Hydrogeology
A new injection testing method to characterize hydraulic properties of fractured reservoirs using shear-thinning fluids
This master project focuses on the development and implementation of a new injection test method using shear-thinning to infer hydraulic properties of fractured reservoirs. Specifically, the student will 1) examine how a shear-thinning fluid injected in the subsurface may select specific thresholds or fracture apertures depending on its rheological behavior through simple modelling exercises; 2) design a field experimental protocol to test the feasibility of the method; and 3) interpret the results and develop inverse model. The method will be tested on an experimental site (Mels or Grimsel, to be defined) with an exceptional logistical support. A first task will consist of designing and developing all technical concerns for the field experiment. The protocol will be first tested under laboratory conditions before deployment at the field site. Data acquired during the field experiment will be analyzed. Fracture geometries and preferential flow paths selected by the shear thinning fluid will be analyzed by coupling i) classical injection and tracer test results already available for the site, ii) shear-thinning fluid injections, and if available iii) geophysical monitoring. The student will receive a unique training in techniques used to characterize hydraulic properties of aquifers at the field scale. She/He will also be trained in modeling techniques used to simulate the flow of Newtonian and non-Newtonian fluids in fractures.
Supervisors: Dr. Clément Roques, Dr. Maria Klepikova, Dr. Reza Jalali
Base Flow Recession of Mountain Streams: Modelling aquifer recharge and groundwater-river exchange processes
The main objective of this master project is to identify the impact of vertical and horizontal aquifer compartmentalization on transient stream flow recession behaviors in mountain. The student will investigate, based on a numerical modeling approach, how these heterogeneities impact the groundwater flow partitioning at the watershed scale. She/He will then quantify and discuss the groundwater-river interaction processes associated to different scenarios of groundwater recharge: snow vs rain dominated recharge processes. The student will also analyze stream recession behaviors in the Alps. The objective is to identify the main factors controlling stream recessions based on previous modelling results. The student will receive a unique training in time series analysis techniques as well as in modeling techniques used to simulate groundwater flow at regional scale.
Supervisors: Dr. Clément Roques
Analysis of long-term pressure and tilt observations at the Grimsel underground research laboratory
The goal of this MSc project is to characterise the magnitude of different forcing factors (such as tidal forces, storage lake level changes, atmospheric pressure) together with its temporal variability in several pressure monitoring boreholes and tiltmeters at the Grimsel Test Site, and to develop quantitative understanding of the processes involved. For example, one has to characterise the responses to lake levels and specifically determine nature of any significant lag between lake level change and interval pressure and whether there is any influence from Räterichsboden (current belief is that dominant influence is from levels of the Grimselsee). Further, one has to model the tidal signal observed with tilt meters and pressure monitoring and other longer-term signals possibly related to surface temperature, or atmospheric pressure. Finally, a robust quantitative model has to be developed for selected datasets, which can then be used to remove the influence of these external forcing factors (lake levels and earth tides) and reveal the influences of other processes (e.g. small responses to testing).
Supervisors: Dr. Valentin Gischig, Dr. Florian Amann
New borehole testing method using granular polyacrylamide gel as temporary sealing material
Open or screened boreholes are often characterized by vertical convective flow along the fluid column resulting from free (buoyancy-driven) convection and/or from differences in hydraulic head between large scale flow paths that connect to the borehole [Berthold, 2010]. By neglecting vertical borehole flow, interpretation of borehole measurements collected in open boreholes may be inaccurate [e.g. Klepikova et al., 2011]. Until now, the range of options for investigation of hydraulic behavior of aquifers from boreholes has been limited to rigid, cumbersome packers, and inflatable sleeves.
Recently we have proposed a new temporary borehole sealing technique using soft grains of polyacrylamide gel as a sealing material (Figure 1). Possible applications of this new technology include convection suppression, chemical samping as well as hydraulic tomography studies. In this Master project, a new borehole testing methods using granular polyacrylamide gel as temporary sealing material will be developed by the student. The student will mainly focuse on active thermal tests where free convection often dominate flow and create thermal disequilibrium between the water in the borehole and the surrounding media. The new borehole sealing technology minimizing the effect of free convection within the well column is beneficial for active thermal tests.
Supervisors: Dr. Maria Klepikova, Dr. Clement Roques