Methods for direct installation of ground heat exchangers in soft ground

In unconsolidated sediments, ground heat exchangers can be pressed or driven into the ground. Table 3 shows the most important techniques. The major advantages of direct pressing or ramming the heat exchanger in place are No problems with stability of borehole walls Good contact to the ground, no grouting required Complete installation in one single step For an economic configuration of ground heat exchangers, steel pipes can be driven radially from one point as shown in Fig. 7. In this...

Special problems for drilling in large dense BHEfields

In large BHE fields, several problems have to be dealt with. To allow completing of more than 100 BHE in a relatively short time, several drilling rigs have to be on site simultanuosly. The available space, the supply of water, BHE pipes and grout, and the disposal of drilling mud all have to be planned diligently in advance. Fig. 10 shows the drilling for the largest central BHE field in the world at Richard Stockton College in New Jersey, USA. Up to four drilling rigs were in use, and the...

Groundwater well drilling and completion

Groundwater wells are drilled by the drilling methods mentioned before. For large diameter wells, the reverse rotary method is well suited. While in normal rotary the fluid is pumped downwards inside the drill pipe and rises through the annulus, the sense of motion here is reversed. This allows for reliable removal of drill cuttings through the pipe and helps to keep the borehole wall stable. There are two basic ways for construction of a well Natural completion lost filter completion

Drilling for exploration purposes

The methods for drilling and data collection vary between countries, but are basically the same as those used for other exploration purposes, like in water well industry, foundation drilling and in the mining industry. The importance of geological exploration for shallow geothermal applications is discussed by Andersson et al. 1997 . Exploration boreholes for shallow geothermal purposes would in most cases be performed by conventional rotary drilling. During drilling, samples of the drilled...

Drilling for borehole heat exchangers

In table 1 possible drilling and installation methods for vertical ground heat exchangers are listed. As can be seen from that table, for the same rock or soil types often more than one suitable method exists. Beside the auger method, where the material from inside the borehole is brought to the surface mechanically, all methods listed use flushing of the borehole. Water or compressed air in DTH is used to remove the cuttings in a constant flow. Problems can arise when inserting the heat...

Introduction To Drilling Methods

Percussive Drilling Method

Drilling is a very old technique, for water supply and for exploitation of mineral resources. Water wells have been drilled in Egypt more than three millenia ago. Fig. 1 shows an example of a quite sophisticated, hand-operated drill rig used in China to drill several hundred meter deep in a few month. Fig. 1 Chinese percussion boring after Chugh, 1985 Fig. 1 Chinese percussion boring after Chugh, 1985 Today, a variety of mechanised drilling equipment is on the market and in use. The size range...

Basic drilling methods

Drilling Rig Bit Diagram

For shallow holes down to app. 100 m, not every drilling method is suitable. Hytti 1987 presents a diagram showing the optimal drilling methods in respect to hole diameter and rock strength Fig. 2 . Fig. 2 Applicable drilling methods revised after Hytti, 1987 Fig. 2 Applicable drilling methods revised after Hytti, 1987 Table 1 lists recommended drilling methods for the various ground conditions. Drilling rates of app. 10 m per hour are realistic when using rotary drilling with drag bits in soft...

Grouting of borehole heat exchangers

A good thermal contact between the pipes and the ground is paramount for the performance of the BHE. In Scandinavia, in hard, crystalline rock the borehole often is just filled with water. With increasing temperature e.g. for borehole heat storage , the water shows convection, and heat transport is increased, as measured during thermal response tests Gehlin amp Hellstr m, 2000 . In most other cases, and in particular if water authorities demand plugging the hole for groundwater protection, the...