Geosciences Rennes

Homepage: https://geosciences.univ-rennes.fr/en

Fractured sites are important for various applications in hydrogeology and subsurface engineering, such as groundwater protection, geothermal energy, or the long-term safety of nuclear waste repositories. Accordingly, the characterization of the hydraulic and structural properties of a fractured site is crucial. Among various other methods, this can be achieved by so-called hydraulic tomography tests.
This master project is dedicated to the inversion of hydraulic tomography experiments conducted at the Ploemeur field site (France). The Ploemeur site (SNO H+, IR OZCAR) is located on an aquifer in fractured crystalline bedrock. This surprisingly productive hard-rock aquifer has been exploited at a rate of 1.1 million m3 annually since 1991, to supply a town of 20,000 inhabitants with drinking water. The site has a very dense piezometric coverage, with some fifty boreholes from 30 to 150 m deep providing both focused experiments and long-term monitoring data. Multiple data, including measurements on core samples, surface geophysical measurements, well logs, and local flow measurements at various scales, are available for the Ploemeur site.
In this study, several hydraulically isolated intervals are utilized. They are located in various boreholes and at different depths. The intervals are isolated using packer systems and serve as pumping and/or monitoring intervals. Pumping in one of the intervals causes a potential response which can be recorded in the monitoring intervals. This procedure is repeated for all combinations of pumping and monitoring intervals. The inversion of the hydraulic tomography data is implemented by iteratively inserting new fractures, deleting existing fractures, or adjusting the properties of fractures, such as hydraulic conductivity or fracture length. This results in a set of fracture networks that match the measured data and the prior information available for the site [Ringel et al., 2022, https://doi.org/10.5194/hess-26-6443-2022, Römhild et al., 2024, https://doi.org/10.1029/2023WR036035].
In this Master project, the student will prepare first an overview of the hydraulic tomography tests conducted at the Ploemeur site (http://hplus.ore.fr/). Then, using the previously developed algorithm, the inversion of the hydraulic tomography data will be performed. Finally, the student will evaluate the obtained results by comparing them with other available models of the site [Klepikova et al., 2014, https://doi.org/10.1016/j.jhydrol.2014.03.018, Dorn et al., 2013, https://doi.org/10.1016/j.advwatres.2013.10.005]. All of these efforts will further advance our understanding of the groundwater flow processes in fractured media.

Skills/Qualifications:
- Experience with computer programming /scripting (Matlab, Python, R),
- Quantitative understanding of geological fluid flow,
- Experience with either reservoir modeling or hydrodynamic modeling is an advantage.

Supervisors: Lisa Maria Ringel, Maria Klepikova

Please send your CV and a letter of motivation to lisa-maria.ringel@univ-rennes.fr