The central aspect of the Energy 1 "Smart Solar Geothermal Energy Grid Ruhr (GeoSmaGriR)" foundation project is the storage of seasonal heat from district heating networks in the mine building of the former coal mining industry. The seasonal supply and removal of heat to and from underground storage facilities results in a cyclical thermal load on the reservoir rocks and fluids. This requires geoscientific characterization and thermo-hydro-mechanical modeling of the mine in order to enable reliable predictions of the long-term reservoir integrity in the context of seasonal heat storage. The aim of the SME project is to forecast the geomechanical behavior of the subsurface when heat is stored, on the basis of available geological investigations, stress field measurements and large-scale thermo-hydraulic subsurface models. The generic underground models for the Ruhr-Carboniferous are transferred to numerical simulations based on the finite and extended finite element method to take account of the geological complexity. On the one hand, the expected temperature and pore pressure field around the injection points are simulated in large-scale models; on the other hand, changes in the stresses due to the thermal expansion of the rock and the changed pore pressure are derived. This in turn can be used to localize surface displacements and potentially geomechanically critical areas in the rock mass, to derive the reactivation potential for existing faults, and to assess the probability of creating new fault zones.
In geothermal energy generation from deep reservoirs one needs to handle with fluids, which are mostly highly saline. These solutions get reinjected into the reservoir under new pressure and temperature conditions. The circulation of the thermal fluid in the reservoir is indispensable to ensure a sustainable, long-term operation at economically reasonable pressure conditions. In the course of this reinjection, it can precipitate minerals in the fracture, pore and crack network of the geothermal reservoir (reservoir scaling). With the reservoir scaling, the hydraulic and mechanical properties of the mountains change, so that the mountain permeability could be reduced significantly. Within the scope of this sub-project, models for describing the variable deformation behavior of discontinuity surfaces are developed based on the investigations of the network partners. The derived models are implemented in an existing software environment (roxol) and then used to describe the changing geomechanical behavior of the region near the drilling.
For the STIMTEC project, hydraulic stimulation methods will be optimized and further developed. Also, the hydromechanical processes that take place will be characterized. It is planned to investigate the emerging and spreading of hydraulic pathways under known boundary conditions in field tests. For this purpose, boreholes will be drilled in an underground research lab that will be used for controlled stimulation tests. Following the tests validation wells are planned to check the effects of the stimulations. The investigations are accompanied by hydraulic pumping tests, laboratory experiments, a high-resolution seismic monitoring and numerical modeling. By subsequently drilling into a stimulated area the clear proof of the acting hydromechanical processes and the associated seismic and hydraulic fingerprints is possible for the first time. STIMTEC is divided into five sub-projects with a total of seven work packages. After geological and structural-geological exploration several boreholes are drilled in a selected section of the mine. With pump tests the hydraulic initial parameters of the boreholes shall be determined. Furthermore, a monitoring network is set up to record seismic and acoustic signals during stimulation. After completion of the stimulation experiments, so-called validation wells are drilled, and additional pumping tests are carried out to contain acting hydromechanical processes and assign the corresponding diagnostic phenomena. The work is accompanied by laboratory experiments and numerical simulations. The possibility to investigate for the first time a rock package directly after the hydraulic stimulation let us expect a considerable gain of knowledge of stimulation processes on a field scale. The result is a concept for the optimized realization and monitoring of hydraulic stimulations.
The Horizon 2020 project S4CE aims at the development, testing and implementation of technologies to successful discover, quantify and reduce the risks related to geoenergy projects in the underground. The projects examined by the consortium are from the fields of geothermal energy, enhanced gas recovery, carbon sequestration and Promotion of unconventional hydrocarbons. In its work packages, geomecon examines the seismicity in the vicinity of the geothermal well in St.Gallen (Switzerland),which was either induced by a gas kick or a poroelastic stress transfer due to the injection.
The success of using geothermal energy according to the Hot Dry Rock (HDR) / Enhanced Geothermal System (EGS) approach is based on the safe drilling of the well and the successful creation of fluid pathways. The multiple fracture method is discussed as an innovative approach to create these fluid pathways. With the multiple fracture concept, two parallel boreholes (doublets) in the reservoir are connected by several hydraulically generated fractures; the heat-transfer fluid circulates through this system of boreholes and hydraulically connected cracks. Depending on the geological boundary conditions, it may be necessary to sink the boreholes in a distracted manner. While the feasibility of the individual technical components of such a geothermal exposure concept has already been shown, this process in the combination of the individual components has not yet been used for geothermal use in the North German Basin. The proposed collaborative research therefore aims to develop an overall geothermal concept based on the multi-crack method by systematically researching the target horizons of Westfal B / C in the North German Basin through laboratory tests (RUB) and to scale the findings obtained by the laboratory tests on in-situ conditions with numerical simulations (geomecon GmbH). The research work is intended to answer basic questions for the multi-crack process that arise in consideration of the geological and procedural boundary conditions for deep geothermal projects in the North German Basin. The findings should lead to a basic understanding of the system for geothermal applications of this stimulation technique in the North German Basin.
In NRW, carbonates are widely available at depths with temperatures sufficient for geothermal heat utilisation. The KarboEx project is dedicated to this. In contrast to the Bavarian Molasse, the carbonates in NRW have not yet been sufficiently explored. Exploration is basically a cost-intensive task, especially when large areas are involved. The proposed project is therefore initially based exclusively on the processing of existing data with this new objective. These are about 1,000 km of 2D seismic, 29 3D seismic measurements and 1,300 deep boreholes from hard coal exploration and findings from hard coal mining. Other existing data, e.g. from analogue surveys, are taken into account. The results of this research project can be used to estimate the geothermal potential of the carbonates of the Carboniferous and Devonian in NRW (at comparatively low cost compared to the usual costs of new exploration) and to control further exploration activities. The ultimate goal is to create the conditions for the construction of a larger number of heating plants at suitable locations (neighbourhood solutions) and the replacement of fossil heat sources such as coal or gas cogeneration with a renewable heat source.