加剂柴油凝点及冷滤点反弹回升的研究

加入低温流动性能改进剂生产的低凝柴油，在储存和使用过程中存在凝点、冷滤点反弹回升现象，因此对辽河原油的常压柴油、加氢裂化柴油进行了加剂研究。在低温储存条件下，实际加剂柴油的凝点、冷滤点反弹回升幅度比常规测试的反弹幅度大，在0℃下放置6小时直接测定的加剂常压柴油的凝点回升幅度已经达到或超过在室温下放置35天的回升幅度。研究发现，加入低温流动性能改进剂能减缓蜡晶生长速度，但不能从根本上阻断蜡晶的生长。加剂柴油长时间处于低温时，柴油中的蜡晶逐渐长大，当蜡晶长大到某一定临界稳定尺寸时，会形成较大三维网状骨架，低温流动性能改进剂就失去降凝作用。     

剪切作用对加剂原油低温流动性影响的研究

加剂输送技术是目前主要的含蜡原油节能输送技术，原油管输过程中受到的剪切作用主要包括过泵加压时受到的高速剪切和管流剪切，在安装了减压阀的大落差段还包括减压阀的高速剪切，在原油析蜡高峰区的温度范围内，这些剪切作用都可能对加剂原油的低温流动性产生影响，这一影响的大小与原油的组成，剪切的温度，强度及时间等因素有关。概述了过泵高速剪切和管流低速剪切对加剂原油低温流动性的影响规律，剪切影响机理和剪切作用的描述方法等的研究现状及进展。     

环庆原油黏温曲线测定研究

为更好地研究原油黏温关系和蜡沉积状况,以环庆原油为研究对象,探讨分析了试验室热处理温度、剪切速率和升降温程序等因素对环庆原油黏温曲线、析蜡点及溶蜡点测定的影响。室内试验结果表明:热处理温度对环庆原油的析蜡点、溶蜡点有较大影响,高温可以显著改善原油低温流动性,但热处理温度过高、恒温时间过长时热处理效果变差;环庆原油溶蜡点比析蜡点高7~11℃左右;测定过程中,在析蜡高峰区附近要避免高速剪切和剪切时间过长;析蜡点测定中降温速率不易控制;溶蜡点在凝点之后的低温区测定结果不稳定。     

阿赛线首站原油流动性改进研究

针对阿赛线原油输油温度高、蜡堵现象严重等生产技术问题,评价与分析阿赛线原油对常用降凝剂EVA的感受性,为降低输油温度、保障输油安全奠定理论基础。以阿赛线首站原油为研究对象,采用原油凝点、流变学测试方法,评价典型国产降凝剂对阿赛线原油的降凝降粘效果,对比分析阿赛线原油加剂前后的蜡晶形态,探讨其低温流动改进的主要影响因素。结果表明,阿赛线原油在70 mg/kg的EVA作用下,凝点、反常点和低温表观粘度均有显著降低,但加剂温度及高速剪切对EVA的作用效果影响较大,当加剂温度低于60℃时,加剂作用效果明显变差;加剂原油在析蜡高峰期受到高速剪切时,其低温表观粘度随剪切作用增强而增大;长时间低速剪切对原油加剂效果影响不大。     

热处理对添加防蜡剂长庆原油流动性及蜡沉积特性的影响研究

基于流变性测试和蜡沉积实验研究了热处理温度对添加EVA/PAMSQ复合防蜡剂的长庆原油的流动性和蜡沉积特性的影响。研究发现加剂原油依然具有热处理效果,50℃热处理条件下加剂原油的流动性改进效果较差,随着热处理温度升高至60、70和80℃,加剂原油的流动特性(如凝点、黏度、小振幅振荡剪切特性)显著改善。80℃热处理条件下,加剂原油的凝点已低于0℃,表明热处理与EVA/PAMSQ复合防蜡剂具有良好的协同效果。同时,随着热处理温度的升高,加剂原油的蜡沉积速率逐渐降低,但蜡沉积物的含蜡量逐渐升高,这可能不利于蜡沉积物的剥离。蜡沉积物呈现出非均质结构,表层蜡沉积物为凝油状,底层蜡沉积物具有比表层蜡沉积物更高的析蜡点和屈服强度。     

加剂长庆原油的流变性研究

通过最佳加剂条件筛先,长庆原油添加30ppm的降凝剂GY3,其凝点,反常点和低温表观粘度有大幅度降约,当重复加热温度低于60℃时,重复加热会对加剂原油的低温流变性产生不利影响,重复加热温度越低,影响越大,当高速剪切温度低于30℃时,高速剪切将恶化加剂原油的低温流娈性,特别是在原油的析蜡高峰区高速剪切,会使原油的低温流变性严重恶化。     

梳型共聚物的相对分子质量调控及其对JENM原油 的降凝效果*

为降低高蜡型JENM原油的输送成本,合成了丙烯酸十八酯-丙烯酸二十二酯-马来酸酐梳型共聚物降凝剂,考察了降凝剂相对分子质量对降凝效果的影响,并通过优化反应条件实现对聚合物相对分子质量的调控,研究了加剂前后JENM原油的析蜡特性和蜡晶形貌的变化。研究表明,随着反应温度升高和反应溶剂用量增加,降凝剂的平均相对分子质量减小;随着引发剂用量的增加,降凝剂的平均相对分子质量先增大后减小。丙烯酸十八酯-丙烯酸二十二酯-马来酸酐降凝剂的平均相对分子质量约为14000时对JENM原油的降凝效果较好,典型优化合成条件为:反应温度100℃、溶剂用量77%、引发剂用量为单体质量的1%,合成的降凝剂加剂量为0.3%时,JENM原油凝点由30℃降至17℃,降幅为13℃;30℃时黏度由9.12 Pa·s降至2.24 Pa·s,降黏率为75%,显著改善了JENM原油的低温流动性。结合DSC和显微分析发现,降凝剂的加入使JENM原油析蜡点和析蜡峰温降低,凝点处析蜡量增加。降凝剂的极性基团抑制了蜡晶生长,促进了蜡分子的分散,使晶种在更低温度才开始析出。同时,由于蜡晶更加细小,析蜡量较大时才使原油失去流动性,从而有效降低了原油凝点。图11表2参18。     

胺解聚合物型原油降凝剂的合成及应用

通过丙烯酸高碳酯与马来酸酐、醋酸乙烯酯、苯乙烯共聚后进行不同系列胺解得到一系列新型高蜡原油降凝剂。考察了该类降凝剂对大庆高蜡原油和尼尔阿曼混合原油的降凝效果。结果表明，胺解聚合物型原油降凝剂具有较好的原油降凝性能，降凝幅度最高达到27℃；同时，测定了加剂温度对降凝剂降凝效果的影响，结果发现，当加剂温度高于原油析蜡温度时，降凝剂的降凝效果才能充分显现出来。     

基于差示扫描量热法的防蜡剂筛选

为了快速筛选评价出适合于J油田井筒的防蜡剂配方,利用差示扫描量热法（DSC）测定原油析蜡过程具有油样少、测试快、精度高的特点,对J油田B26井油样加剂前后析蜡参数进行分析。规范SY/T 0545-2012中采用的5℃/min降温速率并不适合文中所研究的油样,通过对比不同降温速率下的析蜡量与由SY/T 7550-2012所获得的含蜡量得出该油样最适宜的降温速率为13℃/min,以优选出的降温速率对B26井油样分别加入三种防蜡剂前后进行DSC析蜡参数测试。结果表明:DSC法可做为一种防蜡剂的快速筛选评价方法,筛选出的防蜡剂OGD6002效果最好,防蜡率达到66.3%。     

差示扫描量热法在优化原油清蜡剂配方中的应用

利用差示扫描量热法(DSC)测定原油析蜡参数快速准确、信息量大等特点,对取自玉门青西油田不同区块8个原油试样析蜡参数进行分析,得出原油的析蜡点、析蜡量、烃类化合物的碳链长度分布与支化度等参数,在此基础上筛选与之匹配的清蜡剂单剂,组配并优化清蜡剂配方;最后通过DSC法分析加剂前后原油析蜡热特性的变化,采用室内静态溶蜡法测...     

An Experimental Study of Rheological Properties of Nigerian Waxy Crude Oil

Abstract

Nigerian crude oils are known for their good quality (low sulfur, high American Petroleum Institute gravity). However, similar to any other paraffinic-based crudes, most Nigerian crudes contain moderate to high contents of paraffinic waxes. These waxy crudes exhibit non-Newtonian flow behavior at temperatures below the cloud point because of wax crystallization. In order to accurately predict flowing and static temperature profiles, design waxy crude oil pipelines, evaluate flow interruption scenarios, and start up requirements in the handling of waxy crude oils, the effect of temperature and shear rate on the rheology of crude oils must be determined. This work presented some experimental results on the rheology of two waxy crude oils produced from different Nigerian oil fields. A Brookfield DV-III ultraprogrammable rheometer (Brookfield Engineering Laboratories, Middleboro, MA) was utilized. The temperature dependence of rheological properties and thixotropy of these crudes were investigated. The influence of some petroleum-based diluents to depress the wax appearance temperature (WAT), their effect on the thixotropic/yield pseudoplastic behavior of two Nigerian crudes were studied and it was observed that lower wax content crude has higher tendency to regain its cohesive lattice bonding (yield strength) when left undisturbed for some days at its gel point after agitation. The experimental results showed that the addition of petroleum-based diluents to the lower wax content crude oil leads to its lost some of its yield strength regaining capacity.     

热处理温度对长庆原油蜡沉积特性的影响

通过Couette蜡沉积装置及DSC热分析探究了热处理温度对长庆原油蜡沉积特性的影响,发现随着热处理温度的升高,长庆原油蜡沉积速率减缓,蜡沉积层老化速率加快;经50 ℃和60 ℃热处理的长庆原油,蜡沉积层出现了分层现象,其表层为流动性较强的凝油状蜡沉积层,底层为结构较为致密的类固态蜡沉积层;经70 ℃热处理的长庆原油,蜡沉积层极薄且致密,无分层现象,其表面无凝油状蜡沉积层。采用沥青质分散程度分析、DSC热分析及蜡晶形貌显微观察探究了其影响机理,发现随着热处理温度的升高,长庆原油沥青质分散程度增大,从而使其析蜡点降低,蜡晶团聚性增强,原油低温流动性得以改善,进而对其蜡沉积特性产生了显著影响。     

The action mechanism of wax inhibitors (WI) on pour point and viscosity of mixed waxy oil

Several methods had been used to minimize the problems caused by wax deposition in crude oil pipelines during the production and transportation of waxy crude oil; among them, the continuous addition of wax inhibitor (Abbreviation for WI) is considered as the most efficient one. This study uses two kinds of polymeric compounds as wax inhibitors with different solvents on the pour point and viscosity of mixed waxy oils evaluated. These four wax inhibitors defined as WI-1, WI-2, WI-3, WI-4, respectively. Five types of mixed waxy oil have the same wax content but different resin contents. Meanwhile, different resin contents affect the pour point and viscosity of mixed oils. Under different processing temperature, the viscosity of mixed oil measured when the temperature changes among 20 to 60°С. In this work, the results were that the effect of WI-1 and WI-3 relied on the resin content, processing temperature and dosing concentration. For mixed waxy oils, the pour point reductions contacted with dosing concentration and the resin content. The wax inhibitor shows good efficiency when the resin content was between 1.01 and 4.03 wt %. When the WI-1 added, the pour point of mixed oil-1 reduced 30°С at most and viscosity of mixed waxy oil greatly reduced. In sum, toluene as solvent shows better performance of wax inhibitors.     

Viscosity Prediction of Non-Newtonian Waxy Crude Heated at Various Temperatures

Viscosities are important parameters for design and operation of crude pipelines. The heating temperature is the major factor affecting viscosities of waxy crude below the wax appearance temperature. Below the abnormal point, waxy crude exhibits non-Newtonian flow behavior with the viscosity dependent on the shear rate. Both of these make determination of the non-Newtonian viscosities of waxy crude a very time-consuming job. On the basis of the model for predicting non-Newtonian viscosity of waxy crudes as a function of temperature and precipitated wax, an approach to predict non-Newtonian viscosity of waxy crude heated to various temperatures has been developed only based on a few measurements. The accuracy of prediction by this approach has been verified by 468 viscosity data from the Daqing crude heated at various temperatures. The totally average relative deviation between the measured and predicted viscosity is 9.42%.     

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

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) 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.     

Effect of Crude Oil Composition and Blending on Flowing Properties

The effect of crude oil n-paraffin molecular weight distribution on wax crystallization risk was studied. Sixteen highly paraffinic crude oils from Eastern Venezuela were characterized, in terms of hydrocarbon family distribution, by High Temperature Simulate Distillation (HTSD), Gel Permeation Chromatography (GPC), and wax content. n-Paraffin chain length was correlated with crude oil cloud point and pour point. It was demonstrated that high molecular weight linear paraffins are responsible for crude oil wax precipitation. A quantitative correlation between molecular weight distribution and crude oil flowing properties was also obtained. It was found that the wider the molecular weight distribution, the lower is the wax crystallization risk. Blends of different paraffinic crude oils were prepared and their flowing properties were evaluated in comparison with the original crudes. Cloud points below the mean value were obtained. In some cases, a synergistic effect was observed (cloud points below the minimum of the two crude oils). Blends of some of these crudes with condensates afforded improvements on crude oil flow and a reduction of wax crystallization tendency (cloud point). This phenomenon can be attributed to a combination of two factors: I. increases in C24-n-paraffins, and II. a wider molecular weight distribution.     

Non-isothermal crystallization kinetics of waxy crude oil

The crystallization behavior of Shengli waxy crude oil from the sol state to gel state was studied by the microscopic observation and DSC curve. The study shows that as the cooling rate decreases, the number of wax grains becomes smaller, the area is larger and the morphology of wax crystals is more irregular. Moreover, under different cooling rates, wax crystals were homogeneous transient nucleation, but the growth mode of wax crystals was different. When the cooling rate is between 1–4?°C/min, Crystallization Peak 1 wax crystal grows according to the mixed crystal mode of one-dimensional rod crystal and two-dimensional discoid crystal; When the cooling rate is between 6–8?°C/min, Crystallization Peak 1 wax crystal grows according to the mixed crystal mode of two dimensional discoid crystal and three-dimensional spherical crystal; Crystallization Peak 2 wax crystal grows according to the mixed crystal mode of two dimensional discoid crystal and three-dimensional spherical crystal at different cooling rates. Crystallization activation energy of crystallization Peak 1 and Peak 2 are 556.91?kJ/mol and 299.62?kJ/mol, respectively.     

Effect of Crude Oil Composition and Blending on Flowing Properties

Abstract

The effect of crude oil n-paraffin molecular weight distribution on wax crystallization risk was studied. Sixteen highly paraffinic crude oils from Eastern Venezuela were characterized, in terms of hydrocarbon family distribution, by High Temperature Simulate Distillation (HTSD), Gel Permeation Chromatography (GPC), and wax content. n-Paraffin chain length was correlated with crude oil cloud point and pour point. It was demonstrated that high molecular weight linear paraffins are responsible for crude oil wax precipitation. A quantitative correlation between molecular weight distribution and crude oil flowing properties was also obtained. It was found that the wider the molecular weight distribution, the lower is the wax crystallization risk. Blends of different paraffinic crude oils were prepared and their flowing properties were evaluated in comparison with the original crudes. Cloud points below the mean value were obtained. In some cases, a synergistic effect was observed (cloud points below the minimum of the two crude oils). Blends of some of these crudes with condensates afforded improvements on crude oil flow and a reduction of wax crystallization tendency (cloud point). This phenomenon can be attributed to a combination of two factors: I. increases in C24-n-paraffins, and II. a wider molecular weight distribution.     

降凝剂对原油中蜡非等温结晶行为的影响

以乙烯-醋酸乙烯酯共聚物(EVA)和聚丙烯酸高碳醇酯(PA)为主要原料,制备了一种高凝原油降凝剂（PA-EVA）,采用差示扫描量热法研究了降凝剂的添加对原油中蜡的非等温结晶动力学的影响。结果表明：PA-EVA降凝剂起到了异相成核作用,使蜡的结晶峰温升高,结晶速率增大;PA-EVA降凝剂通过增大蜡晶几何尺寸,减少了对液态油的包覆,从而改善原油的流动性。     

A new experimental investigation on upgrading of waxy crude oils by methacrylate polymers

Several methods have been used to reduce problems caused by wax precipitation during the production and/or transportation of waxy crude oil. Polymers are used to improve pour point and rheological behavior of waxy crude oils. In this work, the influence of the polymer inhibitors such as methacrylate polymers, as wax inhibitor, with different range of molecular weight and alkyl side chain carbons on the rheological behavior and pour point of two Iranian waxy crude oils were evaluated. Two Iranian waxy crude oils were selected on the basis of wax and asphaltene contents. The rheological behavior of these crude oils in absence and in presence of methacrylate polymer was studied. The rheological data cover the temperature range of–1 to 12°C. The results indicated that the performance of methacrylate polymer was dependent on the molecular weight, alkyl side chain carbons and the asphaltene content of crude oil. Methacrylate polymers with longer alkyl side chains than 18 carbons would perform best as wax inhibitors in two cases. Also, for crude oil with low asphaltene, higher molecular weight methacrylate polymer is the best flow improver and lower molecular weight methacrylate polymer showed good efficiency for crude oil with high asphaltene content.