南海深水井井下管柱长期处于高温CO₂腐蚀环境，高温及腐蚀协同作用下极易发生完整性失效，严重制约深水井安全高效开发。针对深水高温气井CO₂环境下管柱失效问题，考虑极端服役环境下引起的高温强度衰减及腐蚀损伤，建立了高温及腐蚀损伤耦合作用下的管柱安全评价方法，提出基于复合防控措施的管柱安全设计优化策略，系统评估不同防控措施组合对管柱性能的影响机制，并开展实例分析。结果表明：高温及腐蚀作用将导致管柱损伤，在服役初期，管柱腐蚀轻微，高温下管柱强度衰减起主要作用，随服役时间增加，管柱腐蚀加剧，导致管柱强度迅速衰减；在腐蚀较为严重时，可通过注入缓蚀剂、采用耐蚀合金显著降低管柱腐蚀速率，保障管柱安全，而提升管柱钢级效果相对较弱；但采用80 ksi碳钢+110 ksi碳钢+80 ksi耐蚀合金及缓蚀剂复合分段管柱设计方案可效保障管柱安全的同时降低管控成本。

Subsea well tubular strings in the South China Sea are chronically exposed to high-temperature CO₂ corrosive environments, where the synergistic effects of elevated temperature and corrosion significantly elevate the risk of integrity failure, posing a critical challenge to the safe and efficient development of deepwater reservoirs. To address tubular corrosion-induced failure in deepwater high-temperature gas wells under CO₂ environments, the effects of high-temperature-induced strength degradation and corrosion damage under extreme service conditions were incorporated. A safety evaluation methodology for tubular strings was developed by coupling thermomechanical and corrosion damage mechanisms. Furthermore, an optimized tubular design strategy based on composite mitigation measures was proposed, systematically evaluating the influence mechanisms of different mitigation combinations on tubular performance, followed by case study validation. The results demonstrate that thermal and corrosive interactions lead to progressive tubular degradation. During the initial service phase, corrosion is negligible, and strength deterioration due to high temperature dominates. However, as service duration increases, accelerated corrosion causes rapid strength attenuation. Under severe corrosion conditions, corrosion inhibitors and corrosion-resistant alloys significantly reduce corrosion rates and enhance safety, whereas increasing tubular steel grade provides limited improvement. A hybrid segmented tubular design incorporating 80-ksi carbon steel + 110-ksi carbon steel + 80-ksi corrosion-resistant alloys with corrosion inhibitors injection was shown to optimize structural integrity while minimizing operational costs.