深水测试管柱-隔水管耦合涡激疲劳分析

在深水钻完井测试作业过程中,由于海流作用隔水管易发生涡激振动引起疲劳损伤,由隔水管涡激振动引起测试管柱疲劳损伤问题不容忽略。针对深水高压气井测试作业特点,考虑测试管柱和隔水管之间相互作用,建立测试管柱-隔水管耦合涡激振动模型,提出测试管柱-隔水管涡激疲劳分析方法。结合南海某深水高压气井,研究测试管柱-隔水管耦合系统涡激振动机理、疲劳损伤规律及影响因素。研究结果表明:测试管柱-隔水管耦合系统高流速下更易于发生多模态涡激振动,疲劳损伤沿水深方向呈现波动变化,顶部和下挠性接头附近疲劳损伤最为严重,其中测试管柱疲劳损伤约为0.2~0.25倍隔水管疲劳损伤,适当增大隔水管顶张力和测试管柱提升力可有效改善测试管柱-隔水管耦合系统涡激疲劳性能。

Analysis of VIV-induced fatigue of string-riser coupled system in deepwater

The fatigue damage induced by vortex in a riser occurs frequently during deepwater drilling/completion and testing operations, while the testing string fatigue caused by vortex-induced vibration in a riser also could not be ignored. The string-riser coupled system model was established in the present paper, and the fatigue algorithm was also proposed by considering the characteristics of testing operation in high pressure deepwater gas wells and the interaction between the string and riser. Concentrating on a high pressure deepwater gas well in South China Sea, the vortex-induced vibration mechanism, the fatigue damage rules and the influence factors were investigated. The results show that the multi-modal vibration occurs easier in the string-riser coupled system at a high velocity. The fatigue damage is fluctuating with the increase of the water depth, and the maximum fatigue damage is located on the top side and the lower flexible joint. The fatigue damage of the testing string is about 0.2-0.25 times as big as that of the riser. An appropriate increase of the riser top tension and the string lifting force would effectively improve the vortex-induced vibration fatigue performance of the string-riser coupled system.