In-situ uranium leaching by Multiple Pumping Well System (MPWS) is hampered by differential flow and geochemical reactions attributed to the subsurface heterogeneity in fluvial aquifers. Well operations were optimized to improve MPWS efficiency, but a generic rule for optimizing well operations to overcome the impacts of heterogeneity is still lacking. In this study, synthetic cases are designed to represent typical combinations of well-placement configuration, pumping schedule, and uneven permeability distribution in fluvial aquifers. We find that locating injection wells parallel to the direction of the paleovalley in which sediments were deposited can promote the lateral spreading of the injected leaching agent among injection wells, and thus enhance uranium leaching by enlarging the contact area between fluid and uranium mineral. Furthermore, given the well placement, enlarging the phase shift among pumping rates in injection wells can further improve the uranium leaching. This is because asynchronous injection promotes the lateral spreading of the leaching agent and enlarges the average concentration and reaction rate with the mineral. Numerical simulations on a real-field uranium leaching aquifer justifies that the implementation of optimized well placement increases the uranium production by 9.7%, and further implementing the asynchronous injection rates increases the production by an additional 2.8%. • Joint influence of subsurface heterogeneity and well operations on in-situ uranium leaching by MPWS is revealed. • Injection wells located parallel to the orientation of fluvial deposition mitigated differential reactions and enhanced MPWS efficiency. • MPWS performance is further improved by asynchronous and periodic injection with a high phase shift.
Chen et al. (Wed,) studied this question.
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