POTENTIAL IMPACT OF GEOTHERMAL ENERGY EXTRACTION ON HOT SPRINGS

Geothermal energy, a sustainable resource that can supply heat continuously from deep subsurface, is an attractive alternative future energy. Geothermal resources are economically viable where the geothermal gradient is high, allowing the hot fluid and rock to be accessed by drilling to economically feasible depths, on the order of one to a few kilometers below the land surface. Most existing and promising geothermal resources in the US coexist with hot springs and often in the arid American West. Heat extraction may impact the discharge and temperature of nearby hot springs. There is little study on whether and how geothermal energy development may impact hot springs. For example, how will hot spring flow rate or spring water temperature be affected by geothermal fluid extraction? This study uses groundwater flow modeling and an analytical solution to evaluate the potential impacts of geothermal energy production on hot springs at a hypothetical site that is based on the geologic and geothermal settings near a thermal spring in central Colorado. The hot spring at the foothill of a mountain range is modeled as water flow upwards to land surface from a high permeability fault. One extraction well and one injection well are placed downstream from the fault. Preliminary results suggest that to minimize the negative impact of the heat extraction on the hot spring, it is best to locate the injection well between the hot spring fault and the extraction well. Moreover, a minimum distance between the injection and extraction wells can be determined that would ensure injected water is sufficiently heated before it reaches the extraction well, which is a function of hydraulic and thermal conductivities of the extraction formation. While the actual impact at a particular site depends on the specific hydrostratigraphy and geothermal conditions at that site, modeling a hypothetical site helps identification well parameters and design features of the geothermal extraction infrastructure that minimize negative impacts on hot springs.