In-situ mining in fractured sulfide-bearing rocks: A digital rock assessment

This study evaluates the efficiency of in-situ mining in fractured sulfide-bearing ores by integrating high-resolution X-ray computed tomography (CT), digital rock analysis, and two-dimensional fracture flow simulations. CT-derived digital rock models are used to quantify fracture geometry, mineral distribution, and fracture–mineral intersections. A 2D digital-rock-based flow model is used to simulate fluid flow in fractures and their spatial relationship with the reactive areas. Two representative fracturing methods, Brazilian tensile fracturing and electro-hydraulic fracturing (E-HF), are compared for their ability to deliver leaching fluids toward the sulfide minerals in the rock specimens. We show that E-HF produces complex multi-fracture networks that more frequently intersect electrically conductive sulfide minerals, resulting in a significantly larger reactive area and directing a larger portion of fluids to these reactive areas, despite flow channelization that may bypass the reactive surfaces. In contrast, Brazilian tensile fractures are planar with relatively uniform apertures, resulting in a smaller reactive surface and reactive flow ratio despite less pronounced flow channelization. Our study contributes to the in-situ mining technology and the engineering geology field at large by: 1, establishing a digital-rock-based characterization and flow simulation framework for quantitatively assessing and optimizing fracture-stimulation strategies in sulfide-bearing ore bodies with the introduction of reactive area ratio and reactive flow ratio; 2, using this framework to quantitatively show the higher efficiency of a novel stimulation method, electro-hydraulic fracturing, in creating fractures that intersect more frequently with sulfide minerals and deliver more leaching fluid to these minerals. The research findings of this study can be integrated into large-scale fracture network models to assess the field-scale performance of these stimulation methods in in-situ mining of critical minerals.