Laboratory Monitoring of Long-term Fracture Closure during In-situ Mining

ABSTRACT: In-situ mining is a technology that extracts minerals directly from their natural deposits through dissolution. Compared with traditional mining methods, it is a more sustainable and efficient mineral extraction practice that produces significant amounts of various energy-relevant minerals without excavation or surface disturbance. The success of in-situ mining relies on the effectiveness of the reaction between the lixiviant and the ore and the transport of the ions through rock fractures. However, fracture closure hinders the efficiency by reducing the reaction area and permeability. To better understand the long-term fracture closure during in-situ mining, we developed a non-contact method to monitor long-term fracture closure during laboratory-scale flow through tests to simulate in-situ mining. We adapted proximity sensors into a triaxial system instead of contact-based methods using string potentiometers, strain gauges, or linear variable differential transformers (LVDTs). Our system provides high-resolution reliable measurements of fracture closure. Through the measurements, we show that a large portion of the fracture closure occurs at the beginning of flow tests, while the rest of the fracture closure has a creep-like behavior. Our study will assist in better strategizing the in-situ mining technology.