New Stratigraphic Interpretation Of The Twenty-Eight-Year Old GPK1 Geothermal Well Of Soultz-Sous-Forêts (Upper Rhine Graben, France)

Abstract

The upper rhine graben (Urg) Is characterized by a series of positive thermal anomalies.In northern alsace, the soultz-sous-forêts pilot project for power production (1987) Has been followed recently by an industrial project in rittershoffen for a geothermal application. Both sites have been explored by deep drilling operations aiming to exploit the heat extracted from a deep paleozoic basement covered by a sedimentary sequence. Deep wells reached the granite basement respectively at about 1400 mand 2150 mdepth. As the doublet of rittershoffen (Grt-1, fig. 1 and grt-2, fig.2) Has a very detailed and complete stratigraphic log without major faults and discontinuities (Duringer, 2014;Duringer et orcianI, 2015), it has been used as a geological baselinein order to reinterpret gpk-1borehole, poorly investigated in its sedimentary part. The main goal of this work is todetermine the accurate depth of top and base of each lithostratigraphic unit and to highlight their thicknessvariations between soultz and rittershoffen, located 6 km east (Aichholzer, 2015). Gamma ray logs were used for interpreting the lithostratigraphicunit correlations between those wells (Fig. 1).