A public domain model for 1D temperature and rheology construction in basement-sedimentary geothermal exploration: an application to the Spanish Central System and adjacent basins

Abstract

Brittle basement and sedimentary rocks, in particular if these are underlain by radiogenic crust, are considered a prime target for enhanced geothermal systems (EGS).They are marked by high geothermal gradients, caused by radiogenic heat production, and are well suited to be used for geothermal doublets after hydraulic stimulation. Critical conditions for successful EGS projects are: (a) tectonic stresses close to failure, allowing creation of induced fractures by means of hydraulic stimulation; (b) sufficient high temperatures [150 C, preferably in excess of 200 C, at depths of less than 5 km; (c) sufficient high water flow rates, to be sustained through induced fractures. For geothermal production, knowledge on thermomechanical properties of the lithosphere provides critical constraints on crustal stresses and basement temperatures. We developed a freely available 1D thermal and rheological model for basement-sedimentary areas. This tool helps to understand variability of deep temperatures, as an effect of uncertainties in thermal and rheological properties and tectonic constraints for the lithosphere, important for assessing geothermal prospectivity. The tool is demonstrated on the Central System in Spain and the adjacent Tajo and Duero basins.