MSc Students 2017-2018
Claudia Birrer
Fracture Surface Morphology and Transmissivity under Time-Dependent Hydraulic Fracturing
The geothermal power generation with Enhanced Geothermal Systems (EGS) requires hydraulic stimulation of the rock mass at 5 to 6 km depth into crystalline hard rock to achieve high reservoir permeability or transmissivity of at least 10-16 m2 and temperatures of ideally about 200oC (Amann et al. 2018). However, the goal of sufficiently enhancing permeability has not yet been obtained in a sustained way, using the conventional injection protocols, as induced seismicity always obstructs the EGS projects. In this MSc thesis, along with other two proposed MSc topics, an experimental hydraulic fracturing (HF) setup will be developed to conduct different injection protocols such as monotonic, progressive, cyclic (fatigue), and time-dependent (creep) for HF stimulation of granite cores from Grimsel Test Site. Then the produced fracture will be 3D scanned for surface roughness and it will be finally tested for transmissivity measurements. Some questions that can be addressed in this thesis are as follows:
1.) How do different injection protocols affect the surface morphology, aperture (mechanical and hydraulic) and transmissivity of the produced fracture?
2.) What’s the optimized injection protocol based on the Transmissivity of the produced fracture?
3.) How does effective normal stress change the transmissivity of the produced fracture?
4.) How does an offset in the roughness change the transmissivity of the produced fracture?
Supervisor(s): Dr. Omid Moradian
Joan Emile Justin Delort
David Jordan
Geological Characterization at the Bedretto Underground Laboratory (BUL)
This MSc thesis will be focused on three-dimensional geological modeling of the BUL experiment rock mass volume primarily from structural geological data collection and analysis. The structural geology interpretations will be supplemented with geophysical borehole investigations and mineralogical core analyses in the lab (thin sections). The main data set will be new boreholes drilled during the site characterization phase (planned for fall of 2018).
Supervisors: Prof. Simon Löw, Dr. Xiaodong Ma, Dr. Marian Hertrich
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Sibylle Lacroix
Factors Controlling Stream Flow Recession Worldwide
Glaciers, snowpack and groundwater are the main contributors to stream water during dry periods. Although the characterization of groundwater – surface water interaction is critically needed for water resource management purposes, the factors that control their dynamics at base flow remain poorly understood. The first aim of this master thesis is to perform river recession analysis in catchments worldwide and quantify how results deviate from theories. The results will be analyzed in a statistical framework in order to identify the main factors that might control transient recession behaviors.
Supervisors: Dr. Clément Roques
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Marija Lukovic
Identification and Numerical Simulation of Rock Fall Hazards in the Valley of the Kings (Luxor, Egypt)
The Valley of the Kings (Download Figure 1 (PNG, 3.3 MB)) is located near Luxor, in Egypt. It is set on the West Bank of the Nile River. As it is hidden from sight, this area was used as a burial place for royals and nobles during the New Kingdom (c. 1539–1075 BCE). There are over 60 tombs in the Valley of the Kings hidden around the rock cliffs.
The steep and partly overhanging rock cliffs in the Valley of the Kings are part of the Theban Limestone Formation (Figure 1). This formation is made up of five geological units (Dupuis et al., 2011), containing massive, bedded, and nodular limestones, and marls. The cliffs that surround the valley are part of the lowest unit 1. This unit lies above a weak, swellable shale, the so-called Esna Shale (e.g., Aubry et al., 2009).
The aim of this Master thesis is to map and investigate the slopes of this famous valley to assess potential rockfall hazards and to find out more about past rock falls and landslides. Fracture mapping will be carried out along the cliffs and used to create a rockfall hazards map. Areas prone to rock fall will be analyzed using numerical calculations. A three-dimensional topographic model of the Valley of the Kings will be created with laser scanner and/or photogrammetric methods and used in rock fall runout simulations.
References:
Aubry, M.-P., Berggren, W.A., Dupuis, C., Ghaly, H., Ward, D., King, C., Knox, R.O’B., Ouda, K., Youssef, M., Hassan, W.F., 2009. Pharaonic necrostratigraphy: a review of geological and archeological studies in the Theban Necropolis, Luxor, West Bank, Egypt. Terra Nova 21, 237-256.
Dupuis, C., Aubry, M.-P., King, C., Knox R.W.O’B., Berggren W.A., Youssef, M., Gallal, W.F., Roche, M., 2011. Genesis and geometry of tilted blocks in the Theban Hills, near Luxor, Upper Egypt. Journal of African Earth Sciences 61, 245-267.
Supervisors: Dr. Jordan Aaron and Dr. Martin Ziegler
Jasmin Maria Maissen
Environmental monitoring and analysis of a fractured rock cliff above KV42 (King's Valley, Egypt)
The King’s Valley is well known for archaeological research and it also has a multi-layered geological history visible on past rock slides, flood debris deposits, and various rock mass fractures, such as step, tectonic joints and faults, and younger joints . The valley’s limestone rock cliffs show several places that seem very prone to rock fall. An environmental and displacement monitoring system has been installed in April 2018 in the south-western part of the King’s valley, above tomb KV 42 at a noticeable fracture. An extensometer monitors the one-dimensional movement of the fracture. The measured environmental parameters are temperature, seismic vibration, precipitation, wind speed, humidity, and irradiation. The thesis seeks to analyse these data sets in detail in order to explore the failure mechanism, including local mapping, and find out if and how the fracture propagation behaviour correlates with environmental influences. A numerical model will be used to simulate different possible scenarios that could lead to failure.
Another focus will be on the assessment of the stability of selected pillared halls in deeper environments (few tens to few hundred of meters), where rock stresses are much higher than on the surface.
Supervisor: Dr. Martin Ziegler
Jerry Peprah Owusu
Observation of Fracture Complexity In Time Dependent Hydraulic Fracturing
The creation of large fracture networks by hydraulic fracturing (HF) is an essential task for permeability enhancement in the framework of Enhance Geothermal Systems (EGS) in the low permeability rocks. This is because fluid flow should occur within a large number of fractures that sweep a large surface area of the rock mass (Amann et al. 2018). The damaged zone around and ahead of the hydraulic fracture which is also called stimulated reservoir volume (SRV) is a result of microcracks that later connect and form macrocracks. The size and growth of the created SRV depend on many factors including the in situ stress gradient, natural fracture network and most importantly the fluid injection protocol.
In this MSc thesis, along with other two proposed MSc topics, an experimental HF setup will be developed to conduct different injection protocols such as monotonic, progressive, cyclic (fatigue), and time-dependent (creep) for HF stimulation of granite cores from Grimsel Test Site. Scanning electron microscopy (SEM), thin section microscopy, color tracers, and source locations of the acoustic Emissions will be used to analyze how the formation and growth of the SRV are affected by different injections protocols. Some of the questions that can be addressed are as follows.
1.) How do different injection protocols affect the size and the growth of the produced SRV?
2.) What is the optimized injection protocol based on the produced SRV?
3.) What is the difference between the geometry of the optical SRV (observed by SEM/thin sections and color tracers) and the acoustical SRV (observed by the cloud of the seismic events)?
4.) What’s the link between spatial and magnitude distribution of the seismic events and the optically observed microcracks in the SRV? How many of the optically observed microcracks are seismic and how many aseismic?
5.) What’s the relationship between cracking source mechanism (tensile, shear, …) and the geometry of the SRV?
6.) How is the spatial distribution of tensile and shear cracks in the SRV?
Supervisor: Dr. Omid Moradian
Enea Carlo Storni
Monitoring and analysis of landslide-glacier interactions (Great Aletsch Glacier, Switzerland)
McColl and Davies (2013) studied the displacement characteristics of landslides in New Zealand actively deforming into glacial ice. They conclude that glacier ice has a significant role in mediating the rate of rockslide movements and suggest a model for viscous flow at the ice-rock interface controlling the adjacent landslide displacements. While all past studies refer to empirical observations or simplified back-analyses of landslide velocities in deglaciating environments, monitoring data describing processes at ice-landslide interfaces are virtually non-existing. Monitoring programs designed to collect such data have the potential to unravel some of the controversial hypotheses of paraglacial rock slope failures and are a key topic for this proposal. This MSc project will collect displacement data at the interface between the Great Aletsch Glacier and the adjacent active Moosfluh landslide in order to address the following scientific questions:
Do the rapid Moosfluh landslide displacements cause modifications of the ice flow field in the area around the interface?
Does the viscous ice of the Great Aletsch Glacier has indeed an influence on the adjacent Moosfluh landslide displacement rates?
Supervisors: Prof. Simon Löw, Dr. Andrea Manconi, Marc Hugentobler
Nikola Toshkov
Moosfluh rock slope instability, which is situated at the left flank of the Great Aletsch Glacier Valley (Valais, Switzerland), right at the present-day glacial terminus, is one of the largest active landslides in the Alps. The failure involves around 2.5 million m3 of rock mass and in September 2016 underwent rapid accelerate reaching 50 meters displacement per year. This was mainly due to its transition from toppling to a secondary sliding mechanism.
It is widely accepted that retreating glaciers are one of the major factors influencing paraglacial slope instabilities in mountain regions. The deglaciation processes which includes glacial erosion, stress-release and debutressing of the slopes were previously investigated. They are well understood except debutressing which still prompts a controversial aspect of glacial effectiveness as a slope buttress. It is also not well established how the different slope instability mechanisms like toppling and sliding react to the ice retreat.
This master thesis work endeavour to investigate the controversy about the effectiveness of glaciers as a buttress to sliding and toppling slopes with different geometries. This will be achieved with the help of theoretical discontinuum numerical models by implementing three factors influencing the slope stability – namely ice behaviour, governing structures and geometry complexity. To do so two aspects of each factor will be simulated. The ice will be modelled as ductile (viscous) and brittle (elastic) material, the governing structures will be activated in order to present sliding and toppling mechanisms, and the topography will be changed from simple to more complex.
As a second stage of the numerical geomechanical study, a two-dimensional model of Moosfluh Landslide will be settled in UDEC. The model will aim to represent the real observed geomorphological landslide features and levels of activities. By doing so the goals will be to answer the following three questions - if the position of glacial can explain the crisis of 2016, could the structural model explain the unique landslide geomorphology and how low the strength of discontinuities must be to explain the observed displacements.
Supervisors: Dr. Jordan Aaron and Prof. Simon Löw
Oka Usi
Gilles Olivier Waleffe
Breakdown pressure and Rate/Magnitude of the associated Microseismicity in Time-Dependent Hydraulic Fracturing
Hydraulic fracturing (HF) is a process to create artificial fractures in a rock specimen or rock mass by high-pressure fluid injection and breaking the rock. It has become an essential technique in Enhanced Geothermal Systems (EGS) for geothermal reservoir creation (so-called hydraulic stimulation). However, in the past few years, induced seismicity has become an unavoidable side-product of HF and thus an obstacle to the widespread deployment of EGS technology. As an example, the HF stimulation of the EGS site in Basel, Switzerland, induced a seismic event with a moment magnitude of Mw 3.2 that finally shot down the project (Amann et al. 2018). Consequently, many research projects have been conducted to understand how to perform the HF stimulation in such a way that the induced seismic energy is not a significant problem to pause or terminate the operation.
In this MSc thesis, along with other two proposed MSc topics, an experimental HF setup will be developed to conduct different injection protocols such as monotonic, progressive, cyclic (fatigue), and time-dependent (creep) for HF stimulation of granite cores from Grimsel Test Site. The aim is to find the optimized injection protocol for keeping the breakdown pressure and associated induced seismicity below a hazardous level. Some questions that can be addressed in this thesis are as follows:
1.) How do different injection protocols affect the breakdown pressure and rate/magnitude of the induced seismicity?
2.) What is the optimized injection protocol that causes lower breakdown pressure and lower seismicity?
3.) Can we control the injection rate/pressure with the seismic data to come up with a damage-controlled stimulation?
4.) At which pressure level do micoseismic events start? Do we see “Kaiser Effect (absent in seismicity until the stress level of previous stimulations)” in the cyclic injections?
5.) How does seismicity rate/magnitude change prior to breakdown pressure? Can we predict the breakdown pressure by the seismic precursors?
Supervisor: Dr. Omid Moradian
Keyuan Yin
Dominik Marco Zangerl
Microstructural properties and mechanical behavior of fractures from self-sealed zones in the Opalinus Clay
The goal of this thesis will be to characterize the microstructure and fabric of fractures from well-studied excavation damaged zones (EDZs) of ages 10–20 years at the Mont Terri Underground Rock Laboratory (URL) in order to help identify self-sealing processes. EDZ fractures, natural faults, drilling induced fractures, and intact reference material from outside of the EDZ will be studied in detail. SEM imaging and image analysis will comprise the majority of this work. This data will later be connected to a a number of other laboratory analyses, including EDS (Energy Dispersive Spectroscopy) maps and petrophysical, geochemical, and bulk mineraological tests. There is also the possibility to conduct macro- and/or micro-indentation tests along fracture surfaces to investigate mechanical properties (e.g., stiffness, strength)..
This thesis will be completed within the framework of the SE-P project on self-sealing processes in old excavation damaged zones at the Mont Terri Underground Rock Laboratory. Funding for the SE-P project is through ENSI (Swiss Federal Nuclear Safety Inspectorate, Switzerland). Project partners include BGR (The Federal Institute for Geosciences and Natural Resources, Germany) and Swisstopo (Federal Office of Topography, Switzerland). This project will also involve collaborations with scientists in other groups at ETH Zurich (i.e., ScopeM and the ETH Zurich Clay Lab) and possibly other research institutes in Switzerland.
Supervisors: Dr. Martin Ziegler and Molly Williams