| Abstract |
Over the last two decades, the development of geothermal energy has increased rapidly in the South German Molasse Basin (SGMB). By making use of one of the most promising geothermal reservoirs in Central Europe, more than 20 geothermal plants, providing both electrical power and heat to thousands of households, have been put on stream successfully, with many more to come. Along with the increasing interest in the geothermal potential, well design has evolved over the years. At present, wells can be drilled reliably and cost-effective to depths of about 5,000 m depth, delivering production rates of 50 - 160 l/s. However, suitable drilling locations in the South of Germany are scarce and very expensive, especially in Munich and the vicinity. Therefore, the geothermal energy output of each drilling location must be maximized. The well design and the exploration strategy must be adjusted to reach this goal. So far, the well design focused on minimizing cost and risk while providing a defined yield. “Keep it simple†was the guiding principle of many well designs. For future wells, maximizing the production per well site and minimizing the surface footprint will be the most important goal. To reach this, a range of measures is available, one of them being multilateral technology. Multilateral wells allow the exploitation of a reservoir through several wellbores (branches) originating from one motherbore. In utilizing this approach, the drainage area can be increased while reducing the inflow pressure losses for each well. In this paper, analytical methods and results from a numerical reservoir simulation are used to discuss the concept and its theoretical potential. In addition, the technical aspects of different multilateral technologies are assessed regarding the applicability for geothermal projects in terms of technical suitability, costs, risks, and regulatory requirements. The outcome of this study is the basis for the first multilateral geothermal test well in the South German Molasse Basin, which is drilled and tested during 2020 in Munich. |