低频振动对低渗透砂岩试样铀浸出过程孔隙率的影响

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

为提高低渗透砂岩渗透率,将低频机械振动引入CO_(2)+O_(2)浸出铀过程,针对低频机械振动作用下砂岩孔隙率、渗透率变化展开研究。建立化学侵蚀、物理机械振动共同作用下振动损伤孔隙率方程和渗透率表达式,采用自制的振动浸出试验系统对低渗透砂岩试样进行振动浸出试验,以检验方程的正确性及研究振动对渗透率的影响特性。结果显示:低频振动增大了低渗透砂岩试样孔隙率,显著提高了渗透率。试验条件下振动渗透率增量值可达3.265 md,相比未振动作用提高了6.34倍,并且试验实测渗透率增量值、计算渗透率增量值、计算孔隙率值变化规律相同,计算渗透率增量值和实测渗透率增量值变化范围基本吻合。表明振动使砂岩试样受到损伤,从而孔隙率变大,有效提高了渗透率。因此,方程计算能正确反映不同振动频率、振动作用时间下砂岩试样孔隙率、渗透率的变化规律及渗透率的变化范围,从而为CO_(2)+O_(2)原地浸出低渗透砂岩提供理论依据。

To improve the permeability of low-permeability sandstone,low-frequency vibration is introduced into the process of uranium leaching by CO_(2)+O_(2),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 CO_(2)+O_(2).