Effect of low-frequency vibration on porosity of low-permeability sandstone samples during uranium leaching process

To improve the permeability of low-permeability sandstone, low-frequency vibration is introduced into the process of uranium leaching by CO₂+O₂, and the researches on the permeability and porosity under the effect of vibration are carried out. The porosity equation and permeability expression considering the vibration-induced damage under the combined effects of chemical erosion and physical mechanical vibration are established. The vibration leaching experiments on the low-permeability sandstone samples are performed by using the developed vibration leaching experimental system to test the correctness of the equations and to study the effect characteristics of vibration on the permeability. The results indicate that the low-frequency vibration increases the porosity of the low-permeability sandstone samples, and significantly improves the permeability. The increment value of permeability is up to 3.265 md, which is increased by 6.34 times more than that without the vibration. The variation rules of the experimental and calculated values of permeability increment and the calculated values of porosity are the same. In addition, the variation ranges of the calculated and experimental values of permeability increment are basically consistent. The vibration can result in damage to the samples, thus the porosity increases and the permeability is improved effectively. Therefore, the equations can correctly reflect the variation rules of porosity and permeability of sandstone samples under the action of different vibration frequencies and vibration time as well as the variation ranges of permeability. It may provide a theoretical basis for the in-situ leaching of low-permeability sandstone by CO₂+O₂.