Analyzing variations in rock pore structure under high-temperature thermal cycles is of great significance for the development of deep resource. In this paper, red sandstone from Linyi, Shandong Province, was heated to 200 °C, 400 °C, 500 °C, and 600 °C, followed by five cold thermal cycles. The transverse relaxation times (T₂) of red sandstone treated at various temperatures were observed using nuclear magnetic resonance (NMR), and the porosity and the characteristics of the pore structure were analyzed. The results show that the variations in the pore structure of red sandstone occur primarily owing to the escape of pore water, thermal expansion, and the decomposition of some minerals. In the range of 200 to 500 °C, the escape of free water, bound water, and structural water in the sandstone resulted in a significant increase in the proportion of pores with a volume of r < 0.1 μm. At 573 °C, the phase transition of quartz and the high-temperature decomposition of calcite led to a marked increase in the proportion of mesopores (with a volume of 0.1 μm < r < 1 μm), and the connectivity between pores increased. At the same temperature, the number of mesopores and macropores increases with increases in the number of cycles. At 600 °C, the number of mesopores in sandstone increased significantly after five thermal cycles.

分析高温热循环作用下岩石孔隙结构变化对深部资源开发具有重要意义。在本文中，山东省临沂红砂岩被加热到 200 °C、400 °C、500 °C 和 600 °C，然后进行 5 次冷热循环。横向弛豫时间 ( T ₂)采用核磁共振(NMR)对不同温度处理的红砂岩进行观察，分析孔隙率和孔隙结构特征。结果表明，红砂岩孔隙结构的变化主要是由于孔隙水的逸出、热膨胀和某些矿物的分解造成的。在200～500 ℃范围内，砂岩中自由水、结合水和构造水的逸出导致体积r  < 0.1 μm的孔隙比例显着增加。在 573 °C 时，石英的相变和方解石的高温分解导致介孔比例显着增加（体积为 0.1 μm <  r < 1 μm)，孔隙之间的连通性增加。在相同温度下，中孔和大孔的数量随着循环次数的增加而增加。在 600 °C 时，经过 5 次热循环后，砂岩中的介孔数量显着增加。