The Effect of Commercial Additives as Pour Point Depressants for Fuel Oils

When the crude oil temperature goes below the pour point value wax crystals will come out of solution and tend to plug lines and filters. Additionally, the wax deposited in tanks decreases the storage capacity. In general, wax deposition can cause problems in production, storage, transportation, and consumption. Pretreatment of the crude oil with flow improver or pour point depressants has received the greatest acceptance due to its simplicity and economy. Four commercial additives were evaluated as pour point depressant for fuel oils. The structures of the commercial additives were confirmed by FTIR spectra. The results indicate that the n-alkanes carbon distributions display an obvious normal distribution in fuel oils. The distributions of high carbon n-alkanes are all broad so that wax crystals not precipitate in fuel oil at low temperatures is good. These commercial additives were tested as pour point depressants for fuel oil. The obtained data revealed that the prepared compounds depress the pour point of the fuel oil successfully. Comparison of structures of wax crystals in untreated and treated fuel oil was also done by photomicrographic analysis.     

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.     

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.     

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.     

含蜡原油添加流动性改进剂的研究

采用自行研制的聚丙烯酸高级混合醋作流动性改进剂,在适宜的条件下,可使胜利油田含蜡原油的流动特性(凝点、粘度和屈服值)和石蜡沉积特性得到明显改善。同时研究了实验条件及聚丙烯酸高级混合酯的化学结构对含蜡原油流动特性和石蜡沉积特性的影响,并对聚丙烯酸高级混合酯的作用机理进行了讨论。文中指出,聚丙烯酸高级混合酯的侧链醋基长度必须与原油中石蜡烃长度相适应才能使二者共晶。     

LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART II EFFECT OF WAX COMPOSITION AND CONCENTRATION ON THE DEW AXED CRUDE OILS WITH / WITHOUT ADDITIVES

In this part of the work the effect of wax concentrations on the rheologica! properties of the dewaxed Duliajan (Assam) and Lingaia crude oils have been studied. The dewaxing of the crude oil was done by removing n-paraffins from the crude oil by urea adduction. The urea adducted n-paraffins concentrate-the wax- was characterized by its carbon number distribution. The urea non adducted oil portion - the denormalized crude oil (DNO)- was characterized for its pour point. The wax in different concentration was then added in the DNO and the change in the rheological properties like pour point, yield stress and plastic viscosity were studied using a Haake Rota Viscometer. The effect of carbon number distribution, i.e. the composition of the wax, on these rheological properties was also investigated. Four different commercial pour point depressanl additives have been used to study their effects on the pour point, yield stress and plastic viscosity of the reconstituted (wax mixed DNO) crude oils.

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point of the DNO, and the DNO composition has a small effect. However, as seen in the Part I of this paper, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the composition of the DNO. The additives have shown better response in the DNO having more aromatic concentrate, as has been found in the case of Duliajan (Assam) DNO.     

LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART II EFFECT OF WAX COMPOSITION AND CONCENTRATION ON THE DEW AXED CRUDE OILS WITH / WITHOUT ADDITIVES

ABSTRACT

In this part of the work the effect of wax concentrations on the rheologica! properties of the dewaxed Duliajan (Assam) and Lingaia crude oils have been studied. The dewaxing of the crude oil was done by removing n-paraffins from the crude oil by urea adduction. The urea adducted n-paraffins concentrate-the wax- was characterized by its carbon number distribution. The urea non adducted oil portion - the denormalized crude oil (DNO)- was characterized for its pour point. The wax in different concentration was then added in the DNO and the change in the rheological properties like pour point, yield stress and plastic viscosity were studied using a Haake Rota Viscometer. The effect of carbon number distribution, i.e. the composition of the wax, on these rheological properties was also investigated. Four different commercial pour point depressanl additives have been used to study their effects on the pour point, yield stress and plastic viscosity of the reconstituted (wax mixed DNO) crude oils.

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point of the DNO, and the DNO composition has a small effect. However, as seen in the Part I of this paper, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the composition of the DNO. The additives have shown better response in the DNO having more aromatic concentrate, as has been found in the case of Duliajan (Assam) DNO.     

Synthesis and Evaluation of Copolymers as Pour-point Depressants

-Olefin maleic anhydride copolymers were prepared by reacting C₈ or C₁₄ olefin with maleic anhydride, then esterified with dodecyl or NAFOL 1822B alcohol, purified and characterized through average molecular weight, polydispersity index, and infrared spectroscopy. A waxy crude oil (pour point = 21°C and wax content = 18.9 wt%) was treated with the four synthesized additives as pour-point depressants and determined using x-ray diffractometer. It is found that the x-ray diffraction patterns of waxes with additives are remarkably different from those without additives. The NAFOL 1822B ester of 1-tetradecene maleic anhydride copolymer also show stronger interaction with the wax than NAFOL 1822B ester of 1-octene copolymer, dodecyl ester of 1-tetradecene maleic anhydride copolymer, and dodecy ester of 1-octene maleic anhydride copolymer. These effects can be attributed to the chain length of side hydrocarbon. The wax solubilization is a function of copolymer.     

Synthesis and Evaluation of Copolymers as Pour-point Depressants

Abstract

α-Olefin maleic anhydride copolymers were prepared by reacting C₈ or C₁₄ olefin with maleic anhydride, then esterified with dodecyl or NAFOL 1822B alcohol, purified and characterized through average molecular weight, polydispersity index, and infrared spectroscopy. A waxy crude oil (pour point = 21°C and wax content = 18.9 wt%) was treated with the four synthesized additives as pour-point depressants and determined using x-ray diffractometer. It is found that the x-ray diffraction patterns of waxes with additives are remarkably different from those without additives. The NAFOL 1822B ester of 1-tetradecene maleic anhydride copolymer also show stronger interaction with the wax than NAFOL 1822B ester of 1-octene copolymer, dodecyl ester of 1-tetradecene maleic anhydride copolymer, and dodecy ester of 1-octene maleic anhydride copolymer. These effects can be attributed to the chain length of side hydrocarbon. The wax solubilization is a function of copolymer.     

高凝油渗流特性的实验研究

选择２块人造岩心和２块取自于沈北油田的天然岩心，分别在不同条件下饱和地层水，进行了油驱水实验，实验用油具有较高的含蜡量和凝固点；由实验观察可知，温度是决定高凝油渗流特性的决定性因素，当温度高于反常点时，原油呈牛顿流体，粘度在整个渗流过过程不变，反之则呈非牛顿流体，粘度对温度非常敏感，随温度降低，原油粘度升高，油相渗透率和驱油效率降低，在析蜡前后，变化尤为明显；高凝油的渗流特征还受压力梯度的影响，最     

江汉原油降凝剂的制备及其性能研究

利用溶液聚合反应合成了一系列丙烯酸酯类高蜡原油降凝剂,并对其降凝效果进行研究。研究结果表明：采用摩尔配比为6：3：1的丙烯酸十八酯,马来酸酐和醋酸乙烯酯组成的混合单体制备的三元聚合物高蜡原油降凝剂MVA-3对江汉原油具有明显的降凝效果,在加剂量为1000mg／kg时,可以使江汉原油的凝点降低12℃。高蜡原油降凝剂MVA-3能够同原油中的胶质和沥青质有效结合,可以降低原油中固有的胶质一沥青质聚集体在原油中的析出温度,改变原油中蜡的结晶方式,降低蜡结晶析出温度和蜡结晶析出速度,并能减少原油中蜡的析出总量。     

An Evaluation of the Performance of Selected Wax Inhibitors on Paraffin Deposition of Nigerian Crude Oils

Paraffin deposition in oil production constitutes a critical and difficult to control problem, in terms of productivity and production operation costs, going from the reservoir to surface facilities. In Nigeria, operators spend millions of dollars each year to control the deposition of paraffin and to deal with other paraffin deposition related problems. Expenditures of this magnitude obviously have a significant impact on profits. The main purpose of this work is to assess the net effect of many commercial wax inhibitors on paraffin deposition from a wide range of waxy crude oil systems in Nigeria for the selection of an efficient additive. Deposition from a wide range of waxy crude oil systems from Nigerian oilfields were examined with and without chemical wax deposition inhibitors. The devices used to produce the deposits investigated were cold spot and dynamic flow wax deposition apparatus capable of producing field-like deposits with relatively small volumes of oil in minutes. Results show that most of the commercial wax inhibitors tested could decrease the deposition of wax, but none has the economical capability to solve the paraffin deposition problem for an extended period of time. One intriguing result was that the addition of xylene improved the performance of three wax inhibitors tested. It was also observed that there are subtle differences in inhibitor performance depending on deposition tendencies of crude oil.     

Wax Deposition in Flow Lines Under Dynamic Conditions

The wax deposition in the tubing, pipeline, and surface flow line is the major problem in the oil fields. It generates additional pressure drop and causes fauling and ultimately increases the operating cost during production, transportation, and handling of waxy crude oil. In this work, attempts were made to study the wax deposition in the flow lines due to Indian crude oil under dynamic condition. The experimental work was carried out for neat crude oil and pour point depressants treated crude oil at different ambient/surface temperature and pumping/reservoir temperature. It was observed that temperature has significant effect on the wax deposition of the crude oils. From these studies, ideal temperature of crude oil to pump in the pipeline or flow line was determined. The present investigations also furnishes that the selected pour point depressant in this work decreases the wax deposition significantly and may be used for controlling the wax deposition problems in case of Indian crude oil.     

AN IMPROVED INHIBITION OF PARAFFIN DEPOSITION FROM WAXY CRUDES

A series of cold spot tests of progressively increasing complexity was employed to evaluate the potential of several chemical additives for inhibiting paraffin deposition from waxy crudes. Test data revealed that trichloroethylene-xylene (TEX) binary system has a unique ability to effect substantial pour point depression and improved transport properties for a wide range of waxy crudes. This led to improved inhibition of paraffin deposition by TEX additive in comparison with the perfonnance of some tested, commercial anti-paraffin chemical products.     

LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART I WITH AND WITHOUT POUR POINT DEPRESSANT ADDITIVES

ABSTRACT

The yield stress, plastic viscosity and apparent viscosity and the dependence of the latter on the shear rate have been studied at different temperatures below pour point of Lingala (Krishna-Godavari basin, Eastern coast), Duliajan (Eastern region of Assam), Rava (Godavari basin) and Bombay-High (off-shore western region) indigenous crude oils

Four different commercial pour point depressant additives have been used to study their effects on the pour point, yield stress and plastic viscosity

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point, and crude base composition has a small effect. However, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the liquid matrix. As the temperature is lowered both the yield stress and plastic viscosity increase in case of each crude oil. However, the magnitude is dependent on the nature of the crude oil. With pour point depressant additives, the yield stress and plastic viscosity are decreased and this decrease is a function of nature of the liquid matrix of the crude oil and concentration of the additive     

LOW TEMPERATURE FLOW CHARACTERISTICS OF SOME WAXY CRUDE OILS IN RELATION TO THEIR COMPOSITION : PART I WITH AND WITHOUT POUR POINT DEPRESSANT ADDITIVES

The yield stress, plastic viscosity and apparent viscosity and the dependence of the latter on the shear rate have been studied at different temperatures below pour point of Lingala (Krishna-Godavari basin, Eastern coast), Duliajan (Eastern region of Assam), Rava (Godavari basin) and Bombay-High (off-shore western region) indigenous crude oils

Four different commercial pour point depressant additives have been used to study their effects on the pour point, yield stress and plastic viscosity

From this study it has been found that wax concentration and its composition are primarily responsible for the variation in the pour point, and crude base composition has a small effect. However, the response of the pour point depressant additive in effecting the change in the pour point is primarily governed by the liquid matrix. As the temperature is lowered both the yield stress and plastic viscosity increase in case of each crude oil. However, the magnitude is dependent on the nature of the crude oil. With pour point depressant additives, the yield stress and plastic viscosity are decreased and this decrease is a function of nature of the liquid matrix of the crude oil and concentration of the additive     

AN IMPROVED INHIBITION OF PARAFFIN DEPOSITION FROM WAXY CRUDES

ABSTRACT

A series of cold spot tests of progressively increasing complexity was employed to evaluate the potential of several chemical additives for inhibiting paraffin deposition from waxy crudes. Test data revealed that trichloroethylene-xylene (TEX) binary system has a unique ability to effect substantial pour point depression and improved transport properties for a wide range of waxy crudes. This led to improved inhibition of paraffin deposition by TEX additive in comparison with the perfonnance of some tested, commercial anti-paraffin chemical products.     

Nano-composite pour point depressants in improving the rheology of waxy crude oil

This article mainly describes the advantages of nano-pour point depressants on the low-temperature fluidity of crude oil compared with traditional pour point depressants. The common nano-pour point depressants are mainly divided blend type and polymerization type. It can effectively improve wax crystal structure and strength, thereby improving the low-temperature fluidity of crude oil. Nano-particles have better application prospects in improving rheological properties of waxy crude oil.     

阴离子聚合物St-OMA的合成和应用

采用阴离子聚合法合成苯乙烯（Styrene）-甲基丙烯酸十八酯（Octadecyl methyl acrylate）的二元共聚物St-OMA,评价了不同聚合条件下的聚合物对苏丹原油的降凝效果。通过偏光显微镜和图片处理软件对加剂前后原油中的蜡晶形态和分布进行微观分析,原油中蜡晶由大量片状、针状形态改变为颗粒状,蜡晶尺寸较小,蜡晶间也密实,分散得更细更匀称。这表明降凝剂的加入确实改变了原油中蜡的结晶形态,使析出的蜡晶尺寸变小变密,从而改善了原油的流动性,降低了原油的凝点。     

油气储运中的化学添加剂

为使原油、天然气及其石油产品在储存和运输过程中高效、节能、环保,需要使用各种化学添加剂,以达到降凝、降粘、防蜡、清蜡、减阻、抗静电及抑制烃类挥发和抑制水合物生成等目的。介绍了这些化学添加剂的作用机理、化学结构、应用情况以及不足之处。