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Triassic geothermal clastic reservoirs in the
Upper Rhine Graben
Temperature at 1500m
Temperature at 5km
The goal of this study is to make a first
assessment of the Buntsandstein reservoirs (lower
Trias) at the Rhine Graben regional scale in
order to delimit the most favourable areas for
exploration and exploitation of the geothermal
resource.
gt In France, the main exploited low enthalpy
geothermal reservoirs lie within the Jurassic
fractured limestone formation of Dogger located
in the central part of Paris Basin, where 34
doublets have been heating 600 000 people for 30
years. The development of renewable energy
combined with the energy demand implies to search
other geothermal reservoirs either below the
Paris area or either in other promising areas in
the country.
gt In this framework, Ademe and BRGM co-funded the
CLASTIQ project (CLAyed SandSTones In Question),
in order to study the deep geothermal potential
of the Rhine Graben for heat production, or even
electricity if temperature conditions are high
enough.
Dogger
Trias
Structural map of the Upper Rhine Graben and
temperature distribution extrapolated at 1500m
depth (GGA Hannover database in Genter at al.,
2004).
Cross-section though the Paris basin
Promising geothermal area in France. Green area
with geothermal installations, orange promising
areas red high potential geothermal area.
gt The Rhine Graben is a Cenozoic graben belonging
to the west European rift system (Ziegler, 1990).
It is well-known because of numerous studies for
petroleum and mining exploration (boreholes,
geophysical surveys). Several major subsidence
phases related to the Rhine graben tectonics
generated variable sediment thicknesses.
gt The geothermal resource is located in
argillaceous and clastic formation of the lower
Triassic unit, namely the Buntsandstein
formation.
gt This study is based on old maps from Geothermal
Synthesis of the Upper Rhine Graben (Munck et
al., 1979) published by the Commission of
European Communities. We have digitalized and
georeferenced the characteristic maps of
Buntsandstein formation (top depth of the layer,
bottom depth of the layer and temperature at the
top). The digitalized data have been interpolated
by kriging in taking into account the presence
of faults.
Soultz
Rhine river
Baden-Baden
Core of Buntsandstein sandstones.
Depth of the top of the Buntsandstein from Munck
et al., 1979.
Schematic geological map.
Cross-section through the Rhine Graben.

• gtWe obtain 500m resollution grid map of
• The depth of the top of the Buntsandstein
• The thickness of the Buntsandstein
• The temperature at the top of the Buntsandstein.
• gtTo quantify the geothermal resource, we
  calculate the quantity of heat in the reservoir
  volume.
• gtHowever, only a part of this resource could be
  extracted. The recovery factor R quantifies the
  exploitable reserve.

Heat in place Q r . Cv . V . (Ti -
Tf) (Muffler Cataldi, 1978) Heat exploitable
Qexpl Q . R Recovery factor R RT . RG
Temperature factor RT (Ti Tinj) / (Ti
Tf) Geometric factor RG 0.33 for doublet in
aquifer (Lavigne, 1978)

• Results
• It appears that the north part of the Upper Rhine
  Graben constitutes a more favorable area than the
  south part. In the north part, the top of the
  Buntsandstein reservoir is located around
  2000-3000m depth with a temperature of about
  150C and its sandstone thickness is around
  500-600m. The exploitable geothermal potential is
  between 15 and 30 GJ/m2 (7 GJ/m2 for the
  exploited Dogger in the Paris Basin).
• This study confirms that the Buntsandstein
  formation in the Upper Rhine Graben has a good
  geothermal potential for heat or even electricity
  production.
• Some promising areas have been identified and
  some new geophysical acquisition such as 2D or 3D
  seismic profiles should be very helpful in
  providing relevant information about the
  reservoir structure.

r rock density (2200 kg/m3) Cv heat capacity
(710 J/Kg.K) V reservoir volume Ti initial
temperature of rock Tf final temperature of
rock (10C) Tinj injection temperature (25C)
Authors
References Genter A., Guillou-Frottier L.,
Breton J.P., Denis L., Dezayes Ch., Egal E.,
Feybesse J.L., Goyeneche O., Nicol N., Quesnel
F., Quinquis J.P., Roig J.Y., Schwartz S. (2004)
- Typologie des systèmes géothermiques HDR/HFR en
Europe. Rapport final. BRGM/RP-53452-FR, 165 p.,
75 fig., 10 tabl. Lavigne J. (1978) Les
resources géothermaiques françaises. Possibilités
de mise en valeur. Ann. Des Mines, April,
p.1-16. Muffler P. Cataldi R. (1978) Methods
for regional assessment of geothermal resources.
Geothermics, 7, p.53-89. Munck F., Walgenwitz
F., Maget P., Sauer K, Tietze R. (1979)
Synthèse géothermique du Fossé rhénan Supérieur.
Commission of the European Communities. BRGM
Service Géologique Régional dAlsace
Geologisches Landesamt Baden-Württemberg. Ziegler
P. (1992) European Cenozoic rift system.
Tectonophysics, 2008, p.91-111.
Dezayes Chrystel1, Genter Albert2, Tourlière
Bruno3 1BRGM Dpt Geothermal Energy, 2EEIG Heat
Mining, 3BRGM GEO
ENGINE Final Conference Vilnius, Lithuania
12-15 February 2008