Riser-Soil-Fluid Interactions for Steel Catenary Risers

钢质悬链线立管由厚壁钢管组成，以悬链线形式从浮式系统连接到海床，广泛应用于海上油气田开发中。SCR必须具有足够的强度，以承受恶劣海洋环境和立管作业负荷造成的巨大疲劳负荷。准确预测悬链线立管在触地区域的疲劳寿命是设计中最具挑战性的问题之一。触地区域是悬链线立管离开海床走向浮式系统的地方。在立管、土壤和海水这三个主要领域之间存在着几种复杂的相互作用机制。这会导致SCR向海床的深度渗透，并对疲劳寿命产生重大影响。近年来发展了先进的立管-海床相互作用模型来模拟立管侵彻海床及其对立管疲劳的影响。然而，以前的模型通常只考虑两个相互作用的领域，即土壤和立管。作为第三个区域的立管周围海水的详细影响往往被忽略。此外，过去的模型通常在沟渠的显式建模和埋设的过早稳定方面存在缺陷和不一致之处。最近的研究致力于开发更准确和更全面的模型来更好地预测沟槽形成的机制，如循环立管-土壤相互作用引起的塑性土壤变形，以及由海底流、循环立管振荡和立管-流体相互作用产生的组合涡流引起的土壤侵蚀。在这项研究计划中，将开发一个新的立管-土壤-流体相互作用模型，以解决现有立管-土壤相互作用模型的缺陷，并考虑海水在立管-海床相互作用、沟槽形成以及SCR疲劳性能中的作用。数值模型将根据过去公布的数据进行验证，并应用于全球SCR系统，以预测在一系列环境和操作负荷下的最终沟槽几何形状。此外，还将开发一种新的方法，将沟槽效应纳入SCR疲劳分析。这项研究计划旨在提高海上油田开发中SCR的安全性、完整性和成本效益。考虑到纽芬兰和全球的海上油田开发情况，这项研究在纽芬兰和全球都具有显著的潜在经济效益。此外，高素质的人员将在多学科环境中接受培训，同时在开发高级工程模型、模拟工具和方法方面获得宝贵的技能。

Steel catenary risers (SCRs), comprised of thick-walled steel pipes and attached in a catenary shape from a floating system to the seabed, are widely used in offshore oil and gas field developments. SCRs must have sufficient strength to sustain significant fatigue loads caused by harsh ocean environments and the riser operational loads. Accurate prediction of the SCR fatigue life in the touchdown area, where the catenary riser departs from the seabed towards the floating system, is one of the most challenging design issues. There are several complex interactive mechanisms between the three main domains, i.e., riser, soil, and seawater. This leads to deep penetration of the SCR into the seabed and a significant influence on the fatigue life. Advanced riser-seabed interaction models have been developed in recent years to simulate riser penetration into the seabed and its influence on riser fatigue. However, previous models have typically only considered two domains of interaction, i.e., the soil and the riser. The detailed influence of seawater around the riser as the third domain has often been neglected. In addition, past models generally suffer from shortcomings and inconsistencies in the explicit modeling of the trench and premature stabilization of the embedment. Recent studies have strived to develop more accurate and comprehensive models to better predict the mechanisms contributing to trench formation, such as plastic soil deformation due to cyclic riser-soil interaction, and soil erosion due to combined vortices generated by subsea currents, cyclic riser oscillations, and riser-fluid interactions. In this research program, a new riser-soil-fluid interaction model will be developed to address the shortcomings of existing riser-soil interaction models and incorporate the effects of seawater in riser-seabed interactions, trench formation, and consequently the SCR fatigue performance. The numerical models will be validated against past published data and applied to a global SCR system to predict the ultimate trench geometry under a range of environmental and operational loads. Also, a new methodology will be developed for incorporation of the trench effects into the SCR fatigue analysis. This research program aims to improve the safety, integrity, and cost effectiveness of SCRs in the development of offshore fields. Considering the offshore field developments in Newfoundland and worldwide, this research has significant potential economic benefits both locally in Newfoundland and globally. Also, highly qualified personnel will be trained in a multidisciplinary environment while gaining valuable skills in the development of advanced engineering models, simulation tools, and methodologies.