German Continental Deep Drilling Program
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The continental deep drilling program of the Federal Republic of Germany ( KTB ) was a project carried out in the years 1987-1995 geoscience major research project. The then Federal Ministry for Research and Technology funded the project with 528 million DM ( 270 million euros ), project support was the Lower Saxony State Office for Soil Research. The hole of the main bore is with 9101 meters depth, the deepest in Germany and one of the world's deepest. The deep drilling program brought extensive and partially recognized hypotheses contradictory new insights into the Earth's crust. The successor of the program is the International Continental Scientific Drilling Program ( ICDP ).
From 1996 to 2001, the Research Centre for Geosciences Potsdam operation ( GFZ) in the system, a low observatory, which was responsible for the further scientific use of the two holes in the frame of ICDP. Since then, the land and buildings are owned by the GEO Foundation Center at the KTB, with the GEO center operates a public information and education center since 1998. Visitors can tour the still world's largest onshore drilling rig and to be notified of events and special exhibitions on current geoscientific and geotechnical issues. The scientific use of the two holes is also still possible.
Objectives of the continental deep drilling program
The aim of the continental deep drilling program, which included many individual scientific projects was mainly the exact exploration of the earth's crust. These had to be developed and tested, special drilling and surveillance technology. The KTB was the first German large-scale project of geoscientific basic research.
Planning
A hole was planned to a depth in which a temperature of 300 ° C prevails, since the electronic measuring devices (magnetic field, temperature, etc. ) would only work up to this temperature. At least should be 8000 meters deep and 250 ° C are reached. For the choice of location in the Upper Palatinate compared to a location in the Black Forest, which is considered equivalent from the perspective of potential geological knowledge acquisition to the end, was therefore crucial that the temperature limit was expected of 300 ° C here in about twelve kilometers deep, five kilometers deeper than in the Black Forest.
Geology
The selected location Windischeschenbach (near Weiden in der Oberpfalz) is the so-called zone of Heritage Village Vohenstrauß ( ZEV ). In the north of this tectonic unit ends at the heritage village line, on the west by the Franconian line and on the south by the Luhe- line. The heritage village and the Luhe- line emerged as a result of the formation of the Hercynian mountains, their hulls are digested in the German low mountain ranges, in the formation of Pangaea by the convergence of continents Laurasia and Gondwana. The heritage village line is the border between the two to the contact zone of the former continental plates belonging, running parallel to large floes Saxothuringian and Moldanubicum. The actually been drilled unit, the ZEV, consists of an alternation of metabasites and paragneisses, probably these units were deposited in a continental slope, the former belonging to Saxothuringian, Moldanubicum or Bohemikum is controversial. The earth's crust has because of their history here a highly structured design on, as well as several geophysical anomalies are detected, the at this point about eleven kilometers deep heritage village body with increased seismic reflectivity and velocity. Above are more strongly magnetized areas that were drilled in part, discovered in part by their action at a distance.
1987 feared inhabitants of the municipality Windisch Eschenbach, at the nearby drilling harmful gases could escape. After informing the scientists, the fear was unfounded, since only small amounts of hydrogen, methane and helium -3 have been released.
Drilling action
Between September 1987 and April 1989, a fully executed as core drilling pilot hole was drilled to 4,000 meters. The findings of the pilot hole determined the technical concept of the main bore. So also showed a significantly higher temperature gradient than expected. The starting September 8, 1990 the following in 200 m distance main bore should therefore achieve little in the 10,000 meters. Here a total of 35 isolated core samples the cuttings were taken only below 4,000 meters, but continuously investigated. To limit the friction of the drill string so that the planned depth could ever be reliably achieved, up to 7,500 meters, a self- controlling vertical drill was used, with the lateral deviation was limited to 12 meters. Because of the expected temperature-induced failure of the electronics had to be below this depth further drilled conventionally. The rock was from this depth in the brittle-ductile transition region, so that the well deformed by different in different directions horizontal stresses partially. The drill was repeatedly stuck. Several times he had to be rescheduled after stückweisem filling the drill hole. These operations took approximately one year to complete. Budget and related time constraints were finally decisive for the completion of the hole. The main bore of the continental deep drilling program was completed on 12 October 1994 after 1468 days at a depth of 9,101 meters, about 300 meters lateral deviation and a temperature of 265 ° C. Until 31 December 1994, the three planned large-scale experiments were carried out, and thus completed the main part of the deep drilling program. After the system has been partially taken out of service and other smaller experiments performed. The overall Programme ended on 31 December 1995.