Practical Aspects of 3D Temperature and Heat Flow Modelling for Exploration of EGS Energy Plays

Abstract

Realistic temperature and heat flow modelling relies on the ability to make calculations directly from well-constrained 3D geology models (Gibson et. al. 2008, Meixner and Holgate, 2008). Correct treatment of topography is another key concern for modelling heat flow patterns that replicate those measured in the real world (Stüwe and Hintermüller, 2000; Braun, 2003). Commencing with a synthetic 3D geology model, featuring high topographic relief and variable scenarios of thermal conductivity contrasts, we present results from thermal modelling employing an explicit finite difference method to solve for temperature in the steady state. Our solver scheme populates a Cartesian voxelised grid with resulting in-situ temperatures, heat flow values and temperature gradients. Our synthetic model is a test-bed for the Köflach district of Eastern Austria for which a 3D GeoModeller1 geology model is currently under construction. The Köflach model will demonstrate realistic 3D temperature and heat flow modelling, verified against measured insitu temperatures and heat flow data, whilst always obeying topographic effects. The existence of thermally insulating lignite beds at Köflach lends itself as a possible analogue for Enhanced Geothermal System (EGS) plays which also typically require the existence of shallow insulating horizons to set-up a scenario of anomalously high heat occurrence, at accessibly shallow depths. This work also has implications for geothermal energy exploration in Eastern Australian’s coal-bearing basins.