Abstract
This study examines the combined influence of plasticity and creep on the thermal fatigue behavior of casing materials used in high-temperature geothermal wells. Through advanced numerical simulations and calibrated material models, the research systematically evaluates how creep-induced stress relaxation and plastic deformation interact during repeated thermal cycling, particularly under the extreme conditions typical
of super-hot geothermal environments (>350 °C). Results demonstrate that while plastic deformation contributes to cumulative damage, creep
plays a decisive role in casing integrity-especially during cooling phases, where it can significantly accelerate damage evolution and reduce fatigue life.
The findings highlight that neglecting creep effects can lead to substantial overestimation of casing durability. To address these challenges, the study implements a Thermo-Plastic-Creep constitutive model and an energy-based damage criterion, enabling more accurate prediction of casing performance under realistic operational scenarios. This work underscores the necessity of incorporating both plastic and creep behavior into the design and analysis of geothermal casings. The adoption of advanced material models and strain-based design methodologies is essential to ensure
the long-term reliability and safety of wells operating in super-high-temperature regimes.