Within the GeneSys-Project, the BGR (Federal Institute for Geoscience and Resources) and GGA-Institute (Leibnitz Institute for Applied Geoscience) aim at the extraction of deep geothermal energy (3500-4000m) from the tight sediments of the Northern German Basin. Therefore three new concepts for geothermal heat extraction using a single-well-concept have been developed, since drilling costs are a crucial point to the efficiency of geothermal plants.

All concepts have been developed for the use in low-permeable sediments, which are supposed to provide heat energy for small to medium-sized consumers in the order of 2MWth. 

-	Deep circulation concept: Via a hydraulic fracture a highly permeable geologic fault is connected to the well. Hot water can be withdrawn from the formation.

-	“Huff-Puff”-concept: A hydraulic fracture is created, which acts as a storage reservoir for injected cold water. The cold water heats-up and can be produced as necessary. The cycles of injection and production can be adapted to the needs of the consumer – e.g. injection during weekend and production during working days or injection in summer and production in winter.

-	Two-strata concept: A hydraulic fracture connects two strata of sandstones. Both strata are connected to the well. A tubing passing a packer gives access to the lower stratum while the upper stratum is linked via the annulus of the same well. Water is injected into the lower sandstone, heats-up while migrating through the fracture and is produced from the upper sandstone layer. A persisting circulation is established.

Key technology to all concepts is the water-frac-technique, which is used to create large fractures in the sedimentary rocks. The Huff-Puff and the Two-Strata concept have been successfully applied at the geothermal research well Horstberg Z1 in the Mittlere Buntsandstein formation. By the end of 2007 a 3800 m deep well will be drilled in the town of Hannover to supply office and laboratory buildings of the GEOZENRUM with geothermal heat by using single-well concepts.

Vilnius, Lithuania