Riser-Soil-Fluid Interactions for Steel Catenary Risers

钢悬链线悬挂系统（SCR）由厚壁钢管组成，以悬链线形状从浮式系统连接到海底，广泛用于海上油气田开发。SCR必须具有足够的强度以承受由恶劣海洋环境和立管操作载荷引起的显著疲劳载荷。准确预测接触区SCR疲劳寿命是最具挑战性的设计问题之一，接触区是悬链线立管离开海床朝向浮式系统的地方。这三个主要领域之间存在着几种复杂的相互作用机制，即，立管、土壤和海水。这导致SCR深深地穿透到海床中，并对疲劳寿命产生重大影响。近年来，开发了先进的立管-海床相互作用模型，以模拟立管插入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域，即，土壤和立管。立管周围海水作为第三域的详细影响常常被忽略。此外，过去的模型一般遭受的缺陷和不一致的显式建模的沟槽和过早稳定的嵌入。最近的研究致力于开发更准确和全面的模型，以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土壤塑性变形，以及海底水流、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。在本研究计划中，将开发一种新的立管-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点，并将海水对立管-海床相互作用、沟槽形成以及SCR疲劳性能的影响纳入其中。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载荷下的最终沟槽几何形状。此外，将开发一种新的方法，将沟槽效应纳入SCR疲劳分析。该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。考虑到纽芬兰和世界各地的海上油田开发，这项研究在纽芬兰当地和全球都具有重大的潜在经济效益。此外，高素质的人员将在多学科环境中接受培训，同时获得开发先进工程模型，模拟工具和方法的宝贵技能。

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.