Over the past fifteen years, Bavaria has become a hotspot for deep geothermal utilization in Europe. There are now 24 plants operating in the Molasse Basin that provide climate-friendly heat, electricity and cooling. For example, the state capital plans to cover its district heating supply in a climate-neutral manner and largely from deep geothermal energy by 2040. However, the use of deep geothermal energy is not limited to Munich.

The demand for space heating and hot water calculated in this study is just under 160 TWh. A total of 99 district heating demand areas in Bavaria were identified where district heating is a potential supply technology. These areas correspond to almost 50% of the total heat demand in Bavaria. According to the estimates, the deep geothermal potential in the Molasse Basin alone could supply 80% of the district heating demand (7655 MWth). To raise the enormous potential, theoretically about 500 doublets, i.e. production and injection wells, would be necessary.

The discovery of further geothermal wells, and thus the basic prerequisite for the economic success of deep geothermal energy, can be predicted comparatively well for the Molasse Basin. However, there are significant local differences in terms of predictability. Comparatively good well-finding forecasts are given in particular in Munich, south of Munich and in the eastern Molasse, where there is already a comparatively high number of successful wells today.

Geothermal energy is particularly strong in base load supply. The prerequisite for operating a deep geothermal plant economically is that the heat can be purchased in sufficient quantities via a district heating network. In many parts of the Molasse Basin, particularly favorable geothermal conditions exist, but these do not directly coincide with heat consumers on the surface. In these cases, there is the possibility of using interconnected pipelines to transport the heat to the consumers, thus optimally exploiting the potential. The construction of larger interconnectors increases the amount of geothermal energy extracted and consequently its share in the heat supply - the number of required plants is minimized. If fossil fuels are displaced from the heating network, large amounts of CO2 can be saved - about two million tons per year in the case of base load coverage by deep geothermal energy. The analyses show that the interconnection pipelines can also have a positive effect on the heat generation costs and increase the reliability of plants.

The implementation of a deep geothermal project involves high investment costs. These costs are further increased by the construction of larger interconnectors. However, for interconnection pipelines across municipalities to transport green district heating to neighboring municipalities and beyond, there are currently no equivalent funding mechanisms available as there are for on-site heat production. The technology will become economically attractive for municipalities or investors when the initial costs, especially for drilling, network expansion or interconnection pipelines, become lower and can be supported by society.

Delft geothermal project (DAPwell) is a planned geothermal well doublet, where relatively cold water is going to be injected through one well into a low enthalpy geothermal reservoir to produce hot water from the other well. The volume of the cold water around the injection well will increase over time and, in the end, result in a thermal breakthrough. Thus, it is essential to trace the time-lapse change in the volume of the cold water to monitor the DAPwell efficiently. The invaded reservoir volume by the cold water is associated with a decrease in the pore fluid temperature and salinity. This increases the electrical resistivity of the geothermal reservoir, where the cold front is located. Hence, estimating the time-lapse change in the electrical resistivity of the geothermal reservoir can be used to identify the distribution of the cold water. From a theoretical point of view, the controlled-source electromagnetic (CSEM) method can be used to get information about the change in the electrical resistivity within the geothermal reservoir. In this study, we investigate the feasibility of monitoring a geoelectric model of the DAPwell using land CSEM forward modelling. The optimal source frequency is also investigated as well as the optimal source-receiver offset.

A subsurface model of the DAPwell is illuminated by a horizontal electric dipole source, which emits a sinusoidal field with many frequencies. Based on the numerical experiments, surface measurements do not pick up sufficient time-lapse signal to use them for field applications. On the other hand, the difference in the z-component of the electric field, recorded in a borehole that crosses the reservoir, allows for a feasible detection of the electrical resistivity changes within the geothermal reservoir. However, it is not determined yet if the spatial distribution of the cold water can be adequately revealed from the electric field responses, or this needs to be done through CSEM inversion.