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Investigating anisotropic seismic velocity and permeability of the Bedretto granite and its intrusions
The proposed project offers field experience at the Bedretto Underground Rock Lab in collaboration with the Rock Physics and Mechanics Lab. The student will build their skills in the realm of structural geology and petrophysics.
The Bedretto Underground Rock Laboratory (URL) was established to assess questions related to the validation of stimulation procedures and sustainable utilization of geothermal energy. Several initiatives are in place to characterize the initial stress conditions, hydraulic properties, and mechanical properties of the Bedretto granite rock mass. This master’s thesis project would focus on the characterization of the seismic velocity and permeability anisotropy of the Bedretto granite and its intrusions. Specific attention would be given to core material recovered from the first drilling phase. The drill cores exhibit both isotropic and anisotropic highly laminated sections associated to shearing and faulting processes (Figure 1). In a similar study at the Grimsel Test Site, structures related to ductile shear zones and intrusions are shown to have significant impact on the anisotropic properties of the matrix rock mass (Wenning et al., 2018). These anisotropic properties will then control the hydraulic connectivity of the rock mass (Jalali et al., 2018), fracture mechanics related to hydraulic fracture propagation (Nejati et al., 2019), stress redistribution (Krietsch et al., 2019), and seismic reflectivity (e.g., Wenning et al., 2016).
References
- Jalali, M., Gischig, V., Doetsch, J., Näf, R., Krietsch, H., Klepikova, M., ... & Giardini, D. (2018). Transmissivity Changes and Microseismicity Induced by Small‐Scale Hydraulic Fracturing Tests in Crystalline Rock. Geophysical Research Letters, 45(5), 2265-2273.
- Krietsch, H., Gischig, V., Evans, K., Doetsch, J., Dutler, N. O., Valley, B., & Amann, F. (2019). Stress measurements for an in situ stimulation experiment in crystalline rock: integration of induced seismicity, stress relief and hydraulic methods. Rock Mechanics and Rock Engineering, 52(2), 517-542.
- Nejati, M., Aminzadeh, A., Saar, M. O., & Driesner, T. (2019). Modified semi-circular bend test to determine the fracture toughness of anisotropic rocks. Engineering Fracture Mechanics, 213, 153-171.
- Wenning, Q. C., Almqvist, B. S., Hedin, P., & Zappone, A. (2016). Seismic anisotropy in mid to lower orogenic crust: Insights from laboratory measurements of Vp and Vs in drill core from central Scandinavian Caledonides. Tectonophysics, 692, 14-28.
- Wenning, Q. C., Madonna, C., de Haller, A., & Burg, J. P. (2018). Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock. Solid Earth, 9(3), 683-698.
The Bedretto Underground Rock Laboratory (URL) was established to assess questions related to the validation of stimulation procedures and sustainable utilization of geothermal energy. Several initiatives are in place to characterize the initial stress conditions, hydraulic properties, and mechanical properties of the Bedretto granite rock mass. This master’s thesis project would focus on the characterization of the seismic velocity and permeability anisotropy of the Bedretto granite and its intrusions. Specific attention would be given to core material recovered from the first drilling phase. The drill cores exhibit both isotropic and anisotropic highly laminated sections associated to shearing and faulting processes (Figure 1). In a similar study at the Grimsel Test Site, structures related to ductile shear zones and intrusions are shown to have significant impact on the anisotropic properties of the matrix rock mass (Wenning et al., 2018). These anisotropic properties will then control the hydraulic connectivity of the rock mass (Jalali et al., 2018), fracture mechanics related to hydraulic fracture propagation (Nejati et al., 2019), stress redistribution (Krietsch et al., 2019), and seismic reflectivity (e.g., Wenning et al., 2016).
References - Jalali, M., Gischig, V., Doetsch, J., Näf, R., Krietsch, H., Klepikova, M., ... & Giardini, D. (2018). Transmissivity Changes and Microseismicity Induced by Small‐Scale Hydraulic Fracturing Tests in Crystalline Rock. Geophysical Research Letters, 45(5), 2265-2273. - Krietsch, H., Gischig, V., Evans, K., Doetsch, J., Dutler, N. O., Valley, B., & Amann, F. (2019). Stress measurements for an in situ stimulation experiment in crystalline rock: integration of induced seismicity, stress relief and hydraulic methods. Rock Mechanics and Rock Engineering, 52(2), 517-542. - Nejati, M., Aminzadeh, A., Saar, M. O., & Driesner, T. (2019). Modified semi-circular bend test to determine the fracture toughness of anisotropic rocks. Engineering Fracture Mechanics, 213, 153-171. - Wenning, Q. C., Almqvist, B. S., Hedin, P., & Zappone, A. (2016). Seismic anisotropy in mid to lower orogenic crust: Insights from laboratory measurements of Vp and Vs in drill core from central Scandinavian Caledonides. Tectonophysics, 692, 14-28. - Wenning, Q. C., Madonna, C., de Haller, A., & Burg, J. P. (2018). Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock. Solid Earth, 9(3), 683-698.
The master’s project would consist of establishing a testing protocol that would sample the representative rock types within the Bedretto URL. Once rock types are determined, the student would learn how to orient and subcore samples for anisotropic seismic velocity and permeability measurements. Seismic velocity and measurements would be performed within the Rock Physics and Mechanics Laboratory at ETH Zurich. The seismic velocity measurements would be made from 5 to 300 MPa to cover the range from the Bedretto URL conditions to pressures related to crustal seismology. Permeability measurements would be made from 1 to 15 MPa effective pressure, similar to the conditions in the Bedretto URL. Finally, the student would relate the measured properties to compositional and microstructural differences in the rock using thin-section analysis. The results would be contextualized in relation to hydraulic connectivity in the Bedretto URL, hydraulic fracture propagation, stresses, and seismic reflectivity.
The master’s project would consist of establishing a testing protocol that would sample the representative rock types within the Bedretto URL. Once rock types are determined, the student would learn how to orient and subcore samples for anisotropic seismic velocity and permeability measurements. Seismic velocity and measurements would be performed within the Rock Physics and Mechanics Laboratory at ETH Zurich. The seismic velocity measurements would be made from 5 to 300 MPa to cover the range from the Bedretto URL conditions to pressures related to crustal seismology. Permeability measurements would be made from 1 to 15 MPa effective pressure, similar to the conditions in the Bedretto URL. Finally, the student would relate the measured properties to compositional and microstructural differences in the rock using thin-section analysis. The results would be contextualized in relation to hydraulic connectivity in the Bedretto URL, hydraulic fracture propagation, stresses, and seismic reflectivity.
Quinn Wenning office NO E3, email: quinn.wenning@erdw.ethz.ch
Quinn Wenning office NO E3, email: quinn.wenning@erdw.ethz.ch