Temperature and Fluid Saturation Impact on the Mechanical and Fracturing Behavior of Deccan Basalt under Uniaxial Compression

Enhanced geothermal systems offer a promising solution for green energy generation and net-zero emissions with low operational costs. The Deccan flood basalt in India, covering 0.5 million km2 and reaching up to 2 km in thickness, holds significant geothermal energy potential. Temperature variations and water interaction influence basaltic rocks’ mechanical and fracturing behavior in geothermal reservoirs during hydraulic fracturing. However, the mechanical and fracturing changes brought into these rocks by the coupled impact of heat and fluid treatment are not reported. This study investigates the impact of thermal and water saturation on Deccan basalt’s mechanical and fracturing behavior. Samples were heated to 100–500 °C for 24 h at a rate of 5 °C/min, then cooled, with one set immersed in water for 45 days. All samples were subjected to uniaxial compressive loading to understand the mechanical and fracturing behavior with simultaneous monitoring of Acoustic Emission (AE) signals. The experimental results were inferred to evaluate the extent of damage incurred by the basaltic rocks as a function of thermal damage and water saturation compared to undamaged samples. The results indicate that water saturation has minimal impact on the Deccan basalt’s mechanical and fracturing attributes. This is because the contribution of crack formation from water saturation is significantly lower than the thermal effect on fine-grained basalt. The rise in temperature leads to the generation of micro-cracks, as reflected in the declining mechanical properties of the basalt. Temperature and water saturation were found to have less influence on the fracturing stages, with the fracturing patterns remaining largely consistent despite increased thermal damage. Additionally, temperature rise increased shear cracks, ultimately leading to brittle failure. These findings provide valuable data on basalt behavior in deep geothermal environments, where thermal and water effects are crucial for energy extraction.