ZoDrEx aims to make deep geothermal (EGS) projects more robust and economical in the future. This project therefore serves as an example to demonstrate the complete chain of applications for petrothermal and geothermal systems, from drilling, to completion, to the production and utilization of electricity from geothermal energy. The project includes partners from Switzerland, France, Denmark, Spain, and Germany, among others. The primary application and research facilities for the project will be Fraunhofer IEG in Bochum, the Bedretto tunnel in Switzerland, and the Rittershoffen geothermal power plant near Strasbourg, France.
Subproject by Fraunhofer IEG in Bochum
Germany’s contribution to ZoDrEx focuses in particular on applying and implementing drilling processes such as flushing and mechanical stimulation processes in petrothermal systems. Fraunhofer IEG will focus on drilling small-calibre boreholes up to a maximum of 2 ½ inches (63 mm) in diameter, known as microholes, in very hard rocks such as granites and gneiss formations in the Bedretto tunnel from existing bores at limited running depth. These microholes will provide connections to the formation to secure geothermal production as an alternative to the current, controversial fracking methods, achieving an additional increase in efficiency when using packer systems. The microholes will be realized using pressurized water technology, with both high-pressure jetting and hydraulic micro-percussion/hammer systems. These systems can be initiated accordingly from an existing vertical or horizontal bore using coiled tubing technology. Many experiments and tests on this technique will be performed in advance at Fraunhofer IEG in Bochum in the test borehole on site, as well as in the iBOGS autoclave test station. One advantage of this is that the reservoir conditions can be configured, e.g. the pressure and temperature, which have a significant impact on drilling processes such as jetting. There are also plans to prepare a mobile, activatable sealing or packer-like system for a jetting drill head or hammer in order to carry out “stimulation while drilling” (SWD) operations in the future.