Coralie Aichholzer

Etudiante en thèse

PhD thesis

Subject

Stratigraphic, sedimentary and structural approach to characterize the cover-basement interface in the Rhine Graben. Application to deep geothermal energy.

Scientific field

Geology, stratigraphy, sedimentology, geothermal energy

Abstract

Since the French new pricing of geothermal energy in 2010, Alsace became the most dynamic French region regarding the realization of deep geothermal drillings at high temperatures. Several geothermal doublets are scheduled in the coming years in the Strasbourg area but also in both, northern (Outre Forêts) and southern Alsace. The achievement of the Rittershoffen’s geothermal doublet which ended in 2014, enabled the establishment of a 3 kilometers complete stratigraphic/geological section from Quaternary formations down to the top of the granitic Paleozoic basement. This geological approach was essential to the achievement of the Rittershoffen’s drillings, and will be even more for the future geothermal projects. According to the relative ignorance of the deep basin of Strasbourg, the establishment of such heat operating system requires geological knowledge, and those for several reasons:  

Firstly, it is essential to know the nature and thickness of the geological formations, both for the location of the drilling shoes and for the continuous inventory of the formations down to the granitic basement. A good compilation of the geological knowledge is one of the prerequisites for the drilling operations.

Secondly, these good knowledge of the top and base of each formations and their thickness is a particularly reliable and effective tool in determining the faults, important for fluid circulations.

Thirdly, having a coherent global view of the rocks and the formations constituting the hot water reservoir (geothermal reservoir) located in the transition “Trias-basement” are essential in the understanding of this reservoir.

Today a major new challenge appears with all the deep geothermal projects planned in the “Strasbourg Eurométropole” area (Illkirch, Eckbolsheim, Reichstett). But if most of the sedimentary cover (without faults) is relatively well known, there is still many unknowns for the Strasbourg area:

actual thickness and nature of Tertiary, which could be almost twice thicker and locally more detritic than in the well-known Rittershoffen’s drillings,

nature and intensity of fracturing in Lias, because its nature mainly clayey-marly makes it particularly difficult to define the limits of each formations,

nature and thickness of the transition “cover-basement” (granite/Permian/Triassic). Indeed, it remains poorly documented because of the great diversity of facies, both for the basement (the presence or absence of a granitic basement, or metamorphic whose nature has a direct impact on the exploitation of the heat reservoir) and for the sedimentary cover (existence or absence of the sedimentary series of the Permian and nature of these pre-Triassic formations). Moreover, nothing is known of the actual thickness of these formations, the Cronenbourg’s drilling being stopped in the intra-Permian units without any further details.

This thesis aims to study the stratigraphic column and focus on geological complexes of “cover-basement” transition and to estimate the characteristics and side extensions.

Supervisor

Philippe Duringer (Université de Strasbourg, CNRS)

Industrial supervisor

Albert Genter (ES-Géothermie)

Fundings

The thesis is co-financed as follows: half scholarship and one half from LabEx G-EAU-THERMIE (Strasbourg).

Beginning and end of the contract

October 2016 – September 2019

Scientific contributions

- Publications: 

  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2016) New stratigraphic interpretation of the Soultz-sous-Forêts thirty-year-old geothermal wells calibrated on the recent one from Rittershoffen (URG, France). Geothermal Energy Journal. 4:13 DOI : 10.1186/s40517-016-0055-7

- Extended Abstracts:

Oral presentation

  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2016) New stratigraphic interpretation of the Soultz-sous-Forêts geothermal wells based on Rittershoffen (URG, France). European Geothermal Congress, 19-24 September 2016, Strasbourg, France.
  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2015) New stratigraphic interpretation of the twenty-eight-year old GPK-1 geothermal well of Soultz-sous-Forêts (URG, France). 4th European Geothermal Workshop, 19-20 October 2015, University of Strasbourg, France.

- Abstracts:

Poster presentation

  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2017) The complete chrono-lithostratigraphic log of the geothermal well of Rittershoffen, Alsace (GRT-1): an example of cuttings and field analysis in order to establishe a very precise geological log. International Meeting of Sedimentology, 10-12 October 2017, Toulouse, France.
  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2017) How to establish a very precise chrono-lithostratigraphic log based on cuttings, core samples, gamma ray logs and analogues: application on the Soultz-sous-Forêts and the Rittershoffen geothermal wells (Rhine Graben, France). Mage FP-7, 4-6 October 2017, Akureyri, Iceland.
  • Aichholzer C., Duringer Ph., Orciani S., Genter A. (2017) Stratigraphic, sedimentary and structural approach to characterize the cover-basement interface in the Strasbourg area for new geothermal wells. European Geothermal PhD Days, 1-3 March 2017, Bochum, Germany. 
  • Vidal J., Genter A., Duringer Ph., Aichholzer C., Schmittbuhl J. (2014). Permeable fractures in deep Triassic sediments of the Soultz geothermal wells (Alsace, France), Deep Geothermal Days, April 10 – 11 2014, Paris, France.

- Reports

  • Aichholzer C. (2015) Chronostratigraphic well-to-well correlation from the geothermal drilling data (Soultz-sous-Forêts/Rittershoffen). Master degree 2nd year Confidential report EOST-ESG, University of Strasbourg.
  • Aichholzer C., Wolff C., Duringer Ph. (2014) The Lower Triassic and the Permian sediments in the borehole EPS-1 (Soultz-Sous-Forêts), chronostratigraphic and photography of drill cores. Confidential report EOST-ESG.
  • Aichholzer C. (2014) Importance of logging methods in the recognition of the stratigraphic limits: application of the Rittershoffen geothermal wells. Master degree first year Confidential report EOST-ESG, University of Strasbourg.

Teaching experiences

2017/2018 :

  • Tectonic and rheology, L3 students, 36h
  • Staff member for tectonic and sedimentologic field courses in the French southern Alps, L3 students, 10 days

2016/2017 :

  • Introduction to geosciences, L1 students, 12h

  • Tectonic and rheology, L3 students, 18h

  • Staff member for tectonic and sedimentologic field courses in the French southern Alps, L3 students, 10 days

  • Staff member for geological and sedimentologic fieltrip in the Vosges (Alsace, France), L3 and M1 students, several days