The Integrated Geophysical Exploration Technologies for Deep Fractured Geothermal Systems project (I-GET) was aimed at developing an innovative strategy for geophysical exploration, particularly to exploit the full potential of seismic and electromagnetic exploration methods in detecting permeable zones and fluid bearing fractures.The proposed geothermal exploration approach was applied in selected European geothermal systems with different geological and thermodynamic reservoir characteristics: in Italy (high enthalpy reservoir in metamorphic rocks), in Iceland (high enthalpy reservoir in volcanic rocks) and in Germany and Poland (low to middle enthalpy reservoir in sedimentary rocks).The Groß Schönebeck in-situ geothermal laboratory, located 40 km north of Berlin in northeastern Germany, is a key site for testing the geothermal potential of deep sedimentary basins. The target reservoir is located in Lower Permian sandstones and volcanic strata, which host deep aquifers throughout the Northeast German Basin (NEGB). The laboratory consists of two 4.3-km-deep boreholes.The electrical conductivity of the subsurface is a very important parameter for characterizing geothermal systems as hot and mineralized (saline) fluids of deep aquifers can be imaged as regions of high electrical conductivity. In the first phase of the I-GET project, carried out in summer 2006, MT data was recorded at 55 stations along a 40-km long profile. In order to reduce the effect of the cultural noise, 4 remote reference stations located at distances of about 100 km from the profile were used. This profile is spatially coincident with a seismic tomography profile (Bauer et al., 2010). The main objective of the geophysical site characterization experiments was to derive combined electrical conductivity and P- and S-velocity tomographic models for a joint interpretation in high resolution.The data are provided in EMERALD format (Ritter et al., 2015). The folder structure and content is described in detail in Ritter et al., 2019. The project specific description is available in the associated data description file including information on the experimental setup and data collection, the instrumentation, recording configuration and data processing. Scientific outcomes of this project were published by Muñoz et al., (2010a, 2010b).
Objective: Aim: to determine the physical properties of the granitic basement in the soultz hdr borehole. General information: description: the core samples obtained from the granite section of the soultz gpk-1 borehole will be analysed to determine the properties of the granite such as strength and fracture toughness, thermal parameters, heat production (radiogenic content), and acoustic, electrical and magnetic properties. Achievements: The results of studies carried out on cores and cutting materials of three boreholes to a depth of 3.6 km are summarised. The physical property programme included measurements of density, ultrasonic velocities, seismic anisotropy, elasticity, fracture behaviour, electric and magnetic parameters, thermal properties including radioactive heat production, and radioactive age dating. Heat production in the Soultz granite is 2 to 3 times greater than that in other granites at the surface, although all surface granites in the vicinity show the same intrusion age. The physical property measurement programme has demonstrated that continuous measurements on cores and cuttings are essential for both operational drilling procedures and down hole condition assessment in crystalline rock formations. The European Geothermal Project involved teams from France and Germany who collaborated to test a site in the Upper Rhine Valley for its suitability for terrestrial heat mining (hot dry rock (HDR) energy production). Some British scientists participated in specific tasks. The site was chosen near Soulz-sous-Forets in Alsace at the location of the old oil field of Pechelbronn which was the first oil field exploited in Europe since the 18th century. It is situated on 1 of the summits of a very large thermic anomaly (200 km long and 20 km wide) where the mean geothermal gradient between the surface and 1500 m is known to be higher than 6.5 C/100 m. The programme began in July 1987 with a 2000 m deep borehole. Below at 1375 m thick sediment cover, the granitic basement was penetrated to a depth of 2000 m. The temperature at the bottom of the hole was 140 C. The geothermal gradient within the sediments was unusually high (10 C per 100 m) and diminished to a normal after a series of fractures inside the Buntsandstein producing some water at 116 C with a total salinity 98 g/l. At the depth of 1820 m, hydraulically active natural fissure was reached. The artesian outflow from this zone was 0.15 l/s, with well head pressure of 1.6 bars. The thermal water produced from the well had a high chloride contents and clearly had an identical origin with the fluid collected from the Buntsandstein just above the granite. During the water injection tests, a second active natural fissure was detected normally closed out but which seemed to aquire a noticeable permeability at a well head pressure of about 40 bars.