@article{5ef2d6134ae8492a86767a334ef7d1bd,
title = "Stabilizing and enhancing permeability for sustainable and profitable energy extraction from superhot geothermal environments",
abstract = "Superhot geothermal environments in granitic crusts of ca. 400–500 °C and depths of 2–4 km are recognized as a frontier of geothermal energy. In developing such environments, hydraulic fracturing is a promising way to create or recreate permeable fracture networks to effectively access the energy through enhanced geothermal systems (EGS). However, there is a concern about the possibility of stabilizing or enhancing the permeability created by hydraulic fracturing, required for sustainable and profitable energy production, because pressure solution of the fracture surfaces may reduce permeability. On the other hand, permeability may be enhanced by free-face dissolution of the fracture surfaces even if pressure solution occurs. However, the rates of permeability reduction and enhancement are not fully understood, and the possibility of stabilizing/enhancing permeability is therefore unclear. We have conducted hydrothermal flow-through experiments on 400 °C fractured granite samples to clarify the influences of stress level and plasticity of the fracture on the rate of permeability reduction by pressure solution and the influences of pore water pressure and corresponding mineral solubility on the rate of permeability enhancement by free-face dissolution. Results suggest that permeability may be either stabilized or enhanced in superhot EGS even when pressure solution can occur by keeping the difference between the concentration of the pore water and the solubility of quartz higher than the stress-dependent permeability stabilization criterion.",
keywords = "Enhanced geothermal system, Fracture, Free-face dissolution, Permeability, Pressure solution, Supercritical water",
author = "Noriaki Watanabe and Kohei Saito and Atsushi Okamoto and Kengo Nakamura and Takuya Ishibashi and Hanae Saishu and Takeshi Komai and Noriyoshi Tsuchiya",
note = "Funding Information: The present study was supported in part by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Specially Promoted Research (No. 25000009), Scientific Research (B) (No. 17H03504) and Challenging Research (Exploratory) (No. 18K19039). The authors would like to thank Dr. Shinichi Yamasaki at the Graduate School of Environmental Studies, Tohoku University for helping in using ICP-OES, supported by JST/JICA SATREPS (No. JPMJSA1703) and Dr. Norihiro Watanabe at the Renewable Energy Research Center, National Institute of Advanced Industrial Science and Technology (AIST) for his valuable suggestions in writing this paper. The authors also would like to thank Toei Scientific Industrial Co. Ltd. for manufacturing the experimental system. The data that support the findings of this study are available from the corresponding author upon reasonable request. Funding Information: The present study was supported in part by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Specially Promoted Research (No. 25000009 ), Scientific Research (B) (No. 17H03504 ) and Challenging Research (Exploratory) (No. 18K19039 ). The authors would like to thank Dr. Shinichi Yamasaki at the Graduate School of Environmental Studies, Tohoku University for helping in using ICP-OES, supported by JST/JICA SATREPS (No. JPMJSA1703) and Dr. Norihiro Watanabe at the Renewable Energy Research Center, National Institute of Advanced Industrial Science and Technology (AIST) for his valuable suggestions in writing this paper. The authors also would like to thank Toei Scientific Industrial Co., Ltd. for manufacturing the experimental system. The data that support the findings of this study are available from the corresponding author upon reasonable request. Publisher Copyright: {\textcopyright} 2019 Elsevier Ltd",
year = "2020",
month = feb,
day = "15",
doi = "10.1016/j.apenergy.2019.114306",
language = "English",
volume = "260",
journal = "Applied Energy",
issn = "0306-2619",
publisher = "Elsevier BV",
}