Viscoelastic Properties of Crude Oil Components at Oil‐Water Interfaces. 2: Comparison of 30 Oils

The dilational properties of diluted (0.7 vol/vol in toluene) and undiluted crude oil‐water interfaces have been studied using the oscillation drop method with the objective of understanding the properties contributing to the overall stability of crude oil emulsions. The importance of working with undiluted crude oils instead of model systems when dilational properties of real oil‐water systems are going to be reproduced in the laboratory setting has been discussed. For such studies, molecular exchange mechanisms and the aggregation state of asphaltenes are too dependent on concentration to justify the use of model compounds, i.e. fractionated asphaltenes diluted in a solvent. As expected in the low frequency range (0.01–1 Hz), molecular exchange from the bulk oil phase strongly affected the measured dilational parameters. For the diluted crude oils, the frequency dependence of the dilational modulus increased with its magnitude. The systems that exhibited particularly low magnitude of the dilational modulus were of the heaviest crude oils in the sample set, whereas the systems with greatest dilational modulus were among the lightest crude oils. The overall characteristic time of relaxation of the crude oil‐water interfaces was in the range below 10 seconds. The undiluted crude oil‐water interfaces had similar interfacial properties as the diluted samples except for slightly reduced magnitude of the dilational modulus. The crude oil‐water interfaces appeared to be soluble, but some observations pointed to intrinsic rheological properties of the interfaces. Intrinsic elasticity and viscosity of the films should be studied outside the frequency range used here at low (ω～0 Hz) and high (ω→500 Hz), respectively.     

Effect of Interfacially Active Fractions of Some Egyptian Crude Oils on Their Emulsion Stability

Four samples from different crude oils were used for this study: light and heavy crude oils from Iran and two crude oils from Egypt, namely, Ras Gharb and Suez mix. The asphaltenes were separated from these crude oils and then the maltene (non‐asphaltenic fraction) was fractionated into waxes, aromatics, and resins. All fractions were characterized using FTIR and UV spectroscopic analyses in addition to gel permeation chromatograph (GPC). These fractions were tested for their emulsion stability. For chemometric analysis different parameters (variables) have been used to study the effect of different fractions (objects) on the emulsion stability. Such variables included the integrated areas under the stretching absorption peaks of CH in the range of 3000–2800 cm^?1, C?O in the range of 1750–1650 cm^?1, and the aromatic C?C in the range of 1650–1550 cm^?1, as well as UV absorption value at 235 nm and average molecular weight (MW). Principal component analysis (PCA) and multiple linear regression (MLR) were conducted for examining the relationship between multiple variables and the stability of water‐in‐crude oil emulsions. The results of PCA explain the interrelationships between the observations and variables in multivariate data. The correlation coefficients between different parameters derived from PCA reveals that the UV absorption value and MW are strongly correlated with emulsion stability. It also reveals that the resins, asphaltenes, and maltene have better emulsion stability than waxes and lower molecular weight aromatics. The linear relationship between the parameters and the stability of water‐in‐crude oil emulsions using MLR was modeled according to the better statistical results. The obtained mathematical model can be used to predict the stability of water‐in‐crude oil emulsions from the chemical groups and functionalities in each crude oil fraction.     

DMSO-accelerated rapid gelation of crude oils at room temperature

Dimethyl sulfoxide (DMSO), carrying a highly polarized S = O bond as the H-bond acceptor, possesses an extraordinarily high capacity to compete for H-bond formation. This strongly H-bonding character renders DMSO with a strong ability to interfere with or even disrupt self-assembled structures mediated predominantly by intermolecular H-bonds. While this might be quite disturbing in many applications, in this study, we show that oil gelation actually could benefit significantly from DMSO’s such a strong H-bond-breaking ability. More specifically, we found that use of a minute but optimized amount of DMSO, assisted further by polar acetonitrile of a suitable amount, weakens the H-bonds in the gelling network formed by organogelators to a just right extent so as to allow for a faster disassembly-reassembly of fibers in the wetted powder gelator in oil and subsequent occurrence of rapid room-temperature gelation of both light and heavy crude oils of widely ranging viscosities within 6–25 mins at gelator loadings of ≤12% w/v.     

Stability of Water/Crude Oil Systems Correlated to the Physicochemical Properties of the Oil Phase

A characterization of 30 crude oils has been performed to determine the relative level of influence that individual parameters have over the overall stability of w/o emulsions. The crude oils have been analyzed with respect to bulk and interfacial properties and the characteristics of their w/o emulsions. The parameters include compositional properties, acidity, spectroscopic signatures in the infrared and near‐infrared region, density, viscosity, molecular weight, interfacial tension, dilational relaxation, droplet size distribution, and stability to gravitationally and electrically induced separation. As expected, a strong covariance between several physicochemical properties was found. Near‐infrared spectroscopy proved to be an effective tool for crude oil analysis. In particular, we have showed the importance of the hydrodynamic resistance to electrically‐induced separation (static) in heavy crude oil‐water emulsions. A rough estimate of the drag forces and dielectrophoretic forces seemed to capture the difference between the 30 crude oils. Given enough time, water‐in‐heavy oil emulsions could be destabilized even at very low electric field magnitude (d.c.). When droplets approach each other in an inhomogeneous electric field, strong dielectrophoretic forces disintegrate the films and result in coalescence. The relative contribution from film stability to the overall emulsion stability may therefore be very different in a gravitational field compared to that in an electrical field.     

触变性含蜡原油等温胶凝过程特性及模型研究

综合利用理论推导和流变实验方法对触变性含蜡原油的等温胶凝过程进行了详细的研究, 采用结构参数法建立了静态结构恢复模型, 并经实验结果证明该模型对多种原油的结构变化曲线均有较高的拟合精度. 同时以青海原油为例, 根据实验数据和拟合参数分析了含蜡原油等温胶凝过程特性. 结果表明, 随着温度的升高、预剪切速率的增大以及预剪切时间的增加, 原油在恒温静止过程中形成的结构强度均会减弱. 测量温度越高, 预剪切时间越长, 则原油的结构参数变化速率越大; 而预剪切速率越高, 原油结构参数变化速率在初始阶段越大, 在最终阶段反而越小, 但与未经剪切油样相比, 原油受剪切后其结构参数变化速率在整个测量时间范围内均偏大.     

贯叶连翘挥发油成分的分析

报道了当前全球研究开发的热点抗抑郁植物药贯叶连翘原药材和商品浸膏粉中挥发油成分的分析。贯叶连翘原药材粗粉中挥发油得率0．4％(mL/l00g)，从中鉴定了41种化合物；从浸膏粉的挥发油中鉴定了14种化合物。结果表明：因原料产地、药用部位的不同，以贯叶连翘挥发油为主要成分的油类制剂药效将有所不同。     

A mannitol based phase selective supergelator offers a simple, viable and greener method to combat marine oil spills

Though phase selective organogelators (PSOGs) are thought to be useful for oil spill recovery, all known PSOGs require a water-miscible carrier solvent for their introduction. Providing a simple, cheap, green and practical solution to the problem of oil spills, we report a nontoxic super-PSOG that can be sprayed aerially in a carrier solvent destined to get co-congealed with the oil.     

Characterization of C80 Naphthenic Acid and Its Calcium Naphthenate

A C80 naphthenic acid (tetraacid) and its calcium naphthenate have been characterized with respect to their interfacial properties at both the oil/water and the air/water interfaces as well as their thermal properties. Naphthenic acids in crude oils may give rise to different problems in oil production including naphthenate deposition and formation of stable emulsions. This may lead to severe disturbances of regularity and shut‐in in the oil production. The interfacial activity and film properties of the compounds were examined by the oscillating drop method. The calcium naphthenate film was primarily elastic and solid‐like. Measurements on the acid gave similar results, an elastic, solid‐like film was formed, but the effect was less pronounced than for the calcium naphthenate. Langmuir‐Blodgett films of the acid and its naphthenate were deposited on conducting substrates and subsequently analyzed by scanning electron microscopy, SEM. It was found that the pure acid formed crystalline structures in the interfacial film on compression. The calcium naphthenate, on the other hand, form a continuous amorphous film on the substrate.     

Spectroscopic and Chromatographic Identification of Hydrocarbon Group Types in Pakistani Crude Oils

Two crude oil samples collected from Paniro and Tangri (Sindh) southern Pakistan. The distillate fractions of both crude oil samples were analysed by U.V‐visible spectrophotometer and column chromatography for hydrocarbon group types. It was found from the physico‐chemical study of these crude oils that Tangri crude oil contains mostly paraffinic contents while Paniro crude oil samples are rich in aromatics. It was concluded from all the experiments that Tangri crude oil is paraffinic in nature; while Paniro crude oil is naphthenic in nature, further it was observed that Tangri crude oil processing would be environmentally friendly compared to Paniro crude oil, because Paniro crude contains a high amount of polyaromatics.     

Characterization of Crude Oil Equivalent Alkane Carbon Number (EACN) for Surfactant Flooding Design

Equivalent alkane carbon number (EACN) of crude oil reflects the hydrophobicity of the crude oils, thus it would be helpful to estimate the EACN of crude oil before fine tuning the surfactant selection for enhanced oil recovery field application. In this study, we used the titration methodology to quantify the EACN values for several crude oil samples retrieved from the targeted mature oil fields. The results showed that the method of using extended surfactant was simpler but reliable to determine the EACN of crude oils. The resulting EACN for these crude oils was found to be in the range of 6.0–11.3.     

A Multivariate Analysis on the Influence of Indigenous Crude Oil Components on the Quality of Produced Water. Comparison Between Bench and Rig Scale Experiments

A matrix of 30 crude oils have been analyzed to investigate if there is any correlation between the physiochemical properties of the crude oils and the quality of the produced water. As an approach to study produced water quality, oil. and brine water (3.5 wt%) have been mixed together, and transmission profiles from the separation process have been investigated by means of Turbiscan LAb. The Turbiscan LAb enables the study of stability of colloidal dispersions without any dilution or modification of the sample. The oil-in-water emulsions (30:70) were made by mixing oil and water at low speed to be sure that they separate within a short period of time. Drop size distributions were investigated for all crude oil emulsions by using a Coulter Counter (COULTER Multisizer II). The correlations between transmission profiles and crude oil characteristics were made by using principal component analysis (PCA), a method that helps visualize the most important information contained in a data set and find combinations of variables that describe major trends. A Vortoil K-liner hydrocyclone connected to a mixing rig has been used to separate oil and water in larger scale experiments. The objective with these experiments was to compare the results with separation experiments done at bench scale. Six crude oils have been investigated at the separation rig, and both droplet size distribution and dispersed oil concentration have been performed. The main conclusions from this work are that Turbiscan LAb is a suitable technique to study the separation of oil-in-water with good reproducibility. The results from the multivariate data analysis show that the crude oils group according to if they are light or heavy and according to if they get high or low transmission. From the larger scale experiments it has been shown that the droplet sizes, oil/water density differential, and viscosity have a significant impact on separation efficiency.     

多环芳烃指纹用于渤海采油平台原油的鉴别

采用气相色谱/质谱方法,对渤海海上4个不同区块、5个平台的6口油井原油进行了烷基化多环芳烃系列化合物和美国环保署（EPA）优先控制多环芳烃系列化合物的准确定性定量分析。通过多环芳烃原始指纹谱图、多环芳烃组分分布模式和特征比值的比较对上述原油进行鉴别。结果证明不同区块的原油中多环芳烃指纹信息不尽相同,即使在同一平台不同油井中所产的原油其指纹也存在一定差异。为确保原油鉴别的准确性,分析过程中必须在仪器的稳定性和样品前处理方面实施严格的质量控制措施。     

A coulometric method for determining substances that interfere with the measurement of water in oils and other chemicals by the Karl Fischer method

In order to fulfill a need to measure water in crude oils containing materials that interfere with the measurement of water by the Karl Fischer method, by reacting with iodine or iodide, a coulometric method has been developed and validated using 0.1 mol L(-1) Sodium thiosulfate as a calibrant. These interfering substances were measured in water-mass-equivalents, which were expressed as the mass of water that reacts with an equal mass of iodine in the Karl Fischer method. The SO(2)-free reagent that has been modified reacts quantitatively with sodium thiosulfate, cysteine and ascorbic acid but does not react with vinyl acetate. The level of interfering substances was measured in five transformer oils (including Reference Materials RM 8506 and RM 8507), a high and a low sulfur crude oil (Standard Reference Materials SRM 2721 and SRM 2722 respectively), a white oil, a high-vacuum oil and a high-viscosity base-stock oil. One oil contained less than 10 mg kg(-1) (water-mass-equivalents of interfering substances in oil) and two oils (RM 8507 and Drakeol 35) contained no measurable amount of interfering material (<0.2 mg kg(-1)). SRM 2271, a sour crude oil contained 834 mg kg(-1) (standard deviation (SD)=25 mg kg(-1)) (water-mass-equivalents of interfering substances in oil). Approximately 20% of this material was volatile and an additional 20% appeared to undergo some degradation (possibly oxidation) once the oil was exposed to air. These results indicate that this is a general method for measuring substances in oils that react with iodine and that it is capable of measuring in a variety of oils, using commercial instrumentation, interfering substances that inflate water measurements.     

Wie lange gibt es noch Erdöl und Erdgas? – Reserven,Ressourcen und Reichweiten

Knowledge about the future availability of crude oil and other energy resources is crucial for politics, industry an even the consumer in the face of the drastically increased worldwide oil consumption up to more than 3, 8 Bill. t in 2004. Using oil as an example, reserves and resources, its dynamic, and the influence of non‐conventional oils (tar sands, extra heavy oil) are discussed with respect to future availability.     

Low‐molecular‐weight organogelators as functional materials for oil spill remediation

Oil spills from tankers are one of the major types of man‐made disasters that impact the marine environment, and they have been shown to have long‐lasting effects. On prevention of the spread of oil through rapid cleanup of spills, low‐molecular‐weight organogelators have received much attention because of their ability to tune their properties through rational design. In this mini‐review, I present a brief summary of studies focused on the remediation of oil spills via a chemical method, which involves the use of low‐molecular‐weight organogelators that form organogels with fuel oils or organic solvents. Moreover, recent attempts to create new improved molecular organogels composed of commercially available simple organogelators via a mixing induced enhancement method for solidifying oil are also discussed. In addition, polymer organogelators for oil spills are discussed in relation to low‐molecular weight gelators. Copyright © 2015 John Wiley & Sons, Ltd.     

Laminar Flow Emulsification Process to Control the Viscosity Reduction of Heavy Crude Oils

The formation of heavy crude oil in water (O/W) emulsion by a low energy laminar controlled flow has been investigated. The emulsion was prepared in an eccentric cylinder mixer. Its geometry allows the existence of chaotic flows that are able to mix well highly viscous fluids. This new mixer design is used to produce high internal phase ratio emulsions for three oils: castor oil and two heavy crude oils of different initial viscosity (Zuata and Athabasca crude oils). The influence of the stirring conditions, geometrical parameters, and water volume fraction on the rheological properties of the resulting O/W emulsion is studied.     

Experimental Study of Asphaltenes Flocculation Onset in Crude Oils Using the Densitometry Measurement Technique

The asphaltenes flocculation proceeds with changes of oil composition and causes significant losses in petroleum industry operations. The main objective of this work is to evaluate the reliability of the densitometry technique in studying experimentally the mechanism of aggregation and flocculation of asphaltenes occurring in crude oils. As asphaltene flocculation threshold in crude oils or mixture can be achieved by addition of n-heptane, various n-heptane concentrations were added to crude oil, and their effects have been investigated trough density measurements. Thereby, measurements were based on mixture of crude oil + toluene and cyclohexane + n-heptane, respectively. While asphaltene aggregates form clusters and flocculate, the mixture volumetric mass change and the reduced density of non-Newtonian fluids under investigation have been pointed out as one of appropriate measures of flocculation process. In particular, the curve representing the reduced density as function of the ratio between n-heptane concentration and concentration of crude oil under study featured a break point that well characterizes the flocculation threshold. Besides the quantity needed to initiate and to aggregate asphaltenes within crude oils, the amount required to completely achieve deposition of asphaltenes has also been identified. A quantity of 4 and 20 g of n-heptane per gram of crude oil was found necessary.     

Slurries and emulsions of waxy and heavy crude oils for pipeline transportation of crude oil

The high viscosity of many asphaltic crude oils and the high pour points of many waxy crude oils present significant problems in their transportation over long distances by pipeline and tanker. While heating the oils and insulating the pipelines will help alleviate the problem, there is danger associated with an extended shutdown of flow and either congealing or solidification of the oil. A possible solution which we have studied in the laboratory is the emulsification or dispersion of the oil in water or brine so that shear takes place in the continuous aqueous phase rather than the oil droplets or particles.Synthetic waxy crude oils were prepared by dissolving paraffin wax in white mineral oil at slightly elevated temperatures and then measuring the pour point. One containing 30% wax had a pour point of 43°C and was selected for preparations of the dispersions. This was emulsified in water at a temperature higher than the pour point by using a suitable surfactant as an emulsifying agent. Rheological properties were measured at various temperatures and are reported in the paper. The method shows great promise for use in countries such as China which produce significant quantities of waxy crude oil and have seasonal temperatures significantly lower than the pour point of the crude oil.     

A new method to determine reid vapour pressure for stabilized crude oils by gas chromatography

Summary A new rapid method has been developed to determine Reid Vapour Pressure (RVP) for stabilized crude oils by gas chromatography. The quantity of light hydrocarbons dissolved in crude oil was measured directly by gas chromatographic analysis, while the RVP value was computed utilizing a new correlation with this quantity at constant temperature. A variety of crude oils were investigated and the results revealed the accuracy of this method.     

基于石油烃特征比值的多元统计方法进行原油鉴别

基于原油中有生源意义的生物标志物及原油特征多环芳烃的特征比值,采用主成分分析和聚类分析法,对渤海3个不同区块的4种原油,以及其中1种原油风化7d、15d和30d的风化油样和陆地油田1和陆地油田2各1种原油进行鉴别。结果显示:利用主成分分析和聚类分析可以实现大量油样的快速分类鉴别,不仅可以对差异较大的原油进行区分,还可以对原始原油及其风化原油进行很好分辨,但对差异较小的原油,两种分析方法的分辨能力仍有一定局限性。