Quantitative Characterization of Horizonal Well Leaching Range Using Coupled Well-Reservoir Coupling Model and Particle Tracing Technology

Abstract:

To explore the feasibility of horizontal well technology in in-situ leaching （ISL） of sandstone-type uranium mines in China， it is essential to analyze the hydrodynamic processes and quantitatively characterize the leaching range. The hydrodynamic processes of groundwater in the horizontal well ISL involve well-reservoir coupling simulation， which refers to the coupling of wellbore turbulence and reservoir Darcy flow. By developing numerical simulation techniques for well-reservoir coupling， constructing a groundwater flow model for uranium leaching in the horizontal well network， and creating automatic extraction techniques for the leaching range using particle tracking simulation with MODPATH and the Alpha-shape algorithm， the simulation and characterization of the flow state of the solution and the leaching range during ISL can be achieved. The research results indicate that， compared to the traditional MODFLOW model， the well-reservoir coupling model more accurately depict the interaction flow rate and its variations between the well and reservoir during the injection process in the horizontal well， and the interaction flow rate is positively correlated with the permeability coefficient （K） of the reservoir. Based on the well-reservoir coupling simulation， the range enveloping the particle trajectories captured by the pumping wells during the simulation period can be automatically extracted. By identifying the leaching range corresponding to the flow rate contribution of pumping wells， it is determined that the leaching range corresponding to a 95% flow rate contribution is 40% of the volume corresponding to a 100% flow rate contribution. This indicates that the flow interaction， from the injection of leaching solution from the horizontal well into the reservoir to the extraction of pregnant solution by vertical wells， is primarily concentrated within the leaching range in the early stage of ISL. The flow velocity along the outer trajectories is lower， resulting in a reduced contribution to both the pumping flow rate and the leaching rate.

Key words:in-situ leaching;horizontal well network;hydrodynamics;leaching range;numerical simulation