Glossary

…describes waters/thermal waters with high salinities.

…describes the exploitation of geothermal energy tapped in depths from at least 400 m by deep drillings. Especially hydrothermal and petro-thermal systems are pooled under the term deep- geothermics.

Geothermal exploitation is in both cases based in a cycle which consist of one well, conveying thermal water and where another well is returning the same volume of water back into the available reservoir.

Enhanced Geothermal Systems is a variant of petro-thermal geothermics. Subsurface water is found but its amount or the required rock permeability, essential for a sufficient water flow, is not adequate for geothermal exploitation. Stimulation activities artificially improve initial conditions for potential exploitation.

Within a designated exploration licence The Federal German Mining Law grants the exclusive right to prospect and explore natural resources to its holder. This right is initially temporary but it can be extended if there are no uniquely defined reasons contradicting the specifications of the Federal German Mining Law.

According to the definition of the Association of German Engineers (1998) “…the form of heat stored beneath the earth’s solid surface”.

In regard to the classification of geothermics in practice it is differentiated between the exploitation of deep and near-surface geothermics. This distinction is made by depth, exploitation potential and different techniques required for the particular generation of energy.

…or geothermal exploitation layers. Subsurface zones with sufficient amounts of thermal water appropriate for geothermal exploitation.

HDR-systems refer to dry rocks with the absence of natural water. To enable a subsurface circulation, necessary to sustain a cycle of injected water, hydraulic stimulations (hydraulic fracturing) produce artificial fractures within rock bodies.

For petro-thermal heat exploitation, fluids are injected in wells under high pressure to connect existing fractures, to bifurcate or to create new fractures within a particular exploitation zone.

Precondition of any heat exploitation in hydrothermal geothermics is water with sufficient flow rate and temperature. This water is found in pores of sedimentary rocks or it circulates in small fractures originated in geological processes.

Via a production well thermal water is conveyed to the surface and then fed into a geothermal plant converting thermal energy. An injection well brings the cooled water back into the heat reservoir.

Independent from the existing water volume petro-thermal systems take advantage of hot rocks acting as natural recuperators. According to the natural available water volume and in conjunction with the required flow volume additional water is pumped from the surface into the heat reservoir. Via a still existing or induced system of fractures and fissures the water flows to the production well which is being heated. After having flown through a plant on the surface the water is then returned into the rock body where it is re- heated.

In regard to the term petro-thermal systems it is distinguished between Enhanced Geothermal Systems (EGS) and Hot-Dry-Rock-Systems (HDR).

The prospection and exploration of natural resources comprises both the finding and specification of potential deposits. Precondition for the implementation of any prospection activities within a designated field is an exploration licence.

Abbreviated version of “The Act on Granting Priority to Renewable Energy Sources”

Within Renewable Energy Sources Act the Federal Government of Germany created an instrument to enhance the development of renewable power generation. It regulates both the preferential infeed and remuneration of power, generated by Renewable Energy Sources (RES).

The exploration of the subsurface for potential deposits by geophysical (measurement) methods.