| Title | Comparative Study of EGS and Hydrothermal System Exploration Approaches |
|---|---|
| Authors | Julian McDowell |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | EGS, exploration, hydrothermal |
| Abstract | Conventional geothermal exploration targets naturally convective systems with existing permeability and fluid flow, often located in structural complex geological settings, In contrast EGS exploration focuses on identifying high-temperature rock formations in structurally ‘stable’ geological regions, where the combination of highly deviated or horizontal well paths and fracture stimulation is required to create permeable networks to facilitate fluid flow in the subsurface and extract the heat from the surrounding rock. Structural geology assessment and mapping is a common focus of exploration for both resource types. In traditional geothermal exploration, where surface expressions of the resource, including springs, steam vents and alteration provide clues to the resource below, while EGS exploration leans into blind geothermal exploration techniques, relying more heavily regional heat flow mapping, electrical geophysical methods, gravity and structural mapping. There is particular importance placed on the understanding and the regularity of stress regimes and geomechanical properties of the target reservoir. EGS projects are reliant on the availability and nature of a water source as a circulation fluid to enable heat extraction through the stimulated reservoir. As such, there is also a strong need to integrate hydrogeological assessments into the exploration phase of EGS project, not just for drilling and well stimulation activities but also during operations, depending on the degree of subsurface leak-off. This paper examines key features of EGS exploration, emphasizing the importance of not just thermal gradient/heat flow mapping but also structural geology (detailed structural mapping, stress regime characterization, and rock mechanical analysis) and shallow groundwater resources. |