BMBF Project (drilling)

This research scheme focuses the development of a new technology for the advanced and competetive installation of geothermal probes.

Today the way geothermal probes are sunk is still identical with the traditional well sinking. Due to this a corresponding effort is put into the drilling technology and in the building site equipment. This starts with the transport of the equipment wherefore usally two lorries are required. One lorry carries the drilling-rigg and the other vehicle the rotarty system or the corresponding tubing including lading euqipment. To complete the site container to accomodate the flushing liquid and the drilling waste material are needed.

As the close-to-surface geothermal energy usually is developed with 2-4 probes per appartment, a significant effort concerning change-over times for equipment for hole to hole occurs when larger projects are conducted. Furthermore a comparable large space is needed to accomodate all the technical equipment on site. The used apparats cause considerable environmental damages.

Due to these reasons the traditional procedure hardly is apllicable for projects conducted in existing objects, e.g. when a heating system is replaced.

Moreover it seems that due to the comprehensive equipment and despite the tensed market situatuion a low of drilling costs is reached.

This research scheme aims at the development of a new technology for the installation of geothermal probes. With the help of this new technology medium deep probes of 30 - 50 m are thought to be sunk considerably faster and particulary more competitive.

The Direct-Push-Technology (DP) developed in the USA seems to deliver a valuable basic system. Drilling and probing equipment is sunk with heavy, vehicle attached hydraulic precussion hammer into the ground. Traditional disadvantages of the convential large-scale drilling equipment are avoided, as this process is faster, more flexible and comprises less space. However, compared to the large-scale equipment the Direct-Push system embody the disadvantage of lower power and force, as the plant is lighter. But this disadvantage can be mitigated by the application of high pressure injection technology in the range of 350 bar.

A synergetic combination of the Direct-Push and the high pressure injection technology leads in the scope of this research project to a new drilling technology.

The Direct-Push tubing is provided with a high pressure flushing head. This should foster the dynamical advance and serve as the carrier of the geothermal probe's head.

Due to the supporting flushing with water the  jacket friction is decreased which increases the achievable depths and speeds a probe can be sunk with.

As the water demand of this technology strongly depends on the properties of the soil it is applied in, a further research objective of this scheme is the development of a water flow control unit. To achieve this the projected Direct-Push probe is provided with a geophysical online logging device (geoelectrical dipol / dipol). This device gathers the required data during the drilling process and controls the water volume flow according to the geophysical parameters.

The technological objectives of this research scheme can be summarised as follows:

• faster and more flexible procedures,

• avoidance of tubing and suspension in the drilling process,

• space-efficient probe installation,

• installation and plugging in one single operation,

• DP-Vehicle and equipment can be used withouth any technical changes for in-situ measurements of geophysical parameters.

The technological objectives are realised acompanied by the economic objectives of a sustainable decrease in geothermal probe costs:

• good term engine investment,

• faster drilling procedures,

• decreased change-over times (especially when large-scale with various probe fields are developed).