为探讨砂岩热损伤微观结构与宏观物理特性演化规律，借助核磁共振与SEM电镜扫描技术对砂岩开展100、200、300、400、500、600、700、800、900 ℃的循环热处理试验。结果表明： 400 ℃后，砂岩试样的表观形态、质量和体积等物理参数均发生显著变化，砂岩物理参数发生变化的临界温度在400 ℃左右； 400 ℃后砂岩的微裂纹及孔洞开始发育，700 ℃后新生裂纹快速萌生、扩展和贯通； 300 ℃后孔隙度缓慢增加，热损伤开始发育，500 ℃后岩样受热应力及相变耦合作用，裂纹发育迅速，致使孔隙度急剧增加；渗透率与孔隙度呈现出不同的演化规律； 砂岩小孔呈现出先增加、后降低，中孔呈现出先降低、后增加，大孔则呈现出先增加、后降低、再增加的变化趋势。

The cyclic thermal treatment of sandstone under 100 ℃, 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃ and 900 ℃ is conducted by nuclear magnetic resonance (NMR) nondestructive testing system and scanning electron microscope (SEM) so as to study the evolution characteristics of microstructure and macroscopic physical properties of sandstone thermal damage. The results show that: (1) The physical parameters of sandstone including the apparent morphology, mass and volume changed dramatically when the temperature exceeds 400 ℃; the critical temperature at which the physical properties of sandstone vary is about 400 ℃. (2) The microcracks and voids of sandstone begin to develop when the temperature exceeds 400 ℃, and the new cracks initiated, propagated and connected when the temperature exceeds 700 ℃. (3) The porosity of sandstone increase slowly and the thermal damage begins to develop when the temperature exceeds 300 ℃; the crack develops rapidly and the porosity increases sharply when the temperature exceeds 500 ℃. (4) The permeability and porosity of sandstone show different evolution laws respectively. (5) The percentage of micropores of sandstone first increases and then decreases; on the contrary, the percentage of mesopores decreases first and then increases; and the variation of macropores is different from those of small and medium pores, which first increases and then decreases and increases in the end.