Technical Conditions

The pilot borehole VB has a 150 m long open hole section at bottom hole. The 3850 m long section above is cased. Casing and cementation reliably separate hydraulically the open hole section from the above section.

Technical specifications of the KTB-VB pilot borehole: 
(see also figure 5 )


total depth:                                    4000.1 m

currently accessible depth:               3970 m

cased hole section:                          0 - 3850 m

open hole section:                           3850 m - bottom hole

latitude:                                        49° 48.98' N

longitude:                                      12° 7.16' E

elevation above sea level:                 513.4 m

mud weight (rock fluid & water):         ≈ 1020 kg/m3

pressure at BH:                                ≈ 40 MPa

temperature at BH:                           120°C (248°F)

temperature gradient:                       ≈ 28 K/km

maximum hole inclination:                  11.5° at 1065 m

drilling time:                                    18-SEP-1987 - 04-APR-1989, 560 days

The main borehole, HB, offers unique opportunities to carry out technical operations and geoscientific experiments in-situ at ultra great depths and extreme temperature and pressure conditions. There is no open hole section in the HB accessible with sondes. Sondes can be run downto to a maximum of 6700 m. Below there is a lost sonde with logging cable, prohibiting any deeper sonde runs.

Technical specifications of the KTB-HB main borehole:
(see also figure 5 and figure 6)


total depth:                                    9101m

currently accessible depth:               6700 m

cased hole section:                          0 - 9031m

open hole section:                           9031m - bottom hole

latitude:                                         49° 48' 58.8" N

longitude:                                       12° 07' 19.2" E

elevation above sea level:                 513.8 m

mud weight (rock fluid & water):         ≈ 1020 kg/m3

pressure at BH:                                ≈ 91 MPa

maximum recorded temperature:         256°C (493°F) at 9070 m

calculated temperature at BH:            265°C (509°F)

temperature gradient:                       ≈ 28 K/km

maximum hole inclination:                  20° at 8647 m

drilling time:                                    06-OCT-1990 - 12-OCT-1994, 1468 days