水下井口套管悬挂器的敏感性及疲劳损伤分析

Sensitivity and Fatigue Damage Analysis of Casing Hanger in Subsea Wellhead

套管悬挂器是水下井口的关键部件之一,在温压环境等多场耦合作用下容易引发疲劳失效,破坏油气井井筒完整性。为探究套管悬挂器在复杂环境下的力学性能和疲劳损伤变化规律,以南海东方1-1气田某板块的水下井口为例,分析套管悬挂器温度分布和各类载荷,建立基于热力耦合作用的水下井口套管悬挂器精细有限元模型,对比下放、BOP试压、回收下放工具和完井采油等4种工况下套管悬挂器的力学性能和疲劳损伤,并评估温度和BOP重力等敏感性因素对水下井口套管悬挂器力学性能的影响效果。研究结果表明:在热力耦合作用下,等效应力和变形量均显著增加,井口温度对套管悬挂器性能的影响显著;最大疲劳损伤出现在BOP试压工况下,其值为1.23×10^(-4) d^(-1),在该工况下套管悬挂器的疲劳寿命为22.27 a,满足设计要求。研究成果对水下井筒完整性评估及深水钻采安全作业具有指导意义。

Casing hanger is one of the key components of subsea wellheads.It is prone to fatigue failure under the coupled effects of multiple physical fields(such as pressure and temperature),which compromises the integrity of oil and gas wells.In order to explore the mechanical properties and fatigue damage evolution of the casing hanger under complex environments,taking the subsea wellhead of a block of the Dongfang 1-1 gas field in the South China Sea as an example,the temperature distribution and loads of the casing hanger were analyzed to establish an elaborate finite element model of the casing hanger,considering the thermo-mechanical coupling effect.The mechanical properties and fatigue damage of the casing hanger under four working conditions were compared through the finite element analysis,namely running the casing hanger,BOP pressure testing,retrieving downhole tools,and well completion and production.Furthermore,the influences of sensitive factors(e.g.temperature and weight of BOP)on the casing hanger were investigated.The results show that the equivalent stress and deformation are significantly increased under the thermo-mechanical coupling effect,and the wellhead temperature has significant effects on the casing hanger.The maximum fatigue damage(1.23×10^(-4) d^(-1))occurs during the BOP pressure testing,and the corresponding fatigue life is 22.27 years,which meets the design requirement.The research findings provide guidance for the integrity evaluation of subsea wellbores and the safe operation of deepwater drilling and production.