深水水下井口全钻井过程波激疲劳精细化评估

Fine Evaluation on Wave Induced Fatigue of Deepwater Subsea Wellhead in Full Drilling Process

传统的水下井口波激疲劳评估没有考虑不同钻井阶段水下井口结构组成变化,导致水下井口波激疲劳评估精度有限。为此,提出基于整体-局部交互分析的全钻井过程水下井口波激疲劳损伤精细化评估方法,建立钻井全过程复杂结构水下井口局部精细模型及平台-隔水管-水下井口-导管耦合系统整体模型,研究整体模型与局部模型交互机制,并构建整体模型与局部应力传递关系,精细化评估水下井口全钻井过程波激疲劳损伤。研究结果表明:全钻井过程水下井口结构组成变化对隔水管系统和远离泥线导管处的波激疲劳几乎无影响,但对水下井口局部及泥线附近导管的波激疲劳存在较大影响;钻井第二阶段水下井口波激疲劳损伤最为严重,且水下井口底端始终为疲劳极限位置。所得结论有助于判断钻井过程中水下井口疲劳状态,保证作业安全。

The traditional evaluation on wave induced fatigue of subsea wellhead does not consider the changes in the composition of subsea wellhead structure at different drilling stages,resulting in limited accuracy in wave induced fatigue evaluation of subsea wellhead.A fine evaluation method for wave induced fatigue of subsea wellhead in full drilling process based on global-local interaction analysis was proposed.A local fine model for subsea wellhead with complex structure and a global model for platform-riser-subsea wellhead-conductor coupling system in the full drilling process were built.The interaction mechanism between global model and local model was studied.The transitive relation between global model and local stress was constructed to finely evaluate the wave induced fatigue damage of subsea wellhead in full drilling process.The results show that the changes in the composition of subsea wellhead structure have almost no effect on the wave induced fatigue of the riser system and the conductor far away from the mud line in full drilling process,but have a significant impact on the wave induced fatigue of local part of subsea wellhead and the conductor near the mud line.At the second stage of drilling,the wave induced fatigue damage to the subsea wellhead is the most severe,and the bottom of the subsea wellhead is always at the fatigue limit position.The conclusions are helpful in judging the fatigue of subsea wellhead during drilling and ensuring the safety of drilling operations.