Multiple time scales of fluvial processes — theory and applications

Fluvial processes comprise water flow, sediment transport and bed evolution, which normally feature distinct time scales. The time scales of sediment transport and bed deformation relative to the flow essentially measure how fast sediment transport adapts to capacity region in line with local flow scenario and the bed deforms in comparison with the flow, which literally dictates if a capacity based and/or decoupled model is justified. This paper synthesizes the recently developed multiscale theory for sediment-laden flows over erodible bed, with bed load and suspended load transport, respectively. It is unravelled that bed load transport can adapt to capacity sufficiently rapidly even under highly unsteady flows and thus a capacity model is mostly applicable, whereas a non-capacity model is critical for suspended sediment because of the lower rate of adaptation to capacity. Physically coupled modelling is critical for fluvial processes characterized by rapid bed variation. Applications are outlined on very active bed load sediment transported by flash floods and landslide dam break floods.     

黏弹性聚合物驱驱替动态与不同注入参数分析

基于质量守恒定律,建立三相五组分考虑聚合物弹性增黏、降低残余油和稠油黏弹性效应的聚合物驱数学模型,并采用IMPES方法进行求解.计算分析表明,黏弹性聚合物驱可降低残余油饱和度,增加驱油体系黏度,提高原油采收率;采收率随注入浓度增大先迅速增加后趋于稳定,最优值为2 000 mg·L^-1;随注入速度先增加后降低,存在最优值;随聚合物段塞增大先迅速增加后缓慢增加并趋于稳定,最佳注入量约为0.6 PV;随原油松弛时间增加呈线性增加.     

中低渗透高温高盐油藏驱油共聚物P(AM/AMPSNa/AANa)的合成及性能

在中低渗透高温高盐油藏聚合物驱技术中, 超高相对分子质量聚丙烯酰胺(HPAM)存在不易注入、剪切降粘显著和耐温抗盐性能差等问题。 本文以丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为单体, 采用过硫酸胺(NH₄)₂S₂O₈和甲基丙烯酸N, N-二甲氨基乙酯(DMAEMA)作为支化结构复合引发体系, 通过共聚后水解工艺, 合成含支化结构耐温抗盐驱油共聚物P(AM/AMPSNa/AANa)。 研究了引发温度、链转移剂用量、引发剂用量对共聚物特性黏数的影响, 并通过红外光谱(IR)和¹³C NMR表征了产物结构。 筛选特性黏数1915 mL/g左右的共聚物, 进行性能评价。 实验结果表明, 共聚物具有优异的耐温抗盐性能、抗剪切性能、抗老化性、注入性和驱油性能, 可应用在中低渗透高温高盐油藏三次采油中。     

三元复合驱碱/表面活性剂/聚合物模拟原油乳状液稳定动力学特性

基于两相分离的乳状液稳定模型,研究了三元复合驱模拟原油乳状液稳定动力学特性;通过液膜强度和油水界面张力探讨了碱/表面活性剂/聚合物对模拟原油乳状液稳定动力学特性的影响机理。 结果表明,乳状液稳定模型可以很好的评价乳状液的稳定性,并得到乳状液的稳定动力学特性;碱浓度小于900 mg/L有利于乳状液的稳定,碱浓度大于900 mg/L不利于乳状液的稳定;表面活性剂和聚合物浓度的增加使得形成的模拟原油乳状液更加稳定;模拟原油乳状液的稳定作用主要是通过碱、表面活性剂降低油水界面张力并增加油水界面膜强度,聚合物通过提高界面膜强度实现的,三者存在协同效应。     

基于泡沫微观渗流特征的泡沫驱数学模型

通过泡沫微观渗流实验可以看出泡沫在多孔介质内呈现两种渗流状态:流动泡沫和捕集泡沫.泡沫封堵实验可以看出泡沫封堵能力具有叠加性,当泡沫驱达到稳态后,岩心入口端泡沫封堵压力梯度小于岩心后段封堵压力梯度.基于泡沫总量平衡思想和泡沫性质表征模型,建立泡沫驱多组分数学模型.对该模型进行数值求解,模型采用全隐式方法求解.通过与泡沫封堵实验拟合,验证了模型的有效性,在此基础上研究了泡沫驱过程中不同位置处泡沫数目、压力、含水饱和度等泡沫驱渗流特征参数变化规律.     

油田注聚泵站变频器常见故障及处理

本文描述变频器的工作原理和性能,介绍了在油田注聚泵站应用中变频器常见故障问题、处理方法以及注意事项,对变频器在注聚泵站中的推广应用具有良好的指导作用。     

一种抑制MANET网关洪泛策略

在MANET子网互连架构中,其网关发现采用洪泛通告报文的方式,所形成的广播风暴引起较大控制开销。由此提出一种动态自适应网关发现协议,该协议可根据MANET的移动节点信息自适应设置网关通告报文GWADV的TTL值和发送间隔,同时采用基于距离门限的动态计数DDC网关洪泛通告报文抑制策略。仿真结果表明,该协议可以有效地应对网关洪泛通告报文的问题,在保持较高分组投递率的同时,能够减小时延和控制开销。     

Formation and rupture mechanisms of visco-elastic interfacial films in polymer-stabilized emulsions

Considering the need for low oil price, polymer flooding has been demonstrated to be vitally important for enhanced oil recovery (EOR) in the oil industry. However, polymer-stabilized emulsions form during the displacement process, causing severe challenges in oilfield surface production, including separation performance, high operation and maintenance costs, pollution of facilities, and human health and environmental threats. In this paper, the formation and rupture of visco-elastic interfacial films are described. The emulsification structure of the polymer-stabilized emulsions is emphasized, and the film thickness is both measured and calculated. Furthermore, the thinning behavior of the interfacial films is presented based on the established destabilization process with a pulsed electric field. The emulsion stability theory is in good agreement with experimental results. The concentration of back-produced polymer is responsible for the increase in the elastic modulus of the interfacial films and dominates the formation and stability of the interfacial films. The rupture mechanism of the films and their ability to overcome droplet coalescence primarily depends on the thinning characteristics of the films in polymer-stabilized emulsions. By understanding the destabilization process, an improved thinning rate can be achieved for visco-elastic interfacial films, and the rupturing rate of high-strength films can be promoted.     

Demulsification of produced liquid from surfactant-polymer flooding

Treatment of the produced fluid obtained by surfactant-polymer (SP) flooding is difficult because of the stabilizing effects exhibited by surfactants and polymers on oil-in-water emulsions. For the produced fluid from Xinjiang oilfield, YH-1 (a mixture of 603 and YB-990) showed promising demulsification effects. When the dosage of YH-1 was 20?mg/L at 323?K, the dewatering efficiency reached no less than 72% even when both surfactant and polymer contcentrations were 1200?mg/L. Experimental results showed that YH-1 reduces the water content in crude oil to no more than 20%, which meets the commercial requirements before entering the electronic field. Demulsification performed by thermal-chemical and electric field treatments further reduced the water content in crude oil to less than 2.0%.     

Research on Protecting Against SYN Flooding on a Firewall

1　IntroductionTheSYNFloodingattacksexploitTCP sthree wayhand shakemechanismanditslimitationinmaintaininghalf openconnections,andareper formedbytheattackersubmittingastreamofTCPSYN (connectionrequest)packetstothetargetsys tem ,fillingitsconnectionrequestqueue,andthusdenyinglegitimateusers accesstothetargetsys tem[1 ] .SYNFloodingdoesgreatharmtopopularwebsites,especiallytoe Businessones.Severalapproacheshavebeen proposedtocounterSYNfloodingattacks.SYNCache[2 ] andSYNCookie[3] canmiti…