Thermo-hydraulic drivers of superhot geothermal well performance

Geothermal wells drilled into superhot (>375 °C) conditions have the potential to produce substantially more power than conventional geothermal wells. However, the interplay between reservoir pressure, temperature and permeability in controlling deliverable power remains poorly understood. Using a coupled reservoir-wellbore modeling framework calibrated against IDDP-1 discharge data, this study quantifies single-well power generation potential across a wide spectrum of superhot conditions, ranging from low-pressure (<20 MPa) systems associated with magmatic intrusions at ∼2 km depth to high-pressure systems (30–45 MPa) at 4–5 km depth. The results represent idealized upper bounds on single-well performance under steady-state conditions. Across the parameter space examined, the analysis reveals that reservoir pressure, rather than temperature, exerts the dominant control on power output. High-pressure systems at 30–40 MPa can generate two to three times more power than low-pressure systems despite fluids with lower specific enthalpies, because volumetric enthalpy (energy per unit volume) rather than specific enthalpy (energy per unit mass) governs energy delivery through the wellbore. Near-isenthalpic expansion causes cooling of 50–150 °C from reservoir to wellhead, with high-pressure systems experiencing the most severe temperature drops, often leading wells exploiting single-phase reservoirs at depth to produce two-phase fluids at the surface. However, maintaining high wellhead pressures (>15 MPa) preserves single-phase conditions, reducing risks resulting from liquid condensation in the wellbore and enabling more efficient power conversion. Reservoir temperatures of 450–500 °C maximize power output, beyond which declining mass flows due to lower fluid density overwhelm enthalpy gains. Moreover, achieving power generation >30 MWe per well requires reservoir transmissivities on the order of 1000 md·m. Calibration against IDDP-1 discharge data indicates that values of this magnitude can occur in superhot rock, although they have yet to be deliberately engineered. These findings provide quantitative guidance for targeting and developing superhot resources, demonstrating that reservoir pressure and permeability may be more critical than simply pursuing maximum temperature, though realizing the pressure advantage requires sufficient permeability to sustain flow.