水下采油树设计影响参数分析

通过分析不同类型水下采油树的特点及其优缺点,提出水下采油树设计时所需的主要参数。采油树的类型应根据不同的油田开发模式进行选择,在此基础上再制定水下采油树的整体设计方案。综合考虑水深、油藏的特性、井口装置的型式和采油作业的方式等方面的因素,在保证水下采油树强度、稳定性的条件下,进行具体的结构设计、流动保障设计、热绝缘设计、防腐设计和密封设计。同时,为确保水下采油树的安全性和可靠性,需要特别考虑水下采油树的材料问题,并进行可靠性分析和风险分析。     

基于监测数据的深水水下井口循环弯矩计算方法

水下井口的疲劳完整性是海洋油气田长期安全开采的前提。工业界往往采用贴应变片直接测量水下井口应变来计算弯矩和疲劳损伤,但水下井口应变片粘贴困难且不能长时间连续工作。采用对水下井口监测方法,基于隔水管—防喷器组—水下井口的运动和力学特性,考虑防喷器组惯性力矩建立系统耦合动力学方程,最终形成基于监测数据的水下井口循环弯矩计算方法。以南海某深水水下井口为例,建立隔水管—防喷器组—水下井口系统有限元模型并进行动态分析,提取隔水管底部张力、转角、防喷器组加速度及转角等参数,代入所建立的系统耦合动力学模型,得到水下井口弯矩与有限元计算结果吻合良好。研究表明只需通过在线监测获得所需的输入数据,无需监测水下井口应变即可获取水下井口循环弯矩。建立的系统耦合动力学模型可为水下井口疲劳完整性评估提供理论依据。     

Model and experimental study on jetting flow rate for installing surface conductor in deep-water

Jetting is preferentially adopted for surface conductor installation in deep-water oil and gas facilities. Surface conductor bearing capacity decreases due to soil disturbance, which is the main risk of jetting technology. A calculation model of the minimum jetting flow rate is established based on Bernoulli's theorem and soil mechanics. Jetting experiments are carried out to investigate the effect of jetting flow rate on the bearing capacity of surface conductor. Experiment results show that the bearing capacity of surface conductor decreases exponentially with flow rate. Considering the effect of flow rate both on hydraulic breaking soil capacity and the bearing capacity of surface conductor, a design method of jetting flow rate for installing surface conductor is proposed. This method ensures the successful implementation of jetting technology and has been successfully applied in more than 30 deep-water wells in the South China Sea and West Africa.     

锁块式水下采油树井口连接器性能分析

水下采油树井口连接器是连接采油树和井口的关键设备,对深海水下勘探开发及采油树的安装连接具有不可或缺的重要意义。以一种锁块式水下连接器为例,介绍其结构组成和工作原理,通过有限元建立连接器的三维模型,分析连接器在下放安装工况、连接锁紧工况、正常生产工况和钻完井工况下的连接性能,得出井口与采油树本体接触面作用力、VX钢圈接触应力和锁块受力情况随外部载荷的相互关系。结果表明,VX钢圈在整个过程中都能够保持良好密封,井口与采油树本体接触面未发生分离,弯矩对连接器连接性能影响很大,在额定弯矩作用时连接器部分锁块已发生弹塑性失效。     

A prediction model for overlying rock thickness of subsea tunnel: A hybrid intelligent system

Abstract

The overlying rock thickness of a subsea tunnel controls its vertical line. It not only ensures the safety and stability of tunnel construction period and operation period, but also ensures the economy of subsea tunnel. In the current research, few papers give full consideration to the complex indicators of prediction the overlying rock thickness. However, in this study, a hybrid intelligent system was established to predict the overlying rock thickness of a subsea tunnel based on Qingdao Kiaochow Bay Subsea Tunnel, China. The sea depth, basic quality index of rock mass, soft soil layer thickness, permeability coefficient, and construction management level were selected as the main factors influencing the overlying rock thickness. Using the data obtained from project site exploration, objective weight factors were calculated using rough set theory, and subjective weight factors were calculated using the analytic hierarchy process. Furthermore, the combination of weights was obtained for each factor. Finally, the weight of influencing factors was incorporated into the extension model, and the overlying rock thickness of pending section was calculated. The results of overlying rock thickness prediction model are consistent with the actual value, indicating that the model has good engineering applicability and application value.     

张力腿平台水下丛式井口圆形布局方法研究

张力腿平台(TLP)水下丛式井口布局设计关系到立管服役期间的安全性,是含有丛式井口平台设计过程中考虑的主要因素。根据TLP立管安装、钻井以及防碰等要求,考虑尾流效应对丛式立管的影响,研究水下丛式井口布局设计准则,对丛式井口—立管系统进行碰撞分析以确定水下井口间距阈值,提出水下丛式井口圆形布局方法和相应的布局设计流程。通过算例对计算方法进行了具体运用。研究表明:与目前采用的"等边三角形网格"方法相比,水下丛式井口圆形布局方法可允许水下整体基盘安装位置误差达到水下井口间距阈值的20%,立管的最大倾角可达到0.5°,安装作业窗口增加1倍以上。本方法对水下整体基盘安装位置误差的容错能力强,能有效扩大丛式立管钻井和安装作业窗口,提高丛式立管作业安全性,研究结果可为TLP丛式井口的设计提供参考。     

Study on deepwater conductor jet excavation mechanism in cohesive soil

Conductor casing jetting technique has been increasingly applied in deepwater drilling. The insight into the jetting excavation mechanisms is critical in guiding a successful conductor casing jetting operation. The real- time continuous jet excavation process is simulated with the volume of fluid (VOF) multiphase method of CFD (Computational Fluid Dynamics) ANSYS Fluent calculation software in the current study. The cohesive soil is modelled by using a kind of viscous fluid with Herschel-Bulkley model. In addition, a laboratory half round nozzle jet excavation test is designed for verification by comparison of the observed jet excavation profile with the numerical results. The sensitivity parameters affecting the conductor jetting excavation mechanism in cohesive soil are thus investigated. It is found that the application of Herschel-Bulkley (HB) model for cohesive soil and the VOF method of Fluent can provide a good simulation of jet excavation process. The maximum excavation depth can be determined by the undrained ultimate bearing capacity of the circular foundation with a bearing capacity factor of 6.7. The nozzle position, jet velocity and soil strength have significantly influence on the depth and width of the jet excavation profile in conductor oblique jet.     

Q1井弃井作业复杂情况处理与认识

Q1井在弃井作业过程中遇到复杂情况,对套管的切割回收带来了很大的困难.由于φ244.5 mm套管外水泥环返至井口,使得套管在割断后无法提出,经过多次上移套管切割深度后,采用特殊的作业手段将套管提拉出井眼;后续在回收φ762 mm套管和φ508 mm＊φ339.7 mm变径套管时,由于φ244.5 mm套管割深过浅,使得φ508 mm＊φ339.7 mm变径套管的可切割长度极短,通过设计非常规的切割钻具组合、非常规的打捞方法才得以完成回收.详细介绍了打捞钻具组合设计、打捞方法,对水下井口的非常规弃井回收作业有借鉴意义.     

Feedback control system for blow-out preventer positioning

During the drilling of ultra-deep-water subsea petroleum wells, a blow-out preventer (BOP), a piece of safety equipment, must be assembled on the wellhead. The BOP is suspended using the drilling riser during the wellhead approach operation, and the riser's top end is connected to the floating platform rig. This article presents a feedback control system for the automatic approach of the BOP to the wellhead. Compared to state-of-the-art controls, ours does not require ancillary thrusters installed alongside the riser nor inclination sensors atop of the drilling riser. Additionally, our proposed control embeds a closed-loop dynamic positioning system, thus retaining the characteristics of the original control system and adding an extra closed-loop. This eases implementation of the BOP approach control to an existing platform. To calculate the optimal gains for the BOP controller, we assume a linear system for the riser, including only the pendulum-shape. The simulation is carried out using nonlinear models for both riser and floating platform. We assume an International Towing Tank Conference standard semi-submersible platform, coupled with a 3000-m free-hanging vertical riser for the time-domain simulation. The results show the BOP tracking to be a step-shaped input signal under current and wave loads. A discussion of the performance of feedback control under different environmental loads is also included.     

海底隧道围岩稳定性模糊概率分析

针对采用定值相对极限位移判定隧道围岩稳定性时存在的问题,提出了采用模糊概率理论判定隧道围岩稳定的计算方法.结合厦门翔安海底隧道工程实际,利用曲线回归和模糊概率方法对海底隧道围岩稳定性概率进行了计算分析.参考现行规范并根据海底隧道各个开挖步的变形量综合确定极限相对位移上下限,采用指数函数对海底隧道CRD1部和CRD3部的拱顶下沉收敛曲线进行了回归分析.根据回归参数及实测结果,应用模糊概率公式对隧道围岩的稳定性概率进行了计算,从而为根据某个时刻的相对位移来判断海底隧道稳定性提供了参考.     

饱和软黏土中不同形状深水防沉板基础承载特性研究

防沉板基础是水下井口、管汇节点与管汇终端等的永久支撑结构,其承受的荷载具有明显的复杂性、非线性和不确定性,给防沉板基础的稳定性研究带来了巨大挑战。本文研究了在剪切强度随深度线性增长的不排水饱和软黏土中,相同用钢量条件下矩形、方形、六边形和圆形防沉板基础的承载特性。采用数值模拟方法确定了竖向荷载V、水平向荷载H(H_x、H_y)、弯矩荷载M(M_x、M_y)和扭矩荷载T联合作用下,防沉板基础在V-H、V-M、V-T、H_x-H_y、M_x-M_y、T-H和T-M荷载空间的地基承载力包络线,并建立了相应的拟合公式。研究表明,不同的基础形状对其承载力影响显著,当V较大时,适宜选用圆形基础;当H较为显著时,应选用矩形或方形基础;圆形、方形和矩形基础的抗弯特性分别适用于不同条件下M为主控荷载的情况;当T的影响不可忽视时,矩形或方形基础为首选形式,六边形和圆形基础次之。     

水下井口回接工艺在边际油田开发中的应用及改进

水下井口回接是海洋石油钻井工程中的一项特殊工艺。为降低开发成本,提高边际油田的开发效益,利用临时弃井的井进行水下井口的回接,并在此基础上建造小型生产平台是开发边际油田一项不错的选择。于1988年钻探的BZ34-3-2D井,试油显示较好,采用了保留水下井口的临时弃井。介绍了井口回接工艺以及该工艺在BZ34-3油田的应用中遇到的困难,对常规井口回接工艺进行了改进与创新,利用水下摄像技术观察水下井口情况,最终回接成功,对今后水下井口回接作业有一定的指导作用。     

Back analysis of an operating subsea tunnel considering the degradation of ground and concrete lining

ABSTRACT

An evaluation of the stability of subsea tunnels during operation is very important considering the risks involved with subsea tunnels. Although a large volume of monitoring information can be obtained, back analysis has been performed based on the internal displacement. In this study, the efficiency of an estimation of the safety of an operating subsea tunnel has been improved by implementing the back analysis algorithm based on various monitoring information. The differential evolution algorithm was adopted for back analysis of an operating subsea tunnel. The differential evolution algorithm was improved to accommodate the multiple target variables for back analysis, such as the elastic modulus, cohesion, friction angle of the ground, and the time-dependent elastic modulus of concrete lining. In addition, the elastic modulus of the concrete lining and the properties of reinforced ground can be evaluated with the proposed algorithm using a range of monitoring data, such as the internal displacement and stress acting on the lining. In summary, back analysis with a differential evolution algorithm can be used to evaluate the stability of an operating subsea tunnel.     

不同径厚比的海底管道压溃屈曲研究

为了探索不同径厚比海底管道的压溃屈曲特性,本文分别采用挪威船级社（Det Norske Veritas,DNV）规范、有限元模拟和深海压力舱模型试验,研究不同径厚比海底管道承载外部水压的能力,并就DNV规范压溃屈曲计算公式对不同径厚比管道的适用性进行了讨论,优化了小径厚比海底管道压溃屈曲的设计方法。研究表明：小径厚比管道的压溃屈曲临界压力对管道径厚比的变化更敏感;DNV规范计算小径厚比管道的压溃屈曲临界压力偏小,在进行深海管道的压溃屈曲设计时,建议采用模型试验结合有限元模拟的方法,计算管道实际可提供的压溃屈曲承载力。     

考虑高低温影响因素的金属密封总成性能分析

水下井口系统环空金属密封总成设计是水下油气装备国产化核心技术之一。前期国内相关研究人员已在密封设计、密封机理等方面形成共识,但密封性能评价的全面性和准确性依旧存在不足。鉴于此,提出考虑高低温影响的金属密封总成性能评价方法,构建了“有限元分析+室内测试+无损探伤”的评价流程。评价结果显示:温度是金属密封设计及性能评价过程中不可忽略的重要影响因素;设计温度范围内,该金属密封总成的密封性能及主体结构强度满足设计要求,但仍不同程度地受到温度变化影响;相对于常规方法,该评价方法更加全面准确,可为该领域其它密封设计提供借鉴和参考。     

Axial friction response of full-scale pipes in soft clays

The axial friction response of subsea pipelines in soft clays is a very important aspect for designers of subsea pipelines but the response is not well understood so far. There is a pressing need for the comprehension of the response. In this paper, model tests are performed using full-scale pipes coated with polyethylene (PE) to study the effects of the set-up period, the pipe diameter, the buried depth of the pipe, the shear strength of soft clays and the loading rate on the axial friction response of pipelines in soft clays. The variations of the axial friction coefficient are analyzed using the effective stress method based on model test results. The results show that the axial friction resistance increases with the increasing pipe diameter but the effect of the pipe diameter on the axial friction coefficient can be neglected. The ultimate axial resistance also increases with the increase of the buried depth of pipelines, the undrained shear strength of soft clays and the loading rate. The axial friction coefficient increases with the increasing loading rate. However, the axial friction coefficient decreases with the increasing buried depth. The method to determine the axial friction coefficient is developed by analyzing model test results, which considers the effects of the diameter, the buried depth, the undrained shear strength of soft clays and the loading rate. The study results not only extend the industry data base but also supply a basis to determine the axial friction coefficient of PE-coated pipes in soft clays for ocean engineering geological investigations.     

Seismic stability analysis of subsea tunnels under the effects of seepage and temperature

This study used the strength reduction method to analyze the seismic stability of a subsea tunnel under the effects of seepage and temperature. Excess pore water pressure within the rock mass was first eliminated by calculating the consolidation; then, an earthquake wave was applied to begin the dynamic and time-history analysis and to obtain the maximum horizontal displacement of the model boundary. Finally, a temperature field model was established for the thermal analysis of the structure. The temperature of each node of the structure was regarded as a form of outside load applied to the reduction model; both sides of the vertical horizontal displacement of the boundary nodes and gravity were used as inputs for the static analysis when the vertex horizontal displacement reached its maximum value. By continuously decreasing the shear strength parameters, the safety factor of the tunnel structure was determined. The results show that the plastic zone first appeared in a smaller range on both sides of the tunnel arch feet near the lining and vault of both sides. The safety factor decreased with increasing water depth and overburden layer thickness.     

基于ERA5再分析资料的中国近海浅水区域风能潜力评估

风能潜力评估是风电场选址工作的基础工作。本文基于欧洲中期天气预报中心的ERA5再分析数据,采用风功率密度（Wind Power Density,WPD）中值、容量系数（Capacity Factor,CF）以及鲁棒性变异系数（Robust Coefficient of Variation, RCoV）三种指标,对中国近海浅水区域的风能潜力进行评估,研究结果表明:（1）台湾海峡和东海南部风能资源最为丰富并且风能利用率最高,风功率密度中值和容量系数分别为400~900 和0.45~0.7。总体来看,风功率密度中值从渤海到台湾海峡,呈逐渐增加的趋势,从台湾海峡到琼州湾,呈逐渐减小的趋势,容量系数大小分布情况相似。（2）鲁棒性变异系数大小无明显分布规律,广东湛江近岸海域鲁棒性变异系数在0.70~0.75之间,风能发电量最为稳定,但该地区的风能资源丰富程度较低。（3）福州近岸海域不仅有丰富的风能资源和风能利用率,且发电量较为稳定。在不考虑其它因素的影响下,是中国近海浅水区域建设海上风电场的最佳地点。     

TLP干式钻完井技术特点分析

TLP使得干式井口在深水的应用成为可能,与常规的深水开发模式水下井口相比,TLP降低了钻完井作业的难度和费用,尤其在后期修井和调整并作业时,能够大大降低项目的投资,经济效益明显.TLP目前在墨西哥湾、北海及印度尼西亚深水油气田均有采用.目前针对TLP的钻完井设计和作业程序国内开展研究较少,制约了深水油气田开发前期方案设计工作的开展.因此,重点介绍了TLP对钻完井程序的影响;对于不同的平台钻机配置,总结了TLP的钻完井程序;提出了钻完井设计和作业过程中,TLP对回接套管、升沉补偿等问题的要求,分析了与常规深水湿式井口的温度剖面差异,为开展TLP钻完井技术研究和前期方案设计提供参考.     

砂土地震液化对筒型基础承载力的影响

使用了ANSYS软件对筒型基础进行地震分析,计算了砂土液化情况以及由此导致的承载力的损失,对比了在筒-土界面采用节点耦合和设置接触单元两种形式对该结果的影响,结果显示节点耦合形式既可以保证计算精度,也能提高计算效率。同时,分析了不同长细比筒型基础的砂土液化深度和承载力损失,结果显示较大的长细比有利于减少承载力损失。