Detailed descriptions of the lower-middle Triassic and Permian formations using cores and gamma-rays from the EPS-1 exploration geothermal borehole (Soultz-sous-Forêts, Upper Rhine Graben, France)

Abstract

The Upper Rhine Graben (URG), located in eastern France, is an attractive region for the development of new renewable energy projects, such as deep geothermal energy. Over the last few decades, many projects have taken place in the French part of the URG, including electricity production and/or industrial heating at Soultz-sous-Forêts, Rittershoffen, Illkirch-Graffenstaden and Vendenheim (the latter two being underway). The first Enhanced Geothermal System (EGS) pilot project in the world, located in Soultzsous-Forêts (northwest URG), was drilled in the 1990s. Between 1990 and 1991, for detailed geothermal exploration research, an abandoned petroleum well (called no 4589; reaching the Lettenkohle, 830 m deep) was core-deepened from 930 to 2227 m (the first

Petrophysical properties of the Muschelkalk from the Soultz-sous-Forêts geothermal site (France), an important lithostratigraphic unit for geothermal exploitation in the Upper Rhine Graben

“…The Muschelkalk lithostratigraphic unit is the middle part of the Triassic sedimentary sequence encountered in the Upper Rhine Graben. The Muschelkalk is characterised by marine-to-lagoonal environment deposits (limestones and dolomites) that are rich in marine fauna (e.g., Ménillet 2015;Aichholzer et al 2016Aichholzer et al , 2019. The Muschelkalk is divided, from the top to the base, into three members corresponding to different depositional environments (Ménillet 2015;Aichholzer et al 2019).…”

“…The Muschelkalk is characterised by marine-to-lagoonal environment deposits (limestones and dolomites) that are rich in marine fauna (e.g., Ménillet 2015;Aichholzer et al 2016Aichholzer et al , 2019. The Muschelkalk is divided, from the top to the base, into three members corresponding to different depositional environments (Ménillet 2015;Aichholzer et al 2019). (1) The Upper Muschelkalk, which is characterised by massive limestone at its base and alternating marls and limestones at its top.…”

“…(3) The Lower Muschelkalk, which is characterised by shelly and sandy marls and marly clays. The Muschelkalk core at EPS-1 contains the following formations (see and Aichholzer et al (2019) for more detailed descriptions). (1) Marnes Bariolées (Middle Muschelkalk), which comprises red and grey silty clays and greenish dolomitic marls.…”

“…Indeed, more than fifteen geothermal wells have been drilled in the Upper Rhine Graben since the 1980s (Vidal and Genter 2018). The geology of the region consists of a fractured granitic basement (e.g., Ledésert et al 1993;Genter and Traineau 1996;Genter et al 1997;Hooijkaas et al 2006;Sausse et al 2006;Dezayes et al 2010;Genter et al 2010;Villeneuve et al 2018;Glaas et al 2018) overlain by a sequence of Permian and Triassic sedimentary rocks (Buntsandstein, Muschelkalk, and Keuper; e.g., Haffen et al 2013;Vidal et al 2015;Griffiths et al 2016;Aichholzer et al 2016Aichholzer et al , 2019Heap et al 2017;Kushnir et al 2018a, b;Heap et al 2018Heap et al , 2019Harlé et al 2019), Jurassic sedimentary rocks, and Tertiary to Quaternary graben fill (e.g., Berger et al 2005;Hinsken et al 2007Hinsken et al , 2011Aichholzer et al 2016; (Fig. 1c).…”

Heat flow density estimates in the Upper Rhine Graben using laboratory measurements of thermal conductivity on sedimentary rocks

“…1) project was the first Enhanced Geothermal System (EGS) developed in the world (Baria et al 1999;Genter et al 2010;Gérard et al 2006;Kappelmeyer 1991). The geology at the Soultz-sous-Forêts site is well known thanks to an old exploratory oil borehole, EPS-1, that was deepened for the needs of geothermal exploration and fully cored from 933 (middle Muschelkalk) to 2227 m (Paleozoic basement) (Aichholzer et al 2019;Dezayes et al 2005) e.g., in the zone where convection predominates (Genter and Traineau 1992). The Permian and Triassic sedimentary rocks of the Buntsandstein are described in Aichholzer et al (2016Aichholzer et al ( , 2019 and Vidal et al (2015) and physical properties of the EPS-1 cores studied by Géraud et al (2010), Griffiths et al (2016), Haffen (2012), Haffen et al (2013Haffen et al ( , 2017, Heap et al (2017Heap et al ( , 2018Heap et al ( , 2019, Kushnir et al (2018), Surma and Geraud (2003), Schellschmidt and Clauser (1996), Flores Marquez 1992 andSchulz (1992).…”