基于风险增强的钻井隔水管VIV疲劳评估

VIV Fatigue Assessment of Drilling Riser Based on Enhanced Risk Criterion

涡激振动（VIV）是深水钻井隔水管疲劳损伤的主要来源。合理评估VIV疲劳是进行隔水管疲劳设计的关键问题。应用基于风险增强的疲劳准则进行隔水管VIV疲劳评估。应用设计参数的最佳估计值对隔水管进行标准VIV疲劳分析，以确定隔水管的基本疲劳损伤。识别控制疲劳损伤不确定度的随机变量，并对这些变量进行标准疲劳灵敏度研究，以评价疲劳损伤不确定度。基于风险增强准则确定VIV疲劳安全因子的大小，同时考虑VIV分析模型的内在偏差，以建立对VIV疲劳的接受准则。以南海某深水区钻井隔水管设计为例进行分析。隔水管在设计寿命内的最大疲劳损伤为0．3570，在高、中、低三种安全等级下的许可疲劳损伤分别为0．1274、0．2410与0．5263，该隔水管设计仅满足低等级安全标准。

Vortex-induced vibration is the main source of deepwater drilling riser fatigue damage. The accurate assessment of VIV fatigue is critical to the riser fatigue design. Riser VIV fatigue assessment is carried out using enhanced risk based fatigue criterion. In order to obtain the basic fatigue damage riser standard VIV fatigue analysis is performed using the best estimate design parameters. Stochastic variables governing the uncertainty in the fatigue damage estimate are identified. Standard fatigue sensitivity for these stochastic variables is assessed to determine the uncertainty of the fatigue damage. VIV fatigue safety factors are calculated using enhanced risk based criterion, and the implicit bias associated with the VIV analysis model are considered in order to establish the adequate acceptance criterion for VIV fatigue. VIV fatigue assessment for a deepwater drilling riser in South China Sea is performed. The maximum fatigue damage of the riser is 0.3570, while the allowable fatigue damages for high, normal and low safety levels are 0.1274, 0.2410 and 0.5263 separately, thus the riser satisfies the low safety level only.