Intermittent and multi-stage fracture stimulation to optimise fracture propagation around a single injection well for enhanced in-situ leaching applications

摘要

Artificial fracture stimulation in host rock formations is a potential technique to improve the recovery efficiency of in-situ leaching mining applications, which is gradually creeping in as an alternative mining method for mineral extraction in low-grade ore deposits. In this study, we report two new methods of fracture stimulation by injecting a modified Soundless Cracking Demolition Agent (SCDA) into a target rock through an injection well as opposed to completely filling the injection well once with SCDA to produce a fracture. The first method, intermittent charging (where the injection well is charged intermittently with SCDA), was found to minimize the amount of SCDA used to fracture a finite rock mass. Experimental results suggest a 22.4% improvement in the efficiency (measured by the area of fracture produced per unit mass of SCDA) of fracturing for intermittent charging compared to continuous charging. Numerical simulations were carried out in conjunction using Particle Flow Code 3D (PFC3D) to understand the underlying mechanics of rock fragmentation during intermittent charging. The simulations reveal that during intermittent charging, an additional bending force is applied to the uncharged regions resulting in a supplementary fracture propagation, which improves fracturing efficiency. The second method, multi-stage charging (where SCDA is injected in two consecutive stages using the same injection well) increases the fracture density of a finite rock mass without the need for multiple injection wells. During stage two injection, the fracture density was increased, first by extending the fractures created during the first stage of injection, and second by creating micro hairline fractures around the first stage fractures. The laboratory experiments suggest that the methods introduced in this study can be used to optimize the fracture network generated in a host rock formation.