| Abstract |
The value of a geothermal resource depends on the design of the reservoir and facilities that are used to harvest its heat. This poses a challenge for prospecting. Accessing deeper resources adds to technical challenges, capital costs, and required pumping power but enables higher temperature fluids to be produced. Longer directional wells, more fractures, and more wells add to capital cost but increase productivity. Stimulating fractures with higher injection rates requires higher surface pressure but speeds up completion time. Every system has an optimum design that will produce the most economic power over the life of the project. We combine these factors in a design-aware prospecting tool that identifies the optimal depth, flow rate, and fractured reservoir design that achieves a targeted net generation capacity for a minimized cost. Then, we apply this solution to prospecting by mapping where hot dry rock resources are more likely to be economic. An important result from this effort found that geothermal gradients above 35 °C/km in normally faulted regimes can produce electricity at a cost of less than $80/MWh, or less than $8/MWh for heat. When the gradient exceeds 50 °C/km in this stress regime, the cost of energy plateaus at $50/MWh for electricity and $5/MWh for heat. This result implies that economic geothermal energy has significant scale-up potential because ultra-high grade shallow hot rocks perform only marginally better than the much more prolific medium-grade resources. |