Comprehensive study on the results of tension leg platform responses in random sea

Compliant offshore structures are used for oil exploitation in deep water. Tension leg platform (TLP) is a suitable type for very deep water. The nonlinear dynamic response of TLP under random sea wave load is necessary for determining the maximum deformations and stresses. Accurate and reliable responses are needed for optimum design and control of the structure. In this paper nonlinear dynamic analysis of TLP is carried out in both time and frequency domains. The time history of random wave is generated based on Pierson-Moskowitz spectrum and acts on the structure in arbitrary direction. The hydrodynamic forces are calculated using the modified Morison equation according to Airy’s linear wave theory. The power spectral densities (PSDs) of displacements, velocities and accelerations are calculated from nonlinear responses. The focus of the paper is on the comprehen-sive interpretation of the responses of the structure related to wave excitation and structural characteristics. As an example a case study is investigated and numerical results are discussed.

Nonlinear Random Motion Analysis of A Tension Leg Platform Consider- ing the Set-down Motion of A Floating Body

The dynamic analysis of a Tension Leg Platform （TLP） in random wave is investigated by considering the set-down of a floating body. The nonlinear restoring stiffness is derived with the set-down motion of a floating body and the coupled motion of the tension leg and platform and the differential equations of the motion are established. The study focuses on the influence of the set-down motion on the nonlinear response of the platform. By considering different significant wave heights and currents, motion responses of the platform are calculated and compared. The analysis shows that the set-down motion significantly increases the heave motion with low frequency and the equilibrium position of the heave motion with the set-down motion is much lower than that without set-down motion. The results in this paper indicate that the set-down motion has a major impact on the safety of the platform inproduction operation, and it is also a threat to the strength of tension legs and risers.

Application of a Newly Built Semi-submersible Vessel for Transportation of a Tension Leg Platform

Transportation of tension leg platform （TLP） structures for a long distance has always been associated with the use of a heavy semi-transport vessel. The requirements of this type of vessel are always special, and their availability is limited. To prepare for the future development of South China Sea deepwater projects, the China Offshore Oil Engineering Corporation has recently built a heavy lift transport vessel-Hai Yang Shi You 278. This semi-submersible vessel has a displacement capacity of 50k DWT, and a breath of 42 meters. Understanding the vessel＇s applicability and preparing it for use in future deepwater projects are becoming imminent needs. This paper reviews the current critical issues associated with TLP transportation and performs detailed analysis of the designed TLP during load-out and transportation. The newly built COOEC transportation vessel HYSY 278 was applied to dry transport of the TLP structure from the COOEC fabrication yard in Qingdao to an oil field in South China Sea. The entire process included the load-out of the TLP structure from the landsite of the fabrication yard, the offloading and float-on of the platform from the vessel, the dry transport of the TLP over a long distance, and the final offloading of the platform. Both hydrodynamic and structure analysis were performed to evaluate the behavior of the transport vessel and TLP structure. Special attention was paid to critical areas associated with the use of this new vessel, along with any potential limitations. The results demonstrate that HYSY 278 can effectively be used for transporting the structure with proper arrangement and well-prepared operation. The procedure and details were presented on the basis of the study results. Special attention was also given to discussion on future use based on the results from the analysis.

Governing equations and numerical solutions of tension leg platform with finite amplitude motion

It is demonstrated that when tension leg platform （TLP） moves with finite amplitude in waves, the inertia force, the drag force and the buoyancy acting on the platform are nonlinear functions of the response of TLP, The tensions of the tethers are also nonlinear functions of the displacement of TLP. Then the displacement, the velocity and the acceleration of TLP should be taken into account when loads are calculated. In addition, equations of motions should be set up on the instantaneous position. A theo- retical model for analyzing the nonlinear behavior of a TLP with finite displacement is developed, in which multifold nonlinearities are taken into account, i.e., finite displace- ment, coupling of the six degrees of freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force, Based on the theoretical model, the comprehensive nonlinear differential equations are deduced. Then the nonlinear dynamic analysis of ISSC TLP in regular waves is performed in the time domain. The degenerative linear solution of the proposed nonlinear model is verified with existing published one. Furthermore, numerical results are presented, which illustrate that nonlinearities exert a significant influence on the dynamic responses of the TLP.

基于筋腱失效分析TLP动态响应

对张力腿平台(tension leg platform,TLP)在不同系泊失效条件下的动态响应进行分析,采用全耦合数值工具ANSYS/AQWA建立非线性平台-筋腱模型,并提出一种模拟筋腱失效的方法。主要分析了筋腱失效时的瞬态响应,筋腱同时失效和渐进失效下的平台瞬态响应,以及筋腱失效后平台的性能变化。结果表明:首先,筋腱断裂失效会导致平台产生瞬时过冲;其次,筋腱同时失效下的瞬态响应比筋腱渐进失效的瞬态响应更显著;最后,筋腱失效后平台的性能会发生明显的变化。因此,需提前研究筋腱断裂对平台动态响应的影响,防止平台的安全性受到威胁。

在平台振荡条件下TLP张力腿的涡激非线性响应

给出了预测张力腿涡激横向振动的时域分析，考虑了波浪、海流、张力腿平台的横漂与垂荡诸因素。张力腿平台的垂荡引起张力周期性变化，对张力腿的涡激横向振动起参数激励的作用，使其动力响应更为复杂。讨论了参数激励下涡激响应的共振条件；以尾流振子模型为基础，发展了分析张力腿在动张力作用下的涡激振动的工程方法，并分析了一座ＴＬＰ实例，给出了在横漂周期内张力腿上质点的相对位移、弯矩、剪力幅值的时间历程。结果表明，平台垂荡使张力腿的涡激响应幅值升高、高频成分增加，因此它对张力腿的疲劳设计是重要的。

南海“浅深水”海域经典TLP平台整体运动性能分析

针对经典TLP在中国南海北部水深330 m海域油田千年一遇环境下的整体运动性能和张力腿系统响应情况进行研究,对TLP平台进行全耦合时域计算分析,并对平台运动、张力腿响应及平台甲板气隙等进行分析校核。分析结果表明:千年一遇生存条件下,平台张力腿系统安全;平台水平偏移较大,对立管设计挑战较大;平台甲板气隙较为临界,存在甲板上浪风险。

BROWSE TLP平台CRA管道施工工艺研究

BROWSE DTU TLP平台中CRA管道占到90%左右,该管道极易被污染,工作量大,施工工艺要求严格,制造环境及过程保护要求极高,要求实行清洁制造,有别于传统海洋工程建造工艺。本文针对CRA管道特殊要求,从材料到货、存储及施工过程进行论述,并对一体化设计及一体化建造工艺在其中的应用进行了研究,探讨了相应采取的措施,为该项目及其管道在青岛场地的顺利实施具有一定的参考和指导作用。

南海TLP钢管桩可打入性分析方法研究

随着PCPT技术在海洋地质勘察中广泛应用,使基于该技术的SRD在钢桩的可打入性分析中的应用成为可能.参考Doyle研究的墨西哥湾的4个TLP平台粘性土SRD的结论,结合API规范对砂性土打桩阻力的规定,组合成一种新的SRD计算方法.文中论述的2种SRD计算方法可供南海TLP项目打桩分析参考.

Hill Instability Analysis of TLP Tether Subjected to Combined Platform Surge and Heave Motions

This paper presents the Hill instability analysis of Tension keg Platform （TLP） tether in deep sea. The 2-D nonlinear beanl model, which is undergoing coupled axial and transverse vibrations, is applied. The governing equations are reduced to nonlinear Hill equation by use of the Galerkin＇ s method and the modes superposition principle. The Hill instability charted up to large parameters is obtained. An important parameter M is defined and can be expressed as the functions of tether length, the platform surge and heave motion amplitudes. Some example studies are performed for various envirotnnental conditions. The results demonstrate that the nonlinear coupling between the axial and transverse vibrations has a significant effect on the response of structure. It needs to be considered for the accurate dynamic analysis of long TI2 tether subjected to the combined platfolna surge and heave motions.

Hydrodynamic Comparison of a Semi-submersible,TLP,and Spar:Numerical Study in the South China Sea Environment

The South China Sea contains tremendous oil and gas resources in deepwater areas. However, one of the keys for deepwater exploration, the investigation of deepwater floating platforms, is very inadequate. In this paper, the authors studied and compared the hydrodynamics and global motion behaviors of typical deepwater platforms in the South China Sea environment. The hydrodynamic models of three main types of floating platforms, e.g. the Semi-submersible, tension leg platform （TLP）, and Truss Spar, which could potentially be utilized in the South China Sea, were established by using the 3-D potential theory. Additionally, some important considerations which significantly influence the hydrodynamics were given. The RAOs in frequency domains as well as global motions in time domains under time-varying wind, random waves, and current in 100-y, 10-y, and 1-y return period environment conditions were predicted, compared, and analyzed. The results indicate that the heave and especially the pitch motion of the TLP are favorable. The heave response of the Truss Spar is perfect and comparable with that of the TLP when the peak period of random waves is low. However, the pitch motion of Truss Spar is extraordinarily lar^er than that of Semi-submersible and TLP.

TLP船体系统管道设计综述

张力腿平台(TLP)作为主要的深水油气平台形式之一,近年来得到了广泛的应用。船体系统作为实现调节TLP张力功能的设施,对TLP的稳定运行起着重要的作用。结合TLP的设计标准规范及流花TLP FEED项目的设计工作,介绍了TLP下浮体船体系统管道的设计原则、设计基础、布置要点及各个系统的布置要求,并对船体的压排载系统方案做了详细介绍,对扫舱系统、透气测深等其余系统方案做了简单介绍,可为TLP船体系统管道设计提供一定借鉴和参考。

TLP平台钢管桩的岩土设计

随着海洋工程油气开发逐步向深海进军,对南海深水区油气开发技术的研发已迫在眉睫。目前,主要的深海石油平台型式为张力腿平台,其结构一般由平台本体、张力腿系统和基础3部分组成,基础主要采用打入式钢管桩。结合某TLP平台项目,根据相关标准、规范和文献,对TLP平台钢管桩基的岩土设计内容和方法进行了探讨,对国内TLP平台桩基设计技术发展有积极的推进作用。

Aerodynamic Effects on TLP Type Wind Turbines and Predictions of the Electricity They Generate

This research proposes a new offshore wind energy generation system that uses a tension leg platform (TLP) and describes experiments performed on a TLP type wind turbine in both waves and wind. The following conclusions can be made from the results of this research. 1) In the case of coexisting wave-wind fields, the wind effect stabilizes the pitch motion. 2) The wind effect decreases vibration of the mooring lines when waves and wind coexist. In particular, the springing (2nd or 3rd order force) also decreases in this field. 3) It can be estimated that the reduction in the rate of generation of electrical power can be up to about 6% as a result of the heel angle. In addition, the annual amount of electricity generated was estimated along with the utilization factor based on the experimental results.

液体晃动对TLP泥浆罐侧壁的影响分析

采用SESAM软件对TLP进行水动力分析,根据波浪谱和加速度传递函数得到TLP加速度响应谱,计算了各个方向的加速度极值;基于SESAM的计算结果,采用ANSYS软件建立TLP上部泥浆罐静水压模型和泥浆罐晃动模型,将平台加速度极值作为惯性载荷输入,从结构强度和刚度2个方面分析了泥浆罐内液体晃动对泥浆罐各侧壁的影响,结果表明:液体晃动会在一定程度上增加泥浆罐侧壁应力和变形,其中对波纹板侧壁的应力和变形增大程度较小,而对平板侧壁的变形增大程度极为明显。本文研究成果可为TLP泥浆罐侧壁及内壁的安全设计提供参考。

西非海域TLP辅助钻井时的系泊设计及计算分析

介绍辅助钻井技术(Tender Assisted Drilling, TAD)的概念和发展历程,概述其特点和主要应用优势。以张力腿式平台(Tension Leg Platform, TLP)为例,选择一种适用的半潜式辅助钻井平台,尝试将TAD应用于西非海域。给出TLP的主要尺寸和辅助钻井平台的主要性能数据,根据二者的总体布置设计辅助钻井作业时的系泊系统,该系统包括辅助钻井平台的系泊缆、TLP的回拉缆和两平台间的连接缆。对辅助钻井时的2个浮体进行时域耦合水动力分析,针对西非海域的海况特点定义有强阵风和无强阵风2种计算工况。计算分析预报两平台的最小间距、吊桥最大行程和各缆索最大张力等,并考虑一缆破断时的情况。分析结果表明,系统各项指标基本符合设计要求,在西非海域对TLP应用TAD是可行的。

VIM、VIV对TLP张力腿张力的影响分析

针对多因素影响下的TLP系泊安全问题,以传统式TLP为对象,建立了数值分析模型,进行了时域耦合分析,获得了在正常作业、极端和自存条件下,以及考虑高、低潮位和其他因素影响下的计算结果。计算结果表明,张力腿最大张力和最小张力满足设计要求。在此基础上研究了TLP浮体涡激运动、张力腿涡激振动对张力腿张力的影响。分析结果表明,浮体涡激运动对位于垂直于环境载荷方向的张力腿的张力影响较大,张力腿涡激振动对其张力的影响可以忽略。本文的计算结果和分析方法可为TLP工程设计提供参考。

考虑桩基错动的深水张力腿平台动力响应研究

由于地震、断层、滑坡和沉降等原因,张力腿平台(tension leg platform, TLP)下端的桩基可能发生错动。考虑平台本体有限位移、六自由度运动耦合、瞬时位置和瞬时湿表面、自由表面效应等非线性因素,建立TLP系统的耦合动力学方程。采用变步长龙格库塔算法编写了数值计算程序,得到了波浪作用下平台本体六个自由度运动响应和系泊张力响应。通过文献对比,验证了理论模型和计算程序的正确性。基于南海流花油田一年一遇的设计工况,计算得到桩基下沉0.1 m时16个工况下平台系统的动力响应的时间历程。以正常工况为基准,对比了不同工况中平台本体六个自由度运动、系泊张力的幅值和标准差,研究结果表明:桩基下沉对平台的六自由度响应和张力腿张力幅值产生明显的影响,但不加剧运动响应和张力响应的波动;桩基下沉会破坏平台系统原有的对称性,引起垂荡位移的较大恶化;桩基下沉会引起张力腿张力大幅增大,存在张力腿断裂和系泊失效的风险。

深水张力腿平台与系泊系统的耦合动力响应

把张力腿简化为非线性梁结构,运用Hamilton原理,推导出平面情况下平台本体与张力腿系泊系统的耦合运动方程及边界条件;分析了不同流场条件下,两种不同张力腿模型(非线性梁和无质量弹簧模型)对平台动力响应预测结果的影响;分析结果表明:随着流场条件的不同,采用不同的张力腿简化模型得到的平台动力响应预测结果具有明显的不同。阐明了两种模型所得结果产生差异的原因。

考虑多种非线性因素的张力腿平台动力响应

建立了一种考虑多种非线性因素的张力腿平台(TLP)分析模型,其中包括六自由度有限位移,各自由度之间的耦合,瞬时湿表面,瞬时位置,自由表面效应及粘性力等因素引起的非线性。推导出TLP六自由度非线性运动方程。对某典型张力腿平台ISSC TLP进行了时域上的数值计算,求得该平台在规则波作用下的六自由度运动响应。用退化到线性范围的解与已有解进行了对比,吻合良好。数值结果表明,综合考虑非线性因素后响应明显改变,建议在设计TLP平台的时候,考虑非线性因素的影响。