranium recovery and non-target acid consumption requires validation using a fully calibrated reactive-transport model. Blocks with k < 2 mD and h < 10 m may therefore be recoverable with J-shaped wells.