A first reservoir assessment was performed in the Greater Geneva Basin to develop geothermal resources of low to medium enthalpy (GEothermie 2020 program). A review of the entire basin sedimentary sequence ranging from Permo-Carboniferous to Lower Cretaceous units was first carried out, using data from wells and outcrops. Five promising units were identified and investigated, considering stratigraphic, sedimentological and petrophysical issues. The distribution and geometry of potential reservoir bodies were addressed through the identification of facies and lateral variations, integrated to previous regional studies. The Upper Jurassic Reef Complex unit was highlighted as the best reservoir in the area. Research focussed on this interval, aiming at characterizing its petrophysical properties, and providing new insights on their origin and distribution within this reservoir. A rock typing workflow was built, which aimed at defining petrophysical rock types and propagating reservoir properties vertically along the wells, and subsequently horizontally through the subsurface.