Understanding geothermal systems beneath Corbetti
Project lead: Dr Andy Nowacki
Project objectives
- Better understanding of the geothermal system beneath Corbetti
- Improved uncertainty estimates on elastic properties in a high-enthalpy system
Summary of the project
The Corbetti caldera in the Main Ethiopian Rift (MER) is planned to become the site of Ethiopia’s second and largest geothermal power plant, potentially producing > 1 GW of zero-carbon electricity. Like most ‘high-enthalpy’ geothermal sites, the source of heat is magma injected into the crust, and the heat is transported to the surface along fractures via water-rich fluids. When exploiting such a system, it is critically important to understand the distribution of heat sources and pathways, but there remain significant sources of uncertainty. Reducing uncertainty and quantifying risk in developing geothermal resources is likewise critical. In this project, you will use seismic data to help improve our understanding of the processes at play beneath Corbetti and better image its interior.
Together with your advisors, you will use existing seismic recordings of microearthquakes and make new measurements of surface wave velocities on a network of stations at the caldera. You will then invert these data using new probabilistic methods (Zhang et al., 2020) to reveal the velocity structure of Corbetti, which importantly will include error bounds. You will then integrate this new model with existing geochemical and geophysical models (e.g., Gíslason et al., 2015; Lloyd et al., 2018) to better understand the processes occurring at this volcano, and better constrain the source and pathways for heated fluids. Your work will also help understand other systems in the MER and the structure of volcanoes in general.
References:
- Gíslason, G., Eysteinsson, H., Björnsson, G., Harðardóttir, V., 2015. Results of Surface Exploration in the Corbetti Geothermal Area, Ethiopia, in: Proceedings, World Geothermal Congress, p. 10.
- Lloyd, R., Biggs, J., Wilks, M., Nowacki, A., Kendall, J.-M., Ayele, A., Lewi, E., Eysteinsson, H., 2018. Evidence for cross rift structural controls on deformation and seismicity at a continental rift caldera. Earth and Planetary Science Letters 487, 190–200. https://doi.org/10.1016/j.epsl.2018.01.037
- Zhang, X., Roy, C., Curtis, A., Nowacki, A., Baptie, B., 2020. Imaging the subsurface using induced seismicity and ambient noise: 3D Tomographic Monte Carlo joint inversion of earthquake body wave travel times and surface wave dispersion. Geophysical Journal International 222, 1639–1655. https://doi.org/10.1093/gji/ggaa230
Project outcomes
Better estimates of elastic parameters—and crucially their associated uncertainties—beneath Corbetti will allow us for the first time to objectively compare the geothermal reservoir as seen seismically with models obtained from other methods. Recent work developing a model for the reservoir highlighted the potential for an east–west fault structure to control fluid circulation and heat advection. Improved imaging will allow for a quantitative assessment on how best to produce power here in the future.