New and improved methods to extract energy from hot dry rock are becoming available and, if successful, they could unlock terawatts of energy production from previously untapped resources. Three promising methods include enhanced geothermal systems (EGS), advanced geothermal systems (AGS), and caged geothermal systems (CGS). EGS uses particle propped hydraulically stimulated fractures to convey fluid through low permeability rock to extract heat. AGS uses closed loop flow through an array of deep wells to extract heat without a need for hydraulic stimulation. CGS uses boundary wells to contain high-pressure propped hydraulic fractures while minimizing seismic risk. However, each of these methods comes with its own challenges. EGS risks low production due to proppant degradation and rapid thermal short circuiting. AGS risks extreme capital costs for well drilling and low rates of heat extraction. CGS risks the unproven caging concept and extreme pumping costs. Here, we seek to forecast the performance of each method in an ultra-high uncertainty greenfield scenario that includes natural fractures. Our target site is the Wattenberg geothermal anomaly near Fort Collins, Colorado. Using our open-source Geothermal Design Tool (GeoDT) with only basic input data, we completed a stochastic power and economic risk assessment for future 6 km deep wells. In the conduction-dominated Wattenberg anomaly, we anticipate bottom hole temperatures in the range of 220 to 300 °C. Subsurface stress and fault conditions are unknown. Rock properties are unknown aside from the basement likely consisting of igneous or metamorphic rock. Our analysis predicts that CGS with an ‘X’-pattern of five wells (i.e., XGS) holds the greatest promise for economic heat production at 99 to 220 $USD/MWh, followed by three well EGS at 87 to 2200 $USD/MWh, and then 25-loop AGS at 410 to 860 $USD/MWh.

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