三元梳型共聚物胺化物对油品流动性能的影响

通过自由基聚合和胺化反应合成了马来酸酐-α-烯烃-苯乙烯-g-十八胺三元梳型共聚物胺化物,利用1H NMR分析了梳型共聚物的化学结构,并通过流变学方法考察了三元梳型共聚物胺化物对模型油和高蜡原油油品流动性能的影响。结果表明:梳型共聚物胺化物可降低模型油的屈服应力值,尤其对高沥青质模型油,最高降幅接近90%。对于高蜡原油,梳型共聚物胺化物降低其屈服应力值最高达78%,凝点最高降幅达2.6℃。     

Synthesis and evaluation of alkyl fumarate–vinyl acetate copolymers in combination with alkyl acrylates as flow improvers for Borholla crude oil

A number of alkyl fumarate–vinyl acetate copolymers were prepared and evaluated as flow improvers for high waxy Borholla crude oil. Alkyl fumarate–vinyl acetate copolymers having 19·2 as the average carbon number of the alkyl group in combination with polybehenyl acrylate were found to show optimum activity. Alkyl fumarate–vinyl acetate copolymers reduce the pour point, plastic viscosity and yield stress considerably and polybehenyl acrylate prevents the crude oil from attaining the gel structure on prolonged storage.     

Synthesis of comb‐type copolymers with various pendants and their effect on the complex rheological behaviors of waxy oils

To improve the flowability of waxy crude oil containing a high concentration of asphaltenes (AS), novel comb‐type copolymers of poly(maleic acid polyethylene glycol ester‐co‐α‐octadecene) (PMAC) and poly(maleic acid aniline amide‐co‐α‐octadecene) (AMAC) with various grafting ratios (R_g) of PEG/aniline to maleic anhydride are synthesized. Model oils containing wax mixtures and AS are prepared to explore the effect of asphaltene concentration and the copolymers on the yield stress. The influence of the copolymers on the wax appearance temperature (WAT) of Liaohe high waxy oil is examined by rheological and microscopic methods. Experimental flow curves of shear stress as a function of shear rate are fitted following the Casson model to interpret the rheological properties of gelled waxy crude oil in the presence of AMACs, PMACs, and MAC. Compared with MAC, PMACs, and AMACs are more efficient in reducing the yield stress of both model oil and crude oil, which indicates a better flowability. It is found that PMAC1.0 and AMAC1.0 with a medium R_g can balance the interaction of copolymers with waxes and AS and reduce the yield stress much more than others. Between them, AMAC1.0 that possesses aromatic pendants is better than PMAC1.0, which only has polar pendants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41660.     

A regular,hydrophobically modified polyampholyte as novel pour point depressant

A new regular polyampholyte, namely poly(N,N‐diallyl‐N‐octadecylamine‐alt‐(maleic acid)), was studied as an additive to crude oil. The amphiphilic polyampholyte proved to be an efficient pour point depressant, to inhibit the deposition of wax, and to improve the viscosity of waxy crude oil from the Akshabulak oilfield (Western Kazakhstan). On optimizing the concentration of the polymer, both the kinematical viscosity and the pour point of waxy crude oils were found to be strongly decreased. The morphology of the paraffin aggregates formed was compared before and after heat treatment of the waxy crude oils, in the presence and the absence of the polymer. The rheological characteristics of the waxy crude oil were markedly improved, in particular, by decreasing the plastic viscosity and the yield stress values upon addition the polymer. The inhibition of wax deposits in the presence of the amphiphilic polyampholyte was interpreted in terms of its interference with the wax crystallization process because of the formation of inverse micellar structures. Although the interaction of the cationic and the anionic groups on the polymer backbone stabilizes the smaller size of the aggregates, the hydrophobic side chains of the polymer provide nucleation sites and cocrystallize with the paraffins, thus modifying the paraffin crystal structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2101–2108, 2005     

Effect of wax inhibitors on pour point and rheological properties of Iranian waxy crude oil

A variety of techniques have been employed in order to reduce problems caused by the crystallization of paraffin during the production and/or transportation of waxy crude oil. Flow improvers are used extensively to increase the mobility of crude oil. In this study, the influence of the ethylene-vinyl acetate copolymer (EVA), as flow improver, with different ranges of molecular weight on the viscosity and pour point of five Iranian waxy crude oils was evaluated. Five types of Iranian waxy crude oil were selected based on their similar wax (> 10%) but different asphaltene contents. Also, the effect of asphaltene content on the performance of this flow improver was studied. The rheological behavior of these crude oils, with middle range API gravity, in the absence/presence of flow improver was studied. The rheological data cover the temperature range of 5 to 40 °C. The results indicated that the performance of flow improver was dependent on the molecular weight and the asphaltene content. For crude oil with low asphaltene, higher molecular weight flow improvers are the best additive and lower molecular weight flow improvers showed good efficiency for crude oil with high asphaltene content. Addition of small quantities of asphaltene solvents such as xylene (1 wt.%), alone or in combination with flow improver, can improve viscosity of crude oil with high asphaltene content.     

Heavy crude oil viscosity reduction and rheology for pipeline transportation

Different methods of reducing the viscosity of heavy crude oil to enhance the flow properties were investigated. Experimental measurements were conducted using RheoStress RS100 from Haake. Several factors such as shear rate, temperature and light oil concentration on the viscosity behavior have been studied. This study shows that the blending of the heavy crude oil with a limited amount of lighter crude oil provided better performance than the other alternatives. Experimental measurements in terms of shear stress τ-shear rate and yield stress τ₀ were conducted on the mixture of heavy crude oil-light crude oil (O-light). The results showed a significant viscosity reduction of 375 mPa s at a room temperature of 25 °C. This study shows that the heavy crude oil required a yield stress of 0.7 Pa, whereas no yield stress was reported for the heavy crude oil-light crude oil mixture.     

EVA/纳米蒙脱土复合降凝剂对长庆含蜡原油的作用规律

利用纳米蒙脱土(MMT)特殊的带电性,使用含长烷基侧链的季铵盐对其插层改性得到有机改性蒙脱土(O-MMT)。采用熔融共混法制备O-MMT与EVA(聚乙烯醋酸乙烯酯)降凝剂的复合产物EVA/O-MMT,以国内典型含蜡长庆原油为研究对象,通过流变实验从宏观上评价EVA/O-MMT对长庆油的作用效果,并与EVA降凝剂进行对比,利用DSC和偏光显微镜考察加剂前后原油的结晶特性和蜡晶形貌的变化。结果表明:与纯EVA降凝剂相比较,EVA/O-MMT在最优加剂浓度50 mg·kg^-1下使长庆原油胶凝点、黏度、屈服值进一步降低(胶凝点降低2.5℃,5℃下的平均降黏率为25%,3℃下的屈服值下降55.5 %),从而大幅改善长庆原油的低温流变性。DSC放热特性表明O-MMT的引入可以提升EVA的初始结晶温度,拓宽EVA结晶放热区间,降低原油析蜡点。显微结果表明添加EVA/O-MMT的原油在低温下蜡晶结构更致密。     

中间苍白杆菌对含蜡原油除蜡降粘分析

蜡质不仅使含蜡原油黏度升高，而且会析出积聚在管壁上降低管输效率。从原油污染淤泥中分离出一株产表面活性剂的烃降解菌F-1，经16S rDNA鉴定为中间苍白杆菌。与原油作用7 d 后，能将蜡含蜡量为15.2%的高含蜡原油处理为蜡含蜡量为9.1%的含蜡原油，原油蜡质量分数降低40.1%，原油黏度降低21%以上，细胞疏水性达28.1%。通过傅里叶红外光谱鉴定该菌产生的生物表面活性剂为脂肽类。添加该菌上清液到液体石蜡 可形成91.49 mm的排油圈，能够显著降低培养基表面张力，对液体石蜡乳化系数达到65%。     

Synthesis of polymeric pour point depressants for Nada crude oil (Gujarat,India) and its impact on oil rheology

Five flow improvers have been synthesized to study rheological properties of Nada crude oil (Gujarat, India). Anhydride copolymers were prepared making use of the copolymerization of acrylates of different alkyls with maleic anhydride and the Poly (n-alkyl acrylates-co-N-hexadecylmaleimide) were prepared by the reaction of copolymer with hexadecylamine. The additives were purified and characterized by FTIR, GPC. The prepared polymeric additives shows dual function both as wax dispersants and flow improvers and all of them acts as good pour point depressants. Yield stress and the viscosity of the crude oil at different temperatures and concentrations of additives were evaluated by zero friction advanced rheometer AR-500 of TA instrument. Comparison of morphologies and structures of wax crystals or aggregates in waxy crude oils beneficiated with and without a PPD was also done by micro photographic studies which show the modification in wax crystal morphology due to additives.     

胶凝含蜡原油的连续剪切实验研究

胶凝含蜡原油由于其蜡晶的三维网状空间结构,具有复杂的流变性。胶凝原油的流变性质一直是研究的重点和热点。很多学者对胶凝原油的性质做了详细而又深入的研究,但这些研究一般集中在恒定剪切速率上,对胶凝原油的连续剪切的研究较少。通过控制不同的降温速率和胶凝温度,来研究胶凝原油连续剪切的变化规律。实验结果表明,当降温速率越大时,初始的粘度越小,但剪切一段时间后,不同降温速率下的粘度无多大差别;当胶凝温度越低是,其初始的结构强度越大,并且在结构破坏以后,在同一剪切速率下,其粘度也越大,但不同温度下的差距在减小;当从高到低的剪切情况下,其粘度随着剪切速率的减小,呈增大的趋势,并且这趋势越来越明显,相对于从低到高的剪切情况下,在同一剪切速率下,从低到高情况下的粘度比从高到低的粘度要大。     

含蜡原油的黏弹-触变模型

在胶凝温度以下,因蜡的结晶析出并形成三维空间网络结构,含蜡原油表现出复杂的非牛顿流体特性,如黏弹性、屈服应力和触变性等。目前,含蜡原油的触变性模型均为黏塑性模型,没有考虑屈服点附近及之前物料所具有的黏弹特性。为此,提出了一个包含状态方程和速率方程、共10个未知参数的黏弹-触变模型。模型的剪应力由弹性应力和黏性应力构成,弹性应力为剪切模量与剪应变的乘积,剪切模量正比于结构参数和损耗函数。描述结构参数随时间变化的速率方程,假设结构破坏项与能量耗散率相关,克服了以往速率方程中结构破坏项与剪切率相关这一假设的不足。模型可描述含蜡原油所具有黏弹-触变特性,并且所预测的剪应力能够从以黏弹性为主的阶段平滑过渡到以触变性为主的阶段。利用大庆原油剪切率阶跃和滞回环的实验数据对模型进行验证。结果表明:两种测试的模型拟合值与实测值的平均相对偏差分别在2.0%和5.0%以内;利用由剪切率阶跃测试数据拟合得到的模型参数对滞回环测试进行预测,预测的平均相对偏差约为16%。     

Yield behavior of gelled waxy oil in water-in-oil emulsion at temperatures below ice formation

Paraffinic waxes precipitate from bulk oil when oil temperatures are lower than the oil wax appearance temperature. The oil can form a gel if the temperature goes below the pour point, especially under quiescent conditions. The strength of the gelled waxy oil increases as temperature decreases further. Application of a mechanical shear deforms and fractures the gel. It is shown that this strength reduction in the gel is irreversible under isothermal conditions. In subsequent cooling, the prior fractured gel even showed much less yield stress than the gel from the shear-free condition at measured temperature. This study explored the gel strength behavior in water-in-oil (w/o) emulsion state. Three different model oils, water-free oil, 10 wt.% w/o and 30 wt.% w/o, were used to determine the yield stress using vane method. Both emulsified oils showed less yield stress values at temperatures between the pour points and ice temperature. Compared to water-free oil at temperatures below ice formation, the higher yield stresses were observed in 10 wt.% w/o oil; however, the lower yield stresses in 30 wt.% w/o oil. Subsequent cooling option after prior gel breakage was also examined.     

温度及剪切速率对延长原油粘度的影响规律研究

延长原油为高含蜡原油,原油中石蜡在输送过程中受温度及剪切力的影响较大。因此,采用流变学测试与分析方法对温度及剪切速率对粘度的影响规律进行了研究。研究结果表明：延长原油的凝点为26℃,粘度在温度由28℃降至23℃时由96mPa·s激增至192mPa·s,提高剪切速率可较大幅度的降低原油粘度但增加到100S^-1后对粘度的影响趋于稳定。     

BEM/PMSQ杂化降凝剂对青海含蜡原油作用效果及其机理

基于聚甲基硅倍半氧烷（PMSQ）微球良好的有机相容性与规则的微观球形形貌,将PMSQ微球与BEM降凝剂通过熔融共混制备了BEM/PMSQ杂化降凝剂。以青海含蜡原油为研究对象,通过流变实验评价了BEM/PMSQ杂化降凝剂对原油的凝点、黏弹性、黏度与屈服值的影响,利用偏光显微镜观察了加剂前后原油蜡晶形貌的变化,并与单独添加BEM降凝剂的油样进行了对比。结果表明：不加剂原油凝点27.0℃;在相同的降凝剂加量下（100 μg·g^-1）,降凝效果最好的是BEM/PMSQ 2%杂化降凝剂,可降低原油凝点19.0℃,相较于添加BEM降凝剂,进一步降凝6.0℃,降低胶凝点4.3℃,10℃时平均降黏率39.0%,G'值降低了62.0%。PMSQ微球与BEM/PMSQ杂化降凝剂在十二烷中的分散状态照片表明PMSQ微球表面吸附了BEM降凝剂,从而在原油中作为蜡晶的成核模版存在,使所形成的蜡晶结构更为紧凑,包覆更少的液态油,从而改善原油的宏观流变性。     

变频磁场原油降粘技术的研究

在恒磁场降粘理论基础上研究变频磁场降低原油粘度的技术以及其作用的机理.通过实验得到含蜡原油降粘的最佳温度为38℃左右.实验中应用磁场磁感应强度较小只有0.4 mT,因此磁处理时间要长很多大概30～40 min,降粘率能达到50％.实验确定了变频磁场降粘的最佳波形为正弦波,频率范围1600～2 200 Hz,最佳频率为1 800 Hz.可以说明变频磁场原油降粘技术对原油的采集输运都有很好的应用前景.     

Studies on the composition of some distillate waxes

Structural composition of two distillate waxes obtained from Ankleshwar crude oil tank bottoms have been determined using physical properties correlations, high temperature g.l.c., ¹H-n.m.r. and ¹³C-Fourier transform n.m.r. spectroscopy. Both waxes seem to contain predominantly n-paraffins.     

安塞油田化学清防蜡工艺效果分析

含蜡原油开采过程中,油井普遍存在结蜡现象。行之有效的清防蜡工艺是保障油井稳产的重要因素,化学清防蜡工艺应用效果受沉没度、产液量及含水率等的影响,在油井复杂条件下,其现场应用效果难以评价。为研究清防蜡工艺的应用效果,本文基于清防蜡工艺原理,以安塞油田清防蜡工艺应用前后的高含蜡原油和沉积物为研究对象,分析了原油族组成、蜡组成、蜡含量、析蜡点、黏度和溶蜡速率;通过比较确定了4个评价指标,引入多目标评价方法,建立了清防蜡工艺效果评价体系。研究表明清防蜡工艺应用后原油黏度降低;蜡的碳数C₁₆~C₃₀的百分含量降低,C₃₀以上的百分含量升高;原油平均蜡含量变化率为22.99%;原油平均析蜡点变化率为2.86%;各清防蜡剂溶蜡速率均大于0.0160g/min;CQ-1工艺和CQ-2工艺的综合得分较高,现场应用效果良好。计算结果与安塞油田应用化学清防蜡工艺的方向一致,具有较强的参考性。     

Temporal variation of voids in waxy crude oil gel in the presence of temperature gradient

Abstract

The formation of voids is eminent below the pour point temperature of waxy crude oil. This paper discusses the temporal variation of voids in waxy crude oil gel in the presence of temperature gradient between the waxy crude oil and its ambient condition. Cooling of waxy crude oil to an end temperature of 10?°C was performed in a flow loop rig, after which it was scanned in a 3?T Magnetic Resonance Imaging (3?T-MRI) system. Five consecutive scans with equal intervals were taken and analyzed to observe the variation of voids over the waiting duration. It was observed that the percentage of total voids volume reduced from 7.16% to 6.09%, from 6.59% to 5.71% near a pipe wall, and from 0.57% to 0.38% around a pipe core at waiting duration of 50?minutes. A waiting duration of 10?minutes reduced the voids volume around the pipe wall from 6.59% to 6.33%, and this was the maximum when compared with observations at higher waiting durations. The rate of voids disappearance was also higher at shorter waiting durations, with a maximum of 0.032%/min rate of change of voids observed at 10?minutes. Conversely, a minimum of 0.002%/min rate of change of voids was observed at 40?minutes waiting duration, beyond which the difference was almost insignificant. The disappearance rates were small that the change in voids volume became minimal over longer waiting durations, showing insignificant voids variation with surrounding weather conditions.     

Synthesis and characterization of nanohybrid of poly(octadecylacrylates derivatives)/montmorillonite as pour point depressants and flow improver for waxy crude oil

In this paper, a novel series of nanohybrid of poly(octadecylacrylate derivatives) montmorillonite (ODA/MMT) was prepared by successfully dispersing the inorganic nanolayers of MMT-clay on the organic polymer matrix via in situ free-radical polymerization by different ratios. The prepared nanohybrid polymers were characterized by FTIR and Raman spectroscopy, X-ray diffraction (XRD), HRTEM, GPC, DSC, and TGA instruments. The XRD confirmed the presence of an exfoliated/interacted clay structure in the prepared polymer. Moreover, the molecular weight of the prepared polymer nanohybrids is higher than the corresponding polymer. The results of applying the polymer as pour point depressants showed a considerable reduction from 27°C (initial pour point) to −3 °C, facilitating the process of oil flow at lower temperatures than earlier. The apparent viscosity of waxy crude oil was also decreased significantly by the addition of the (ODA/MMT) polymers, and the long-term stability of the prepared nanohybrid polymers was superior to that of a conventional polymer. The efficiency of polymers nanohybrid in reducing the pour point of crude oil associated with improved oil flow is one of the most important processes of charge and transportation process. The mechanism of enhancement of the flow properties by the polymers nanohybrid is predicted. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47333.     

Mixture temperature prediction of waxy oil–water two-phase system flowing near wax appearance temperature

Temperature sensitivity of waxy crude oils makes it difficult to study their flow behaviour in the presence of water especially near their wax appearance temperature(WAT). In this study a method was proposed and implemented to mitigate such difficulties which was applied in predicting mixture temperatures(Tm) of a typical Malaysian waxy crude oil and water flow in a horizontal pipe. To this end, two analytical models were derived firstly from calorimetry equation which based on developed two correlations for defining crude oil heat capacity actualized from the existed specific heat capacities of crude oils. The models were then applied for a set of experiments to reach the defined three predetermined Tm(26 °C, 28 °C and 30 °C). The comparison between the predicted mixture temperatures(Tm,1and Tm,2) from the two models and the experimental results displayed acceptable absolute average errors(0.80%, 0.62%, 0.53% for model 1; 0.74%, 0.54%, 0.52% for model 2). Moreover,the average errors for both models are in the range of standard error limits(±0.75%) according to ASTM E230.Conclusively, the proposed model showed the ease of obtaining mixture temperatures close to WAT as predetermined with accuracy of ± 0.5 °C approximately for over 84% of the examined cases. The method is seen as a practical reference point to further study the flow behaviour of waxy crudes in oil–water two-phase flow system near sensitive temperatures.