The 'Genesys Project': New Concepts for Geothermal Heat Extraction from Tight Sedimentary Reservoirs

Ralf Junker¹, Torsten Tischner², Stefan Wessling¹, Reiner Jatho², Peter Kehrer², Hans Sulzbacher¹, Knut Hofmeister², Hermann Evers², and Reinhard Jung^3
1Leibniz Institute for Applied Geosciences (GGA), Hannover, Germany
²Federal Institute for Geosciences and Natural Resources (BGR), Hannover, Germany
³Jung-Geotherm, Hannover, Germany

The Leibniz Institute for Applied Geosciences (GGA) and the Federal Institute for Geosciences and Natural Resources (BGR) are working together in the “GeneSys” project, which aims at the extraction of geothermal heat from tight sedimentary rocks of the Northern German Basin. A 3800 m deep well will be drilled in 2008 into mid-triassic sandstone formations to heat the GGA and BGR buildings from a 140 °C geothermal reservoir. The project’s innovation is to consider heat extraction through one single borehole, which requires appropriate concepts to ensure a high productivity.

The concepts have been tested at the drilling test site Horstberg Z1 near Hannover, which targets the same formations as scheduled for the Hannover site. The tight reservoir has been stimulated by massive water injection to create a large fracture. The fracture provides a large area for heat exchange between fluid and rock.

Two concepts have been proven as a promising way for geothermal heat extraction:

(1) Huff-Puff concept, based on weekly or yearly cycles of injection and production. Water is injected into the formation and stored in the fracture for heat-up. Afterwards hot water is extracted during working days or winter for heat production.

(2) Deep circulation - two strata: Two poorly permeable sandstone layers (Detfurth- and Solling-Sandstone) are connected via a hydraulic fracture. Water is injected into the upper sandstone and migrates through the fracture into the lower sandstone while it heats up. Production from the lower sandstone and re-injection into the upper strata establishes a persisting circulation.

In this contribution, we present the concepts and results obtained from in-situ hydraulic tests. Concluding from calibrated numerical simulations, we will show that the huff-puff concept can provide geothermal heat for some decades.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas