Groundwater and heat flow simulations for groundwater and geothermal energy production

In the project JHPC28, we simulate the heat- and mass-transport in a highly resolved numerical model representing the subsurface beneath a city quarter of Geilenkirchen, a city in the Lower Rhine Embayment. This project is part of the “Water for Energy” Work package of the H2020 EU-project Energy oriented Center of Excellence for computing applications (EoCoE).

We developed a four-stage workflow from data acquisition to a feasibility study for borehole heat exchangers (BHEs) (Fig. 1), for assessing the geothermal potential in this area with associated uncertainty. Based on a detailed geological model, we estimated the spatial variance of hydraulic model parameters in the model by performing stochastic forward simulations. It turned out that thin lignite seams in the target area significantly impact temperature and hydraulic potential in the subsurface. Accordingly, the numerical model needed to resolve even thin geological layers, yielding a numerical grid consisting of > 8 million cells. The forward simulations yielded a prior ensemble of 500 equally likely realizations. After conditioning the prior ensemble with measured groundwater data, the resulting decreased ensemble (called posterior) is used for assessing the impact of uncertain groundwater flow on temperature in the subsurface (Fig. 2).

Simulation results of the posterior ensemble are used for evaluating the performance of potential direct-heat installations in the city quarter, which could substitute conventional heating systems using fossil fuels.

Figure 1: Conceptual workflow of the Project. Simulation time on the JARA HPC partition was used for performing stochastic simulations of heat- and mass transfer in the previously built geological model.

Figure 2: Average and uncertainty interval of temperatures along three monitoring boreholes in the simulation model