Correlations Between the Pour Point/Gel Point and the Amount of Precipitated Wax for Waxy Crudes

Abstract:

The amount of precipitated wax is one of the key factors that governs the flow properties of waxy crudes. Experimental results of 24 crudes have shown that approximately 2 wt% precipitated wax is sufficient to cause a virgin waxy crude gelling. Accordingly, a correlation between the pour point and the temperature at which 2 wt% of wax has precipitated out from a crude oil; i.e., T _c (2 wt%), and a correlation between the gel point and T _c (2 wt%) have been developed. The proposed correlation of the pour point is in accordance with the correlation developed by Letoffe et al. (1995) Letoffe, J. M., Claudy, P., Kok, M. V., Garcin, M. and Vollet, J. L. 1995. Fuel, 74(6): 810–817. [CSA][CROSSREF][Crossref] , [Google Scholar] on the basis of 14 crudes from eight countries. The development of the gel point correlation and further verification of the pour point correlation indicate that there is a relationship between the gelling of virgin waxy crudes and the amount of precipitated wax. According to these correlations and the amount of precipitated wax, which can be determined only with a little sample by thermodynamic models or Differential Scanning Calorimetry (DSC) experiment, the gel point and pour point of virgin waxy crude can be predicted even if the oil sample is very limited. Heat treatment and chemical treatment can greatly improve flow behavior of waxy crudes, and more precipitated wax is present when the beneficiated (thermally beneficiated or PPD-beneficiated) crude oils gel. Experimental results showed that approximately two or three times the amount of precipitated wax presents at the gelling temperature when the oils were in their beneficiated (thermally beneficiated or PPD-beneficiated) conditions.     

前南高蜡原油降凝剂的研究

文章选择了几种不同的单体进行聚合反应,得到了两种三元聚合物,并分别和EVA进行复配。依次考察了两种复配型降凝剂在不同加剂量和不同温度下对前南原油的降凝效果。实验结果表明:在加剂温度为70℃时,AMS-EVA复配降凝剂的最佳加剂量为0.03%,可使前南原油凝点降低9℃;AVS-EVA复配降凝剂的最佳加剂量为0.1%,可使前南原油凝点降低10℃。这两种复配型降凝剂均可以降低前南原油的黏度,改善其低温流变性。     

用于高含蜡原油的双聚合物降凝剂的研制

通过在有机溶剂中进行的引发聚合 ,由摩尔比 2∶3∶3的马来酸酐、丙烯酸十八酯、醋酸乙烯酯合成了共聚物降凝剂A ,由摩尔比 1∶2∶3的苯乙烯、马来酸酐、丙烯酸十八酯合成了共聚物降凝剂B。A和B均为质量分数 30 %的溶液。简介了合成方法。A +B组合实验和组合物加量实验结果表明 ,对于密度 86 8.9kg m3、含蜡量 2 6 .6 %的辽河曙光原油 ,质量比 3∶1的A +B的降凝降粘效果最好 ,加入量为 0 .5 %时原油凝点由 2 9℃降至 2 1℃ ,80℃、15 0s- 1下的粘度由 2 0 0 0mPa·s降至 95 0mPa·s,降粘率达 5 2 .5 % ;对于密度 886 .7kg m3、含蜡量 18.9%的吉林新民渣油(原油减压蒸馏釜底残液 ) ,质量比 1∶2的A +B的降凝降粘效果最好 ,加入量为 0 .4 %时渣油凝点由 13℃降至 1.0℃ ,80℃、15 0s- 1 下的粘度由 95 0mPa·s降至 2 6 0mPa·s,降粘率达 72 .6 %。降凝剂A +B加量增大时 ,原油和渣油的凝点、粘度均降低。表 3参 8。     

聚合物/微纳米复合含蜡原油降凝剂的研究进展

含蜡原油中蜡分子的结晶析出会使原油的低温流变性显著恶化,降低原油管输的安全性和经济性.添加少量的聚合物型降凝剂能够改变蜡分子的结晶习性,改善原油的宏观流动性.加降凝剂原油的凝点越低、低温黏度越小,意味着输送的能耗越低、安全性越高,因此人们对原油降凝剂的降凝降黏效果追求是无止境的.利用不同的微纳米颗粒,研制高效的聚合物/...     

降凝剂对高蜡稠油的改性效果及机理研究

实验研究了工业品原油降凝剂WHP改善含蜡56.9%、其中96.6%为正构烷烃的胜利郑王庄稠油流动性的效果。WHP含乙烯/醋酸乙烯/乙烯醇嵌段聚醚三元共聚物30%-35%。在60℃将WHP加入稠油中,测定其凝点和32℃、0-42.6 s^-1范围5个剪切速率下的黏度,均随WHP加量的增加（50-300 mg/L）而降低,200 mg/L为最佳加量,在该加量下0.32 s^-1黏度由34.16 Pa·s降至79.2 mPa·s,凝点（℃）、屈服值（Pa）、稠度系数（Pa·s^n）分别由49.0、32.42、31.57降至39.5、0.1297、0.02142,流型指数由0.1176升至0.9790。由黏温曲线求出,加入200mg/L WHP使该稠油析蜡点由65℃降至58℃,反常点由70℃降至50℃。根据空白和加剂原油扫描电镜照片显示的蜡晶形态,利用共晶机理分析讨论了WHP这种高分子表面活性剂的降凝、降黏、改善流动性的作用。图3表3参5。     

Prediction of Viscosity Variation for Waxy Crude Oils Beneficiated by Pour Point Depressants During Pipelining

Pour-point-depressant (PPD) beneficiation is an emerging technology for facilitating pipelining of waxy crude oils. However, it was found both in lab studies and field tests that the viscosities of PPD-beneficiated waxy crude oils may increase as a result of pump shear or pipe flow shear during pipelining, called the shear effect. Current method for understanding this viscosity variation is to measure the viscosities by experimental simulation, which is quite time- and effort-consuming for long-distance pipelines. A new method for predicting the viscosity variation during pipelining is presented in this article based on a mathematical model for predicting viscosity of PPD-beneficiated waxy crude oils at certain temperature after shear and a model for predicting non-Newtonian viscosity of waxy crude oils as a function of temperature and precipitated wax. As verification, viscosity variations of five PPD-beneficiated waxy crude oils during pipelining are predicted by using the presented method and compared with the measured data from experimental simulations. The predicted viscosities are in good agreement with the measured data, with an average absolute deviation of 14.1% for all 52 data points. Comparisons between the measured or predicted viscosities during pipelining and viscosities obtained from the fast cooling experiment of PPD effectiveness evaluation demonstrate that the evaluation of PPD effectiveness for practical application should take the shear effect into consideration. The presented method provides a new way to evaluate the PPD's effectiveness in pipelining application quickly and effectively.     

The Formation of Waxy Crude Oil-in-water Emulsions for the Reduction of Pour Point and Viscosity

Waxy crude oil is characterized by high pour point and poor flow properties, which bring great difficulty to the oil exploitation and transportation. In this study, the fluidity of waxy crude oil with the pour point of 47°C was highly improved by emulsification with synthetic formation water used as aqueous phase. It was found that the combination of CAO-35 and sodium oleate was an effective emulsifier mixture to form stable waxy crude oil-in-water emulsion and when the mass ratio of oil to water was 7:3, the optimum composition of emulsifying additives with respect to the total mass of the emulsion was obtained as follows: emulsifier mixture (the mass ratio of CAO-35 to sodium oleate was 8:2) 0.4% (w/w), sodium triphosphate 0.028% (w/w), NaOH 0.05% (w/w), and polyacrylamide 0.15% (w/w). Diverse factors affecting the pour point of the formed emulsion were also studied. It was found that the pour point of emulsion increased as oil content increased and the optimum mixing speed and cooling rate were 600 rpm and 0.5°C/min, respectively. Under the optimum emulsifying conditions, when mixing speeds were 250 and 600 rpm, respectively, by forming O/W emulsions with the oil content of 70%, the pour point reductions were 20 and 25°C, respectively, and the corresponding viscosity reductions were 89.79% and 97.46% (40°C), respectively. Thus the pour point and viscosity of waxy crude oil are obviously reduced by forming oil-in-water emulsion, which is highly promising for the exploitation and transportation of waxy crude oil.     

BEM系列原油流动性改进剂的研制

通过对EVA的醋酸乙烯含量、熔融指数对含蜡原油的降凝影响的研究 ,探讨EVA对含蜡原油的最佳加入量以及不同的结构表面活性剂对原油降凝剂抗重复加热和抗剪切能力的作用 ,BEM降凝平均相对分子质量与含蜡原油蜡碳数分布之间的关系等。研制的BEM降凝剂广泛用于鲁宁线、中洛线等多条管输管道     

辽化蜡油降凝剂的合成

以反丁烯二酸、14醇与26醇的混合物(混合醇)、醋酸乙烯酯为原料,采用"先酯化后聚合"的方法,合成了一种适用于辽化蜡油的降凝剂——反丁烯二酸混合醇酯-醋酸乙烯酯(简称酯-酯)共聚物。利用FTIR,1H NMR,GPC等方法分析了该共聚物的结构。通过单因素及正交实验确定了合成该共聚物适宜的酯化条件和聚合条件分别为:n(反丁烯二酸)∶n(混合醇)=1∶1、酯化溶剂甲苯的用量25.0%(w)(基于反应体系质量,下同)、对甲苯磺酸催化剂用量1.5%(w)、酯化时间3.0 h;n(反丁烯二酸混合醇酯)∶n(醋酸乙烯酯)=1∶1.25、聚合溶剂甲苯的用量50.0%(w)、过氧化苯甲酰引发剂用量1.75%(w)、聚合温度85℃、聚合时间3.5 h。酯-酯共聚物用作辽化蜡油降凝剂时,适宜的降凝条件为:共聚物用量0.4%(w)(基于辽化蜡油的质量)、热处理温度70℃、热处理时间30 min。     

降凝剂对高蜡原油流变性的影响

研究了降凝剂对高蜡原油流变性的影响,进行了降凝剂的筛选、不加剂和加剂高蜡原油粘温曲线的测定,考察了重复加热和高速剪切对降凝剂改性效果的影响及降凝剂的静态稳定性。实验结果表明,在70℃温度下,原油中加入100μg/g(EVA AA)降凝剂,原油凝点从35℃降至23℃,并使原油反常点降低,原油的牛顿流体温度范围变宽,非牛顿流体温度下的粘度减小;当重复加热温度低于70℃时,降凝剂的改性效果显著恶化,重复加热温度越低,影响越大;在原油析蜡高峰区,高速剪切将使降凝剂改性效果变差;静态稳定性实验结果表明,该降凝剂静态稳定性较好。     

管输原油降凝剂的研究进展

总结了石蜡结晶机理及其影响因素,并对国内外含蜡原油降凝剂的发展过程、作用机理、常用降凝剂的种类以及影响降凝剂作用效果的各种因素进行了介绍;指出了降凝剂在研究和应用中存在的问题,对降凝技术的发展进行了客观评价和展望。     

甲基丙烯酸十八酯-顺丁烯二酸酐-醋酸乙烯酯-苯乙烯降凝剂对原油蜡晶形态的影响

用偏光显微镜(PLM)观察甲基丙烯酸十八酯-顺丁烯二酸酐-醋酸乙烯酯-苯乙烯(OMVS)降凝剂添加量对原油蜡晶形态的影响。实验结果表明,随OMVS降凝剂添加量的增加,蜡晶由不规则的棒状和片状逐渐变为粒径小、分散均匀的近似球状的蜡晶;PLM表征结果显示,加入OMVS降凝剂的非洲原油和国产原油的蜡晶颗粒数均由不到100个增至大于1300个和1700个,原先占主导地位的表面积较大(非洲原油150～250μm2和国产原油100～200μm2)的蜡晶个数由超过60%降至1%以内,表面积较小(5～50μm2)的蜡晶个数由不到10%增至90%以上。通过指数回归可确定OMVS降凝剂添加量-蜡晶平均表面积-降凝幅度的内在关系,计算结果与实验结果吻合。     

高含蜡柴油用PCH降凝剂应用效果评价

简述了国内外降凝剂发展概况,分析了南阳石蜡精细化工厂生产的柴油对目前国内外降凝剂感受性差的主要原因,选择PCH降凝剂作为高含蜡柴油降凝剂。实验及工业应用表明,PCH降凝剂能有效地降低该厂柴油的冷滤点,当加入量为0．05％,调合柴油的冷滤点下降4℃,满足了油品的使用标准;并使柴油收率提高2％,经济效益明显。PCH降凝剂与现行国内外降凝剂产品相比,具有独特效果,对高含蜡柴油具有极好的推广应用价值。     

高蜡原油化学降凝作用机理与影响因素

阐述了国内外原油降凝剂的发展概况,介绍了原油降凝剂的降凝机理,考察了影响降凝效果的因素,包括原油组成和性质、相对分子质量、胶质、沥青质等。提出应加强对原油降凝剂降凝机理、原油降凝与不同化学剂互配的影响以及原油降凝剂研究方向等问题的研究。     

新型蜡晶分散助剂的制备及柴油降凝研究

以乙二胺、丙烯酸甲酯、丙烯酸高碳酯为原料，乙醇钠为催化剂，通过Michael加成和酰胺化反应，合成了一种含有长链烷基和多氨基、酰胺基极性官能团的柴油蜡晶分散助剂。红外光谱检测表明产物与理论设计相符。降凝实验表明，单独添加1000μg/g蜡晶分散助剂时，冷滤点降低2—4℃；与降凝剂T1804复配时，凝点最大降低15℃，冷滤点最大降低9℃；与自制降凝剂复配后，凝点最大降低11℃，冷滤点最大降低7℃。说明制备的蜡晶分散助剂与降凝剂有良好的协同效应。     

高凝原油降凝剂使用效果及性能

对一种新型液体原油降凝剂KYJN-1进行了室内模拟试验,考察了该降凝剂在实际运行环境下的使用性能及存放条件.试验结果表明,在加剂量为50 mg/L,热处理温度为75℃的最佳条件下,该降凝剂能降低原油凝固点8～13℃,现场生产运行环境对降凝效果没有影响,降凝剂现场存放温度为40～45℃.     

高凝油/水相对渗透率的确定

高凝油／水相对渗透率是研究高凝油多相渗流规律和进行油田动态预测的重要依据。由于高凝油在低于其析蜡点的某一温度下，呈非牛顿流作的流动特征，故常规的确定油／水相对渗透率的方法不完全适全于高凝油／水体系。文中以辽河油田沈北高凝油为样品，采用加压式细管流变仪，确定了高凝油在不同温度下的流变性。证明沈北高凝油在低于析蜡点某一温度下，是幂律流体，推导了关于蜡沉积所产生的岩石渗透率降低系数的计算公式。依据高凝油流变性及石蜡在岩石孔道表面的沉积两个因素，修正了常规计算油水相对渗透率的JBN方法。利用修正的公式计算了高凝油／水的相对渗透率，得到了准确反映高凝油渗流规律的结果。     

旅大原油降凝剂的研究

针对旅大原油高含蜡特性,比较了本实验优选合成的EVA改性型降凝剂ZLX-01与市售7种降凝剂对旅大原油的降凝效果,并探讨了影响加剂效果的因素。实验结果表明,旅大原油最佳热处理温度为50～55℃,降凝剂ZLX-01最优加剂量为300 mg/L,原油凝点由加剂前的22℃降至9℃,反常点由加剂前的35℃降至30℃。在原油温度25℃、剪速12 1/s下,加入300 mg/L的降凝剂ZLX-01后,原油表观黏度由加剂前的420 mPa.s降至116 mPa.s,降黏率为72.4%。重复加热温度低于40℃时会恶化加剂原油的低温流变性,此外加有ZLX-01的原油还具有较好的静态稳定性。图2表4参2     

苯乙烯—马来酸酐—丙烯酸十八烷基酯三元共聚物的合成及其降凝性能

合成了用作降凝剂的苯乙烯－马来酸酐－丙烯酸十八烷基酯三元共聚物。研究表明,当苯乙烯、马来酸酐、丙烯酸十八烷基酯三种单体摩尔比为1∶3∶3,原油预热温度为60℃,三元共聚物在江汉原油中加量为300mg/L时,此三元共聚物可使江汉原油的凝固点为28℃降到13℃。它是一种新型的原油降凝剂。     

Experimental Research on the Wax Crystal Particle Size Distribution of Waxy Crude Oil

The total settled mass of waxy crude oil has a close relationship with the particle size distribution of wax crystals. Wax crystal images of four kinds of crude oils were obtained with OPTIPHOT2-POL polarizing microscope. The wax particle size distribution was confirmed by image processing and data analysis. The results strongly suggest that wax particle size correspond to gamma distribution. Moreover, the range of wax particle size distribution expands with the increasing of temperature.