Liquid nitrogen (LN₂) ultra-low temperature fracturing presents a broad application range for geothermal energy development. Therefore, studying the effect of LN₂ cooling on the pore characteristics of high-temperature limestone is critical. In this study, Rizhao limestone obtained from Shandong Province was selected as the test object and subjected to heat treatment at different temperatures (25–600 °C) to investigate the changes in the pore characteristics of limestone after rapid LN₂ cooling based on nuclear magnetic resonance. The total porosity of limestone continuously increases due to the continuous expansion of original fractures in the limestone and the generation of new fractures caused by thermal stress resulting from high temperatures and the rapid LN₂ cooling. For heat treatment of 600 °C, no high amplitude is observed in the damage process. The fractal dimension of permeable pores (D_P) initially decreases and then increases with an increase in the quenching temperature difference, and the fractal dimension of total pores (D_T) shows a general decreasing trend. The compressive strength increases with an increase in D_T. Acoustic emission (AE) technology was used to monitor the deformation and failure of rocks. The low amplitude of AE is mainly distributed in the low-frequency band.

液氮（LN ₂）超低温压裂为地热能开发提供了广阔的应用范围。因此，研究LN ₂冷却对高温石灰岩孔隙特征的影响至关重要。本研究以山东日照石灰岩为试验对象，在不同温度（25~600 ℃）下进行热处理，研究快速LN _{2后石灰岩孔隙特征的变化。}基于核磁共振的冷却。_{由于石灰岩中原有裂缝的不断扩大以及高温和LN 2}快速冷却产生的热应力引起的新裂缝的产生，石灰岩的总孔隙度不断增加。对于 600 °C 的热处理，在损伤过程中没有观察到高幅度。渗透孔分形维数(D _P )随着淬火温差的增大呈先减小后增大的趋势，总孔分形维数(D _T )总体呈减小趋势。抗压强度随 D _{T的增加而增加}. 声发射（AE）技术用于监测岩石的变形和破坏。AE的低幅度主要分布在低频段。