Enhancing permeability in deep, medium-temperature granitic geothermal systems via chelating agent stimulation

Chemical stimulation using a chelating agent solution is a promising technique for enhancing fracture permeability through selective mineral dissolution in geothermal reservoirs. However, its application to deep, medium-temperature granitic geothermal reservoirs (2–5 km, <200 °C) requires further investigation. This study comprehensively examined the characteristics and effectiveness of chemical stimulation on fractured granitoid core samples using an acidic solution containing the chelating agent N,N -bis(carboxymethyl)- L -glutamic acid (GLDA). Experiments were conducted under varying conditions of temperature (150 or 200 °C), stress (10 or 50 MPa), and fracture type (tensile or shear). The results demonstrated that rapid and substantial permeability enhancement—up to several dozen times within two hours—occurred due to the formation of voids through selective dissolution of Fe-bearing minerals. This effect was observed across all tested combinations of temperature, effective stress, and fracture type, indicating its potential applicability to deep, medium-temperature granitic geothermal reservoirs. • Chelating agents enhance permeability by selectively dissolving Fe-bearing minerals. • Effective permeability enhancement regardless of confining stress conditions. • Selective mineral dissolution controlled by pH in temperature range 150–200 °C • Chelating agents improve complex fracture connectivity by dissolving fragmented minerals.