UPscaling and heat simulations for improving the efficiency of deep GEOthermal energy – UPGEO

To sum up, the main methods of UPGEO will be:
- Use well-logs, especially NMR, and cuttings/plugs for µCT scan to characterize facies, microstructure and petrophysic.
- Use of statistics to populate facies and stratigraphic geometries of carbonate and clastic reservoirs.
- Integrate data from outcrop analogues by drone photogrammetry acquisition into 3D reservoir models.
- Propose new concepts of reservoir connectivity, from geostatistical models, to increase reliability of flow simulations.
- Propose new equations for the upscaling (THM equations which include the quasi-static Biot equations) for flow simulation in non-fractured sands/sandstones and fractured carbonate reservoirs.
- Implement simulation codes integrating the upscaling in specific plug-ins on platform such as softwares Eclipse, PumaFlow, OpenGeoSys or DuMuX.
- Develop predictive models for flow simulation in carbonate and clastic geothermal sedimentary system.
- Propose an application of the new method to a specific installation to estimate the geological risk for deep geothermal exploration in the Paris Basin, and thus assist in decision-making for a municipality or agglomeration that wants to build a geothermal doublet.
- Provide innovative workflow for simulation applicable to other sedimentary basins.

Result 1: The combination of drone photogrammetry on the world-class outcrops of the Roda Sandstone (South Pyrenean Basin; Ypresian age, about 50 Ma), and a facies study with an almost unique dataset, has enabled to detail facies heterogeneities of a deltaic system influenced by fluvial and tidal flows. Field and laboratory work on the digital outcrop allowed the geometries of this complex system to be defined with a resolution rarely achieved for such a sedimentary geobody. The dimensions of the sand bars, their connectivity, their amalgamation rate and their depositional dynamics can thus be assessed from upstream to downstream of the reservoir system.

Result 2: The petrophysical characterisation of the geological environment made it possible to define the nuclear magnetic resonance (NMR) response of reservoir carbonate facies in the laboratory and to differentiate them from non-reservoir carbonate facies. These results will allow optimal use of the NMR sensor deployed during drilling operations, and to rapidly define the reservoir layers during the construction of future geothermal doublets.

Result 3: Sedimentary and diagenetic heterogeneities of the Middle Jurassic carbonate geothermal reservoir were identified at different scales: (1) at the micrometer scale with thin section and X-ray microtomography, (2) at the core scale (metric), (3) at the reservoir scale (hundred meters) and (4) at the regional scale (multi-kilometer). The heterogeneities are scaled to the finest possible XYZ grid of 50 m x 50 m x 3.5 m. The result is a static model of these properties where the most favourable areas form permeable lenses of about 4 m of thickness, 1600 m length and 1100 m width. The prediction of this heterogeneity of geological properties constitutes an important advance, which is an essential prerequisite for de-risking and for the future implementation of doublets.

Result 4: «A coupled system for flow and mechanical deformation in a porous medium«. We studied a poro-mechanical system, where the unknowns are the liquid pressure p and the mechanical deformation u. This problem was proposed by Andro Mikelic and Mary Wheeler. We prove error estimates between analytical and numerical solutions for a class of numerical schemes, called gradient discretization schemes.

Expected findings from this project will contribute to a better understanding of the deep geothermal systems in a large metropole (Paris). It will help us to refine our knowledge on flow simulation including heat evolution of groundwater. UPGEO will make it possible to optimize the implementation of new geothermal doublets and thus develop the use of network heating, which produces only small quantities of greenhouse gas emissions. UPGEO meets the challenges of the energy transition for green growth set by the law of 18 August 2015. The fundamental work performed in the UPGEO project should help to develop new methodologies to significantly reduce the cost of assessment of the geothermal potential around Paris for public authorities (commune, city agglomeration, Grand Paris metropole…), quantifying and reducing risks. Simulations will minimize the potential conflicts of use on the water resource (drink water versus heat or storage). The expertise acquired on sandstone and carbonate aquifers in Ile-de-France can be exported elsewhere in France and internationally (e.g., Bordeaux, Lille, Lyon, Geneva Basin, Baviera, Amsterdam…).

- Gao, Y., Hilhorst, D., Vu Do H. C., 2021. A Generalized Finite Volume Method for Density Driven Flows in Porous Media. Energies, 14 (19), 6151 doi.org/10.3390/en14196151

- Thomas, H., Brigaud, B., Blaise, T., Saint-Bezar, B., Zordan, E., Zeyen, H., Andrieu, S., Vincent, B., Chirol, H., Portier, E., Mouche, E., 2021. Contribution of drone photogrammetry to 3D outcrop modeling of facies, porosity, and permeability heterogeneities in carbonate reservoirs (Paris Basin, Middle Jurassic). Marine Petroleum Geology, 104772, doi.org/10.1016/j.marpetgeo.2020.104772

- van Duijn, C.J., Mikelic, A., Wick, T. 2020. Mathematical theory and simulations of thermoporoelasticity. Computer Methods in Applied Mechanics and Engineering, 366, 113048, doi.org/10.1016/j.cma.2020.113048.

Geothermal energy, namely the mobilization of the subsurface heat at very low, low or high temperatures, is one of the methods to achieve the energy transition. The energy-climate strategy plans to increase deep geothermal heat produced in Ile-de-France in 2030 by a 3.5 factor compared to 2015. The current average development rate will not allow this objective to be achieved, it would be necessary to reach a 6 to 10 times higher rate, so the new multiannual renewable geothermal energy programming is being revised downwards in France. Feedback on recent operations in Ile-de-France has raised technical and/or scientific locks to be removed for an efficient and sustainable operation of geothermal doublets, such as the high but unquantified risk of low water flow / thin thickness of reservoir (meter-scale), the risk of interference between geothermal systems in high density of well infrastructures or the risk of early thermal breakthrough. There is a real risk that an installation may not reach a geothermal resource with sufficient flow and temperature characteristics to ensure the cost-effectiveness of the project during its life time. This risk constitutes a real obstacle for the future development of geothermal energy in Ile-de-France. It is clearly established in the energy-climate strategy to work on innovation by proposing solutions that optimize and explore the development of new reservoirs. The optimization of the use of deep geothermal energy is a major challenge for the Région Ile-de-France, which has a population of nearly 12 million inhabitants and still growing. This optimization of geothermal production of aquifers requires (1) precise knowledge of the reservoir heterogeneity in terms of sedimentary geometries, porosity/permeability, reservoir connectivity and (2) reliable numerical simulations of flows and temperature evolution in the underground 30 years or even 100 years after production starts. The main objectives are to successfully perform the upscaling pore-scale laboratory measurements and kilometre-scale sedimentary connectivity of reservoir bodies in order to better predict the resource. The homogenization will give the equations valid at every point of the domain, for both fluid and solid constituents, and in the same time the effective coefficients such as porosities, permeabilities, mechanical deformation (Gassman’tensor and Biot’s coefficient) and effective heat dispersivity. Their determination from the geological data will be the main challenge of this project coupling geological and mathematical concepts.