Permeability reduction due to mineral dissolution/precipitation in fractured reservoirs is a major concern in geothermal reservoir operations. In order to investigate the evolution of fracture aperture/permeability caused by fluid-fracture surface interactions, a flow-through test was performed on a phyllite specimen retrieved from DB2 well (depth of 1.26 km) at the Blue Mountain geothermal field, Nevada, USA. Permeability evolution of the fractured phyllite specimen was investigated under different states-of-stress (confining pressure and differential pore pressure) at rock temperature of 130 °C and injected geothermal fluid temperature of 65 °C. Fracture aperture/permeability evolution was analyzed using hydraulic data recorded during the course of the experiment. Pre- and post-test X-ray Micro-CT imaging were performed to investigate the flow-induced changes in fracture aperture. Influent and effluent chemistry were analyzed using inductively-coupled plasma optical emission spectrometry (ICP-OES) to determine mineral dissolution during the test. Results indicated a decline in permeability of the specimen due to fracture closure caused by stress corrosion and geo-chemical interactions between the injected geothermal fluid and fracture surface. ICP-OES analyses of the effluent and image analyses indicated that the decrease in fracture aperture was driven by both mechanical and chemical processes.

Press the Back button in your browser, or search again.

Copyright 2019, Stanford Geothermal Program: Readers who download papers from this site should honor the copyright of the original authors and may not copy or distribute the work further without the permission of the original publisher.