Numerical Investigation of the Dynamics for Low Tension Marine Cables

This paper presents a numerical investigation into the dynamics of marine cables which are extensively used in offshore industry. In this numerical study, the Euler-Bernoulli beam model is adopted to develop the governing equations of the cable. Bending stiffness is considered to cope with the low tension problem in local area of towing cable, and thus a more accurate solution with the consideration of the axial elongation can be given.The derived strongly-coupled and nonlinear governing equations are solved by a second-order accurate, implicit,and large time step stable central finite difference method. The quadratically convergent Newton-Raphson iteration method is applied to solving the discrete nonlinear algebraic equations. Then a towed array sonar system(TASS)problem is studied. The numerical solutions agree reasonably well with the experimental data and the simulated results of the references. The specified program of the present paper shows great robustness with high efficiency.

Synthesis of Petroleum Sulfonate Surfactant with Ultra-Low Interfacial Tension in Rotating Packed Bed Reactor

Petroleum sulfonate is one of the most important surfactants used in surfactant flooding for enhanced oil recovery, which is mainly obtained by treating high-boiling petroleum fractions in a stirred tank reactor(STR) or in a fallingfilm reactor(FFR). The synthesis of petroleum sulfonate with ultra-low interfacial tension from viscous petroleum fractions was carried out in a rotating packed bed(RPB) reactor using dilute liquid sulfur trioxide as the sulfonating agent in this study. The effects of various experimental conditions on components content and oil-water interfacial tension(IFT) were investigated. Under the optimum conditions, the active matter content could reach up to 50.3% and the IFT could be equal to 4.7×10-3 m N/m. Compared with the traditional reactor, the active matter content is by 14.12% higher in the RPB as compared to that obtained in the STR. The uneven change of the test oil droplets during the IFT measurement was also discussed. The increase of heavy components content not only can eliminate the contraction phenomenon, but also can reduce the IFT to a minimum. This can be conducive to explaining the reason for producing IFT and the preparation of proper formulations for practical application.

Individuals with and without normal tension glaucoma exhibit comparable performance on tests of cognitive function

AIM:To evaluate aspects of cognition impacted by individuals with and without normal tension glaucoma.METHODS:Fifty normal tension glaucoma(NTG)and 50 control patients≥50 y of age were recruited from the UCSF Department of Ophthalmology.Demographic data and glaucoma parameters were extracted from electronic medical records for both groups.Tests of executive function[Executive Abilities:Measures and Instruments for Neurobehavioral Evaluation and Research(EXAMINER)]and learning and memory[California Verbal Learning Test–Second Edition(CVLT-II)]were administered to both NTG and controls.Race,handedness,best-corrected visual acuity,maximum intraocular pressure,optic nerve cup-todisc ratio,visual field and optic nerve optical coherence tomography parameters,and a measure of general health(Charlson Comorbidity Index)were compared between NTG and controls as well as within NTG subgroups.Multivariate linear regression was used to compare group performances on the EXAMINER battery and CVLT-II while controlling for age,sex,and years of education.RESULTS:NTG and controls were comparable with respect to age,sex,race,education,handedness,and the Charlson Comorbidity Index(P>0.05 for all).Performance on the EXAMINER composite score and the CVLT-II did not differ between NTG and controls(P>0.05 for both).CONCLUSION:This is the first prospective study in which the cognitive function of subject with NTG were evaluated using a comprehensive,computerized neurocognitive battery.Subjects with NTG do not perform worse than unaffected controls on tests of executive function,learning,and memor y.Results do not suppor t the hypothesis that individuals with NTG are at higher risk for cognitive dysfunction and/or dementia.

The Feasibility of ASP Flooding with Low Alkali Concentration in Heterogeneous Reservoirs

In this paper, as far as the ASP flooding in the pilot area of Daqing oilfield is concerned, the effect of apparent viscosity of ASP solution on enhanced oil recovery have been studied by comparison of experiments on artificial heterogeneous cores with on natural cores. The results showed that the decrease in the concentration of alkali could increase the apparent viscosity of ASP solutions, namely, the apparent viscosity increased and the IFT couldn’t get ultra low, and the oil recovery efficiency by ASP solution with a reasonably lower concentration of alkali was not less than that with a higher concentration of alkali and ultra low IFT. The experiments with models having impermeable interlayers between adjacent layers, and by means of “co-injection and separate production” showed that the ASP solution with a higher viscosity and a lower alkali concentration was more beneficial to starting-up medium and low permeability layers and enhancing total oil recovery. Therefore, to heterogeneous reservoir, as factors of affecting oil recovery, the apparent viscosity may be more important than the ultralow IFT. Furthermore, on the premise that the concentration of surfactant and the concentration of polymer keep constant, ASP flooding with low alkali concentration not only enlarges the selectable range of surfactants and decreases the cost of ASP flooding, but also solves the problem of alkali scales. Finally, a dynamic absorption experiment was performed with a 05 meter long linked-up natural core to determine alkali wastage in formation. The result being accord with the application case in the pilot confirmed that it was not necessary to add the alkali too much in ASP flooding from a new direction.

耐盐型阴/阳离子表面活性剂高效渗吸体系构筑及性能评价

针对长庆安塞油田油藏条件,构建了阴离子表活剂APGSHS和双十八烷基阳离子表活剂复配的耐盐型高效渗吸体系。在矿化度为74.11 g·L^(-1)、温度为50℃的条件下,通过界面张力优选出适合该油田的最佳渗吸体系,并研究了该渗吸体系的润湿性能、乳化性能以及渗吸采油效果。结果表明:复配体系可将油水界面张力维持在10^(-3)mN·m^(-1)数量级;同时,该体系具有优异的润湿反转能力以及较佳的乳化性能,该复配体系针对0.3~30.0 mD的岩心渗吸采收率可达40%以上。

基于准零刚度机构与间接力控制的恒拉力系统设计与分析

现有的悬吊式微低重力模拟恒拉力系统常采用力传感器数值作为反馈直接控制系统,但实际情况下力作为反馈信号常会产生突变,影响系统控制精度。为了改进刚性控制策略下系统稳定性差与大冲击条件下力误差大的状况,文中设计了包含准零刚度机构的恒拉力系统,通过控制准零刚度机构长度间接对恒拉力系统输出拉力进行控制。对准零刚度机构进行受力分析,明确影响准零刚度机构性能的关键指标和准零刚度机构的工作行程区间,建立恒拉力系统动力学模型,设计控制系统。为了验证系统控制精度与系统抗干扰性能,进行了动力学联合仿真对设计进行验证,仿真结果表明:该恒拉力系统拉力的控制误差可控制在2%以内,且具有较好的鲁棒性。

The Impact of Core Firing on EOR of Low Salinity-Surfactant Flooding

The combination of injection of lower saline brine and surfactant will increase recovery in sandstone rocks than either when any of the techniques is singly applied. In this work, core IFT test, pH test, flooding experiments and measurement of dispersion were performed on four core samples which were grouped into two: group A which were not fired and group B which were fired at a temperature of 500°C for 24 hours. Two low saline brines were prepared: LS1 which was derived by the dilution of seawater four times and LS2 which was derived by ten times diluting the seawater. The surfactant used was ethoxylated alcohol surfactant. Coreflood experiments were then performed on the rock samples starting with the injection of low saline followed by low saline brine combined with surfactant (LSS). Results from the experiments show that with the injection of LS1 brine and LSS1 higher increment in recoveries were obtained for group B than for group A cores. The same trend was also noticed with the injection of LS2 and LSS2. From the results, LS1 gave higher increment in oil recovery than LS2. Also LSS1 gave higher recoveries when compared with LSS2. In all the cases tested, core samples which were fired gave higher recoveries even though they had low permeabilities of 993 md for sample 3 and 1017 md for sample 4 than those which were not fired with higher permeabilities of 1050 md and 1055 md for samples 1 and 2 respectively. This was attributed to the alteration of wettability as well as that of permeability caused by sample firing. The dispersion profiles of the rock samples show that all samples are homogeneous.

Thermal Tensioning Effects to Prevent Welding Buckling Distortions in Manufacturing of Thin-Walled Aerospace Shells and Panels

To prevent buckling distortions of thin-walled elements, Low Stress No Distortion welding techniques have been pioneered and developed for product engineering and component manufacturing of aerospace structures with material thickness less than 4 mm. In this paper, the nature of Low Stress No Distortion (LSND) welding techniques using thermal tensioning effects is described and special emphases are given to the mechanism of localized thermal tensioning effect. The fundamental principle of Low Stress No Distortion welding is to create active in-process control of incompatible (inherent) plastic strains and stresses formation during welding to achieve distortion-free results implying that no post weld costly reworking operations for distortion correction is required. Finite element analysis is applied to predict and optimize the localized thermal tensioning technique with a trailing spot heat sink coupled to the welding heat source. Comparisons of the thermal elastic-plastic stress-strain cycles are given between conventional gas tungsten arc welding and GTAW with a trailing spot heat sink.

钢板混凝土剪力墙拉弯剪性能试验研究

超高层建筑“细柔”特征容易引起底部剪力墙在强震下处于拉-弯-剪复合受力状态,中国《超限高层建筑工程抗震设防专项审查技术要点》(建质[2015]67号)建议墙肢采用配置型钢/钢板的方式来改善该种抗震性能,但缺乏相关试验研究。为此,进行了6片钢板混凝土剪力墙的低周往复荷载试验,研究了轴拉比、含钢率及剪跨比对墙肢拉弯剪性能的影响。研究表明:拉弯剪作用引起钢板混凝土剪力墙密集的裂缝分布和显著的钢材强化,并导致其剪切-拉弯耦合破坏。轴拉比增大,墙肢承载力、初始抗侧刚度和延性分别降低22%、41%和39%;剪跨比减小,墙肢承载力和抗侧刚度至少提升23%;同时增大含钢率和降低剪跨比,墙肢延性提高10%。相比其他国家规范,中国规范对拉弯剪作用下钢板混凝土剪力墙的抗剪承载力预测效果更好,但其未能考虑高含钢率对裂面销栓力的影响,故建议采用暗柱的初始含钢率进行修正。

低渗致密气藏防水锁剂配方性能评价

基于吐哈油田低渗致密气藏,研发一种新型气藏防水锁剂GY-HE85,对其界面张力、表面张力和润湿性等基本性能进行研究,并分析了岩心渗透率恢复效果。实验结果表明,氟碳表面活性剂与碳氢表面活性剂复配后,碳氢表面活性剂除降低界面张力的作用之外,由于异电性亲水基之间强烈的静电吸引作用,表面活性剂分子在更低含量即可达到饱和吸附,还可降低表面活性剂的使用量。防水锁剂GY-HE85含量为0.1%~0.5%(w)的溶液时,表面张力为20.23~47.52 mN/m,随着溶液含量减小,拟黏附功逐渐降低,降幅呈“先快后慢”趋势,防水锁剂GY-HE85溶液优选含量为0.3%(w)。防水锁剂GY-HE85溶液具有较好的抗吸附性能,岩心渗透率恢复率在86.44%~91.20%,较好地预防了致密气藏储层“水锁”现象的发生。

ECAP和时效对Mg-4Zn-1Mn-0.5Ca合金组织和性能的影响

将铸态Mg-4Zn-1Mn-0.5Ca合金在300℃热挤压成棒材,对棒材进行180℃时效处理和200℃等通道转角挤压(ECAP)。研究了热挤压合金、ECAP 8道次合金和时效后ECAP 8道次合金的组织和性能。随后对试样进行室温和150℃低温单轴拉伸。结果表明:8道次ECAP后合金比热挤压态合金具有更细、更均匀的晶粒组织,同时提高了合金的室温屈服强度。时效后ECAP 8道次合金的150℃断裂伸长率比未时效ECAP8道次合金提高17.4%,说明时效处理对合金性能起着重要作用。

层内自生低界面张力泡沫调驱技术研究与应用——以渤海KL油田A20井组为例

针对渤海KL油田A20井组平面注水突进、纵向吸水不均及常规调剖体系难以注入等问题,开展了层内自生低界面张力泡沫调驱性能评价实验。采用界面流变仪、泡沫扫描仪和泡沫调驱动静态评价装置等设备,筛选优化了层内自生低界面张力泡沫体系的组成药剂及最佳复配浓度比,并采用多功能物理模拟驱替装置考察了该体系的动态调驱性能。结果表明:优选组成药剂及配比为10%生气药剂A+10%生气药剂B+2%释气药剂C+0.5%起泡剂PA-5+0.3%稳泡剂PJ(质量浓度),该复配体系可在可视化填砂管中稳定生泡;一维填砂管驱油效率可在水驱的基础上提高19.1%;非均质填砂管并联驱油时,注入复配体系可进一步驱洗高渗填砂管残余油并有效封堵高渗通道,扩大低渗填砂管的波及系数,分液率从0增至34%。从矿场实践来看,A20井组实施层内自生低界面张力泡沫调驱作业后,生产曲线呈含水下降、产油上升的形态,3个月内累计增油2007.29 m3,初步说明层内自生低界面张力泡沫调驱技术在海上油田具有广阔的推广应用前景。

低碳钢及其不锈钢复合钢材低周疲劳行为的对比研究

不锈钢复合钢材在土木工程结构中得到了越来越多的关注和应用,但是其在循环荷载作用下的力学行为还缺乏足够的认识。通过单轴拉伸试验和不同应变幅条件下的对称应变控制加载低周疲劳试验,对比研究了2 mm+10 mm热轧304+Q235B不锈钢复合钢材及其基层Q235B碳钢钢材的循环弹-塑性特性和低周疲劳寿命;结合数值模拟得到的疲劳试件截面应力分布,分析了复合钢材低周疲劳失效模式的力学机理。结果表明,在拉伸和循环荷载下,复层304不锈钢与基层Q235B碳钢之间均没有出现界面剥离现象;复合钢材及Q235B碳钢均表现出与加载应变幅正相关的循环硬化行为,且前者的循环应力响应大于后者;复合钢材的低周疲劳初始裂纹均出现在Q235B碳钢侧,这是由于复层不锈钢和基层碳钢不同的拉应力状态和塑性变形能力共同造成的,但是复合钢材与Q235B碳钢的低周疲劳寿命未表现出明显的区别。该批次304+Q235B不锈钢复合钢材具有良好的低周疲劳性能,可代替Q235B碳钢用于对腐蚀防护性能具有较高要求的工程构件中。

SIAPES的合成及低温油藏原位乳化驱油体系构建与性能

W/O型乳液驱油是一项有效提高老油田采收率技术。但低温条件下常用的乳化体系不能同时满足形成W/O型乳液和降低界面张力。本文合成并表征了异构十三醇聚氧乙烯醚磺酸钠(SIAPES),并与椰子油烷基二乙醇酰胺(CEDA)复配构建了低温油藏原位乳化驱油体系,评价了体系的乳化性能、降低了油水界面张力并改善了岩石润湿性能力。同时利用在线NMR驱替系统揭示了原位乳化驱油体系在低温油藏条件下提高采收率的潜力。结果表明:原油-地层水自乳化相变点为60%,利用原位乳化驱油体系对油水自乳化进行干预后,乳液相变点提高到65%,且发生相变后乳液黏度明显高于自乳化乳液的黏度,流度控制能力增强;原位乳化驱油体系能将油水界面张力由12.00 mN/m降低至0.12 mN/m,改善亲油岩心润湿性至亲水;在渗透率级差为12,水驱至经济极限的条件下,0.6 PV的原位乳化驱油剂驱和后续水驱使采收率提高了26.8%。

电力线路施工中张力或低张力放线的施工要点及管理对策

在电力系统建设工程的施工过程中,线路施工是最重要的一个施工环节。随着时代的不断发展,在电力系统施工技术水平不断提高的形势下,如果继续使用传统的放线方式,不仅影响整个电力线路施工的效率,还有可能出现导线磨损问题,使电力系统投入运行后存在较大的安全隐患。张力或低张力放线是一种全新的放线施工方式,本文重点针对这种全新放线方式在电力系统施工中的应用要点和管理对策进行了详细的分析,旨在提高整个电力线路的施工效率与施工质量,以供同行参考。

天然来源的表面活性剂在超低渗油藏开发中的应用

因为国内大部分油田目前已经进入开发后期,在孔渗较好的圈闭已经钻探殆尽的大背景下,超低渗油藏开发便成了主要研究方向。在开发实践中,采用皂苷为原料制备了一种新型表面活性剂,这种活性剂为天然来源,并通过界面张力、接触角和石油采收率评估等实验说明其在以碳酸盐岩为代表的超低渗储层中具有良好的应用价值。评估了表面活性剂产生泡沫并在微观和宏观尺度上建立稳定乳液的能力。研究结果表明,当表面活性剂质量浓度达到1800 mg·L^(-1)时,界面张力将大幅度降低,最低达到0.39 mN·m^(-1)。此外,通过优化盐度,界面张力将降低到最低0.36 mN·m^(-1),这表明了盐度控制对于降低界面张力的作用。实验结果表明,该天然来源的新型表面活性剂在其临界胶束浓度下表现出优异的乳液稳定性,持续了6个月性质未发生显著变化;这种新型的表面活性剂产生的泡沫同样表现出了显著的稳定性,半衰期长达30 min。因此,在最佳条件下进行的驱油实验中,该新型表面活性剂溶液处于其临界胶束浓度并且盐度和碱度水平得到优化,原油采收率显著提高了25%,相比于传统的表面活性剂具有更为良好的化学性质,为未来的超低渗透油藏开发带来显著增益。

钻井液用耐低温乳化剂的研制与性能评价

油基钻井液性能稳定,常应用于复杂地层开发,但在零下低温环境中存在黏度、切力上涨过快的问题。为解决这一问题,制备了一种耐低温高性能乳化剂ZF-SB,该乳化剂具有超低凝点(-33℃),解决了传统液体乳化剂零下低温无法流动的问题,可显著降低油水界面张力,由其配制的乳状液粒径在0.6~4.2μm之间,粒径分布窄,其破乳电压为1397V,有利于油基钻井液在低温条件下的稳定状态。另外,由耐低温乳化剂ZF-SB配制的油基钻井液在0℃以下仍具有良好的流变性,避免了油基钻井液由于低温增稠效应而造成井底当量循环密度(ECD值)高、井漏和压力控制难等问题。

奥氏体不锈钢全奥氏体组织熔敷金属中Ni含量对力学性能影响

为了研究Ni含量对全奥氏体组织熔敷金属力学性能的影响,采用铬当量相近、Ni质量分数不同的6种E316LMn-15焊条,通过控制其它化学成分,避免金属间化合物的形成并减弱了热裂倾向。分别对SMAW施焊后熔敷金属进行光学金相组织观察、铁素体测量、室温拉伸试验和-196℃冲击试验。结果表明,熔敷金属均为以奥氏体模式凝固的全奥氏体组织,具有良好的室温拉伸性能,抗拉强度均在520 MPa以上,屈服强度均超过380 MPa,断后伸长率也都在35%以上;同时熔敷金属均具有较高的低温韧性,-196℃平均冲击吸收能量均超过60 J。Ni的质量分数在15.58%~16.04%范围内,-196℃平均冲击吸收能量提升幅度大于Ni质量分数在16.04%以上的熔敷金属,且Ni质量分数在16.27%以上的熔敷金属低温冲击吸收能量趋于稳定,Ni质量分数为16.85%的试样-196℃平均冲击吸收能量高达90.4 J。

一种应用于低渗透储层的高性能防水锁剂

低渗透油气藏具有岩石致密、物性差和孔喉细小的特点,外来流体在毛细管力作用下进入储层孔喉中,造成水锁损害,严重影响低渗透储层油气藏的产量。针对这一问题,以全氟辛酸、单乙醇胺和氯乙酸钠为原料制备高性能氟碳防水锁剂(FS-1),通过红外光谱对其结构进行了表征,并研究了该氟碳防锁水剂对盐水溶液在岩心孔喉中水锁性能的影响。结果表明,该防锁水剂显著降低盐水溶液的表面张力(小于15 mN/m),且使蒸馏水在砂岩表面的接触角增大至85.3°,表明防水锁剂FS-1可将岩心表面润湿性由亲水性反转为中性湿,有降低了水相对岩心的水锁损害。另外,防锁水剂FS-1含有多个吸附、抗盐基团,提高分子在岩石表面的吸附能力,且使其耐盐能力达到了7%(NaCl)。渗吸实验、渗透率测试实验和核磁共振实验发现该防水锁剂减缓岩心的自吸作用,降低了岩心孔喉对盐水的束缚能力和岩心的水锁损害,提高了岩心渗透率恢复率。

低渗透油藏用纳米乳液性能评价与应用

结合低渗透油藏驱油技术特点,研究了纳米乳液降低界面张力能力、耐温抗盐能力、改变岩石润湿性能力和驱油效果。试验结果表明,纳米乳液质量浓度为1 000 mg/L时,与原油的界面张力能够达到10-3mN/m数量级,并且表现出较强的耐温抗盐和改善岩石润湿性的性能,质量浓度为2 000mg/L的纳米乳液的水溶液能在岩心水驱的基础上进一步将采收率提高20%以上。该纳米乳液产品已在江苏油田井组应用,取得了显著的驱油效果。