Abstract
To address the absence of fire resistance evaluation methods for drilling wellhead structures under gas well blowout fires, this study firstly conducted experiments to investigate the mechanical properties of wellhead materials under high-temperature conditions. Subsequently, a temperature model and a mechanical response model of the wellhead structure under fire were established and validated respectively based on thermo-mechanical coupling methods. Furthermore, a fire resistance limit evaluation method of wellhead structures in well blowout fires was developed. The results indicated that with clearance operations at the well site, a thermal radiation threshold existed; Only when the thermal radiation exceeded this threshold, the wellhead reached its fire resistance limit and failed. Without clearance operations at the well site, the wellhead structure was certain to reach its fire resistance limit and failed. The upper surface of the wellhead had the largest displacement and reached its fire resistance limit first. The convective heat transfer coefficient, pressure load on the upper surface of the metal sealing ring, and casing gravity load had minimal influence on the fire resistance limit. Without clearance operations at the well site, the wellhead surface temperature approached the flame temperature, and the rubber seal reaches its decomposition point, leading to seal failure. The research findings could provide valuable references for the safety assessment of wellheads during gas well blowout fires and contribute to the development of effective response strategies for blowout fire control.