Thermal integrity analysis of metal seals in 175 MPa casing head hangers: From cryogenic to elevated temperatures

As oil and gas exploration expands into ultra-deep wells and extreme temperature environments, the metal seal of the casing head suspension must maintain reliable sealing under ultrahigh pressures (UHPs) of 175 MPa coupled with extreme temperatures. To investigate the performance of metal seals in casing head hanger under extreme temperatures (−47 °C and 125 °C) and UHP (175 MPa), this study systematically conducted simulation analysis and experimental validation. The thermo-mechanical sequentially coupled simulation results indicate that during heating to 125 °C and cooling to −47 °C, the stress distribution and effective contact width of the sealing ring exhibit low sensitivity to temperature variations. Under high-temperature conditions, the variance of contact stress decreases by an average of 5.3%. Furthermore, the influence of the sealing ring's installation preload on metal seal performance under the combined effects of 175 MPa UHP and extreme temperatures was investigated. When the preload is below 2.45 mm, increasing the preload significantly enhances the effective contact width and improves the uniformity of contact stress distribution. This suggests that a preload close to 2.45 mm ensures sealing reliability and stability under UHP and extreme temperatures. Finally, a 175 MPa high/low-temperature sealing test was performed on an 8 1/8″ full-metal-seal mandrel-type casing hanger. Under 125 °C/175 MPa conditions, the pressure drop was 0.6 MPa after 15 min of pressure holding, while under −47 °C/175 MPa conditions, the pressure drop was 1.16 MPa, confirming the robust reliability of the metal seal. This study provides an important reference for the sealing structure design of ultra-deep and UHP wellhead equipment. Future research may further expand the temperature range and hold duration to more comprehensively evaluate long-term service reliability.