高温花岗岩遇水冷却后孔隙结构及渗透性研究

Study on Pore Structure and Permeability of Granite Subjected to Heating and Water Quenching

为研究20~600℃花岗岩遇水冷却后孔隙特征及渗透率变化规律,采用压汞法测试了样品的孔隙结构特征,采用瞬态脉冲衰减法测试了样品的渗透率,并将实测的渗透率与基于Katz-Thompson模型(简称"K-T模型")计算所得的渗透率进行了对比分析。结果表明:随着花岗岩温度的升高,遇水冷却后花岗岩的孔隙率及渗透率均呈现指数式增加,500~600℃是花岗岩遇水冷却后孔隙率及渗透率变化的阈值温度区间;高温花岗岩遇水冷却后形成的内部新孔隙以中孔为主,中孔含量的增加是花岗岩孔隙率及渗透率大幅提升的主要原因;基于K-T模型的渗透率预测值能够较好地反映真实渗透率的变化趋势。研究结果可为高温岩体地热开发工程的设计及施工提供参考。

In order to obtain the pore characteristics and permeability change law of water-quenched granite subjected to different temperatures, the water-quenched granites from 20 ℃ to 600 ℃ were used as the research object. Pore structure characteristics of the samples were tested by mercury intrusion porosimetry and permeability of the samples were measured by the transient pulse attenuation method. And the measured permeability was compared with the calculated value which was predicted based on the K-T model. The following conclusions were obtained: with temperature increasing, the porosity and permeability of water-quenched granite increased exponentially. 500~600 ℃ was the threshold temperature range for the change of porosity and permeability of water-quenched granite. Most of the new pores in the granite induced by high temperature and water quenching were mesopores. The significant increase of the porosity and permeability of water-quenched granite can be attributed to the growth of the mesopore content. The predicted permeability based on the K-T model can reflect quite well the variation trend of the true permeability. The research results can provide reference for the design and construction of high-temperature geothermal development projects.