An Overview of Deepwater Pipeline Laying Technology

The technology and methods involved in pipeline laying in shallow water have evolved to the level of routine and commonplace. However, regarding the unexpected deepwater complexity, the traditional pipeline laying techniques have to confront many new challenges arisen from the increase of the water depth, diameter of the pipe and the welding difficuhy, all of which should be modified and/or innovated based on the existed mature experiences. The purpose of this investigation is to outline the existing and new engineering laying techniques and the associated facilities, which can provide some significant information to the related research. In the context, the latest deepwater pipeline laying technology and pipe laying barges of the renowned companies from Switzerland, Norway, Italy etc., are introduced and the corresponding comparison and discussion are presented as well.

A Singular Perturbation Method for Parametric Investigation on J-lay Installation of Deepwater Pipelines

The maximum bending moment or curvature in the neighborhood of the touch down point （TDP） and the maximum tension at the top are two key parameters to be controlled during deepwater J-lay installation in order to ensure the safety of the pipe-laying operation and the normal operation of the pipelines. In this paper, the non-linear governing differential equation for getting the two parameters during J-lay installation is proposed and solved by use of singular perturbation technique, from which the asymptotic expression of stiffened catenary is obtained and the theoretical expression of its static geometric configuration as well as axial tension and bending moment is derived. Finite element results are applied to verify this method. Parametric investigation is conducted to analyze the influences of the seabed slope, unit weight, flexural stiffness, water depth, and the pipe-laying tower angle on the maximum tension and moment of pipeline by this method, and the results show how to control the installation process by changing individual parameters.

A Review of Deepwater Pipeline Construction in the U.S. Gulf of Mexico-Contracts, Cost, and Installation Methods

The offshore pipeline network in the U.S. Gulf of Mexico is the largest and most transparent system in the world. A review of deepwater projects in the region provides insight into construction cost and installation methods and the evolution of contract strategies. Pipeline projects are identified as export systems, infield flowline systems, and combined export and infield systems, and three dozen deepwater pipeline installations from 1980–2014 are described based on Offshore Technology Conference(OTC) and Society of Petroleum Engineers(SPE) industry publications and press release data. Export lines and infield flowlines are equally represented and many projects used a combination of J-lay, S-lay and reel methods with rigid steel, flexible line, and pipe-in-pipe systems. The average 2014 inflation-adjusted cost for pipeline projects based on OTC/SPE publications was $2.76 million/mi and ranged from $520 000/mi to $12.94 million/mi. High cost pipelines tend to be short segments or specialized pipeline. Excluding the two cost endpoints, the majority of projects ranged from $1 to $6 million/mi. The average inflation-adjusted cost to install deepwater pipelines in the U.S. Gulf of Mexico based on available public data is estimated at $3.1 million/mi.

Status and challenges of Chinese deepwater oil and gas development

There have been nearly 33 oil and gas fields with billions bbl resources found in deepwater areas all over the world since 1970,so deepwater areas are of prime importance for petroleum exploration and development.With the achievements of a series of deepwater petroleum exploration technology projects in the USA,Europe and Brazil,the GOM,Brazil and West Africa are becoming the focus of deepwater oil and gas exploration.The oil productivity derived from deepwater areas exceeds that of shallow water areas in GOM and Brazil since 2001.Deepwater is becoming very important for petroleum industries and the top area of technology innovations.On the basis of analyses of world deepwater technological innovations,this paper briefly introduces the history of the China National Offshore Oil Corporation （CNOOC）,and then presents the status and challenges of Chinese deepwater oil and gas development.

Multiaxial Fatigue Analysis on Reeled Deepwater Steel Catenary Risers with Girth Weld Defects

In the present study, we simulated the reel-lay installation process of deepwater steel catenary risers（SCRs） using the finite element method and proposed multiaxial fatigue analysis for reeled SCRs. The reel-lay method is one of the most efficient and economical pipeline installation methods. However, material properties of reeled risers may change, especially in the weld zone, which can affect the fatigue performance. Applying finite element analysis（FEA）, we simulated an installation load history through the reel, aligner, and straightener and analyzed the property variations. The impact of weld defects during the installation process, lack of penetration and lack of fusion, was also discussed. Based on the FEA results, we used the Brown-Miller criterion combined with the critical plane approach to predict the fatigue life of reeled and non-reeled models. The results indicated that a weld defect has a significant influence on the material properties of a riser, and the reel-lay method can significantly reduce the fatigue life of SCRs. The analysis conclusion can help designers understand the mechanical performance of welds during reel-lay installation.

深水测试平台地面管道冲蚀速率预测模型

深水测试平台地面管道易受高压携砂介质冲蚀损伤,准确预测其冲蚀速率,对保障其运维安全具有重要意义,但常用Tulsa冲蚀预测模型主要针对碳钢和铝材,不适用于深水测试平台地面管材为低合金钢AISI4130特殊材质的冲蚀预测。为了扩大Tulsa模型在深水测试平台地面管道冲蚀速率预测的适用性,采用显示动力学方法建立了颗粒冲击靶材的有限元模型,考虑颗粒冲击速度与冲击角度对冲蚀预测模型关键参数的影响,从而改进Tulsa模型中的关键参数,最后将改进后的冲蚀速率预测模型计算结果与文献实验数据以及Tulsa模型计算结果进行了对比。结果表明:①颗粒冲蚀靶材的机理主要是切削和变形磨损,冲蚀速率随颗粒冲击角度增大呈先升高后下降趋势,最大值出现在30°;冲击速度增加引起冲蚀速率呈幂函数升高;②通过模拟颗粒多角度冲击靶材的情况,得到了更加准确的颗粒冲击靶材的分段多项式函数,相较原Tulsa模型仅通过10°与15°两种冲击角度试验,拓宽了Tulsa模型在深水测试平台地面管道冲蚀速率预测的适用性,其中分段角度为30°,与冲蚀速率最大值出现在30°的冲击角度相对应;③颗粒冲击速度较大时(大于10m/s),改进后的预测模型计算结果优于Tulsa模型计算结果,且相对误差随冲击速度的升高而减小,表明本文预测模型适用于深水测试平台介质高速流动的实际工况。

某深水海底管道牺牲阳极消耗异常的原因

近年来,南海东部海域出现了海底管道牺牲阳极加速消耗的情况,深水阴极保护系统面临失效风险。为了探究海底管道牺牲阳极消耗异常的原因,对管道开展了设计资料调研与室内评价试验,其中室内评价试验包括管线钢的保护电流密度需求量试验、阳极电化学性能评价试验和海管与水下系统结构电连接的室内缩比试验,着重探究了温度以及海管与水下结构物电连接对牺牲阳极消耗的影响。结果表明:温度不是引起海底管道阳极消耗异常的主要因素,而当管道与阴极保护状态较差的水下结构物电连接时,靠近水下结构物的海管牺牲阳极输出电流增大,阳极使用寿命将大幅降低,这是造成牺牲阳极加速消耗的主要原因。

冲喷式柔性管缆挖沟机在海底管缆铺设挖沟施工中的应用

深水水下管缆的铺设是开发深水油气资源的关键施工作业项目。深水水下挖沟作业具有技术难度大、施工复杂、投资巨大等特点。在深水海域油气开发工程中冲喷式柔性管缆挖沟机应用广泛,因此对其产品性能、实际深水功能测试、挖沟作业工序、挖沟沟型、挖沟效果等关键技术问题进行分析,经过实践验证,该设备能够独立完成千米级深水域水下挖沟施工。

南海深水海底管道S形铺设技术

南海深水海域环境复杂多变并且频繁有内波流发生,在南海深水海域进行海底管道铺设面临诸多困难。为此,针对南海流花29-1气田深水海管铺设项目,对千米级水深海底管道S形铺设中铺管工艺设计、内波流监测与应对措施、深水铺管精度控制等方面的技术难点进行了研究,并完成了工程应用。工程应用结果表明:深水海管S形铺管工艺能确保海管水下状态完好和铺管精度满足要求;内波流实时监测预警系统实测流速大于1 m/s时,可提醒铺管船注意防范,能够对内波流进行较好的监测和预警;采用的动力定位船起始铺设、弧线段路由铺设精度控制、终止铺设精度控制等技术方案,可保证深水海管铺设精度。所得结论可为南海深水油气田的进一步开发提供技术借鉴。

深水油气管道流动保障的全局化管理

流动保障技术通过综合分析深水油气管道流动安全各相关因素对所运输介质流动特性的影响,进而提出综合预防措施来实现深水油气管道的安全运行。随着油气开发进入深水区,流动保障工作任务艰巨,传统管理模式已难以为继,必须对流动保障的各个环节进行全局的管理,才能更好的应对日益复杂的环境。本文主要介绍了实施流动保障全局管理的时代大背景,论述了流动保障在设计、生产及后期改造三个方面的应用及进展,最后深入论述了流动保障全局化管理的必要性。

Frictional behaviors of rough soft contact on wet and dry pipeline surfaces:With application to deepwater pipelaying

Elastic rubbers are widely used in nature and engineering.In order to better understand soft rough contact under dry and wet conditions during deepwater pipelaying process,various polyurethane(PU)discs both in PU-pipe and PU-steel sliding combinations have been investigated by using self-developed tribometer.The tribological test results show that the friction coefficient can be clearly seen:PU90<PU80<PU70,under dry conditions.Experimental results also indicate that the two dramatic increases of the frictional coefficient exist in the rough soft PU-pipe contact.The potential influence of asperities and thin liquid film is discussed.

海底管道拖管法铺设技术研究进展综述

对海底管道铺设常采用的拖管法的研究进展进行总结,并结合其发展趋势提出后续研究建议。详细阐述浮拖、底拖、离底拖和控制深度拖等海底管道拖管法的铺设方式及其优劣势,系统地总结不同拖管法在国内外诸多油气田项目中的工程应用情况,展示多种基于传统拖管法组合的复合式拖管法及拖管法创新技术。从理论分析、试验研究和数值模拟等3个方面对国内外的拖管法研究现状和发展趋势进行调研,展望拖管法未来在管道运输中的发展,并给出相关研究建议。

外夹式超声波流量计在深水油气田中的应用

随着海洋油气开发不断向深水方向发展,长距离管道输送的要求越来越高,伴随着高压力、长距离的药剂计量,给深水油气田开发与设计带来了相关问题。基于南海某深水油气田开发对长距离药剂输送计量所选用的外夹式流量计作为研究,为从根本发挥外夹式超声波流量计作用,本文以其概述为基础,针对其优点与缺点展开详细分析,提出其在实际应用中的选型及应用环境。最后指明安装及注意事项,对后期的深水油气田开发设计提供参考。

深水气田井流物净化研究与实践

南海荔湾区块深水气田采用水下采输系统,井流物从水下井口产出后与水合物抑制剂、各类化学药剂掺混形成复杂组合流体。生产运行中发现井流物中不溶物和悬浮固体含量增加,洁净度下降,流程中各类滤器频繁发生堵塞。通过化验分析和电镜扫描对比,明确了井流物杂质成分为乙二醇再生单元中颗粒过滤器的助滤剂硅藻土以及处理设备中的腐蚀产物。由于助滤剂的强吸附性,使杂质吸附了大量重烃组分,成分更加复杂,同时在海管段塞作用下不断富集加强,井流物成分均质性不断遭到破坏,加剧了工艺处理的难度。针对上述问题,将颗粒过滤器滤布规格由35L/(m^(2)·s)提高至21L/(m^(2)·s),控制助滤剂漏失量,同时持续投用脱盐闪蒸单元抑制系统腐蚀问题,有效降低井流物杂质含量,提升了系统洁净度。另外,采用精细控压携液策略,抑制深水海管井流物段塞的形成。

高静水压力作用下深海油气管道的局部屈曲

以有初始缺陷的厚壁钢管为研究对象,开展外部高静水压力作用下管道结构的模型试验和有限元数值模拟分析.通过在压力缸内泵入水的方式对钢管试件施加均匀外部压力,测得钢管发生局部屈曲时的压力峰值.基于ABAQUS软件,数值模拟分析试验钢管在静水压力作用下的屈曲和后屈曲行为,得到钢管的失稳压力和屈曲后的形态,与试验结果相比吻合较好.利用建立的数值模拟方法,分析不同材料性能、径厚比和初始椭圆率对钢质管道屈曲的影响.结果表明:材料硬化系数较大的管道,失稳压力较大;随着初始椭圆率的增加,管道的失稳压力显著减小;对于深水或超深水油气管道的屈曲失稳压力,国外规范的计算公式偏保守,而且不能解释不同材料硬化系数的影响.

深水开发的新型立管系统——钢悬链线立管(SCR)

1种全新的深水立管系统——钢悬链线立管（Steel Catenary Riser，SCR）在翠西哥湾（Golf of Mexico）、坎普斯湾（Campos Basin）、北海（North Sea）和西非（West Africa）得到了成功应用。它的适用水深为300～3000m，且适用现有任何浮式结构，从浅水的固定式平台到极深水的浮式生产储运系统（FPSO）。因此，它取代了传统的柔性立管和顶张力立管，成为深水油气开发的首选立管，被认为是深水立管系统的成本有效的解决方案。

海底管道的管材选用探讨

本文针对海底管道的特殊性,以DNV OS F101和API Spec 5L作为基本技术标准,通过对管道的主要性能指标和尺寸公差进行分析考虑,总结出海底管道的管材选用原则;根据DNV OS F101的相关补充要求,并结合荔湾3-1项目的深水管材选用情况,从厚径比、止裂韧性和塑性变形方面提出深水海底管道的管材选用建议。

深水海底管道铺设焊接系统设计

为了满足南海深水油气田开发的需要,研制了以焊接工作站为核心的深水海底管道铺设焊接系统。焊接工作站配备2套独立的双炬焊接系统,焊接小车外形尺寸小、质量轻,特别适合于海管铺设工程应用。焊接工作站控制系统采用CANOpen现场总线和网络技术,不仅增加了系统柔性和可靠性,而且实现了现场焊接设备的远程监督。

深水油气管线天然气水合物生成条件预测方法及应用

在深水油气田开发中,为了有效防止天然气水合物的生成,迫切需要对天然气水合物生成条件进行准确预测。为此,根据深水环境压力高和多温度梯度的特点,应用气液两相流理论与传热学原理建立了适用于深水油气管线的温度预测模型;在现有实验数据的基础上,对5种天然气水合物预测方法进行了对比优选,结合Beggs-Brill方法建立了预测深水油气管线天然气水合物生成条件的模型,并编制了相应的计算程序。实例研究结果表明,管线流量越大、绝热材料导热系数越小、绝热层厚度越大、停产时间越短时,天然气水合物的生成区域就越小。该模型可用于制订合理的管线流量指标、选择恰当的管线保温材料和准确计算无接触时间,对深水油气田的安全生产提供了技术支持。

小径厚比深水管道的压溃屈曲研究

深水管道所处的特殊海洋环境极易导致其发生压溃屈曲破坏。通过深入分析不同径厚比深水管道的压溃屈曲特点,并对具有不同径厚比及初始椭圆度的深水管道模型进行了压溃屈曲及后屈曲行为的计算分析。研究发现,压溃屈曲的经典理论公式并不适用于小径厚比深水管道。文章基于经典理论和数值模拟结果,得到了适用于小径厚比深水管道压溃屈曲分析的临界压力修正公式,进而对小径厚比深水管道的压溃屈曲评估提供理论支撑和工程推荐。