How did the requirements of a drilling diameter of 150 mm come about in connection with a borehole heat exchanger? : Bohrdurchmesser eines Erdwärmesondenbauwerkes

Abstract

In summary, concerns about insufficient sealing of the geothermal probe bore with "small bore diameters" are unfounded. In other words, the drilling diameter has no influence on the quality of the annular space sealing of a borehole heat exchanger. And since the borehole is visited several times and the drill string rotates, the borehole is anyway larger than the bit diameter. In order to make geothermal probe bores deeper than 150 m marketable in Germany, the connection with the then used 40 mm double U probe (probe diameter about 110 mm) and an annular gap of 60 mm on all sides would have to be eliminated, so that deeper geothermal probe bores with a final depth of 150 mm could also be used large bore can be constructed with the drilling equipment customary in Germany.