Beitrag
Deep geothermal resources of the North German Basin: The hydrothermal reservoirs of the Stuttgart Formation (Schilfsandstein, Upper Triassic)
Franz, Matthias; Nowak, Kerstin; Niegel, Sebastian; Seidel, Elisabeth; Wolf, Marco; Wolfgramm, Markus
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften Band 169 Heft 3 (2018), p. 353 - 387
127 Literaturangaben
veröffentlicht: Oct 31, 2018
Manuskript akzeptiert: Aug 24, 2018
finale Ms. Revision erhalten: Aug 21, 2018
Manuskript-Revision angefordert: Jul 13, 2018
Manuskript erhalten: May 23, 2018
ArtNo. ESP171016903005, Preis: 29.00 €
Abstract
Franz, M., Nowak, K., Niegel, S., Seidel, E., Wolf, M. & Wolfgramm, M. (2018): Deep geothermal resources of the North German Basin: The hydrothermal reservoirs of the Stuttgart Formation (Schilfsandstein, Upper Triassic). – Z. Dt. Ges. Geowiss. 169: 353–387, Stuttgart. The enormous geothermal resources of the North German Basin are bound to Palaeozoic petrothermal and Mesozoic hydrothermal reservoirs. Based on previous exploration campaigns, six Mesozoic reservoir complexes were identified among which the hydrothermal reservoirs of the Stuttgart Formation were underexplored so far. To evaluate the potential of these reservoirs, an interdisciplinary exploration strategy was applied to a large database of cores, wireline logs and seismic data. Repeated transgressions from Tethyan waters resulted in formation of inland seas covering large parts of the basin. Accordingly, the deposition of the Stuttgart Formation was primarily controlled by 3rd- and 4th-order T-R sequences; in particular the basinwards-directed progradation of the fluvio-deltaic Lower and Upper Schilfsandstein members are related to lowstands. Within both members, fine- to medium-grained sandstones of channel fills and levee/crevasse splay complexes form compound reservoirs representing the main target of geothermal exploration. For the Lower Schilfsandstein, this channel belt reservoir type is characterised by a median thickness of 23 m, median porosity of 22.7 % and median permeability of 443 mD. For the Upper Schilfsandstein, the channel belt reservoir type is characterised by a median thickness of 17 m, median porosity of 24 % and median permeability of 546 mD. The quality of these reservoirs is limited by the generally low compositional maturity of sandstones being lithic arkoses and feldspatic litharenites, the partly high content of detrital matrix within pores and substantial diagenetic cementation. The resulting high lateral variability of reservoir qualities contributes to considerable exploration risks. Despite this, reservoirs of high quality could be proven for individual localities where they may be considered an alternative option if the development of Upper Keuper or Middle Jurassic hydrothermal reservoirs fails.
Schlagworte
Triassic • Keuper • Stuttgart Formation • geothermal resources • reservoir • seismic interpretation