The Rotliegend of the North German basin is the target of an interdisciplinary
investigation program to develop a technology for the generation of geothermal
electricity from low-enthalpy reservoirs in deep sediments. An in-situ downhole
laboratory was established in the 4,3 km deep well Groß Schönebeck with the purpose
of developing appropriate stimulation methods to increase permeability of deep
aquifers by enhancing or creating secondary porosity and flow paths. The research the
in situ laboratory is now concentrated to drill the second well into the EGS in the
low permeable Rotliegend formation.
The stepwise strategic approach is aimed to establish and improve the practical
experience to drill into deep sedimentary geothermal reservoirs and to recover data
• the reopening of an abandoned gas exploration well,
• tests and comprehensivestimulation experiments,
• drilling of an production well and stimulating that well,
• a circulation test of the system and
• the installation and operation of a demonstration power plant.
The drilling of the second well is ongoing and the design considered
• the deep static water table of the reservoir and the respective withdrawal during
• the option for an additional protecting casing in the top hole region (housing for
the submersible pump),
• the distance between the two wells of the doublet in the target horizon by using
the directional drilling techniques,
• a drilling mud concept, which enables a protecting penetration through the reservoir,
• the opportunities of increasing the inflow conditions by an inclined well and later
by implementation of multiple fracs, and
• the geological conditions known from the analysis of previous wells in the
vicinity of the Groß Schoenebeck site.
Spotlights of the 9 months lasting drilling operations will be given with the focus
on the specific conditions of the drilling rig, the applicability of available
drilling performance data with respect to a significant larger hole diameter, and the
encountered drilling difficulties ranging from circulation loss during cementation
via collapsing of casings within the Permian salt up to the occurrence of natural gas
indications during drilling the very last borehole section.
A summary of the lessons which had to be learned is given and some future research
tasks are addressed.