Experimental investigation of deformation and failure of sandstone under different recharge rates

Geothermal energy is a stable and sustainable resource vital for global carbon goals. While its prolonged extraction from sandstone can cause land subsidence and other environmental risks. Existing research has focused on suspended particles in reinjected water, leaving the role of production pressure difference poorly understood. To address this, the impact of production pressure during tailwater recharge on sandstone reservoir integrity was examined. The reinjection process under various pressures was simulated through core flooding experiments employing Guantao Formation samples. Through these experiments, the influences of drawdown pressures on sand production, permeability, and rock damage could be monitored in real time. Results show that increasing the pressure differential from 0.3 to 0.6 MPa caused a significant 143.96% rise in the permeability growth rate. The observed phenomenon is primarily attributed to intensified fluid-rock interactions under higher pressure, which exacerbates formation damage and consequently leads to more substantial alterations in rock permeability. These results offer critical insights for geothermal production optimization, establishing a scientific foundation to mitigate reservoir damage and improve the long-term efficacy and safety of reinjection. By elucidating the previously overlooked role of production pressure, our findings contribute meaningfully to the sustainable development and environmental compatibility of geothermal energy systems.