Influence of Rotation Speed and Air Pressure on the Down the Hole Drilling Velocity for Borehole Heat Exchanger Installation

Abstract

The relation between rotation speed, air pressure and the velocity of air-rotary drilling using the down the hole method is determined in an empirical manner. For the study, velocity measurements are obtained for combinations of the aforementioned parameters during fieldwork for the installation of borehole heat exchangers near Lublin, Poland. The tests consider three drill bit diameters—110, 127 and 140 mm; three rotational speeds—20, 40 and 60 1/min; and three air pressures—16, 20 and 24 bar. The borehole heat exchangers need 100 m deep wells. The lithology consists mainly of loess and clays to 24 m, sand and carbonate rocks to 36 m, and marls and limestone to 100 m. It is found that the highest drilling velocity is achieved when the greatest pressure is applied, while the lowest drilling velocity is connected to the lowest pressure. However, the relation between rotation speed and drilling velocity is more complex, as drilling velocity seems to be more affected by depth. Therefore, lithology can be a major factor. The results may find direct use in drilling, and provide a basis for further studies on the optimization of drilling technology.

An Outlook of Drilling Technologies and Innovations: Present Status and Future Trends

“…Sliwa et al [31] conducted a study to improve the impact understanding of rotational speed, drill bit diameter, and air pressure on drilling velocity for the down-the-hole (DTH) drilling method, for a given lithology. The study approach was validated using well information from the Lubin Basin in Poland with such an enhanced solution aiding drilling efficiency and process for wellbore heat exchanger (BHE) installations for selected locations.…”

Investigation of Old Exploration Boreholes in the Lublin Basin with Regard to Potential Rotary-Percussion Drilling of Shale Gas Wells

“…In Poland, this method was used, e.g., in the drilling of a borehole near Lublin [46]. The drilling began with the use of a ∅140 mm drill bit at the hammer, a ∅168.3 mm bit at the casing pipes to 60 m of depth.…”

“…Figure 8. Geological profile and filtration schematics of the test borehole, which is common for every borehole under study[46].…”

Research on Fresh and Hardened Sealing Slurries with the Addition of Magnesium Regarding Thermal Conductivity for Energy Piles and Borehole Heat Exchangers

“…The heat from the rock mass by means of borehole heat exchangers [10][11][12][13][14][15] or energy piles [16][17][18][19][20]; -Hot Dry Rocks (HDR systems) [21][22][23][24] and Enhanced Geothermal System (EGS) [21,[24][25][26]; -Salt domes [27,28]; -Water from drainage, e.g., underground or opencast mines [29][30][31]; -Closed mines [27,32]; -Waters accompanying the multi-phase exploitation of hydrocarbons [33].…”

“…Borehole exchangers are made by placing an appropriate pipe structure (single U-tube, double U-tube, coaxial system) in boreholes specifically drilled for this purpose [14,41,54,55]. There are also analogous systems with three U-tubes [56].…”