Effect of Alkali on Daqing Crude Oil/Water Interfacial Properties

Alkaline-surfactant-polymer （ASP） flooding using sodium hydroxide as the alkali component to enhance oil recovery in Daqing Oilfield, northeast China has been successful, but there are new problems in the treatment of produced crude. The alkali added forms stable water-in-crude oil emulsion, hence de-emulsification process is necessary to separate oil and water. The problems in enhanced oil recovery with ASP flooding were investigated in laboratory by using fractions of Daqing crude oil. The oil was separated into aliphatics, aromatics, resin and asphaltene fractions. These fractions were then mixed with an additive-free jet fuel to form model oils. The interfacial properties, such as interfacial tension and interracial pressure of the systems were also measured, which together with the molecular parameters of the fractions were all used to investigate the problems in the enhanced oil recovery. In our work, it was found that sodium hydroxide solution reacts with the acidic hydrogen in the fractions of crude oil and forms soap-like interfacially active components, which accumulate at the crude oil-water interface.

Study on Viscoelastic Behaviors of Waxy Crude Water-in-Oil Emulsion

Emulsion of waxy crude oil is one of the common states in the subsea pipeline. At low temperatures in offshore environment, waxy crude oils with water could form the crude oil emulsion gel of oil-in-water emulsion. Thus, the waxy crude oil emulsion viscoelastic behavior for deep sea transportation and restarting pipeline safety is particularly important. By means of MASIII HAAKE rheometer which is produced by German company, waxy crude oil emulsion viscoelastic behavior is explored at different volumetric water contents and different shear stresses. By analyzing the rate of change of shear rate in the initial stage, the influence rules of viscoelastic properties were summarized, with the change of volumetric water content and the applied shear stress and based on the experimental results, the law of emulsion is explained from the micro level. It is proposed that brittle fracture exists between wax crystals, and flexible fracture was found in the interaction between water droplets and wax crystals.

Nonlinear Behavior and Domain Feature at Oil/Water Interface

Studies on nonlinear behavior at oil/water interface membrane were performed. This system showed rhythmic oscillations and chaos of electrical potential in a given concentration domain. The nonlinear behavior response at the liquid membrane apparently resembled that of biological chemoreceptive membrane. The possibility of developing a new type of chemical sensor with the ability to simulate substance equilibrium in living organisms was suggested in the paper.

An experimental and numerical study of chemically enhanced water alternating gas injection

In this work, an experimental study combined with numerical simulation was conducted to investigate the potential of chemically enhanced water alternating gas （CWAG） injection as a new enhanced oil recovery method. The unique feature of this new method is that it uses alkaline, surfactant, and polymer additives as a chemical slug which is injected during the water alternating gas （WAG） process to reduce the interfacial tension （IFT） and simultaneously improve the mobility ratio. In essence, the proposed CWAG process involves a combination of chemical flooding and immiscible carbon dioxide （CO2） injection and helps in IFT reduction, water blocking reduction, mobility control, oil swelling, and oil viscosity reduction due to CO2 dissolution. Its performance was compared with the conventional immiscible water alter- nating gas （I-WAG） flooding. Oil recovery utilizing CWAG was better by 26 % of the remaining oil in place after waterflooding compared to the recovery using WAG conducted under similar conditions. The coreflood data （cumulative oil and water production） were history mat- ched via a commercial simulator by adjusting the relative permeability curves and assigning the values of the rock and fluid properties such as porosity, permeability, and the experimentally determined IFT data. History matching ofthe coreflood model helped us optimize the experiments and was useful in determining the importance of the parameters influencing sweep efficiency in the CWAG process. The effectiveness of the CWAG process in pro- viding enhancement of displacement efficiency is evident in the oil recovery and pressure response observed in the coreflood. The results of sensitivity analysis on CWAG slug patterns show that the alkaline-surfactant-polymer injection is more beneficial after CO2 slug injection due to oil swelling and viscosity reduction. The CO2 slug size analysis shows that there is an optimum CO2 slug size, around 25 % pore volume which leads to a maximum oil recovery in the CWAG process. This study shows that the ultralow IFT system, i.e., IFT equaling 10 2 or 10 3 mN/ m, is a very important parameter in CWAG process since the water blocking effect can be minimized.

The Colored Oil Property Effect on Switching Behavior of Electro-Fluidic Display

The switchable oil layer driven by electrowetting gives visible color and light valve control, which is the basis of Electro-Fluidic Displays. The colored oil’s property is a key factor that influences the Electro-Fluidic Displays switching behavior. A purple oil was formulated by the oil-soluble purple dye in decane in this study. The dye molecule itself is nonpolar and it doesn’t dissolve in water. The concentration of colored oil influenced the oil/water interfacial tension and oil viscosity. The relationship of EFD switching behavior with oil/water interfacial tension, oil viscosity, and oil conductivity has been systematically investigated. The oil/water interfacial tension decreased with increasing oil concentration, in the meanwhile, the conductivity increased. Oil conductivity was one of the key factors that influenced the Electro-Fluidic Displays optical property. We found for the first time that at the lower oil concentration (2% - 10%), the interfacial tension plays a main role effect on the rupture voltage and response time, but as the conductivity of higher concentration of colored oil increased (at 20%), the rupture voltage-controlled both by conductivity and interfacial tension.

表面活性剂对水驱普通稠油油藏的乳化驱油机理

为了研究乳化降黏驱油剂对不同渗透率的水驱普通稠油油藏的驱油效率和孔隙尺度增效机理,选取了烷基酚聚氧乙烯醚(J1)、α-烯基磺酸盐类表面活性剂(J2)、十二烷基羟磺基甜菜碱(J3)、J3与烷基酚聚氧乙烯醚羧酸盐复配表面活性剂(J4)作为驱油剂,开展了4种驱油剂一维驱油和微观驱油模拟实验,明确了乳化降黏驱油剂在孔隙尺度的致效机理。结果表明,降低界面张力对提高驱油效率的作用大于提高乳化降黏率。在油藏条件下,乳化降黏驱油剂需要依靠乳化降黏和降低界面张力的协同增效作用,才能大幅提高驱油效率。乳化降黏驱油剂的乳化能力越强、油水界面张力越低,驱油效率增幅越大。当化学剂乳化降黏率达到95%时,油水界面张力从10^(-1)mN/m每降低1个数量级,化学剂在高渗透和低渗透岩心中的驱油效率依次提高约10.0%和7.8%。乳化降黏驱油剂注入初期通过降低界面张力,使得高渗透岩心和低渗透岩心中的驱替压力分别为水驱注入压力的1/2和1/3,从而提高注入能力。注入后期大块的原油被乳化形成大量不同尺寸的油滴,增强原油流动性,提高驱油效率。乳化形成的界面相对稳定的稠油油滴,能暂堵岩石的喉道和大块稠油与岩石颗粒形成的通道。油滴的暂堵叠加效应,使高渗透和低渗透岩心的驱替压差分别为水驱压差的5.2倍和32.3倍,大幅提高了注入压力,从而扩大平面波及面积。降黏驱油剂驱油实现了提高驱油效率的同时扩大波及范围。研究结果为水驱稠油开发用驱油剂的研发提供参考,为大幅提高水驱普通稠油采收率奠定基础。

汽提净化水回用原油电脱盐过程的溶解性有机物转移特征

汽提净化水回用原油电脱盐是炼化企业重要的节水措施。本研究基于气相色谱-质谱和静电场轨道阱高分辨质谱组合分析,从微观层次上探究了汽提净化水回用电脱盐过程的溶解性有机物转移特征。电脱盐过程中,汽提净化水有13种芳香胺类、34种含氮杂环类、13种中长链烷基酚类和1种醚类化合物转移到油相,对油品品质影响轻微,对油品收率有所促进,同时可将电脱盐污水的有机负荷总量降低约50%。原油中的8种环烷酸类、7种含氧杂环类、3种短链烷基酚类、504种低不饱和度的O_(2)、O_(4)、O_(3)S_(1)和N_(1)O_(3)类以及186种高不饱和度的O_(4)S_(1)和N1O_(2)类化合物转移到水相,使得电脱盐污水的有机污染组成更为复杂,急性生物毒性更强。本研究对于掌握高浓度点源污水的水质特性、提高炼化企业污水管控水平具有指导意义。

水包油乳状液稳定性影响因素分析研究综述

管道运输是油品运输的重要方式之一,所以稠油乳状液在运输过程中的稳定性对运输效率起到决定性作用。不同类型的表面活性剂、界面张力、油水比、乳化温度、分散相粒径、化学添加剂、界面电荷等对稠油乳状液稳定性有着不同的影响,而影响水包油乳状液稳定性的主要因素是稠油乳状液分散性粒径的大小、界面张力和油水界面膜的性质。分析了平均粒径、界面张力和油水界面膜性质对水包油型稠油乳状液的稳定性影响,探究了使其稳定的机理和影响平均粒径、界面张力、油水界面膜性质的因素,并对水包油乳状液稳定性研究的发展前景进行展望。

乳状液体系中气体水合物成核过程研究进展

乳状液中气体水合物成核行为研究可用于评估油-气-水体系在亚稳态下稳定存在的时间,对低温环境下多相混输管道的安全运行和水合物风险控制策略的制定具有重大意义,因而成为深水管道流动安全保障的重点问题和研究热点。本文着眼于油水乳状液体系中气体水合物的成核过程,总结了实验研究中水合物成核速率的量化方法,细致分析和比较了当前研究中诱导期定义方法的异同,梳理了温度、压力、扰动强度、含水率和原油组分等环境条件和体系组成对水合物成核行为影响的研究成果及水合物成核速率预测模型。总体来看,油水乳状液中水合物的成核行为已经得到了较为深入的研究,在影响因素定性分析和模型定量描述等方面取得了一定成果,但在诱导期定义方法的统一和模型的工程化应用等方面仍需进行更为细致的研究。未来,应逐步建立统一的诱导期定义标准和更为普适性的诱导期预测模型,借助谱学仪器和分子动力学模拟等手段加深对水合物成核过程分子尺度信息的认识,更加深入理解水合物成核机理并逐渐实现量化模型的工程化应用。

纳米颗粒间相互作用对油-水界面张力的影响机制

为了研究油-水界面上纳米颗粒的动态吸附过程及其对界面张力的影响,采用耗散粒子动力学模拟方法,建立纳米颗粒在油-水界面物理模型,研究单颗粒的吸附动力学过程及多颗粒相互作用对界面张力的影响机制。结果表明:单颗粒在油-水界面的吸附分为自由扩散、界面吸附、动态平衡3个阶段;单颗粒吸附过程自由能变化远大于颗粒的动能,颗粒吸附可自发、快速进行,且吸附后能稳定在界面上;多颗粒间的相互作用力随颗粒间距离的增大而振荡衰减,这是由颗粒间的溶剂粒子所产生的溶剂化效应所致;当颗粒间相互作用为引力时,界面张力增大,当颗粒间相互作用为斥力时,界面张力减小。

油田深度调剖化学剂驱油效率与机理

随着石油资源的日益紧张,提高油田开采效率成了石油行业面临的主要挑战。选用3种不同的化学剂(PAM、SDBS、PAA)并通过测定岩心渗透率和油水界面张力进行驱油效率实验。实验结果显示,PAA在提高岩石渗透率方面表现最为突出,从130.14 m D增加到212.43 m D,增幅为63.2%,而SDBS则在降低油水界面张力方面表现最佳,从38.92 m N·m^(-1)降至21.00 m N·m^(-1),降低了46.2%。此外,在中温(40℃)和中压(20 MPa)以及适中的注入流量(100 L·min^(-1))下,驱油效率达到最优。化学剂在改变岩石孔隙结构及降低油水界面张力方面的作用,共同促进了油水流动性的提升,从而显著增强了整体的驱油效果。研究结果对于指导实际油田作业中化学剂的选择和应用具有重要的参考价值,为油田开发提供了新的视角和方法。

高效深度调剖化学剂在提高采收率中的应用及机理研究

通过高效液相色谱分析、界面张力仪测量、岩心驱替实验和扫描电子显微镜观察等实验方法,探究了高效深度调剖化学剂在提高采收率中的应用及其作用机理。结果表明:该化学剂主要由交联聚合物(58.6%)、表面活性剂(29.5%)和纳米粒子(11.9%)组成,具有良好的流变性能和热稳定性。化学剂在25℃时的黏度为121.6 mPa·s,随温度升高而降低,但在100℃时仍保持58.3 mPa·s的黏度;化学剂能显著降低油水界面张力,从32.6 mN·m^(-1)降至9.6 mN·m^(-1);在岩心驱替实验中,使用该化学剂后的额外采收率达到了19.2%,总采收率提高到47.8%,最佳的注入参数组合为化学剂质量分数0.5%,注入速率0.5 mL·min^(-1),注入量1.0 PV。机理分析表明,该化学剂通过降低油水界面张力、改善油藏渗透性、调整流动阻力和改变孔隙结构等多重机制,有效提高了采收率。该研究为油田的高效开发提供了新的技术支持,对于提高油田采收率具有重要的理论意义和应用价值。

Theoretical Insight into the Effect of Steam Temperature on Heavy Oil/Steam Interface Behaviors Using Molecular Dynamics Simulation

The interfacial behavior between heavy oil and steam is one of the vital pointers affecting the development efficiency of steam injection for heavy oil recovery.However,the underlying mechanisms of the interaction between heavy oil and steam at high temperature and pressure remain elusive.Herein,we have investigated the molecular-scale interactions on the interface between heavy oil droplet and steam phase at high temperatures(473 K,498 K,523 K,and 548 K)via molecular dynamics simulations.The results show that the interfacial thickness between heavy oil droplet and steam phase increases gradually with temperature,while the interfacial tension decreases constantly.Moreover,high temperature can damage hydrogen bonds,resulting in lower interaction energy between heavy oil droplet and steam phase.The radial distribution function results demonstrate that the interaction between heavy oil fractions and steam phase can be weakened by high temperature.Furthermore,the evolutions of interface are directly observed by the two-dimension density cloud maps at different temperatures,and the mean square displacement and self-diffusion coefficient demonstrate the evolution mechanism of heavy oil fractions and steam.In particular,the heavy oil/steam systems with asphaltenes at the interface are more likely to achieve high diffusivity and emulsifying capacity.This work provides a molecular-level insight for understanding the interfacial interaction mechanisms of heavy oil/steam systems during a steam injection process.

Effect of water salinity on oil/brine interfacial behaviour during low salinity waterflooding: A mechanistic study

In recent years,controlling the salinity and composition of the injected water has become an emerging enhanced oil recovery(EOR)technique,often described as low salinity(LS)waterflooding.This work is done with the intention to contribute to the ongoing discussions about LS waterflooding mechanism(s).For this purpose,a series of different experiments were conducted.At first,the effect of salinity on the interfacial tension(IFT)and the contact angle was evaluated with a crude oil sample.Then to achieve more accurate results in observing oil/water interface,similar IFT experiments were also carried out on a synthetic oil containing asphaltenes.Thereafter,microscopic visualization using glass micromodel was performed on the interface of the synthetic oil sample and brines.Four brine solutions including Sea Water(SW),it's dilutions and formation water(FW)were used for various experiments.Finally,to investigate the presented mechanism by other authors,a series of Environmental Scanning Electron Microscopy(ESEM)analysis on the synthetic oil was carried out to understand better the phase behaviour after contacting both synthetic oil and water phases from the micromodel experiment.Based on the existing mechanism,there exists an optimal concentration beyond which dilution is no longer an effective process.

Preparation of Hollow Calcium Silicate Microparticles by Simple Emulsion

Hollow calcium silicate microparticles were prepared by mixing a water-in-oil (W/O) emulsion containing silicate ions in aqueous phase with an oil phase containing a calcium/di-2-ethylhexyl phosphoric acid (D2EHPA) complex. The inorganic precipitation reaction at the oil-water interface was accelerated by using a simple W/O emulsion. Hollow microparticles were obtained when the mole ratio of D2EHPA and calcium in the oil phase was nearly 2:1. The shell formation of the par-ticles depended on the acceleration of the precipitation reaction, which could be accomplished by controlling the concentrations of the calcium and silicate ions.

二氧化碳响应型表面活性剂与稠油的相互作用

CO_(2)驱是提高稠油采收率的重要发展方向,使用各种助剂辅助CO_(2)进一步提高采收率是常用手段,但智能型阳离子表面活性剂与稠油之间的相互作用及其乳化降黏性能的研究鲜见报道。通过十六烷基三甲基氢氧化铵(1#)与CH_3COOH、CO_(2)反应制备了表面活性剂2#—4#,研究了1#—4#表面活性剂表面活性、对十二烷的乳化能力、1#—4#溶液与稠油的界面张力以及对稠油的乳化行为。研究结果表明,2#—4#的表面活性以及对十二烷的乳化能力与1#的变化不大;但1#对稠油会发生反相乳化,而2#—4#对稠油有明显的降黏能力。特别是CO_(2)反应比例较低时,可以与CTAOH生成一种“拟双子型”表面活性剂(4#),油水界面张力可达到10^(-3)mN/m超低数量级,乳化降黏率达98%以上。利用该类表面活性剂的温度响应的特点,通过升高温度可以加速乳状液的油水分离,从而实现驱油效果好和采出液易处理两方面的兼顾。本文研究结果对于稠油二氧化碳驱技术增效具有借鉴意义。

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.

分子动力学模拟表面活性剂降黏效果

目前应用于原油降黏方面的表面活性剂种类众多,宏观实验方法无法全面准确地描述降黏机理。利用计算机模拟实验过程及结果,对油田自主研发的三种表面活性剂PS-30、BS-12以及复配型表面活性剂FP1进行降黏效果对比,以分子动力学方法按照油水混相模拟分析并得到以下结论:三种加剂油水体系中,BS-12油水体系的界面生成能为-615.04kJ/mol,PS-30油水体系为-2312.42kJ/mol,FP1复配油水体系为-4156.32kJ/mol。界面生成能的绝对值越大,说明其降低油水界面张力的能力越强,降低界面张力的能力为:FP1>PS-30>BS-12。分子模拟中各表面活性剂加入体系后,FP1、PS-30和BS-12油水体系模型的密度分别降低至0.84g/cm^(3)、0.85g/cm^(3)和0.87g/cm^(3)左右,降黏效果的排序为:FP1>PS-30>BS-12。根据各原油体系石油分子的径向分布函数显示,BS-12、PS-30、FP1原油体系的峰值依次为9.784、9.202、8.347,峰值越低,油水黏附力越小,故FP1的降黏效果最佳。

突缩管内环状流界面波动研究

油水环状流通过突缩管时,缩颈和细管入口处会形成涡旋,加剧两相界面波动,两相界面波特性的研究对探索油水环状流的流型演变、管内压降等具有重要意义.通过大涡模拟研究突缩管内油水环状流的界面特性,结果表明:突缩管内的二次流、脱体涡的产生和发展对油水两相界面有较大影响,随着水相表观流速的增大,细管入口涡区增大并向下游延伸,出现涡脱落,对油水界面造成明显的扰动.水相表观流速与管径比越大,两相界面波动越剧烈;表面活性剂可提高水环稳定性和管输能力.数值模拟了在不同浓度活性剂溶液作用下的界面特性:涡区有不同程度的增大,涡度略有减小,对两相界面波动影响不大.

不同水油黏度比下乳化对稠油复合驱的影响

化学复合驱是稠油提高采收率的关键技术之一,当前复合体系研发中越发强调乳化降黏机理,形成了高效乳化体系,但是强乳化产生的驱油增量尚不清楚,难以判断乳化对驱油的实际贡献。利用性能显著不同的1#(超低界面张力复合体系)、2#(乳化复合体系)、3#(兼顾超低界面张力和乳化的双效复合体系)体系,开展了系列的界面张力、乳化性能和不同水油黏度比下的驱油对比研究。结果表明,2#乳化复合体系和3#双效复合体系较1#超低界面张力复合体系更能稳定稠油乳状液。乳化对稠油复合驱的贡献因水油黏度比的不同而存在差异:水油黏度比小于0.200时,3#双效复合体系较1#超低界面张力复合体系采收率增幅高3.6%~6.7%,乳化能够增强体系驱油能力;当水油黏度比大于等于0.200时,3种复合体系驱油效果相近,乳化的影响显著减小,甚至可以忽略。泡沫复合驱较二元复合驱采收率增幅显著提高,且其可将稠油驱替对复合体系乳化性能要求的水油黏度比界限从0.200减小到0.150。对于稠油复合驱,应依据水油黏度比的差异,确定对复合体系性能的要求。