TY - JOUR
T1 - Novel chemical stimulation for geothermal reservoirs by chelating agent driven selective mineral dissolution in fractured rocks
AU - Watanabe, Noriaki
AU - Takahashi, Kaori
AU - Takahashi, Ryota
AU - Nakamura, Kengo
AU - Kumano, Yusuke
AU - Akaku, Kohei
AU - Tamagawa, Tetsuya
AU - Komai, Takeshi
N1 - Funding Information:
The present study was partially supported by the Japan Society for the Promotion of Science (JSPS) through Grants-in-Aid for Scientific Research (B) (No. 17H03504), Challenging Research (Exploratory) (No. 18K19039), and Challenging Research (Pioneering) (No. 21K18200). The present study was also supported by JSPS and the Deutsche Forschungsgemeinschaft (DFG) under the Joint Research Program (JRPs-LEAD with DFG) (No. JPJSJRP20181605). We would like to thank Dr. Shinichi Yamasaki at the Graduate School of Environmental Studies, Tohoku University, for assistance during the ICP-OES analyses, supported by JST/JICA SATREPS (No. JPMJSA1703).
Publisher Copyright:
© 2021, The Author(s).
PY - 2021/12
Y1 - 2021/12
N2 - Improving geothermal systems through hydraulic stimulation to create highly permeable fractured rocks can induce seismicity. Therefore, the technique must be applied at a moderate intensity; this has led to concerns of insufficient permeability enhancement. Adding chemical stimulation can mitigate these issues, but traditional methods using strong mineral acids have challenges in terms of achieving mineral dissolution over long distances and highly variable fluid chemistry. Here, we demonstrate a novel chemical stimulation method for improving the permeability of rock fractures using a chelating agent that substantially enhances the dissolution rate of specific minerals to create voids that are sustained under crustal stress without the challenges associated with the traditional methods. Applying this agent to fractured granite samples under confining stress at 200 °C in conjunction with 20 wt% aqueous solutions of sodium salts of environmentally friendly chelating agents (N-(2-hydroxyethyl)ethylenediamine-N, N′, N′-triacetic acid and N, N-bis(carboxymethyl)-l-glutamic acid) at pH 4 was assessed. A significant permeability enhancement of up to approximately sixfold was observed within 2 h, primarily due to the formation of voids based on the selective dissolution of biotite. These results demonstrate a new approach for chemical stimulation.
AB - Improving geothermal systems through hydraulic stimulation to create highly permeable fractured rocks can induce seismicity. Therefore, the technique must be applied at a moderate intensity; this has led to concerns of insufficient permeability enhancement. Adding chemical stimulation can mitigate these issues, but traditional methods using strong mineral acids have challenges in terms of achieving mineral dissolution over long distances and highly variable fluid chemistry. Here, we demonstrate a novel chemical stimulation method for improving the permeability of rock fractures using a chelating agent that substantially enhances the dissolution rate of specific minerals to create voids that are sustained under crustal stress without the challenges associated with the traditional methods. Applying this agent to fractured granite samples under confining stress at 200 °C in conjunction with 20 wt% aqueous solutions of sodium salts of environmentally friendly chelating agents (N-(2-hydroxyethyl)ethylenediamine-N, N′, N′-triacetic acid and N, N-bis(carboxymethyl)-l-glutamic acid) at pH 4 was assessed. A significant permeability enhancement of up to approximately sixfold was observed within 2 h, primarily due to the formation of voids based on the selective dissolution of biotite. These results demonstrate a new approach for chemical stimulation.
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U2 - 10.1038/s41598-021-99511-6
DO - 10.1038/s41598-021-99511-6
M3 - Article
C2 - 34620962
AN - SCOPUS:85116572142
VL - 11
JO - Scientific Reports
JF - Scientific Reports
SN - 2045-2322
IS - 1
M1 - 19994
ER -