| Abstract |
The cost of geothermal well construction, especially in areas of low enthalpy, is very often prohibitive to obtaining investors and launching projects. Between 50 and 70 percent of project investments are related to drilling and completing typically two wells. The motivation to reduce drilling expenditure is high. Within a large-scale conceptual and technical investigation, detailed reference case calculations revealed the potential of cost savings for geothermal borehole construction in specific formations of Northern and Southern Germany, which are the most promising geothermal areas in the country. In South Germany, where Germany has a major hydro-thermal reservoir, the Molasse Basin, cost savings of up to 15%, equivalent to about 2 M EUR per well, can be achieved by applying the monobore casing construction approach. An additional 10% cost savings can be achieved by applying automated closed-loop drilling and reaming systems, which enable an increase of the effective rate of well completion. A third cost-saving potential is based on the strict application of automated wellbore integrity and tool health performance concepts, leading to another saving of 5%. Therefore, a savings of up to 30% of the wellbore construction cost can be realized. The usability of the mono-diameter well design depends upon certain geological conditions. Certain overpressure regimes, for example, limit the application of this alternative casing concept. In addition to direct cost savings, the mono-diameter design delivers a larger final diameter and enables starting with a smaller surface casing than the standard telescopic well. |