Sektion 4.8: Geoenergie
Wir entwickeln die Nutzung der oberen Kruste für Geothermie und Speichersysteme. Dazu gehören Technologien, um den Untergrund im Rahmen einer nachhaltigen, umweltfreundlichen Energieversorgung zu nutzen. Wir konzentrieren uns auf neue Heiz- / Kühlkonzepte aus hydrothermalen und petrothermalen Wärmequellen sowie die Entwicklung von Optionen für die geologische Speicherung großer Mengen (TWh) von überschüssiger Wärme und Energieträger. Der Hauptzweck unserer Arbeit in der Sektion Geoenergie ist die Erforschung und Erschließung von tiefen Reservoiren für Energienutzung. Da wir uns diesen Themen umfassend und ganzheitlich nähern, verfügen die Forscher in unserer Abteilung über Hintergrundwissen in verschiedenen Disziplinen der Geowissenschaften und Ingenieurwissenschaften.
Providing solutions to discover targets for urban heating and subsurface storage space based on methods of rock (incl. geomechanics) and fluid physics , experiments under simulated in situ conditions, incl. seismic & electrical tomography (Lab) and their integration in field exploration to the temperature and hydraulic field of the Earth, lithology, and structures in collaboration with special geophysical competence groups. The characterization includes enlightening natural processes based on experimental studies of fluid-fluid-rock/mineral interactions (e.g. H2) where target material is involved.
Temperature Field of the Earth
Especially in geothermal exploration, the success rates of identifying new geothermal resources can be increased and the risk and development costs can be lowered through implementing pertinent data on heat sources dimensions and geometry as well as thermal rock properties into advanced conceptual models. Research focuses on both the thermal parameters at lithospheric scale and more specific also on those in the depth domain that can be explored by borehole drilling. Furthermore, we characterize the thermal field and thermal rock parameters at regional as well as local scale, the latter of which directly feed into the development of hydrothermal and petrothermal (EGS/HDR) energy projects. We use data from borehole and surface geophysical surveys, analyze chemical and physical rock properties and develop numerical, geology-assisted subsurface models down the base of the Earth crust by working at the interface of pure and applied geothermics. Our expertise has developed during work performed in different geodynamic settings in the world, e.g. in the North German Basin, the Erzgebirge and Luxembourg in Europe, the North American Midcontinent, the Andean subductionzone in Bolivia and Chile, the Arabian Shield in Israel and Jordan, as well as in India.
Based on their energy content, geothermal resources could be classified as high-enthalpy resources, medium-enthalpy resources, and low-enthalpy resources. While high-enthalpy resources are often located near plate boundaries and zones with active volcanism, low-enthalpy resources are preferentially found in older sedimentary basins of the continents. The success of geothermal exploitation concepts strongly depends on the heat transport processes involved (conduction, convection or hydraulic permeability). For the characterization and assessment of geothermal resources we combine geological, geophysical and geochemical methods and integrate their respective results in geological models. The integration is performed by interdisciplinary cross-scale interpretation resulting in consistent parameterized (scale-dependent) structural models. In this way, locations can be characterized reliably and risks for the development and operation of geothermal plants could be minimized.
The research topics we address result from sustainable use of geothermal energy, carbon dioxide sequestration, and the use of natural methane hydrate deposits. In addition to characterizing a rock’s actual state investigations on dynamic processes and time-dependent physical changes are conducted. All experiments are performed under controlled pressure and temperature conditions that represent possible in situ conditions during reservoir use. Our experimental methodology is continuously developed further to conduct experiments at progressively more extreme, e.g. supercritical, conditions. Linking reservoir exploration and exploitation of geological reservoirs our scientific results contribute to their sustainable use.
Workflows to develop targets for the energetic underground use, which includes methods of reservoir engineering, such as its stimulation und testing, thermal und hydraulic well logging, and innovative technologies of fibre optics such as DTS (temperature) and DAS (acoustics). Integration of data from actions in deep boreholes and laboratory process simulation using HTMC-modelling will lead to deliver safe man made treatments of the underground.
The competency cluster “Fluids” is involved in researching the chemical behavior and physical properties of geothermal fluids. The cluster is also responsible for online fluid and gas monitoring at the research platform Groß Schönebeck. The working group has an analytical-experimental orientation and possesses several laboratories, wherein measurements and experiments can be performed at in-situ reservoir conditions. Interdisciplinary work with other research groups at the ICGR is performed, for example, in the areas of corrosion and scaling, fluid-rock interactions and thermodynamic parameterdetermination for reservoir modeling. We research an assortment of topics in cooperation with several national and international project partners.
Reservoir-Engineering is essential for an appropriate development of geothermal resources. Optimum economic utilization of geothermal reservoirs requires analysis of the geological system together with adequate planning. These include chemical and petropysical reservoir characterization, reservoir stimulation and modelling as well as understanding of the processes and interaction of the borehole-reservoir system. The control of the amount of fluids produced, well path design, well placement, rate of injection and many other means help to optimize the heat recovery.The reservoir engineer estimates the heat in place, the thermal breakthrough time and optimize the reservoir performance by four major activities: observations, assumptions, calculations (analytical and numerical methods) and development decisions.The research wells drilled by GFZ at Groß Schönebeck make possible to access and circulate formation fluids in the horizons between 3,9 and 4,4 km at temperatures up to 150 °C. This downhole laboratory provides the opportunity to perform various borehole measurements and in situ experiments, to validate and improve model in use or develop new ones.
Competencies of this group comprise exploitation technologies demonstrated by operation of plants to recover geothermal heat and enable thermal storage, CO2 -, or H2-storage. Operation of research platforms (e.g. Groß Schönebeck, Berlin/Potsdam-projects) and the integration of geoenergy in energy supply systems and outreach of the results to the public are in the focus. Main task is monitoring of systems in operation to ensure wellbore integrity and safeness of the environment. Monitoring technologies based on integrative geophysical and geochemical multimethod systems strongly contribute to the validation of simulation of the operations.
We investigate the effects of natural and artificially induced flow processes within the subsurface. Innovative borehole measurement methods are developed and applied within field experiments. The integration with other geophysical and geochemical methods enables a quantitative registration of spatial and temporal changes of subsurface conditions and reservoir properties. We work on methods which are specially tuned to the requirements of new types of subsurface use, like new ways of extracting geothermal energy (e.g. enhanced geothermal systems, supercritical reservoirs), underground storage (e.g. carbon dioxide, thermal energy), or production of unconventional fossil fuels (e.g. gas hydrates). Moreover novel methods for monitoring of borehole integrity (e.g. cementation) are developed. The measured data enables to derive important information for the safe and efficient use of geological reservoirs.
Process and Plant Technologies
By accessing geothermal resources it is possible to use stored heat from the deep subsurface for direct heat provision, to transfer the heat to a higher or lower (“cold”) temperature level using appropriate techniques, or to convert it into electricity. For conversion into electricity, typically, power plant cycles applying the Clausius-Rankine or a modified Clausius-Rankine process are used. Although the use of geothermal heat for production or storage of energy is based on the same thermodynamic processes as in conventional energy engineering, most importantly, effects of geological conditions have to be considered and adjusted design algorithms as well as optimization strategies have to be developed. The competence cluster “Process and Plant Technologies” is concerned with investigations on energy and process technological aspects of subsurface use as part of a sustainable energy supply. Our research applies to the fields of energy and process engineering, materials selection as well as test and pilot plant engineering which also includes related economic and ecological aspects.