Exploration risks of geothermal projects are high, as required economic production rates are often not achieved. Stimulation methods from the oil and gas industry, such as radial jet drilling (RJD), which can be used to cost-effectively create flow paths around a main borehole, are usually not applicable in geothermal applications due to especially hard reservoir formations. Because of that, a novel technology called micro-turbine drilling (MTD®) has been developed, which allows for the drilling of micro-sidetracks from cased boreholes even into very hard reservoir rock.
The approach is based on the principles of the RJD operation. However, instead of a jetting nozzle, a microdrilling turbine is used to drive a bit that mechanically drills rock.
This study presents the results of the proof of concept for MTD, which was conducted in the BedrettoLab in Switzerland at a depth of up to 1,053 ft (321 m) in granite rock.
This abstract is taken from paper SPE-218378-PA by N. Geissler, Fraunhofer-Einrichtung für Energieinfrastrukturen und Geothermie IEG and Fraunhofer-Chalmers Research Center for Industrial Mathematics; F. Garsche, Vitalii Samus, and Berker Polat, Fraunhofer-Einrichtung für Energieinfrastrukturen und Geothermie IEG; F. Di Mare, Ruhr-Universität Bochum; and R. Bracke, Fraunhofer-Einrichtung für Energieinfrastrukturen und Geothermie IEG. The paper has been peer reviewed and is available as Open Access in SPE Journal on OnePetro.