Experiment on rock breaking with supercritical carbon dioxide jet

Rock breaking with SC-CO2 has the advantages of low threshold pressure and high rate of penetration, so it has attracted full attention. In order to clarify the law of rock breaking with SC-CO2 jet, and enable it to serve SC-CO2 drilling better, the SC-CO2 jet system for rock breaking was used to carry out the experiments, which demonstrated that jet pressure, jet temperature, confining pressure, jet distance, rotary speed of core samples and jet time are the main factors to influence the rock-breaking performance and efficiency. The results showed the effects as follows. Jet pressure and confining pressure are the direct factors to affect rock-breaking performance. With the increase of jet pressure, the rock-breaking efficiency increases gradually, while as the confining pressure increases, it decreases with constant jet pressure or has the maximum around the critical jet pressure with constant pressure difference. With the increase of jet temperature, the efficiency increases at first and then decreases, and the relationship curve showed in parabolic function. Under the experimental conditions in this paper, the optimal jet distance is about 3-4 times of nozzle diameter. The rotary speed of core sample has no substantial influence on the erosion depth, but on the average width or diameter of eroded grooves. The average width and the size of the eroded cuttings are smaller when the rotary speed is higher. The erosion depth increases but the trend gradually decreases with the jet time being prolonged. (C) 2015 Elsevier B.V. All rights reserved.