AN ARTIFICIAL FRACTURE STIMULATION TECHNIQUE FOR ENHANCED IN SITU RECOVERY USING NON-EXPLOSIVE DEMOLITION AGENTS

摘要

Conventional mining methods (open-pit and underground) are becoming increasingly uneconomical with declining ore grades. In-situ recovery (ISR) is becoming an alternative technology which could potentially replace conventional mining operations provided that the existing limitations of ISR can be addressed. Industrywide application of one limiting factor of ISR is the poor recovery rates due to the low permeability of the host rock formations. In this study, we developed a patent-pending non-explosive rock fracturing compound called 3G-DTM, which can be used for artificial fracture stimulation in sensitive environments (such as marine environments and aquifers) where conventional methods of fracturing such as explosive blasting and hydraulic fracturing cannot be used. The fracturing compound 3G-DTM was successfully tested in the laboratory to fracture low permeability sandstone specimens under confining stresses up to 20 MPa. Due to the fracturing nature of 3G-DTM, the fracture density can be significantly improved (by 116%) with an increase in the confining pressure (from 70 kPa to 20 MPa). Furthermore, the rock is subjected to a gradual fracturing process in 3G-DTM fracturing (10-15 h in the laboratory experiments) allowing for a safer, more controlled fracture propagation, making 3G-DTM a substitute for conventional rock fragmentation in sensitive environments. Following the fracturing tests, the fracture permeability of the specimen was calculated. Compared to the miniscule intact rock permeability of 7.6 x 1020 m2 of the sandstone specimen an improved permeability of 1.48 x 10~(13) m~2 at a confining pressure of 30 MPa was observed after fracturing the specimen using 3G-DTM, which makes 3G-DTM charging a potential method for permeability enhancement in ISR applications.