A coupled thermal–mechanical model for wellhead uplift in gas wells: Incorporating wellbore heat transfer, cement sheath failure, and multi-casing interaction

Wellhead uplift (WU) in high-temperature (HT) gas wells poses significant risks to well integrity and operational safety. Existing models often oversimplify the actual downhole environment by neglecting coupled thermal–mechanical processes and cement sheath failure, which are key factors that contribute to additional active casing length and sustained annular pressure. This study proposes a novel coupled model that integrates heat transfer and elastoplastic mechanical behavior of the casing-cement-formation system to accurately predict WU. The model innovatively tracks the evolution of the active casing length by evaluating cement sheath failure under thermal and mechanical loads based on a proposed failure criterion. The overall stiffness method is then employed to synthesize the contributions from thermal expansion, annular pressure, and historical loads across multiple casing strings. Validation against laboratory experiments and field data from an actual HT gas well demonstrates high accuracy in uplift and temperature prediction. The results indicates that wellbore heat transfer induces cement sheath sealing failure, thereby increasing both the active casing length and the risk of sustained annular pressure. Sensitivity analysis reveals that annular pressure is a dominant factor, with its influence proportional to the annulus cross-sectional area. While gas production elevates wellbore temperature, it indirectly affects WU via inducing annular pressure buildup rather than direct thermal expansion when cement returns to the wellhead. Furthermore, casing prestress is quantified as an effective mitigation strategy. This work provides a robust predictive approach and deep insight into the WU phenomenon under complex wellbore conditions.