Maximizing permeability of fractured volcanic rocks through chelating-agent-assisted and pH-controlled selective mineral dissolution
Luis Salalá, Jonathan Argueta, Jiajie Wang, Noriaki Watanabe, Noriyoshi Tsuchiya
Abstract
Chemical stimulation of geothermal reservoirs through mineral dissolution using environmentally friendly chelating agents has been suggested as a new method to complement hydraulic stimulation. However, the permeability enhancement mechanism and optimal pH remain unexplored. In this study, we conducted flooding experiments on a fractured andesitic rock at 200 °C using 20 wt% N,N-bis(carboxymethyl)-L-glutamic acid (GLDA) solution, at pH 2–10. GLDA selectively dissolved Fe-bearing minerals (e.g., pyroxenes and magnetite) under acidic conditions and quartz in the groundmass under alkaline conditions, resulting in 9.1-fold and 98-fold permeability enhancements at pH 4 and 10, respectively. Therefore, the injection of a chelating agent with different pH values based on an investigation of rock mineralogy enhanced the permeability of volcanic rocks. These findings support the feasibility and effectiveness of chemical stimulation as a viable approach for widespread global utilization for enhancing geothermal systems.