Coupled Geothermal - Hydraulic 3D Modeling of the Southern Vienna Basin. a State of the Art Decision Planning Tool for Sustainable Hydrothermal Exploitation Inside an Environment of Sensitive Hydraulic Circulation Systems.

Abstract

Situated at the transition zone of the Eastern Alpine and Carpathian Orogeny, the Southern Vienna Basin marks a region of traditional geothermal utilization in terms of well-ness and spa facilities. Geothermal springs, which are strongly related to fault systems at the margin of the basin, are known and used since roman age. Deep wells, primarily executed for hydrocarbon exploration purposes, proofed the existence of far-reaching circulation systems into depths of several kilometers beneath surface. The proximity of the large city Vienna enhances the demand for energetic geo-thermal utilization for district and agricultural heating pur-poses. This in fact provokes risks of over-exploitation of natural geothermal systems of the Southern Vienna Basin, which have to be considered as sensitive.
The outcome of the presented study will be represented by steady state physical models (3D) of subsurface temperatures due to conductive and convective heat transport. Based on these calibration models detailed reservoir simulations can be extracted for investigating the thermal influence of future geothermal utilization, and in turn allows to quantify heat- and fluid extraction rates as well as to monitor relevant hydrothermal reservoirs.
The complex lithotectonic build-up of the Southern Vienna Basin leading to several different autochthonous and alloch-thonous floors, as a result of an altering tectonic evolution, offered particular challenges for geological 3D modeling, which represents the fundament of the executed basin anal-ysis. Furthermore, sparse and partially poorly documented deep wells, which represent the crucial data sources, led to the demand for elaborating statistical and analytical ap-proaches for prediction of rock parameters and thermal boundary conditions. The presented paper intends to give a detailed overview how to deal with numerical hydrothermal analysis based on 3D modeling at complex basin structures at the absence of detailed reservoir information, which may, for example, be derived out of 3D seismic blocks.