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1.
A mathematical model is presented to study the main characteristics of severe slugging in a downward inclined pipeline followed by a catenary riser. In this model, both simplified transient model and phase distribution model are included so that the flow characteristics of each stage for severe slugging can be accurately reproduced, especially for blowout stage. The results show that the flow features of severe slugging can be simulated by the proposed mathematical model. A good agreement between the experimental data and the numerical results is observed. The model can predict the transient fluctuation of many respects, such as the superficial gas velocity at the bottom of the riser and the average velocity at the outlet of the riser. 相似文献
2.
The vibration response of a free-hanging flexible riser induced by internal gas-liquid slug flow was studied experimentally in a small-diameter tube model based on Froude number criterion. The flow regime in a curved riser model and the response displacements of the riser were simultaneously recorded by high speed cameras. The gas superficial velocity ranges from 0.1 m/s to 0.6 m/s while the liquid superficial velocity from 0.06 m/s to 0.3 m/s. Severe slugging type 3, unstable oscillation flow and relatively stable slug flow were observed in the considered flow rates. Severe slugging type 3 characterized by premature gas penetration occurs at relatively low flow rates. Both the cycle time and slug length become shorter as the gas flow rate increases. The pressure at the riser base undergoes a longer period and larger amplitude of fluctuation as compared with the other two flow regimes. Additionally, severe slugging leads to the most vigorous in-plane vibration. However, the responses in the vertical and horizontal directions are not synchronized. The vertical vibration is dominated by the second mode while the horizontal vibration is dominated by the first mode. Similar to the vortex-induced vibration, three branches are identified as initial branch, build-up branch and descending branch for the response versus the mixture velocity of gas-liquid flow. 相似文献
3.
海底混输管线严重段塞流动的预测与控制 总被引：1，自引：0，他引：1
随着海洋油气田开发向深水海域发展,海底混输管线距离过长,且存在立管系统,容易形成严重段塞流动的现象日益严重.在严重段塞流工况下,管线的流动参数,如压降、段塞长度、段塞频率、持液率都随时间变化,并且表现为周期性变换的压力波动以及间歇出现的液塞.严重段塞流的不稳定性给油气田集输系统的设计及运行管理造成了巨大的困难.本文介绍了海底混输管线中严重段塞流动预测与控制的实验与理论研究进展,同时,对于节流、气举、分离等8类15种控制严重段塞的方法分别进行了评述,旨在为进一步开展海底油气混输管线严重段塞流动的研究提供借鉴,为工程实践提供参考. 相似文献
4.
5.
A numerical model of the steel catenary riser(SCR) is built based on the slender rod model. The slender rod model,which describes the behavior of the slender riser in terms of the center line position, can solve the geometrical nonlinearity effectively. In a marine environment, the SCR is under the combined internal flow and external loads,such as wave and current. A general analysis considers only the inertial force and the drag force caused by the wave and current. However, the internal flow has an effect on the SCR; it is essential to explore the dynamic response of the SCR with the internal flow. The SCR also suffers the lift force and the fluctuating drag force because of the current. Finite element method is utilized to solve the motion equations. The effects of the internal flow, wave and current on the dynamic response of the SCR are considered. The results indicate that the increase of the internal flow density leads to the decrease of the displacement of the SCR, while the internal flow velocity has little effect on the SCR. The displacement of the SCR increases with the increase of the wave height and period. And the increasing wave period results in an increase in the vibration period of the SCR. The current velocity changes the displacements of the SCR in x-and z-directions. The vibration frequency of the SCR in y-direction increases with the increase of the current velocity. 相似文献
6.
《中国海洋工程》2020,(3)
An experimental investigation on the disturbance effect of jet-type active vibration suppression device on vortexinduced vibration of deep-sea riser was carried out in the wave-flow combined flume. The vibration suppression device was designed in which the jet pipe was horizontally fixed to the front end of the riser. By varying three different excitation spacings and multi-stage outflow velocities, the influence law of the dominant frequency,dimensionless displacement and other dynamic response parameters was studied under different excitation spacings,and the mechanism and sensitive characteristics of the disturbance suppression were explored. The results indicate that the variation of excitation spacing makes gas curtain enter the strong disturbed flow region at different velocities and angles, and the coupling relationship between excitation spacing and reduced velocity is the key factor to enter the strong disturbed flow region to achieve the optimal disturbance suppression. In the strong disturbed flow region,the influence of gas curtain on the dominant frequency is obviously affected by the flow velocity, while the vibration displacement is stable at the same amplitude and is weakly affected by the flow velocity. Gas curtain can effectively disturb the formation of vortex shedding, destroy the strong nonlinear coupled vibration of the riser, and achieve better vibration suppression effect. In the weak disturbed flow region, the vortex length of the riser tail is prolonged,the strong nonlinear coupled vibration of the riser is gradually restored, and the vibration suppression effect of the device gradually decreases. 相似文献
7.
Steel catenary risers (SCRs) are usually cost-effective solutions in the development of offshore fields and the transferring of the hydrocarbons from the seabed to the floating facilities. These elements are subjected to the fatigue loads particularly in the touchdown zone (TDZ), where the oscillating SCR is exposed to cyclic contact with the seabed. The slug-induced oscillation is a significant contributor to the fatigue loads in the TDZ. The cyclic seabed soil softening under the wave-induced riser oscillations and the gradual penetration of the SCR into the seabed are widely accepted to have a significant influence on SCR fatigue performance. However, this has never been investigated for slug-induced oscillations due to the lack of integrated access to comprehensive numerical models enabling the simulation of the riser slugging and nonlinear hysteretic riser-seabed interaction at the same time. In this paper, an advanced interface was developed and verified using the multi-point moving tie constraint in order to examine the influence of cyclic seabed soil softening on slug-induced oscillations of SCR. The interface was integrated with a pre-developed user subroutine for modeling of the nonlinear hysteretic riser-seabed interaction and incorporated into a global SCR model in ABAQUS. A comprehensive parametric study was conducted to investigate the influence of slug characteristics and nonlinear seabed soil model on slug-induced, wave-induced, and combined wave/slug induced oscillations of SCR in the TDZ. It was observed that the nonlinear seabed model could significantly affect the embedment of the SCR into the seabed under the slug-induced oscillations and consequently improve the fatigue life. The developed user interface was found to be a strong framework for modeling riser slugging. 相似文献
8.
海洋油气混输时,气液两相流与混输立管之间的双向流固耦合作用机理十分复杂.针对柔性立管与气液两相流的流固耦合响应问题,在气液两相循环试验装置中开展了不同流型两相流流动特性及柔性立管振动响应的测试,利用高速摄像非介入测试技术同步捕捉了柔性立管的振动位移与管内的流型演变过程,对比了不同流型气液两相流诱导的立管振动响应特性,通过对比固定和振动立管内的气液两相流动特性,辨析了振动对管内两相流动的影响.结果表明:柔性立管中出现了泡状流、泡状—段塞流、段塞流、段塞—搅拌流和搅拌流五种流型,不同流型的气液两相流诱导立管振动的机理不同,在段塞—搅拌流作用时立管的振动响应最剧烈.与固定立管相比,强烈的振动不同程度地改变了气液两相流的流动特性,振动立管中部分两相流流型转变的临界条件有明显地调整,相对而言,振动对搅拌流和泡状流的影响较小. 相似文献
9.
Laboratory experiments on conically shaped oil collectors beneath a marine riser are described. The collection concept involves oil, water and gas entering the collector and being driven into a separating sytem by gas-lift. A parametric study involving various collector shapes, heights above the wellhead, and gas, oil and water flow rates was carried out. The important dimensionless variables were identified and quantified with the conclusion that effective collection is possible if the collector height is sufficiently small and the ratio of water pumped to gas flow is sufficiently large. Increased collector heights can be accommodated at the expense of requiring increased water flows by use of larger diameter risers. The amount of gas required for most efficient oil collection is found to be much less than is expected to come from most blowouts when a single collector and riser system is used. This difficulty can be greatly diminished by the use of a specially designed gas-separating collector which passes most of the gas to the surface through a riser separate from the one which carries the liquids. 相似文献
10.
A prediction model of the deepwater steel catenary riser VIV is proposed based on the forced oscillation test data, taking into account the riser-seafloor interaction for the cross-flow VIV-induced fatigue damage at touch-down point （TDP）. The model will give more reasonable simulation of SCR response near TDP than the previous pinned truncation model. In the present model, the hysteretic riser-soil interaction model is simplified as the linear spring and damper to simulate the seafloor, and the damping is obtained according to the dissipative power during one periodic riser-soil interaction. In order to validate the model, the comparison with the field measurement and the results predicted by Shear 7 program of a full-scale steel catenary riser is carried out. The main induced modes, mode frequencies and response amplitude are in a good agreement. Furthermore, the parametric studies are carried out to broaden the understanding of the fatigue damage sensitivity to the upper end in-plane offset and seabed characteristics. In addition, the fatigue stress comparison at TDP between the truncation riser model and the present full riser model shows that the existence of touch-down zones is very important for the fatigue damage assessment of steel catenary riser at TDP. 相似文献
11.
海洋环境荷载下输液立管的静、动力特性研究 总被引：1，自引：1，他引：1
考虑管内流动流体和管外海洋环境荷载共同作用 ,建立海洋立管侧向运动微分方程。用Hermite插值函数离散 ,在微机上编写海洋立管静、动力分析程序 ,通过计算分析研究管内流体对立管侧向变形和应力的作用 ;另外 ,探讨管内流体的流动速度和立管顶端的预张力对立管动力特性的影响。结果表明 ,立管变形和应力均随管内流体流动速度增加而增大 ,同时内流速度的增大会降低立管的固有频率 ,但适当增大立管顶端预张力会抵消内流流速增加引起的固有频率下降。 相似文献
12.
A three-dimensional Lump-Mass formulation of a catenary riser, capable of handling irregular seabed interaction, with bending and torsional stiffness is presented in this paper. This formulation uses only three degrees of translational freedom and one independent torque variable for each computational node. The generality of the present formulation permits static and dynamic analyses of a wide range of offshore-related slender structure systems such as mooring cables, rigid and flexible risers as well as submarine pipelines. Four sets of results are presented for (i) a hanging catenary, (ii) as (i) but subjected to end torsion, (iii) a wire, chain and spring buoy mooring and (iv) a steel catenary riser on an irregular seabed. 相似文献
13.
深海悬垂取水管的设计趋向于大直径、高内流流速,内流对取水管振动特性的影响不可忽略,分析内部流动引起的管道动态失稳行为以及评估失稳临界流速具有重要工程意义。基于小尺度模型试验,研究内流对深海悬垂取水管道振动特性的影响规律,结果表明：随着内流流速增加,取水管模型会发生动态失稳行为,表现为一种间歇性的近周期运动,该运动主要由管道一阶弯曲模态引起的不稳定性诱导。管道材料、顶端连接方式及底部配重块均影响其动态稳定性,顶端固定连接时质量比小的管道更易发生动态失稳;顶端变为铰接时,质量比大的管道失稳临界流速变小,质量比小的管道失稳临界流速变大。相比顶端边界条件,底部配重块对管道失稳临界流速影响不显著但可以减小其振动幅值。 相似文献
14.
钢悬链线立管（steel catenary riser， 简称SCR）是一种优质的深水开发设备，近几年广泛用于深海环境下油气资源的开采。在浮式平台的周期性升沉运动和海浪海流的载荷作用下，立管的触底区会产生较为严重的疲劳破坏问题。为保证深海立管的高效与安全运行，清管作业是一项必要的维护手段。目前对于清管载荷作用下钢悬链线立管的位移变化规律研究比较匮乏。基于ABAQUS有限元软件和缩比试验准则，设计并开展有关清管载荷作用下钢悬链线立管的位移变化规律的缩比模型试验研究，从清管载荷的大小和作用位置等角度分别研究立管的X向与Y向的位移变化特征。研究结果表明，清管器在立管的触底段中运行并逐渐靠近触底点的过程中，清管器所在立管处的X向与Y向的位移会产生逐渐减小的趋势；当改变清管载荷的大小时，对于立管的同一位置来说，清管载荷的变化会导致立管的X向位移产生较Y向位移更加显著的变化；在清管器通过立管某一位置的前后过程中，X向位移变化呈现先增大后减小的趋势，而Y向位移仅在清管器通过该处时会有明显的减小。 相似文献
15.
国外深水钢悬链线立管研究发展现状 总被引：2，自引：0，他引：2
介绍国外在新型深水立管系统--钢悬链线立管关键技术方面的研究发展现状,论述浮体一、二阶运动对钢悬链线立管疲劳寿命的影响、浮体升沉运动对钢悬链线立管触地点疲劳寿命的影响;钢悬链线立管与海底相互作用机制的实验研究及结果;钢悬链线立管涡致振动与疲劳的研究现状.并简要论述钢悬链线立管触地点问题的研究结论. 相似文献
16.
《中国海洋工程》2015,(5)
Steel catenary riser(SCR) is the transmission device between the seabed and the floating production facilities. As developments move into deeper water, the fatigue life of the riser can become critical to the whole production system, especially due to the vortex-induced vibration(VIV), which is the key factor to operational longevity. As a result, experimental investigation about VIV of the riser was performed in a large plane pool which is 60 m long, 36 m wide and 6.5 m deep. Experiments were developed to study the influence of current speed and seabed on VIV of SCR. The results show that amplitudes of strain and response frequencies increase with the current speed both in cross-flow(CF) and in-line(IL). When the current speed is high, multi-mode response is observed in the VIV motion. The amplitudes of strain in IL direction are not much smaller than those in CF direction. The seabed has influence on the response frequencies of riser and the positions of damage for riser. 相似文献
17.
Steel catenary riser (SCR) is the transmission device between the seabed and the floating production facilities. As developments move into deeper water, the fatigue life of the riser can become critical to the whole production system, especially due to the vortex-induced vibration (VIV), which is the key factor to operational longevity. As a result, experimental investigation about VIV of the riser was performed in a large plane pool which is 60 m long, 36 m wide and 6.5 m deep. Experiments were developed to study the influence of current speed and seabed on VIV of SCR. The results show that amplitudes of strain and response frequencies increase with the current speed both in cross-flow (CF) and in-line (IL). When the current speed is high, multi-mode response is observed in the VIV motion. The amplitudes of strain in IL direction are not much smaller than those in CF direction. The seabed has influence on the response frequencies of riser and the positions of damage for riser. 相似文献
18.
触地段(Touchdown zone, TDZ)是在役钢悬链线立管(Steel catenary riser, SCR)的关键部位,在复杂载荷作用下,极易形成损伤缺陷,其载荷寿命的评估是深海结构工程中的一个关键问题。本文以大型有限元软件ABAQUS为平台,运用损伤管道实体单元与土弹簧阻尼单元相互作用的模型模拟触地段损伤海底管道在复杂载荷作用下的动力响应,数值计算考虑了管-土相互作用过程中的材料非线性、几何非线性以及接触非线性。讨论了单一环向体积损伤位于触地段管道的不同位置时,触地段损伤管道在不同载荷作用下的动力特性及特征点的动力响应。结果表明,管道所受内外压力以及管道提升端的竖向位移载荷会影响结构的自振频率;体积损伤部位的动力响应较完好部位更剧烈;体积损伤的位置和动力载荷频率对管道动力放大系数的影响很大;当动力载荷的激励频率越接近结构基频时,损伤管道的动力响应及动力放大系数越大。 相似文献
19.
钢悬链线立管(SCR)与海床土体的接触问题对立管的疲劳寿命影响很大.运用ANSYS有限元软件中的接触单元模拟SCR与海床接触处的相互作用,考虑海床土体的非线性,建立SCR与海床系统有限元模型,并同已有的等价梁-弹簧模型进行了比较和验证.运用该模型进行计算分析,探讨了管道重量、土体模型和摩擦系数等对管道入土深度和弯矩的影响,为进一步研究SCR与海床的相互作用提供参考. 相似文献
20.
深水开发的新型立管系统——钢悬链线立管(SCR) 总被引：12，自引：0，他引：12
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。 相似文献