Investigation of additional target horizons for the geothermal utilisation of the GeneSys GT 1 well in Hannover, and developing methods for the characterisation of geothermal reservoirs.
The main priority of the "Geothermal horizons" project is the practical investigation of single-well concepts for extracting geothermal heat from tight sedimentary rocks. The project follows up directly on the investigations already carried out at the Horstberg well and continues these during and after the drilling of the GeneSys GT1 geothermal well in Hannover, but is instead aimed at new horizons to exploit geothermal energy, and to develop new methods to characterise geothermal reservoirs. It provides the accompanying scientific research as part of the GeneSys Hannover demonstration project of the Federal Institute for Geosciences and Natural Resources (BGR).
The GeneSys GT1 well reached a total depth of 3901 m (Lower Bunter Sandstone) in November 2009 after drilling for 157 days. The in-situ production test was carried out during the drilling phase, and three 15-18 m long cores were cut, and 23 sidewall cores were taken from interesting sandstone horizons. Petrophysical analysis carried out on the cores reveals the characteristics of the formations (e.g. with respect to porosity and hydraulic permeability), and therefore an assessment of their suitability as potential target horizons.
In principle, the use of geothermal energy is linked to the presence of horizons with good hydraulic permeability underground. However, because these only represent a very small proportion of potentially exploitable horizons deep underground, it is planned to inject massive amounts of water into tight formations such as the Bunter Sandstone to create large artificial fractures within the rock mass. These act as heat exchangers. In addition, natural water migration paths are hydraulically connected to the well which enables the productivity of the well to be significantly boosted.
Comprehensive testing in the form of stimulation and development measures are planned this year to test the various concepts for geothermal exploitation.