The deepwater subsea wellhead(SW)system is the foundation for the construction of oil and gas wells and the crucial channel for operation.During riser connection operation,the SW system is subjected to cyclic dynamic loads which cause fatigue damage to the SW system,and continuously accumulated fatigue damage leads to fatigue failure of the SW system,rupture,and even blowout accidents.This paper proposes a hybrid Bayesian network(HBN)-based dynamic reliability assessment approach for deepwater SW systems during their service life.In the proposed approach,the relationship between the accumulation of fatigue damage and the fatigue failure probability of the SW system is predicted,only considering normal conditions.The HBN model,which includes the accumulation of fatigue damage under normal conditions and the other factors affecting the fatigue of the SW system,is subsequently developed.When predictive and diagnostic analysis techniques are adopted,the dynamic reliability of the SW system is achieved,and the most influential factors are determined.Finally,corresponding safety control measures are proposed to improve the reliability of the SW system effectively.The results illustrate that the fatigue failure speed increases rapidly when the accumulation fatigue damage is larger than 0.45 under normal conditions and that the reliability of the SW system is larger than 94%within the design life.
LI Jia-yiCHANG Yuan-jiangLIU Xiu-quanXU Liang-binCHEN Guo-ming
在海洋石油工程向深水迈进过程中,海洋工程勘察从业者关注到具有潜在威胁的地质现象,发现了若干与浅水区域具有明显差异的独特地质灾害,对钻井平台就位、导管架平台和浮式平台设计、海底管缆路由优选,均造成了一定影响。本文基于多个深水海洋工程勘察案例,通过对工程物探调查、工程地质调查及海洋环境调查数据分析,阐述深水地质灾害特征及其对海洋工程影响,优化海洋工程设计方案。研究表明,深水区广泛发育沙波、陡坎、硬质海底、断层、海底峡谷、块体搬运沉积体(mass transport deposits,MTDs)等地貌和灾害类型,采用自主式水下航行器等近底潜载调查方式,可以获取厘米级分辨率的调查成果,结合船载调查数据和土工试验数据,能够进行斜坡稳定性分析与海底浅地层划分,为海洋工程建设提供设计依据。
