Fig. 3

a 2D conceptual geology at Soultz [modified after Dezayes et al. (2005a, Fig. 28, 2005b) and after Aichholzer et al. (2016, Fig. 3)]. Trajectories of GPK1, EPS1, GPK2, GPK3 and GPK4 wells are shown with colored lines. b Temperature–depth profiles after drilling operations superimposed to the simplified reservoir model with four main geological units (Cuenot et al. 2008). Here, \( {e}_{1}\) , \( {e}_{2}\) , \( {e}_{3}\) and \( {e}_{4}\) correspond to the unit thicknesses, \( {e}_{1}\) is inverted from a back-analysis (Vallier et al. 2019) using: \( {e}_{2} = 1.4\,\text {km} - {e}_{1}\); \( {e}_{1} + {e}_{2} + {e}_{3} = 3.9\,\text {km}\); \( {e}_{1} +{e}_{2} +{e}_{3} +{e}_{4} = 5.4\,\text {km}\)