Аңдатпа
The use of liquid nitrogen (LN₂) as a freezing agent has been shown to help enhance the permeability of the rock, making it easier for fluids to pass through, which improves how much water or steam can flow from the reservoir. This is especially useful in Hot Dry Rock (HDR) systems. This study looks at how exposing granite to low temperatures affects its strength after it has been cooled down after being heated. Fracture Toughness Tests were done on granite samples after they were first baked at different temperatures from 100 °C to 400 °C before being quickly cooled with LN₂ to copy what happens when something gets suddenly cooled quickly. The tested granite samples were taken from a place that is around 50 km away from Astana, in the Akmola region of Kazakhstan. Experimental measurements helped find important mechanical values like the maximum load the sample could handle, how much stress builds up at the tip of the crack, and how much energy it takes to make the sample break. The results show that using liquid nitrogen makes it much easier for cracks to start and spread in the sample, and doing LN₂ treatment at higher pre-treatment temperatures makes it happen even faster. A consistent decrease in both the stress intensity factor and fracture energy as the temperature went up could be seen. These findings show that using LN₂ to freeze and crack the rocks can be a useful way to help boost the flow of geothermal energy from certain types of hard rocks.