Geothermal resources of the North German Basin: exploration strategy, development examples and remaining opportunities in Mesozoic hydrothermal reservoirs

Abstract

The North German Basin yields enormous geothermal resources of more than 13 000 EJ (exajoule: 1 EJ = 1 × 1018 J) heat in place bound to Paleozoic petrothermal and Mesozoic hydrothermal reservoirs. So far, these resources are only exploited at a few localities. Thus, geothermal energy is considered an underutilized energy resource. Despite long-term experience in exploiting Rhaetian hydrothermal reservoirs, the exploration risk remains high, which is mainly related to high expectations on reservoir thickness and quality. Previous exploration campaigns have identified potential hydrothermal reservoirs in six Mesozoic reservoir complexes. But, as high-resolution subsurface maps are not available, the reliable prediction and targeting of reservoirs remains an unsolved problem.As such, an exploration strategy integrating methods of sedimentology, palaeontology, petrography and reservoir characterization was applied to a large database of cores and wireline logs. This contribution details the key results of the exploration of Upper Keuper and Middle Jurassic reservoir complexes, including high-resolution subsurface facies, sandstone thickness and reservoir quality maps. Sets of these maps enable the reliable prediction and targeting of individual hydrothermal reservoirs, and, thus, make a significant contribution to a lowered exploration risk.

Mesozoic resource potential in the Southern Permian Basin area: the geological key to exploiting remaining hydrocarbons whilst unlocking geothermal potential

“…Figure 6 shows an estimate of the geothermal district heating production and targets for various countries in the study area and, although not specific to the Mesozoic, gives an example of the gap to potential for this energy source. As suggested by Franz et al (2018), there is considerable potential for the use of geothermal energy in Germany, a statement which can also be extended to The Netherlands and Poland. The resources of, for example, Denmark and the UK are not yet fully defined.…”

“…Pilot projects, often with a combination of Triassic and Cretaceous targets, have been undertaken which have highlighted the importance of sound geological understanding, through facies and porosity prediction in achieving economic water production rates (e.g. Pluymaekers et al 2012;De Vaal 2017;Franz et al 2018;Vondrak et al 2018). For example, Figure 7a illustrates the growth of geothermal systems in The Netherlands (both in operational projects (2016, n = 12) and associated energy production).…”

“…Various projects have also been undertaken in NE Germany. For example, in Neubrandenburg, production has been achieved from Triassic Rhaetian sandstones (Wolfgramm et al 2009;Franz et al 2018), with further potential in the Middle Jurassic fluvial sandstone sequence Franz et al 2018). Various regional and local governmental organizations are supporting both further research into geothermal energy (with a number of technical and mapping tools now available: e.g.…”

Numerical and experimental simulation of fault reactivation and earthquake rupture applied to induced seismicity in the Groningen gas field

“…With the ongoing energy transition, broader use of the subsurface will include geothermal energy production (Stichting Platform Geothermie et al, 2018), aquifer thermal energy storage, as well as natural gas, CO2 and perhaps H2 storage in depleted reservoirs. Many low-temperature geothermal systems and storage projects in the Netherlands and Northwest and Central Europa target porous sandstone reservoir formations (Buijze, van Bijsterveldt et al, 2019;Evans et al, 2012;Franz et al, 2018;Vrijlandt et al, 2019). In the Netherlands these include (lateral equivalents of) the Slochteren sandstone in smaller depleted gas fields, as well as depleted Triassic (Bunter) reservoirs and Triassic and Jurassic/Cretaceous aquifers (Muntendam-Bos et al, 2008;Veldkamp et al, 2015;Vrijlandt et al, 2019;Willems, 2017).…”

New insights on subsurface energy resources in the Southern North Sea Basin area

“…Firstly, because of the risk that hydrocarbons could be encountered, and secondly as geothermal wells aim for the highest accessible temperature, downdip and graben settings are more obvious target locations for the production well. The newly available data from more deeply buried reservoirs in geothermal wells resulted in better understanding of reservoir distribution, for example of Upper Jurassic and Lower Cretaceous fluvial reservoirs in (palaeo-)graben settings (Franz et al 2018). Circulating vast volumes of formation water under changing conditions of temperature, pressure and composition owing to, for example, degassing, poses challenges for the prevention of scaling and corrosion of the installation.…”