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.     

降凝剂在海上含蜡原油管道中的应用

降凝剂在海上和陆上含蜡原油输油管道上的应用结果表明,降凝剂可降低含蜡原油凝点,改善含蜡原油低温流动性能,延长停输时间,减小停输再启动压力等,特别适用于海洋和沙漠中不宜建中问加热站的含蜡原油管道。对降凝剂的作用机理及其在海底管道的应用特点进行了介绍和论述。     

The Thixotropy of Daqing Waxy Crude

The thixotropic behaviors of Daqing waxy crude were studied experimentally with the help of the advanced strain controlled rheometer (ARES-G2). The experimental results indicated the decrease in viscosity can be divided into two continuous steps, and the recovery of viscosity consists of three continuous processes. Then a new method was used to model the thixotropic behavior combined with the experimental data, and the new method was based on a potential function that can characterize the recovery capability of the inner structure, it is reasonable for to describe the thixotropic behavior of Daqing waxy crude properly.     

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.     

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.     

新疆塔河重质原油及其乳状液不同温度和压力下的粘度

自行设计并制造了高温高压落球法液体粘度测定仪,简介了主要构件,用乙二醇、丙二醇、丙三醇等校准,粘度测定值的相对误差小于1%。在温度分别为40℃、50℃、60℃、70℃、80℃,流体静压力分别为0.1、1、5、10、15、20MPa,含水率分别为0%、10%、20%、30%、50%、70%、90%的条件下,测定了新疆塔河油田高粘重质原油(含蜡4.14%,密度0.9586g/cm3)及其水乳状液的粘度,共计得到了210个粘度数据并列表给出。粘度随温度升高而降低,符合一段规律。在每一含水率和温度下,粘度随流体静压力升高而增大,增幅随温度升高而减小。在每一流体静压力下,粘度～含水率曲线通过峰值,峰值位于含水率20%处,峰高随温度升高而减小,含水率超过20%后原油乳状液由油包水型转变为水包油型。给出了4组粘度～温度和粘度～含水率曲线作为示例。典型粘度数据:781.4mPa·s(含水0%,50℃,0.1MPa);1406mPa·s(含水0%,50℃,20MPa);431.5mPa·s(含水30%,50℃,0.1MPa)。图5表1参2。     

含蜡原油加热处理后粘度和析蜡点研究

介绍了一种自动测量粘度与温度曲线的方法。并对含蜡原油加热处理后粘度和析蜡点的变化规律进行了研究。实验结果表明;加热处理后含蜡原油的粘度和析蜡点降低。     

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。     

基于能量及原油物性定量分析的油-水混合液黏度预测模型

高含水油-水混合液往往不能形成稳定的乳状液,而是原油将其中一部分水乳化,形成了油包水(W/O)乳状液液滴和游离水的掺混体系.传统的乳状液黏度模型并不适用于这种非稳定乳化的油-水混合体系.采用搅拌测黏法测定并研究了搅拌转速、含水率及温度对油-水混合液表观黏度的影响.结果表明:油-水混合液的表观黏度随着搅拌速率的增大、含水...     

Prediction of the Kinematic Viscosity of Crude Oil Fractions

Abstract

A generalized equation based on modified Eyring's theory for predicting kinematic viscosity of petroleum fractions is proposed in this work. The equation uses two reference fluids including a pair of (C6 and C10), (C10 and C14), or (C14 and C20) for petroleum fractions of molecular weight higher than 70 and lower than 300.

Validity and accuracy of this equation have been confirmed by comparing the obtained results of this equation with experimental data. In contrast to other correlations that require so many specific parameters for oil viscosity prediction, this type of equation requires only molecular weight and true boiling point. The results obtained in this work are in agreement with experimental data with an average absolute deviation (AAD) of less than 5%.     

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。     

Rheology of Doped Nigerian Niger-Delta Waxy Crude Oil

Abstract

Precipitation and deposition of wax, which usually results from temperature lowering, has detrimental effects on petroleum industry operations. To appreciate and understand the physicochemical mechanics of wax precipitation, rheological experiments were carried out on three doped and undoped Nigerian waxy crude oils. The characteristic shear stress straining rate shows an initial constant shear stress below 50 sec^?1 shear rate, followed by a gradual increase above 50 sec^?1 which is indicative of energy consumption in the partial break-up of wax matrix bonds. Doping greatly ameliorates the rheological properties and pour points of the crude oils. The Bingham plastic model excellently fit the experimental data, with a correlation coefficient ≥ 0.97721.     

含蜡原油相态转换边界值的计算

对含蜡原油相态转换边界值的计算进行描述，同时用实例进行数值分析，近年来，为提高原油产量，对油田开发不断地进行研究，同时也发展了许多新方法，在油层不断开采的情况下，由于复杂的渗流变化，伴随产生了油气相态转变和油气中各项密度和粘度的变化，因此，研究油层中油层相态转变，保持高压气体和富气来驱动原油开采是非常重要的。     

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。     

状态方程与粘度模型匹配预测原油粘度

基于改进的Ｄｅａｎ－Ｓｔｉｅｌ粘度模型，提出了将状态方程与之结合进行原油粘度预测的方法，采用Ｐａｔｅｌ－Ｔｅｊａ状态方程预测结果最好，平均相对误差为６．２７％。     

The Viscosity of Crude Oils in 1,4-Dioxan

Viscosities of crude oil solutions from 0.1 to 1.0% (v/v) have been studied in 1,4-Dioxan as a solvent at temperature ranging from 293 to 313 K. Huggins, Kraemer, Martin, and Schulz-Blaschke relations were used by viscosity data to evaluate intrinsic viscosities and viscometric constant values. Degree of viscosity reduction (DVR) was also calculated. The size of the isolated molecule was evaluated in terms of intrinsic viscosity and shows that interactions between solute and solvent decrease with the rise in temperature.     

含蜡原油流动性改进机理实验研究

将配方组分在100℃搅拌1小时，由25号变压器油，50号、60号粗晶蜡或80号微晶蜡(单种蜡或混合蜡)及60号道路沥青(只用在个别配方中)配成了一系列模拟含蜡原油及其加剂油，加剂量400mg／kg，药荆为以聚丙烯酸高碳醇酯为主的商品降凝剂GY1。测定了空白和加剂模拟油的相关特性，考察了20℃下析出的蜡晶在偏光显微镜下的形态结构，讨论了化学剂改进含蜡原油流动性的机理。加入GY1使模拟油浊点(析蜡点)只下降0～2℃，使30℃时析蜡量增加10％～35％，因此这两点都不是使流动性改进的因素。GY1的降凝效果随模拟油中蜡的标号增大、含量减小而增大，降凝效果较好时，在接近凝点温度下的屈服值降低率和降粘率也较大。降凝、降粘的共同切入点是抑制蜡晶形成网状结构或拆散蜡晶网状结构。化学剂改进含蜡原油流动性的机理是改变蜡晶表面性质。促使蜡晶长大，形成形状对称性高的蜡晶聚集体。图12表3参6。     

A More Precise Determination of Gear Oil Viscosity at Low Temperatures

Low temperature fluidity of gear oils is an important fluid property as it directly impacts the useful life of a gear set.This paper compares low temperature fluidity measurement precision of ASTM D682...     

The Artificial Neural Network's Prediction of Crude Oil Viscosity for Pipeline Safety

Abstract

Predicting crude oil viscosity is a challenge faced by reservoir engineers in production planning. Some early researchers have propounded some theories based on crude oil properties and have encountered various problems leading to errors in forecasted values. This article discusses work carried out with a model using an artificial neural network (ANN) for predicting crude oil viscosity of Nigerian crude oil. The model was started through adoption of a classical regression technique empirical method for dead oil viscosity as a function of American Institute for Petroleum (API) and reduced temperature. The Peng–Robinson equation of state and other thermodynamic properties are introduced, coupled with the Standing model for calculating bubble point pressure (P_b). The developed model was evaluated using existing measured real-life data collected from 10 oil fields within the Niger Delta region of Nigeria. Both the predicted and measured viscosities were plotted against each corresponding reservoir pressure to establish the model's level of reliability. The superimposition of the pressure-viscosity relationship shows that at each point, the viscosity model captures the physical behavior of viscosity variations with pressure. In each case, the ANN does not require a data relationship to predict the crude oil viscosity but rather relies on the field data obtained for training. For this reason, it is recommended that the ANN approach should be applied in oil fields for reduction in error, computational time, and cost of overproduction and underproduction.     

稠油低温乳化降粘剂BL-1的研制及应用

乳化降粘剂BL－1的主剂是阴离子－非离子混合表面活性剂，在矿场应用时加入适量碱（NaOH)，是针对大庆黑帝庙低温（15℃）稠油油藏的开采而研制的，以黑帝庙稠油（20℃密度0．918g/cm^3,15℃ 粘度2680mPa.s。酸值0．818mgKOH/g)为油相，混合表面活性剂在地层水（矿化度4456mg/L)中的5g/L溶液为水相，油水体积比70／30－50／50，研究了该混合表面活性剂15℃时的乳化降粘性能，根据不同静置时间的脱水率和稳定性评定测定结果，油水比70／30时形成相当稳定的O／W乳状液，其粘度比稠油粘度降低94％，油水比60／40和50／50时粘度降低率更高；该混合表面活性剂不影响破乳剂（SP－169和F－68）对稠油乳状液的破乳脱水效果，该混合表面活性剂也适用于新疆克拉玛依K1稠油（30℃）和胜利临盘S74－11井稠油（60℃），乳化降粘度为95．1％－99．8％，在现场应用时，该混合表面活性剂的碱水溶液连续地通过油套环空注水油井，使井内表面活性剂浓度不小于5g/L，油水体积比不小于70/30，在黑帝庙油田的一口处于注汽后采油后期的蒸汽吞吐稠油井进行了为期各15天的两轮乳化降粘剂BL－1注入试验，试验期间停止掺60－70℃的热水，生产正常进行，采出液含水率和抽油泵电机电流明显降低。