Visco-elastic Properties of VES Diverting Acid for Carbonate Reservoirs

Storage modulus and loss modulus is the main performance index of visco-elastic properties.In this paper the storage modulus and loss modulus of a new diverting acid and their influencing factors were systematically investigated.Besides,the constitutive equations of the diverting acid at different temperatures were elicited from shearing experiments,which show that the visco-elastic surfactant(VES)acid system is a non-Newtonian power law fluid at low temperature and a Newtonian fluid at high temperature.The storage modulus and loss modulus at different temperatures,pH,and VES content in the acid are critical for the design of acid stimulation for oil well,especially when the VES acid is used in this field only on trial and the basic data are in urgent needed for the design and construction of the acidification stimulation.

Nursing care of 22 patients with complex intracranial aneurysms treated with flow-diverting stents:A retrospective study

Objective:To summarize the nursing treatment of patients who underwent implantation of a blood flow diverter to treat complex intracranial aneurysms.Methods:Data from 22 patients with complex aneurysms,diagnosed at an interventional center for blood flow diverter implantation between February 2015 and February 2016,treated in the Henan Provincial People’s Hospital(Zhengzhou,China),were retrospectively analyzed.Nursing methods,including preoperative,intraoperative,and postoperative care,were analyzed.Results:All 22 patients underwent successful surgery,with no related complications or hospital mortality,and were cured in hospital.Conclusion:Interventional flow diverter therapy for patients with complex intracranial aneurysms is a new technology,and involves intensive care by nursing staff and appears to be a promising new treatment method.

Compact Pneumatic Pulse-Jet Pump with Venturi-Like Reverse Flow Diverter

A compact pneumatic pulse-jet pump with a Venturi-like reverse flow diverter,which consists of a nozzle and diffuser,is designed for lifting and transporting a hazardous fluid through a narrow mounting hole.The pumping performance for a liquid mixture or a liquid-solid mixture is examined in terms of the effects of liquid viscosity,particle mass concentration,lifting height,and compression pressure.Results reveal that the pumping performance of the compact pneumatic pulse-jet pump is controlled by jet inertia and the flow resistance of the riser tube positioned after the diffuser.The capacity of the compact pneumatic pulse-jet pump increases with compression pressure and decreases with liquid viscosity.However,even for a liquid mixture with a high viscosity of 7.38 mPa·s,a pumping capacity of 170.7 L·h-1 was observed.For a liquid mixture,two dimensionless indices of performance were found to be the ratio of Euler numbers Euout/EuDV and the suction factor q.As the liquid-solid mixture was lifted to elevation of 6.74 m by the compact pump,the particle size distributions of the liquid-solid mixture in the tank and from the riser tube outlet were determined by a particle size analyzer and found to coincide well.

Plasma discharge characteristics of segmented diverter strips subject to lightning strike

In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.

Effects of Geometric Configurations on the Performance of Reverse Flow Diverters in Reverse Flow Mode

The reverse flow diverter (RFD) consisting of a nozzle and a diffuser is a key component in pneumatic pulse jet pumps. We investigated the effects of suction gap and diffuser configurations on RFD performance during the reverse flow mode. Three suction gap configurations were examined: (1) an axisymmetrical cylinder, (2) a cuboid whose bottom plane had no half-circle groove and was level with the diffuser entrance lower border, and (3) a cuboid with a half-circle groove on the bottom plane. Among them, the second one resulted in the highest RFD pumping capacity. The effect of receiver presence before the diffuser was also examined. RFD pumping efficiency was found to be enhanced in the presence of a receiver before the diffuser when the suction gap length is small and the jet outlet velocity at the nozzle exit is high enough. Based on experimental data, a dimensionless performance curve of the suction factor q versus the ratio of Euler numbers in sections out-out and 0-0 Eu out /Eu 0 was derived. This curve is insensitive to suction gap configurations.

Growth rate of peeling mode in the near separatrix region of diverted tokamak plasma

An analytical expression of the peeling mode in the near separatrix region of diverted tokamak plasma is derived. It is shown that in diverted plasmas both with single and double X points, though the perturbed potential energy of the unstable peeling mode tends to be large, its growth rate becomes very small due to the even larger kinetic energy. Compared to some recent studies that give qualitatively correct results about this growth rate, our result is directly related with the diverted equilibrium quantities suitable for application to realistic experiments.

Self-consistent diverted tokamak equilibria with nonzero edge current

The semi-analytical method, previously used to construct model double-null and single-null diverted tokamak equi- libria （Bingren Shi, Plasma Phys. Control Fusion 50 （2008） 085006, 51 （2009） 105008, Nucl. Fusion 51 （2011） 023004）, is extended to describe diverted tokamak equilibria with nonzero edge current, including the Pfirsch Schliiter（PS） cur- rent. The PS current density is expressed in a way suitable to describe a diverted tokamak configuration in the near separatrix region. The model equilibrium is expressed by only two terms of the exact separable solutions of the Grad Shafranov equation, one of which is governed by a homogeneous ordinary differential equation, and the other by an inhomogeneous one. The particular merits of such a model configuration are that the internal region inside the separa- trix and a suitable scrape-off layer can be simultaneously described by this exact solution. To investigate the physics in the region near the X-point, the magnetic surfaces can be satisfactorily described by approximate hyperbolic curves.

Experimental study of the temporary plugging capability of diverters to block hydraulic fractures in high-temperature geothermal reservoirs

The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.

基于divert socket的应用层防火墙

针对包过滤防火墙和状态检测防火墙的安全控制层次较低、控制能力有限、不能依据数据包内容进行控制的缺点,介绍一种在FreeBSD的IPFW防火墙之上,使用转发套接字建立进程级应用层防火墙的技术。通过这种技术建立的应用层防火墙既保留包过滤防火墙和状态检测防火墙对用户透明的优点,又具有针对特定应用进行访问控制的能力。

自升式钻井平台Diverter Flooding系统设计

由自升式平台主船体潜水泵出口管路直接为泥浆分流器提供flooding海水，与传统flooding系统相比，该设计方案海水供水管线的水压、流量均可达到泥浆分流器预期工作要求，且不影响平台其他用水设备的正常运转，使平台钻井工作可以顺利进行。

Diverting agents in the oil and gas industry:A comprehensive analysis of their origins,types,and applications

During the life of a well,treatments are carried out to boost productivity by stimulating initially unproduced zones.These treatments include hydraulic fracturing,matrix acidization,and acid fracturing,among others.Hydraulic fracturing treatment is generally applied to deeper reservoirs of oil or natural gas for enhanced recovery.By infusing proppant,water,and chemicals under extreme pressure during the fracturing procedure,fissures in and beneath the reservoir layer can be accessed and expanded.Another stimulating procedure,matrix acidization,involves injecting acid down the drilling hole to permeate the rock fissures at stresses lower than the fracture stress.In addition,carbonate reservoir acid fracturing stimulation is commonly used as an acid treatment technique whereby a pressure greater than the formation disintegration pressure or spontaneous fracture closure pressure is used to compress acid into the reservoir.These treatments allow existing wells to sustain hydrocarbon production without new wells being drilled.Diverters,when employed efficiently,can prevent the need to use a rig to provide momentary physical barriers,thus lowering the cost of the workover.Recent improvements in diversion technology make use of a variety of degradable particles that act as momentary bridges,either at the perforation entries or inside the existing fractures.The aim of this study is to introduce different types of mechanical and chemical diverters used to enhance the productivity of wells.This study explains the concepts of different types of diverters and their applications in several formations,it will also help readers to understand the selection procedures based on the suitability and requirements of diverter use by case studies from around the world.

A proposed design of flow diverter and it’s hemodynamic validation

Flow diverter intervention is a cutting-edge treatment for intracranial aneurysms by altering the flow field and reducing the pressure in the aneurysm sac.However,the rupture rate and complications rate are still high.In this study,a new design of flow diverter based on Bernoulli’s equation was proposed and hemodynamics evaluation of it was conducted.The numerical model of a patient specific internal carotid aneurysm was established based on computed tomography scan images(Model C).The aneurysm models with normal diverter(ND)and local stenosed diverter(LSD)were modified from the patient-specific model.The blood flow characteristics were obtained and analyzed by numerical simulation while the in vitro experiments were conducted using three-dimensional printed silicone models and pressure measurement system.In both ND and LSD models,the blood flow into the aneurysm have been significantly blocked by the diverters and the pressure in the aneurysm sac have been decreased.The pressure drop and the wall shear stress on the aneurysm wall in the LSD model are higher than that in the ND model.The oscillatory shear index and relative residence time in the aneurysm wall of LSD are lower than that in the ND model.The pressure measurement in the vitro experiment also qualitatively verified the results of pressure comparison in the numerical simulation.In conclusion,the simulation results and in vitro experiments verified that diverter can certainly reduce the pressure in the aneurysm,and the newly design diverter with local stenosis can strengthening this effect.

Transient simulation of a differential piston warm gas self-pressurization system for liquid attitude and divert propulsion system

In order to obtain the dynamic characteristics of a differential piston warm gas selfpressurization system for liquid attitude and divert propulsion system, a transient model is developed using the modular modeling method. The system includes the solid start cartridge,pressure-amplified tank with liquid monopropellant, liquid regulator, gas generator, and pipes.The one-dimensional finite-element state-variable model is applied to the pipes and the lumped parameter method is adopted for the other modules. The variations of the system operation parameters over time during the startup, steady-state, and pulsing operational processes are obtained from the transient model, and the characteristics of starting time changing with different system parameters are also analyzed. It is shown that the system startup process can be divided into three distinct processes. The starting time monotonically changes with variations of the liquid regulator parameters, first decreasing and then increasing with the mass change of the solid propellant charge of the start cartridge, initial gas cavity volume of the pressure amplified tank and initial gas cushion of the propellant tank. The starting time can be reduced to less than 1.0 s（0.68–0.75 s for the current system）. For meeting the deviation requirements of ±10% of the steady-state propellant tank pressure, the positive deviation requirement is assured by the self-locking pressure and the negative deviation can be assured within an allowable maximum propellant tank volume flowrate（1.6 times the design value for the proposed system） for downstream thrusters for a designed system. The results from the simulation are useful as a guide for further system design and testing.

Computational methods applied to analyze the hemodynamic effects of flow-diverter devices in the treatment of cerebral aneurysms:Current status and future directions

Flow diverter(FD)devices have been widely employed to treat cerebral aneurysms.Despite the well-documented clinical benefits,considerable inter-patient variability in clinical outcome has been reported,which implies the necessity of patient-specifically evaluating hemodynamic changes following FD treatment,especially those associated with posttreatment intra-aneurysmal thrombus formation or complications.Computational fluid dynamics(CFD)methods,owing to the advantages in hemodynamic quantification,cost,and flexibility over traditional in vivo measurement or in vitro experiment methods,have increasingly become a major means for addressing hemodynamic problems related to FD treatment.Relevant CFD-based studies have extensively demonstrated that the results of hemodynamic computation can reasonably explain the clinical outcomes in different patient cohorts and provide useful insights for guiding the selection or optimization of FD devices.Nevertheless,CFD models are inherently unable to predict FD implantation-induced mechanical changes in the walls of aneurysm and its parent artery.In addition,the boundary conditions of most existing CFD models were not fully personalized for purpose of simplicity or due to the difficulty of measuring flow velocity in nearaneurysm regions,which may however considerably compromise the fidelity of the models in reproducing in vivo hemodynamics.To address these issues,the following studies would be expected:(1)perform fluid structure interaction simulations to explore the associations between wall stress/tension and posttreatment adverse vascular remodeling or aneurysm rupture,and(2)develop geometrical multiscale models based on available in vivo data to generate patient-specific boundary conditions for CFD models localized to aneurysm regions.

Hemodynamic analysis for endovascular treatment in small unruptured intracranial aneurysms:a matched comparison study of flow diverter versus LVIS

Background:We compared the treatment of small unruptured intracranial aneurysms(UIAs)with flow diverter and LVIS-assisted coiling to determine the effects of hemodynamic changes caused by different stent and coil packing in endovascular treatment.Methods:Fifty-one UIAs in 51 patients treated with pipeline embolization device(PED)were included in this study and defined as the PED group.We matched controls 1:1 and enrolled 51 UIAs who were treated with LVIS stent,which were defined as the LVIS group.Computational fluid dynamics were performed to assess hemodynamic alterations between PED and LVIS.Clinical analysis was also performed between these two groups after the match.Results:There was no difference in procedural complications between the two groups(P=0.558).At the first angiographic follow-up,the complete occlusion rate was significantly higher in the LVIS group compared with that in the PED group(98.0%vs.82.4%,P=0.027).However,during the further angiographic follow-up,the complete occlusion rate in the PED group achieved 100%,which was higher than that in the LVIS group(98.0%).Compared with the LVIS group after treatment,cases in the PED group showed a higher value of velocity in the aneurysm(0.03±0.09 vs.0.01±0.01,P=0.037)and WSS on the aneurysm(2.32±5.40 vs.0.33±0.47,P=0.011).Consequently,the reduction ratios of these two parameters also showed statistical differences.These parameters in the LVIS group showed much higher reduction ratios.However,the reduction ratio of the velocity on the neck plane was comparable between two groups.Conclusions:Both LVIS and PED were safe and effective for the treatment of small UIAs.However,LVIS-assisted coiling produced greater hemodynamic alterations in the aneurysm sac compared with PED.The hemodynamics in the aneurysm neck may be a key factor for aneurysm outcome.

适配变压器全档位切换暂态分析的有载分接开关电路模型构建

有载分接开关(on-loadtap-changer,OLTC)是换流变压器的核心组件,其可靠切换过程关乎换流变的安全。然而目前国内在运特高压换流变用OLTC完全依赖进口,仿真获取OLTC不同运行状态的暂态特性数据是支撑OLTC关键电气参数设计与国产化制造的基础。经典的OLTC模型仅改变变压器变比或仅模拟单级档位切换过程,难以满足全档位电压调整与各级档位暂态特性数据同步获取的需求,导致OLTC设计优化、参数选型及故障分析缺乏足够的仿真数据支持。该文首先以真空OLTC为研究对象建立切换开关和极性开关等效电路模型,根据OLTC复杂的调压功能建立分层控制系统。其次,在PSCAD中搭建交流仿真系统,获取有载调压过程的暂态特性数据波形,与解析计算得到的电压和电流相比误差小于0.2%,证明该模型满足OLTC电磁暂态仿真研究的精度要求。最后,开展循环调压仿真,获得负载电压数据与波形。结果表明:该文提出的OLTC模型能够接收外部控制信号,进行全档位调压与极性转换仿真分析,能够为OLTC的调压研究、故障溯源分析和过渡电阻设计选型等提供基础模型。

营商环境与企业“脱实向虚”

基于A股上市公司数据,探讨在“以国内大循环为主体,推动国内国际双循环相互促进”背景下的营商环境改善对企业“脱虚向实”的影响及其内在作用机制。研究发现,地区营商环境越好,企业的金融资产投资水平越低;基于“行政审批中心设立”的准自然实验,进一步证实营商环境的改善显著降低了企业的金融资产持有水平。机制检验发现,这一效应的产生是通过降低企业经营风险和提高实体投资效益两条路径实现的。拓展性研究发现,营商环境改善在降低企业金融资产投资的同时,提高了企业对研发的投资;这些效应在中小企业和非国有企业中尤为显著。上述结果表明营商环境的改善有助于激励企业“脱虚向实”,这在政策层面意味着改善营商环境可能是解决经济“脱实向虚”和民营企业、中小企业纾困发展两大问题的一剂良药。

转向酸用缓蚀剂的制备及缓蚀机理

转向酸广泛应用于碳酸盐岩储层酸化酸压,由于黏弹性表面活性剂分子结构特殊,常规缓蚀剂配伍性较差,且缓蚀效率大幅降低。采用1-氯甲基萘、4-乙基吡啶、氯化苄和2,3-环戊烯并吡啶合成了2种吡啶季铵盐缓蚀剂SI-1和SI2。采用腐蚀仪、流变仪考察了SI-1和SI-2在转向酸中的缓蚀性能及其对转向酸黏度的影响;通过扫描电子显微镜、能谱仪、原子力显微镜和X射线光电子能谱等实验手段,从微观角度分析钢片腐蚀前后表面形貌和化学成分;采用分子动力学模拟方法对缓蚀剂SI-1和SI-2的缓蚀机理进行了探讨。结果表明:合成的2种吡啶季铵盐缓蚀剂在转向酸中的缓蚀性能良好,对转向酸黏度影响小,适用性强,成本低。其中缓蚀剂SI-2性能更优,1%加量下,90℃腐蚀速率为1.04 g/(m^(2)·h),120℃腐蚀速率为7.43 g/(m^(2)·h),VES残酸最终黏度可稳定在190 mPa·s以上,成本可降低20%。加入1%缓蚀剂后钢片表面均未出现明显腐蚀,Fe含量大幅上升,表面粗糙度大幅降低,其中添加缓蚀剂SI-2后,Fe含量从86%上升至94%,Ra从137 nm下降至84 nm。钢片表面均检测到C—N与Organic C=O(羰基),表明存在缓蚀剂吸附膜。分子动力学模拟显示缓蚀机理为:SI-2能隙小,吸附能大,缓蚀剂吸附到钢片表面后可形成致密吸附膜,隔绝腐蚀介质与钢片表面的接触,极大地抑制钢片腐蚀。SI-2在渤海油田和伊拉克米桑油田进行了现场应用,施工效果良好。

强非均质砂岩清洁暂堵转向酸化研究:以塔中志留系为例

酸化是低渗砂岩油藏有效开发的主要改造手段之一。塔中志留系储层小层多,非均质性强,酸化中酸液易进入高渗层,导致低渗层改造欠缺,目前尚无合适的砂岩转向酸化技术。本文采用了可完全水溶降解的清洁暂堵粉末,并配合螯合酸解决了非均质砂岩储层均匀酸化难题。通过并联岩心酸化流动仪,研究了清洁暂堵粉末封堵特性和不同级差下暂堵转向酸化能力。室内实验结果表明,清洁暂堵粉末降解主要受温度控制,在超过90℃后完全降解,降解后溶液清澈透明,且呈酸性,有效提升岩心渗透率20%。浓度为0.1%的暂堵粉末随螯合酸注入岩石后,能够形成内外阻挡层,增加暂堵表皮系数,最大封堵压差可达1.87 MPa,是单纯注螯合酸酸的6.7倍。并联岩心酸化实验表明100目清洁暂堵粉末在0.1%使用浓度下适用于渗透率级差小于15的储层,可有效降低岩心渗透率非均质差异,提高低渗岩心改造程度。此外,在塔中11-9井酸化施工中,暂堵转向酸化后增压效果明显,酸化后产量大幅增加。现场试验及应用证明,暂堵转向酸化技术在志留系储层取得了良好的增产改造效果,对长井段非均质砂岩储层酸化均匀改造具有重要的借鉴意义。

吕家坨选煤厂粗煤泥分选回收工艺改造

阐述了吕家坨选煤厂为解决原有粗煤泥分选与回收系统分选效果差、回收效率低的问题,采用超级煤泥重介质旋流器+两段弧形筛+煤泥离心机回收工艺,对原有粗煤泥分选系统进行技术改造。改造后超级煤泥重介质旋流器对0.25~0.10 mm粒级分选可能偏差E pm低至0.087 kg/L,分选下限低至0.10 mm,两段精煤泥弧形筛筛分效率高达80.55%,增加精煤产率约0.6%,每年可给选煤厂增加税前利润3600万元。