THERMOGEOLOGY ASSESSMENTS OF GEOTHERMAL ENERGY IN THE SHALLOW HETEROGENEOUS SUBSURFACE
To assist the geoexchange community in maximizing their efficiency and reduce the overall cost of installation, we have developed a methodology including thermogeology to characterize the complexity and heterogeneity of the shallow subsurface; spanning the critical zone in the upper 100 m. In this depth interval, the mixing of deep and shallow groundwater impacts thermal processes. By integrating geologic mapping, geophysical logging, thermal property analyses, and fiber-optic distributed temperature sensing, we can detect sub-meter scale variations in the physical and thermophysical properties. Our results show that physical properties of sediment and rock, including moisture content, mineralogy and hardness, are strongly correlated with the variability in thermal gradient.
In this talk, we will demonstrate the application of the assessments at various sites in central Illinois where research and applied energy studies are being performed. Besides the influence of near-surface temperature changes and the Earth's geothermal heat flux from below, groundwater flow may be responsible for the conduction of heat, which should be considered in modeling the thermal profile.