Optimizing and Remote Monitoring Repeated Thermal Shocking of Tight Lithologies

Increasing permeability and pore surface area in hot rock benefits enhanced geothermal systems. One method to achieve both is cyclic thermal shocking, which induces thermal cracks through repeated rapid cooling. In laboratory experiments, we tested carbonate, granodiorite, and alkali trachybasalt, applying up to ten cycles and monitoring crack evolution via time-lapse electron microscopy, permeability, and compressional/shear wave velocities under confining pressure. Results show carbonate responds most effectively, followed by granodiorite, while trachybasalt shows minimal impact. Favorable cracking occurs in rocks with minerals of varying thermal properties, large grains, or irregular vugs. Despite limited porosity changes, wave velocities decreased by over 10% across all lithologies with multiple cycles. These findings indicate that velocity models based on dry-rock properties must consider both the number of thermal shock cycles and pressure effects, providing insights into optimizing permeability enhancement in geothermal systems.