Geology

Geomorphology

Civil engineering

Biology

Geochemistry

Drilling

Basement

Geothermal exploration

Engineering

Genetics

Mechanical engineering

Sedimentary rock

Geothermal energy

Membrane

Graben

Geothermal gradient

Lithology

Geophysics

Structural basin

Permeability (electromagnetism)

Petrology

Geothermics

Since the 1980′s, more than 15 geothermal wells have been drilled in the Upper Rhine Graben (URG), representing more than 60 km of drill length. Although some early concepts were related to purely matrix-porosity reservoirs or Hot Dry Rock systems, most projects in the URG are currently exploiting the geothermal resources that are trapped in fracture networks at the base of the sedimentary cover and in the granitic basement. Lessons-learnt from the European EGS reference site at Soultz-sous-Forêts reveal highest natural permeability in the uppermost altered crystalline basement. Here, we present a compilation of related information to examine a more general validity of this hypothesis for the central URG. In this respect, 15 geothermal wells were analyzed concerning their lithologies, temperature distribution with depth, and their hydraulic yields. Among others, permeable fractures in Triassic sediments were observed among others during drilling operations at Soultz-sous-Forêts, Rittershoffen, Cronenbourg (Fr...

Overview of naturally permeable fractured reservoirs in the central and southern Upper Rhine Graben: Insights from geothermal wells