深水钻井隔水管时域随机波激疲劳分析

确定深水钻井隔水管时域随机动态分析和疲劳计算方法,采用第三代波浪模式WAVEWATCH计算中国南海波浪谱,并与相应的P-M谱、JONSWAP谱进行比较;开展不同边界条件下的隔水管波激疲劳分析,研究边界条件对隔水管波激疲劳寿命的影响;计算不同边界条件下隔水管疲劳损伤变异系数与分析时长的关系,确定不同边界条件下隔水管波激疲劳分析的最低时长;最后以中国南海某油井为例计算隔水管时域随机波激疲劳寿命。结果表明:南海海域波浪谱的谱峰值和谱形状都与JONSWAP谱较接近,建议选用JONSWAP谱;边界条件对隔水管波激疲劳寿命影响较大,疲劳分析时应考虑钻井船的慢漂运动;随着分析时长的增大,隔水管疲劳损伤变异系数呈指数式减小,考虑钻井船的慢漂运动后大大增加了分析时长。

Time domain random wave-loading fatigue analysis on deepwater drilling risers

A method for time domain random wave-loading dynamic analysis and fatigue calculation of deepwater drilling riser was presented.Wave spectrum in South China Sea was simulated according to the third wave model WAVEWATCH and compared with P-M and JONSWAP wave spectrums.Wave-loading fatigue under different boundary conditions was calculated and compared.The effects of boundary conditions on the riser wave-loading fatigue life were studied.The relationship between coefficient of riser fatigue variation and analysis time under different boundary conditions was computed and the minimum analysis time was determined.Finally,wave-loading fatigue life of the riser system in South China Sea was calculated according to the proposed method.The results show that JONSWAP wave spectrum is recommended since its peak size and shape are similar with wave spectrum in South China Sea.Boundary condition is important to riser fatigue life and low frequency vessel motion should be considered in fatigue analysis.The coefficient of riser fatigue variation reduces exponentially as analysis time increases.The analysis time increases greatly if low frequency vessel motion is considered in fatigue analysis.