Study on the influence factors of rock breaking by supercritical CO2 thermal fracturing

Abstract

At present, there is a growing demand for safe and low-pollution rock-breaking technology. The rock breaking technology of supercritical CO₂ thermal fracturing has many advantages, such as no dust noise, no explosion, high efficiency, controllable shock wave and so on. Fully considering the combustion rate of energetic materials, heat and mass transfer, CO₂ phase change and transient nonlinear flow process, a multi-field coupled numerical model of rock breaking by supercritical CO₂ thermal fracturing was established based on the existing experiments. The influence factors of CO₂ thermal fracturing process were studied to provide theoretical guidance for site construction parameters optimization. The numerical simulation results were in good agreement with the experimental observation results. The results showed that the maximum temperature of CO₂ and the growth rate of CO₂ pressure during the fracturing process would decrease accordingly with the increase of CO₂ initial pressure. But the change in CO₂ peak pressure wasn't significant. Appropriately increasing the heat source power could improve the heating and pressurization rate of CO₂ and accelerate the damage rate of rock. The relevant results were of great importance for promoting the application of rock breaking by supercritical CO₂ thermal fracturing technology.