Decision support under uncertainty for geothermal applications: case selection and concept development

In order to meet climate goals and provide energy security, geothermal energy can play an important part in Belgium’s energy production portfolio. The current implementation of geothermal energy in Belgium is very limited, making accurate forecasts about the economic potential difficult. In the DESIGNATE project, tools and workflows are developed to investigate the potential of deep geothermal energy and geothermal applications in abandoned mines in Belgium, considering uncertainties at reservoir, technology and economic level. The goal of this project is to make forecasts about the role of these geothermal applications in the Belgian energy portfolio and provide support for strategic planning of subsurface activities by: explicitly considering uncertainties in modelling non-standard geothermal resources; creating tools for integrated forecasts under uncertainty; setting up a methodological framework for territorial LCAs considering surface and subsurface impacts; and analysing interferences and their consequences for geothermal energy deployment in Belgium. These workflows will be developed for and applied to five real and theoretical case studies throughout Belgium, in different geological settings. A first case is the Balmatt deep geothermal project, a deep geothermal research project led by VITO in Mol, of which two wells are operational as a doublet. To allow for a realistic economic assessment, this case takes the basic structure and development of the Balmatt project, but as if it would be a commercial doublet project at the same location and in the same Carboniferous strata. A second case is a deep doublet system in NW Turnhout, currently under development by the geothermal development company HITA. This project allows supplying heat to part of the city of Turnhout’s residential and tertiary sector’s buildings. A third case involves the application of a novel single-well technology for geothermal heat extraction To compensate for the unknowns of the new technology, a more uniform and predictable reservoir type was chosen for this application: the Cretaceous deposits in the Campine Basin. The fourth case will investigate a new deep geothermal doublet in the Mons Basin, the Deep Mons project. At Porte de Nimy, close to a hospital, two wells of about 2.5km depth are planned to reach the Carboniferous. A fifth and last case is the application of an open geothermal system in former coal mine galleries. Preliminary, the Péronnes-lez-Binche coal mines were selected, as the structural separation of the galleries in a shallower colder part and a deeper warmer part allows for several applications such as seasonal use of heat and cold. Because a portfolio of methods will be developed to analyse different aspects of these projects, a solid common base is needed across all methods. These “project concepts” start from a decision tree, listing the major decision steps for each case, such as seismic exploration, well drilling, and the potential use cases. Additionally, options for waiting and abandoning the project are also included. Other data such as duration and cost are tied to this framework. Figure 1 shows a flow chart of such a decision tree for the Balmatt case. Because of their flexibility and speed, analytical solutions will be developed from numerical models for simulating the reservoir behavior and predict the evolution of temperature and pressure. The project uses an innovative approach by stepping away from simple well designs and homogeneous reservoirs, and introducing uncertainty. These analytical models will provide direct input for a geological techno-economic assessment (G-TEA), a territorial life cycle assessment (LCA), and a new version of the PSS simulator. Project development is simulated considering the analytical reservoir models as resource, the technical and economic aspects of project development, heat transport, energy demand, environmental impact, energy market and the policy framework. Acknowledgements This research is carried out under the DESIGNATE project, which receives funding from the BELSPO BRAIN-be 2.0 research programme under contract nr B2/191/P1/DESIGNATE.

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