Review – Exploratory Potential Methods in Geothermal Power Generation
Willi Freeden and Helga Nutz: Exploratory Potential Methods in Geothermal Power Generation. A Survey on Innovative Gravimetry and Magnetometry. 207 pp, Birkhäuser, 106,99 € (Book) or eBook 89,99 €, ISBN 978-3-031-54411-8 (Book), ISBN 978.3-031-54412-5 (eBook).
In most European countries and also in Germany, seismic methods have been used as the standard method for exploration. The development of gravimeters with higher measurement accuracy and, in geomathematics, mollifier evaluation methods have led to the fact that even weaker anomalies can be detected and thus the high costs of the seismic method are no longer incurred. Geothermal energy, which is important for the energy transition, can thus be tapped more effectively. The success of this exploration technique is based on the fact that, in practice, for the use of gravimetric and magnetometric measurement results, the geological structures to be determined can be clearly distinguished from the surrounding ones by differences in density, such as in the case of a salt dome or an ore deposit. Due to the significantly improved measurement accuracy and the application of the new geomathematical methods, it is possible to detect and model even weaker density differences. Its bridging function can be described as essential for this book: It spans the arc from geoengineering, geodesy, geophysics to geomathematics and geology and back.
The measurements carried out on the Earth’s surface must enable a downward continuation through the mathematical methods to be used, which creates an “ill posed problem” because data are not available in this area within the Earth’s body. To solve this inverse gravimetry problem, two methodologically different approaches are used. On the one hand, the Mollifier-Newton wavelet inversion, a discrete inversion method that creates a subsurface model from gravitational data, incorporating already known information about the exploration area, which is intended to reduce or overcome the imponderables caused by the mathematically determined situation of the “worse position” of the gravimetry problem. The Mollifier Newtonian wavelet functions with their spherical carriers in combination with a new “smoothing idea”. On the other hand, the Mollifier-Newton spline inversion, which is essentially a discrete nonlinear minimization problem and consists in the application of the Newton potential operator to the core function generated by the Newton core.
Geomathematics occupies a key position in this book, especially since the easily understandable presentation of the methods used form the core of the book. An insight into the current state of gravimetric multiscale research is provided and largely in the Saarland test area but also in the test area of the Bavarian Molasse Basin near Traunreut it has been proven that gravimetry and magnetometry can now be reduced to easily accessible and thus calculable decorrelation models and that it is possible to apply potential methods in exploration. This new exploration technique, which results from the combination of measurement and modelling techniques, is therefore the best ideally suited for the exploration of geothermal energy, as it has been shown that an improvement in the cost/risk ratio can be achieved if appropriate geomathematical solution methods are applied under the assumption of suitable data.
Bertold Witte, Institute of Geodesy and Geoinformation, University of Bonn
