Advanced Numerical Analysis of Well Integrity and Thermal Dynamics in Superhot Geothermal Reservoirs

Abstract Superhot geothermal wells represent one of the most technically demanding frontiers in the energy transition, offering immense potential for zero-carbon baseload power. However, the extreme thermal and multiphase conditions encountered, especially under lost circulation and fluid flashing, present significant risks to wellbore integrity. This study develops an advanced simulation framework that couples transient multiphase thermal modeling with a fully coupled thermoporoelastic stress analysis to evaluate well integrity in superhot geothermal environments. Using a representative geometry of the IDDP-2 well in Iceland, we simulate a wide matrix of injection scenarios, including no-loss, partial, severe, and total loss conditions with varying pump rates and ramp durations. Results show that total fluid loss and rapid injection can induce severe thermal shocks, particularly around casing shoe, where casing temperatures drop from 320 °C to 115 °C. These thermal gradients reduce bottomhole pressure due to diminished hydrostatic head and initiate high tensile and compressive stresses in the casing–cement–formation system. Model predictions are validated against temperature logs from the IDDP-2 injection test and show good agreement. To evaluate structural resilience under these conditions, detailed cement integrity analysis was performed. The results show that the thermal perturbation experienced by the cement sheath depends not only on the final temperature but also on the cement setting temperature and its initial stress state. For example, assuming a cement setting temperature of 150 °C, the combined thermal variation may range from –35 °C to +170 °C. The analysis demonstrates that without pre-stress, the cement sheath is vulnerable to failure across a narrow operational window. In contrast, with a favorable initial stress state (e.g., 10 MPa), the safe temperature variation range expands significantly to –90 °C to +250 °C. The findings underscore the need for high-resolution thermal modeling and integrated stress assessment in geothermal well design and highlight operational strategies to mitigate thermal integrity risks in future superhot developments.