Enhancing the exploitation of sedimentary basins for the energy transition: From hydrocarbon resources production to geothermal heat generation

International audienceAs part of the energy transition, the geothermal potential of the Earth need to be studied in order to cope with climate change. In this context, the Horizon 2020 program is funding the MEET project to investigate the development of Enhanced Geothermal Systems in different geological settings, including sedimentary basins and the conversion of oil wells for geothermal purposes. Within this European project, we are investigating a Triassic reservoir made of sandstones and dolomites in order to evaluate the co-production potential of geothermal and oil resources. Our study is intended to provide insights on the interrelations between rock physics properties and microstructures in a newly defined stratigraphic framework. The main objectives are focused on the geological controlling factors of the transport properties. The studied rocks were accumulated on the western part of the Paris Basin during the Upper Triassic. Eight wells were characterized, combining sedimentary logging of 470 meters of rock cores and analyses of well-log dataset (Gamma Ray, Photoelectric absorption factor, Neutron Porosity, Density, Sonic). Lithofacies were defined based on core description, together with facies associations definition and depositional environment interpretation. Furthermore, a sampling of 159 plugs was done, for performing petrophysical analysis. Rock physics measurements were acquired on those plugs in order to complete an existing petrophysical dataset of more than 700 samples (permeability, κ and porosity, Φ). Furthermore, a petrographic work was conducted, including 250 thin-sections observations using conventional microscopy and 32 thin sections using cathodoluminescence. Based on a systematic petrographic description, we show that the combination between sedimentary texture and diagenetic overprint may greatly impact the porous network of the studied rocks, conducting to the definition of 3 main rocks types displaying distinctive κ-Φ trends. Furthermore, using both sedimentary descriptions and well-log dataset, seven electrofacies corresponding to three main depositional environments were defined, namely alluvial fan deposiqts (conglomerates & sandstones), floodplain/lacustrine deposits (heterolytic clays) and dolomitic paleosols (dolomitization of siliciclastic deposits). Then, a high resolution correlation transect was designed using genetic stratigraphy principles, including seven main genetic sequences that show the spatial evolution of depositional environments. In addition, the integration of rock types within the correlation transect provides a high resolution definition of the reservoir compartmentalization. To go further, we want to build a 3D static geological model that will serve as a basis for the development of future numerical simulations of fluid flow and heat transfer at the scale of the reservoir