EFFECT OF ASPHALTENE AND RESINS ON THE STABILITY OF WATER-IN-WAXY OIL EMULSIONS

Asphaltene, resins and paraffin waxes, their mutual interactions and their influence on the stability of water-in-oil emulsions have been studied. 20 wt % paraffin wax dissolved in decalin was used to model the waxy crude oil. Asphaltene and resins separated from a crude oil were used to stabilize the water-in-oil emulsions. Synthetic formation water was utilized as the aqueous phase of the emulsion. The emulsion stability increased with increasing the concentration of asphaltene with a subsequent decrease in the average particle size distribution of the emulsion. Resins alone are not capable of stabilizing the emulsion, however, in the presence of asphaltene they form very stable emulsions. Dynamic viscosity and pour point measurements provided evidence for resins-paraffin waxes interactions. Asphaltene in the form of solid aggregates form suitable nuclei for the wax crystallites to build over with a mechanism similar to that of paraffin wax crystal-modifiers. As asphaltene are polar in nature they are derived at the oil/water interface which was proved by the ability of asphaltene to reduce oil/water interfacial tension. Consequently, nucleation of the wax crystallites by asphaltene and resins at the interface will add to the thickness of the oil-water interfacial film and hence increase the stability of the emulsion.     

Stability of Water-in-Crude Oil Emulsions: Effect of Oil Aromaticity,Resins to Asphaltene Ratio,and pH of Water

Abstract

The formation of tight water-in-oil emulsions during production and transport of crude oils is a great problem challenging the petroleum industry. Tremendous research works are directed to understanding the mechanism of formation, stabilization, and controlling of oil field emulsions. This article presents experimental results of some of the factors controlling the formation and stabilization of water-in-crude oil emulsions. In this study, asphaltenes and resins separated from emulsion samples collected from Burgan oil field in Kuwait have been used to study emulsion stability. Model oils of resin to asphaltene ratio of 5:1 and toluene-heptane mixtures have been used to study the effect of oil aromaticity on emulsion stability. Results indicate that at low toluene content (below 20%) or high content (above 40%) less stable emulsions are formed. At a threshold value of 30% toluene, a very tight model oil emulsion is formed. The effect of resins to asphaltene (R/A) ratio on stability of model oil has also been investigated. Results reported in this paper show that as the R/A increases the emulsions become less stable. The effect of pH on stability of model oil emulsion made of 50/50 heptane-toluene mixture having R/A ratio of 5:1 have been studied. Experimental results revealed that as the pH of the aqueous phase of model oil increased from 2 to 10, the emulsion became less stable. At high pH, the asphaltene particles are subjected to complete ionization leading to destruction of the water-oil interface and eventually breakdown of the emulsion.     

Characterization of Asphaltenes and Resins Separated from Water-in-Oil Emulsions

Abstract

Knowledge of the properties and behavior of asphaltenes and resins is indispensable for the design of preventive and curative measure for emulsion problems created by the presence of asphaltene, resins, and other organic and inorganic solids. In order to understand the phenomena of water-oil emulsions formed in Kuwaiti oil fields and determine the factors involved in the stabilization of these emulsions, the role of asphaltenes, resins and wax separated from various samples of oil field emulsions formed in Burgan oil field have been evaluated. Physicochemical properties of asphaltenes, resins, wax, and de-asphalted de-resined (DADR) oil samples have been studied via FT-IR, ¹H, and ¹³C NMR, elemental analysis, and differential scanning calorimetry (DSC). These emulsion samples contain different amounts of water ranges from 24 to 35%, asphaltene content ranges from 0.9 to 1.7%, and resin content from 3.7 to 4.6%. IR-FT spectra were performed to identify the various functional groups which have an effect on the stability of water-oil emulsions. The freezing behavior of an emulsion was characterized by differential scanning calorimetry to determine whether the water in the emulsion is free water or emulsified water.     

The Asphaltene and Wax Deposition Envelopes

ABSTRACT

Asphaltene and wax phase behavior is quite different than the conventional “PVT” phase behavior. Asphaltenes exhibit a behavior at some thermodynamic states called flocculation. That is, asphaltene particles or micelles aggregate or flocculate into larger aggregates or flocs. The locus of all thermodynamic points in a P-T-x phase diagram at which flocculation occurs is called the Asphaltene Deposition Envelope (ADE). Paraffin waxes, on the other hand, at some thermodynamic states, exhibit the phenomenon of crystallization. The locus of all thermodynamic points in a P-T-x phase diagram at which wax crystallization occurs is called the Wax Deposition Envelope (WDE). Asphaltene flocculation can be both reversible and irreversible (as expected from the asphaltene colloidal nature). Wax crystallization is generally a reversible process. However, paraffin waxes more than often precipitate together with resins and asphaltenes (which are said to be responsible for the observed irreversible thermodynamic phenomena). Hence, some wax precipitation is occasionally reported as irreversible. Measurement of the ADE and WDE boundaries, at in-situ conditions, is a challenging task. Measurement of asphaltene and wax solubility at in-situ conditions inside the ADE and WDE is even more challenging. The ADE and WDE data have practical significance and are very useful for modeling of reservoir fluid behavior. Asphaltene and wax data for a number of oils are presented and analyzed. This paper introduces and compares two powerful thermodynamic diagrams that summarize the phase behavior of asphaltenes and waxes, the ADE and WDE.     

原油复配破乳剂的配方设计

研究了水相pH值、非离子破乳剂和助剂对沙轻原油、阿曼原油、杰诺原油、胜利原油乳液稳定性的影响 ,考察了破乳剂与助剂的协同效应。结果表明 :沙轻原油在水相 pH =6～ 7时乳液的稳定性最差 ;破乳剂通过降低界面张力和使沥青质胶团向油相解缔而破坏乳液的稳定性 ;有机小分子助剂改变界面极性环境或增加芳香度使沥青质增溶而破坏乳液的稳定性 ,它们与破乳剂有很好的协同效应     

油包水乳状液中胶质和沥青质的界面剪切黏度和乳状液稳定性的关系

 采用红外和紫外光谱分析了胜利原油中胶质和沥青质的结构，采用界面剪切黏度对其油、水界面膜强度进行了表征，测定了胶质和沥青质模拟油油包水乳状液的稳定性。结果表明，沥青质和胶质的结构和相对分子质量不同，沥青质含有更多的芳环结构，相对分子质量比胶质大，界面膜强度也比胶质强，其乳状液更稳定。     

长庆油包水乳状液的稳定性与沥青质含量的关系

以长庆轻质原油为例,探讨了原油组分对乳状液稳定性的影响规律;采用煤油萃取轻质组分及二 甲苯溶解沥青质两种方法证实了沥青质是稳定轻质油包水乳状液的主要因素;采用流变仪、布氏黏度计 和光学显微镜等仪器测定了含水原油乳状液界面膜强度、油相黏度和乳状液尺寸。结果表明,取决于沥 青质的油 水界面膜强度和油相黏度是影响原油乳状液稳定性的主要因素,沥青质含量越高,油 水界 面膜强度和油相黏度越大,乳状液越稳定。     

Characterization of Asphaltenes and Resins Separated from Water-in-Oil Emulsions

Knowledge of the properties and behavior of asphaltenes and resins is indispensable for the design of preventive and curative measure for emulsion problems created by the presence of asphaltene, resins, and other organic and inorganic solids. In order to understand the phenomena of water-oil emulsions formed in Kuwaiti oil fields and determine the factors involved in the stabilization of these emulsions, the role of asphaltenes, resins and wax separated from various samples of oil field emulsions formed in Burgan oil field have been evaluated. Physicochemical properties of asphaltenes, resins, wax, and de-asphalted de-resined (DADR) oil samples have been studied via FT-IR, ¹H, and ¹³C NMR, elemental analysis, and differential scanning calorimetry (DSC). These emulsion samples contain different amounts of water ranges from 24 to 35%, asphaltene content ranges from 0.9 to 1.7%, and resin content from 3.7 to 4.6%. IR-FT spectra were performed to identify the various functional groups which have an effect on the stability of water-oil emulsions. The freezing behavior of an emulsion was characterized by differential scanning calorimetry to determine whether the water in the emulsion is free water or emulsified water.     

疏水缔合聚合物驱体系中原油乳状液性质及破乳规律

采用瓶试法考察了原油组成及疏水缔合聚合物（Hydrophobically associating polymer, HAP）质量浓度对原油乳状液稳定性的影响,用油 水界面张力、界面电性、界面扩张流变、界面剪切黏度等多个参数表征了HAP驱采出液油 水界面性质的变化规律,用一系列酚胺树脂聚醚破乳剂对模拟采出液进行破乳。结果表明,原油中胶质和沥青质是影响原油乳状液稳定的重要因素;实验浓度范围内,随着HAP浓度升高,原油乳状液稳定性增强。HAP具有界面活性,吸附在油 水界面可降低界面能,利于乳化;HAP在界面上形成交联网状结构,提升了界面膜的扩张模量和剪切模量,同时增强了界面膜的负电性,利于稳定乳状液。环氧乙烷与环氧丙烷各占一半的酚胺树脂聚醚破乳剂与1%甲苯二异氰酸酯（TDI）交联后,5 min即可完全将原油乳状液破乳。     

Influence of polymers on the stability of Gudao crude oil emulsions

The influence of different types and concentrations of polymers on the stability of Gudao crude oil emulsion was investigated by measuring the volume of water separated from the emulsions and the interfacial shear viscosity of the oil/water interfacial film. Experimental results indicate that the simulated water-in-oil emulsion with 40 mg/L of partially hydrolyzed polyacrylamide （HPAM） 3530S could be easily broken by adding demulsifier C and was readily separated into two layers. However, HPAM AX-74H and hydrophobically associating water-soluble polymer （HAP） could stabilize the crude oil emulsion. With increasing concentration of AX-74H and HAP, crude oil emulsions became more stable. Water droplets were loosely packed in the water-in model oil emulsion containing HPAM 3530S, but water droplets were smaller and more closely packed in the emulsion containing AX-74H or HAP. The polymers could be adsorbed on the oil/water interface, thereby increasing the strength of the interracial film and enhancing the emulsion stability.     

The Asphaltene and Wax Deposition Envelopes

Asphaltene and wax phase behavior is quite different than the conventional “PVT” phase behavior. Asphaltenes exhibit a behavior at some thermodynamic states called flocculation. That is, asphaltene particles or micelles aggregate or flocculate into larger aggregates or flocs. The locus of all thermodynamic points in a P-T-x phase diagram at which flocculation occurs is called the Asphaltene Deposition Envelope (ADE). Paraffin waxes, on the other hand, at some thermodynamic states, exhibit the phenomenon of crystallization. The locus of all thermodynamic points in a P-T-x phase diagram at which wax crystallization occurs is called the Wax Deposition Envelope (WDE). Asphaltene flocculation can be both reversible and irreversible (as expected from the asphaltene colloidal nature). Wax crystallization is generally a reversible process. However, paraffin waxes more than often precipitate together with resins and asphaltenes (which are said to be responsible for the observed irreversible thermodynamic phenomena). Hence, some wax precipitation is occasionally reported as irreversible. Measurement of the ADE and WDE boundaries, at in-situ conditions, is a challenging task. Measurement of asphaltene and wax solubility at in-situ conditions inside the ADE and WDE is even more challenging. The ADE and WDE data have practical significance and are very useful for modeling of reservoir fluid behavior. Asphaltene and wax data for a number of oils are presented and analyzed. This paper introduces and compares two powerful thermodynamic diagrams that summarize the phase behavior of asphaltenes and waxes, the ADE and WDE.     

原油乳状液油-水界面上活性物的结构和活性

通过综合的方法分离出大庆原油和胜利原油乳状液油-水界面上的活性物，用元素分析、红外、核磁、色质联用等方法分析其化学结构，并在油饿水模型体系中测定了它们的动态界面张力，考察其化学结构与界面活性之间的关系。结果表明，水相的pH值影响原油中的含氧化合物在油．水界面膜上的吸附；沥青、胶质和蜡是界面活性物的主要成分，对油-水界面膜的形成和稳定起着重要的作用；原油的酸性组分对油-水界面膜的动态界面张力有着决定性的影响。     

Influence of surfactants used in surfactant-polymer flooding on the stability of Gudong crude oil emulsion

The influences of an anionic-nonionic composite surfactant and petroleum sulfonate, used in surfactant-polymer flooding in Shengli Gudong oilfield, East China, on the interfacial properties of Gudong crude model oil and synthetic formation water was studied by measuring interfacial tension, interfacial viscoelasticity and Zeta potential. The influence of the surfactants on the stability of Gudong water-in-oil (W/O) and oil-in-water (O/W) emulsions was evaluated by separating water from the W/O emulsion and residual oil in the aqueous phase of the O/W emulsion respectively. The results showed that the two kinds of surfactants, namely anionic-nonionic composite surfactant and petroleum sulfonate, are both able to decrease the interfacial tension between the oil phase and the aqueous phase and increase the surface potential of the oil droplets dispersed in the O/W emulsion, which can enhance the stability of the W/O and O/W crude oil emulsions. Compared with petroleum sulfonate, the anionic-nonionic composite surfactant is more interfacially active and able to enhance the strength of the interfacial film between oil and water, hence enhance the stability of the W/O and O/W emulsions more effectively.     

RHEOLOGY,PARTICLE SIZE DISTRIBUTION,AND ASPHALTENE DEPOSITION OF VISCOUS ASPHALTIC CRUDE OIL-IN-WATER EMULSIONS FOR PIPELINE TRANSPORTATION

The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mixture has been studied. The investigated crude oil has a non-Newtonian, time dependent, shear thickening, rheopectic behavior with a relatively high yield stress. The relatively high yield stress of this crude oil is attributed to the presence of a relatively high asphaltene and resins content. The viscosity ofhe crude oil decreases when it is emulsified with synthetic formation water in the form of an oil-in-water type of emulsion using a nonionic or an anionic surfactant. It has been found that, the maximum oil content required for forming an oil-in-water emulsion of acceptable viscosity is the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mixture of oil-in-water-in-oil type of emulsion. The presence of the anionic and the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic surfactant has a positive contribution in forming emulsions with low viscosity. Meanwhile, the anionic surfactant contributes in stabilizing the emulsion at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies that it is safe to use the investigated surfactants in forming oil-in-water emulsion for viscous asphaltic crude oils without any fear of asphaltene deposition.     

RHEOLOGY, PARTICLE SIZE DISTRIBUTION, AND ASPHALTENE DEPOSITION OF VISCOUS ASPHALTIC CRUDE OIL-IN-WATER EMULSIONS FOR PIPELINE TRANSPORTATION

The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mixture has been studied. The investigated crude oil has a non-Newtonian, time dependent, shear thickening, rheopectic behavior with a relatively high yield stress. The relatively high yield stress of this crude oil is attributed to the presence of a relatively high asphaltene and resins content. The viscosity ofhe crude oil decreases when it is emulsified with synthetic formation water in the form of an oil-in-water type of emulsion using a nonionic or an anionic surfactant. It has been found that, the maximum oil content required for forming an oil-in-water emulsion of acceptable viscosity is the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mixture of oil-in-water-in-oil type of emulsion. The presence of the anionic and the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic surfactant has a positive contribution in forming emulsions with low viscosity. Meanwhile, the anionic surfactant contributes in stabilizing the emulsion at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies that it is safe to use the investigated surfactants in forming oil-in-water emulsion for viscous asphaltic crude oils without any fear of asphaltene deposition.     

原油乳状液稳定性研究Ⅰ界面压与乳状液稳定性

影响油包水型原油乳状液稳定性的最重要的因素是包在水滴周围的具有一定强度的界面膜的存在.从热力学角度看,加入表而活性剂会降低界面张力,而界面张力越低,乳状液就越稳定这可部分解释表面活性剂能稳定乳状液的原因但彭响乳状液稳定性的更重要的是动力学问题界而膜的强度是影响乳状液稳定性动力学的最重要的因素之一,而界血压则是与界面膜强度密切相关的重要参数通过理论分析和对以胶质、沥青质组分为表而活性剂乳化形成的乳化液稳定性与界面压的研究,证明界面压(而不是界面张力)是度量乳状液稳定性的一个重要参数L当表而活性剂类型一定时.可以用界面压的大小来衡量乳状液稳定性的高低.     

原油中天然表面活性剂的分离和性质研究

用乳化法分离出Ｐｒｅａｌｐｉｎｅ地区油中的天然表面活性剂,将它分散到液体石蜡中,测定了该分散液的表面张力,界面张力。考察了盐度水相ＰＨ值对界面张力的影响。另外,还以此分散液制备了一些太液,比较了它们的稳定性,了盐度和水相ＰＨ值对状液稳定性的影响。     

Investigation of factors affecting on viscosity reduction of sludge from Iranian crude oil storage tanks

Crude oil is a kind of water/oil emulsion, which the oil phase consists of organic molecules with different molecular weights such as alkanes, paraffin, asphaltene, and resins. Due to the change in physicochemical conditions during the production, transportation, storage, and refining, heavier molecules can precipitate from crude oil. Thus, viscous sludge formed at the bottom of storage tanks can cause many problems including reduction of storage capacity of tank, oil contamination, corrosion, repair costs, environmental pollution, etc. The reduction of sludge viscosity can be achieved by reduction of its interfacial tension. In this study, different chemical and physical factors, influencing prepared emulsions (made of sludge, water and surfactant), such as surfactants, solvents, temperature, pressure, and mixing conditions were investigated. Results showed that non-ionic surfactants (like bitumen emulsifier), and solvents (such as mixed xylene, AW-400, and AW-402), injection of additives, applying pressure, and mixing operations had a positive effect on reduction of emulsion viscosity. All experiments were carried out with sludge obtained from crude oil storage tanks at Kharg Island, Iran.     

胶质、沥青质对水-苯乳状液稳定性的影响

为深入研究胶质、沥青质对原油乳状液稳定性的影响,从孤岛渣油中分离出胶质和沥青质,用滴体积法、Ｌａｎｇｍｕｉｒ膜天平、单滴寿命法、瓶试法等研究了它们的水－苯界面活性、Ｌａｎｇｍｕｉｒ膜压,阻止水－苯界面上的水滴向水相融并的能力及稳定水－苯乳状液的能力。结果表明,胶质比沥青质具有更强的水－苯界面活性;沥青质比胶质具有更大的Ｌａｎｇｍｕｉｒ膜压;沥青质阻止水－苯界面上的水滴向水相融并的能力远大于胶质;沥     

应用正交实验设计法研究石蜡基高蜡原油微波破乳规律

 原油含水不利于石油储运、加工,影响产品质量,还会对设备造成很大危害, 因此原油脱盐、脱水是石油工业中不可缺少的环节。我国开采的原油以石蜡基高蜡原油居多,这类原油的特点是含蜡高、凝点高、粘度大和低温流动性差。石蜡基高蜡原油中含有的微晶蜡是一种天然乳化剂,不仅能增加原油粘度,同时易于形成网状结构,吸附在油水界面,阻碍水滴的聚并,加大原油乳化液破乳难度。本文采用正交设计法,对大庆石蜡基高蜡原油在乙酸钠存在下微波辐射破乳规律进行研究。结果表明,添加极少量的乙酸钠能显著提高石蜡基高蜡原油乳化液的破乳效果。利用SH9402微波反应系统,在剂油比为0.05、系统压力为0.7MPa、恒压时间为12min,微波辐射功率为225W条件下,可使含水50%的大庆高蜡原油乳化液脱水率达95.83%。