Presentation Title
Experimental Study of Fracture Permeability Evolution in Phyllite Reservoir Rock Specimen from Blue Mountain Geothermal Field
Abstract
Permeability reduction due to fluid-fracture surface interactions is a major concern in a fractured such as geothermal reservoir. The evolution of fracture aperture/permeability caused by fluid-fracture surface interactions was investigated by conducting a flow-through test 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 at below, at, and above in-situ stress conditions 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.
Primary Faculty Mentor Name
Ehsan Ghazanfari
Status
Graduate
Student College
College of Engineering and Mathematical Sciences
Program/Major
Civil Engineering
Primary Research Category
Engineering & Physical Sciences
Experimental Study of Fracture Permeability Evolution in Phyllite Reservoir Rock Specimen from Blue Mountain Geothermal Field
Permeability reduction due to fluid-fracture surface interactions is a major concern in a fractured such as geothermal reservoir. The evolution of fracture aperture/permeability caused by fluid-fracture surface interactions was investigated by conducting a flow-through test 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 at below, at, and above in-situ stress conditions 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.