含蜡原油特征温度实验研究

用旋转粘度计对原油在温度扫描条件下的粘-温关系进行的实验研究表明,原油在低温时呈胶凝状态。根据原油低温凝胶化理论,用常规方法对实验数据进行了处理,得到了动态降温条件下含蜡原油流动性变化的特征温度,即开始出现最大成胶活化能时所对应的温度。对于同一种原油,特征温度越高其低温流动性能越差。对实验数据的分析表明,特征温度与原油经历剪切过程的粘性流动熵产呈幂函数关系,并据此拟合出相应的经验式。利用该经验式,通过计算管输原油过程中所产生的粘性流动熵产,可确定原油的特征温度。6种空白原油及4种加剂原油的92组特征温度数据的计算值与实测值的最大偏差为0.86℃,平均绝对偏差为0.3℃。该关系式可用于管输含蜡原油流动的安全性评价。     

剪切作用与加剂原油粘度关系的数学模型

分析了剪切作用对加剂大庆原油粘度的影响规律,建立了剪切后加剂原油粘度与剪切过程中粘性流动熵产关系的数学模型.根据剪切效应的一般规律及机理,提出了近似确定模型中参数的简易方法.按照此方法,只须测定一定温度下空白原油的粘度或表观粘度、未剪切时加剂原油的粘度或表观粘度,及在某一个剪切温度下及某一个粘性流动熵产条件下原油的粘度或表观粘度,即可近似确定该数学模型中的参数,从而预测在不同温度时剪切后的原油在该温度下的粘度或表观粘度.结合含蜡原油粘度与温度关系机理模型,还可以预测同一加剂原油经受剪切后在其他温度下的粘度.对中原原油和加剂轮南丘陵混合原油加剂试验数据的验证结果表明,该模型有较好的预测准确性.     

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。     

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     

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。     

锦州高含蜡原油降凝剂的筛选及现场应用

锦州原油高含蜡量高,凝点普遍在20℃以上,低温流动性差。为了保证冬季的安全输送,对实验室内开发研制的G5系列降凝剂进行了筛选,得到降凝效果最好的G51,并对影响其降凝效果因素进行了分析研究。实验结果表明,最佳加剂温度为60℃,合理的加剂浓度为400mg／L,可使原油的凝点由原来的22℃降至13℃,并且降凝剂具有良好的静态稳定性和配伍性,能保证管道的安全运行。     

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。     

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。     

加剂模拟高蜡原油热性能的研究

用自由基溶液聚合法合成了丙烯酸十八酯/马来酸酐/苯乙烯共聚物,用正十六胺胺解共聚物中的酸酐基团,得到共聚物的不完全长链酰胺化产物,即为原油降凝剂PMB.以4种不同熔点的切片石蜡混合物在0号柴油中的溶液为模拟含蜡原油,以2℃/min的速率降温至约-50℃后升温测试,得到空白和加剂油的DSC曲线.含蜡25%的空白油,蜡晶型转变和蜡晶熔化溶解峰合并形成低宽峰,相变能29.28 J/g,加剂(200μg/g)油的两峰分离,后一峰很尖,出峰温度上移,熔程变长,相变能148.5 J/g,表明PMB参与共晶,且与蜡有良好的匹配性.含蜡30%的空白油的两峰明显分离.加剂量增大时(200～600μg/g),起始峰温移向低温方向,放热量(相变能)有所减小,原油降凝幅度增大,对于含蜡25%的模拟含蜡原油(凝点35℃),凝点降低幅度由6.5℃增至17.5℃,与加剂温度20℃时相比,加剂温度为50℃时的平均降凝幅度平均增加2.5℃.     

管输过程中加剂原油流动参数的预测

管输过程中加剂原油的流动性受剪切和热力条件影响,对其进行准确的模拟与预测有重要的理论意义和应用价值。本文结合流体力学能量方程,运用能量耗散理论,在室内模拟试验与现场测试的基础上,建立了原油加剂并在65℃处理后凝点、粘度与管输过程中的定性温度、能量耗散关系的数学模型。通过预测结果与现场实际运行结果的对比,证明此数学模型是可靠的,能够模拟现场实际运行工况。     

Characteristic Temperatures of Waxy Crude Oils

Gel point or pour point is widely used to evaluate the low temperature flowability of crude oil. However, it is not adequate to describe the gelling properties of waxy crude oils under flow conditions with gel point or pour point, since the rheological behavior of crude oils is dependent on shear history. Waxy crude oils tend to gel at a low temperature. Based on gelation theory, the characteristic temperature of waxy crude oil was determined by analyzing viscosity-temperature data. Two mathematical models were developed for calculating characteristic temperatures of virgin crude oils and pour point depressants (PPD) beneficiated crude oils, respectively. By using these two models, the characteristic temperatures of crude oils that have experienced shearing and thermal histories can be predicted. The model for predicting the characteristic temperature of virgin crude oils has an average relative deviation of 4.5%, and all predicted values have a deviation within 2 ℃. Tested by 42 sets of data, the prediction model for crude oil treated with PPD has a high accuracy, with an average relative deviation of 4.2%, and 95.2 percent of predicted values have a deviation within 2 ℃. These two models provide useful ways for predicting the flowability of crude oils in pipelines when only wax content, wax appearance point and gel point are available.     

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.     

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.     

Synthesis,characterization and evaluation of a novel asphaltene inhibitor to control organic solid deposition in petroleum formation

This research work deals with synthesis of N-phenylamino hexanol tetramer to be used as an asphaltene inhibitor for crude oil in pores of reservoir. The synthesized additive was characterized using FTIR and Proton NMR spectroscopy, which confirms the formation of tetramer. Asphaltene deposition in the pores of sandstone core is studied by flooding the virgin and additive beneficiated crude oil indicating less deposition in beneficiated crude oil. Wettability alteration studies showed less contact angle hysteresis for virgin crude oil compared to the synthesized inhibitor beneficiated crude oil, which also aids to the lesser deposition of solid in the later one.     

高凝原油降凝剂的制备及其降凝机理研究

 由丙烯酸十八酯、马来酸酐和醋酸乙烯酯三元共聚物的胺解改性物（MAVA）和乙烯-醋酸乙烯酯的共聚物（EVA）为原料,通过复配制备了一种高凝原油降凝剂(PPD),并对其降凝效果和降凝机理进行了研究。结果表明,所制备的高凝原油降凝剂对凝点为43℃的胜利原油具有明显的降凝效果,在加剂量为400?g/g时,原油的凝点降低了11℃;由原油中的沥青质和胶质所形成的聚集体结构是原油的蜡晶成核剂,降凝剂可以同原油中的沥青质和胶质结合形成新的沥青质-降凝剂-胶质聚集体结构,该聚集体结构作为加剂原油的蜡晶成核剂,可以改变蜡的结晶方式,延缓蜡晶的析出速率,大幅地降低了原油的凝点。     

Application of bayesian regularized artificial neural networks to predict pour point of crude oil treated by pour point depressant

The pour point of the crude oil treated with the pour point depressant (PPD) is easily affected by the shear history effect. Models for pour point of PPD-treatment crude oil affected by the shear history effect based on Bayesian regularized artificial neural network (BRANN) were established. The results showed that BRANN models not only had a good ability of fitting to the training data, but also had a good ability of predicting the testing data. By evaluating network performance with several statistical indicators, the three models have excellent performance, high accuracy, and strong generalization ability. The influence of each parameter on the pour point were also investigated through a sensitivity analysis, which shows that the entropy generation due to viscous flow is the most important parameter in predicting the pour point.     

Change of Yield Stress of Daqing Crude Oil With Thermal and Shear History

Abstract

Daqing crude oil is a typical waxy crude oil with a wax content of 26.6 wt.% and a gel point of 32°C. The yield stress of waxy crude oils is an important property in the process calculation and flow safety analysis for heated oil pipeline. The Daqing crude oil was studied and the yield stress change with shear history was explored through simulation experiment of pipelining. It was found that the change of throughput variation or shear rate showed little effect on yield stress. There existed a peak yield stress on the relation curve of yield stress with final dynamic cooling temperature. The prediction model of yield stress for waxy crude oil under the condition of shutdown was developed and can be used to predict the yield stress of Daqing crude oil at certain heating temperature, final dynamic cooling temperature, and measurement temperature. For the 139 groups of yield stress data of Daqing crude oil from the simulation experiment of pipelining, the result of prediction with this model showed that the average relative deviation between the yield stress measured and predicted is 30.27%, and the coefficient of correlation is 0.9623.     

The Variation of the Gel Point of Daqing Crude Oil with Pipelining History

Abstract

Daqing crude oil is a typical waxy crude oil with a wax content of 26.6 wt% and a gel point of 32°C. In order to conduct the safety analysis of pipeline operation, the variation of gel point of Daqing crude oil with thermal and shear history was studied through pipelining simulation experiments. The experiments were performed under different annual throughputs and shear rates of pipeline flow. The results suggest that the change of shear action has little effect on the gel point of crude oil. As the final dynamic cooling temperature is increased, the change of gel point experiences two stages, staying constant at first and then decreasing. Through 13 groups of pipelining simulation experiments, the effects of heating temperature ranging from 45°C to 65°C on gel point of Daqing crude oil were studied. It has been indicated that the gel point increases as the heating temperature is increased under the same final dynamic cooling temperature. The relation equation was constructed to be used to predict the gel point under certain heating temperatures and final dynamic cooling temperature. The average absolute deviation of 52 predicted values of gel point is 0.58°C.