In situ leaching of copper: Challenges and future prospects

Abstract

In situ leaching offers a potentially attractive way to extract copper from the subsurface without costly fragmentation and processing. Applicability of in situ leaching is limited to deposits where sufficient permeability exists and where the copper and gangue mineralogy is amenable to leaching. A key challenge from past projects is establishing uniform contact between the fluid and the formation in fractured environments, particularly if fractures become blocked by gypsum and jarosite precipitation during leaching. Previous projects have demonstrated that in situ leaching of copper sulfides is feasible by regenerating ferric iron using atmospheric bacteria cultures, pressurized oxygen gas, or chemical oxidants. Oilfield technologies, including polymer injection for permeability modification and nanoparticle tracers, may have future applications for diagnosing and mitigating short circuiting between wells. Geophysical techniques such as electrical resistance tomography have the potential to provide real-time data on lixiviant movement in the subsurface, thus aiding in both recovery optimization and environmental control. In this review, data from past copper in situ leaching projects are assembled, with a focus on recovery without prior permeability enhancement. The resulting database includes key operating variables from copper in situ leaching projects ranging from field scale pilots to commercial operations.