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.     

DSC and Rheometry Investigations of Crude Oils

Thermal characteristics and rheological behaviour of eight crude oils covered a wide range of fluid composition and properties were studied by differential scanning calorimeter (DSC) and viscometry. Wax appearance temperatures (WAT) of crude oils were determined by DSC and viscometry. Good agreement is obtained between the results. The dynamic viscosity in the Newtonian temperature range of the crude oils (above 30°C) generally obeyed a simple first-order Arrhenius type of temperature dependence. Activation energies of flow in the non-Newtonian range are not uniquely defined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Characteristics of bicyclic sesquiterpanes in crude oils and petroleum products

This study presents a quantitative gas chromatography–mass spectrometry analysis of bicyclic sesquiterpanes (BSs) in numerous crude oils and refined petroleum products including light and mid-range distillate fuels, residual fuels, and lubricating oils collected from various sources. Ten commonly recognized bicyclic sesquiterpanes were determined in all the studied crude oils and diesel range fuels with principal dominance of BS3 (C₁₅H₂₈), BS5 (C₁₅H₂₈) and BS10 (C₁₆H₃₀), while they were generally not detected or in trace in light fuel oils like gasoline and kerosene and most lubricating oils. Laboratory distillation of crude oils demonstrated that sesquiterpanes were highly enriched in the medium distillation fractions of ∼180 to 481 °C and were generally absent or very low in the light distillation fraction (boiling point to ∼180 °C) and the heavy residual fraction (>481 °C). The effect of evaporative weathering on a series of diagnostic ratios of sesquiterpanes, n-alkanes, and biomarkers was evaluated with two suites of weathered oil samples. The change of abundance of sesquiterpanes was used to determine the extent of weathering of artificially evaporated crude oils and diesel. In addition to the pentacyclic biomarker C₂₉ and C₃₀ αβ-hopane, C₁₅ and C₁₆ sesquiterpanes might be alternative internal marker compounds to provide a direct way to estimate the depletion of oils, particularly diesels, in oil spill investigations. These findings may offer potential applications for both oil identification and oil-source correlation in cases where the tri- to pentacyclic biomarkers are absent due to refining or environmental weathering of oils.     

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.     

Effect of temperature and composition on density,viscosity and thermal conductivity of fatty acid methyl esters from soybean,castor and Jatropha curcas oils

This work is focused on experimental determination of density, viscosity and thermal conductivity as a function of temperature and composition for fatty acid methyl esters (FAME) from soybean, castor and Jatropha curcas oils. Results show that an increase in temperature, over the range of (273 to 363) K, resulted in a decrease of all properties studied. FAME from soybean and J. curcas oils presented similar rheological behaviour, while FAME from castor oil presented higher values for density and viscosity. Density, dynamic viscosity and thermal conductivity data for all systems obtained here were correlated using empirical equations with good agreement between experimental and calculated values. Experimental data presented here may be useful as a database for specification purposes and equipment design and plant operation in the biodiesel industry.     

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.     

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.     

Dispersion of T1 and T2 Nuclear Magnetic Resonance Relaxation in Crude Oils

Crude oils, which are complex mixtures of hydrocarbons, can be characterized by nuclear magnetic resonace diffusion and relaxation methods to yield physical properties and chemical compositions. In particular, the field dependence, or dispersion, of T₁ relaxation can be used to investigate the presence and dynamics of asphaltenes, the large molecules primarily responsible for the high viscosity in heavy crudes. However, the T₂ relaxation dispersion of crude oils, which provides additional insight when measured alongside T₁, has yet to be investigated systematically. Here we present the field dependence of T₁‐T₂ correlations of several crude oils with disparate densities. While asphaltene and resin‐containing crude oils exhibit significant T₁ dispersion, minimal T₂ dispersion is seen in all oils. This contrasting behavior between T₁ and T₂ cannot result from random molecular motions, and thus, we attribute our dispersion results to highly correlated molecular dynamics in asphaltene‐containing crude oils.     

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.     

Experimental Investigation of Rheological and Morphological Properties of Water in Crude Oil Emulsions Stabilized by a Lipophilic Surfactant

Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 µm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content and surfactant concentration. The crude oils behaved as Newtonian fluids over a wide range of shear rates, whereas the emulsions behaved as non-Newtonian fluids, indicating shear-thinning effects over the entire range of shear rates. The viscosity, storage modulus and degree of elasticity were found to be significantly increased with the increase in water content and surfactant concentration. The maximum viscosity was observed at the point close to the phase inversion point where the emulsion system changes from water-in-oil emulsion to oil-in-water emulsion. The results also indicated that the rheological properties of crude oils and their emulsions are significantly temperature-dependent.     

Analysis of Crude Oils by Frequency Domain Spectroscopy—Effect of Composition and Physical Properties on Conductivity and Dielectric Response

The dielectric properties and the composition of fourteen light to heavy crude oils have been analyzed. Frequency domain spectroscopy (FDS) has been used in order to determine their dielectric response in the frequency range 0.01 to 1000 Hz. For all the crude oils, over the whole frequency range under study, dielectric loss, ?″, shows a linear dependence of frequency indicating a pure direct current (DC) conductivity. As temperature is gradually increased, the dielectric loss, ?″, increases as well, showing a strong temperature dependence. The storage modulus, ?′, shows an explicit behaviour at low frequency that could be due to adsorption of oil components onto the electrodes. We tried to correlate some physical and chemical properties (density, viscosity, SARA, TAN, water content) of the studied crude oils with their conductivity measured at various temperatures. No correlation was found and different hypothesis are suggested by the authors to explain this phenomenon.     

Generalized correlation for predicting the kinematic viscosity of liquid petroleum fractions

A two-parameter viscosity model proposed previously for pure liquids is extended to correlate the kinematic viscosity–temperature behavior for liquid petroleum fractions. The coefficients in the viscosity equation are related to the characterization properties of the petroleum fractions and a generalized kinematic viscosity–temperature correlation is then developed, which needs only specific gravity at 15.6°C and 50% boiling point as input parameters. The present method, when tested by predicting the experimental kinematic viscosities of 47 fractions from 15 world crude oils with total 250 data points, yielded reasonable results with an overall average absolute deviation of 4.2%.     

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.     

The analysis of kerogens by pyrolysis—gas chromatography—mass spectrometry using selective ion monitoring: 2. Alkylnaphthalenes

Kerogens isolated from sediments have been analysed by pyrolysis—gas chromatography—mass spectrometry using the mass spectrometer as a selective ion detector. Monitoring one or more of the with m/z values of 141, 142, 156 and 170 provides information concerning the abundance and distribution of naphthalenes (containing one, two and three substituent carbon atoms) which are present in the kerogen pyrolysates. This information, which is less-readily obtainable by other means, gives some indication of the occurrence and nature of naphthalenic nuclei in kerogens. The selective ion monitoring method has also been applied to the analysis of naphthalenes in crude oils, this being a preliminary investigation of the possibility of providing information on the relationships between kerogens and crude oils.     

Phytochemical investigation,physicochemical characterization,and antimicrobial activities of Ethiopian propolis

Propolis is a natural resin substance produced by honeybees by collecting from parts of plants, buds, and exudates that are used for several biological activities such as antimicrobial, and fungicide functions. This study aimed to analyze the phytochemical, physicochemical, and antimicrobial activity of propolis collected from Boji Dirmaji and Fincha’a districts of western Ethiopia. The physicochemical characteristics, phytochemical screening, and antimicrobial activity of Ethiopian propolis against Aspergillus niger, Escherichia coli, and Staphylococcus aureus were evaluated using the disk diffusion method from its essential oils and crude ethanol extract were evaluated based on standard procedures. The results indicated that propolis was rich in saponins, tannins, flavonoids, steroids, triterpenes, and glycosides. Physicochemically, n-hexane extractable substances ranged between 8.6 and 33.9%, resins soluble 14.8–16.8%, insoluble residues 70.8–85.5%, moisture 1.7–4.6%, and ash content 2.8–9.7%, and 4.8 pH. The antimicrobial activities of essential oils propolis were active against Escherichia coli with an average inhibition zone of 18.3 ± 0.52 mm and 18.9 ± 0.06 mm at concentrations of 10 and 20 μl in Dirmaji districts. Moreover, the crude ethanol extracted propolis had nearly the same effect of inhibition to Escherichia coli. However, both crude extract and its essential oils didn’t show any activity on Staphylococcus aureus and Aspergillus niger. The analyzed propolis is promising antimicrobial activity from Gram-negative which is very notorious for people of the world.     

Investigation of Oil–Asphaltene Slurry Rheological Behavior

The presence of asphaltene means additional difficulties related to transport and processing due to the increased crude oil viscosity caused by the asphaltene. For a better knowledge of the flow properties of asphaltene containing crude oils, it is necessary to understand how asphaltene affects the rheological properties. The aim of this article is to provide information on such rheological properties of oil–asphaltene slurry systems. The results of rheological experiments show that the non-Newtonian flow curves can be approximated by the Bingham plastic model to determine the apparent viscosity and the yield stress as a function of asphaltene concentration and temperature. An explanation is also provided for the observed behavior.     

Leptospermum petersonii as a Potential Natural Food Preservative

Leptospermum petersonii (family Myrtaceae) is often cultivated for ornamental purposes but also serves as a rich source of bioactive essential oils. While several studies focused on the activities of the essential oils, this study analysed the potential of spent L. petersonii leaves as a natural food preservative. Method: We investigated the in vitro antioxidant and antimicrobial activities of crude L. petersonii extracts against activities of the purified isolated flavonoid, 6-methyltectochrysin, which was characterized using spectroscopic methods. The antioxidant assays followed ORAC, FRAP and TEAC tests. The antimicrobial activities of the extract and purified flavonoid were analysed against six multi-drug resistant microbial strains in broth dilution assays. Result: The results revealed that both the crude extracts and isolated 6-methyltectochrysin exhibited positive radical ion scavenging antioxidant potential, however the crude extract was about 6-fold more potent antioxidant than the purified 6-methyltectochrysin. The crude extract also showed strong antimicrobial activities against Bacillus cereus, and even more potent antimicrobial agent than the reference ampicillin antibiotic against Klebsiella pneumoniae subsp. pneumoniae. A higher resistance was observed for the tested Gram-negative strains than for the Gram-positive ones. 6-methyltectochrysin was generally inactive in the antimicrobial assays. Conclusion: The crude methanolic extract showed significant bioactivity which validates the medicinal relevance of the plant. The observed biological activities, especially against a notorious strain of B. cereus, suggest that L. petersonii could be a promising natural source of food preservatives.     

Selecting a reduced suite of diagnostic ratios calculated between petroleum biomarkers and polycyclic aromatic hydrocarbons to characterize a set of crude oils

A set of 34 crude oils was analysed by GC-MS (SIM mode) and a suite of 28 diagnostic ratios (DR) calculated. They involved 18 ratios between biomarker molecules (hopanes, steranes, diasteranes and triaromatic steroids) and 10 quotients between polycyclic aromatic hydrocarbons. Three unsupervised pattern recognition techniques (i.e., principal components analysis, heatmap hierarchical cluster analysis and Kohonen neural networks) were employed to evaluate the final dataset and, thus, ascertain whether the crude oils grouped as a function of their geographical origin. In addition, an objective variable selection procedure based on Procrustes Rotation was undertaken to select a reduced set of DR that comprised for most of the information in the original data without loosing relevant information. A reduced set of four DR (namely; TA21, D2/P2, D3/P3 and B(a)F/4-Mpy) demonstrated to be sufficient to characterize the crude oils and the groups they formed.     

A Review of: “Dispersing Powders in Liquids (Handbook of Powder Technology,Vol. 7)”. Ralph D. Nelson,Jr. Elsevier,Amsterdam, 1988. pp. xviii+244. $84.25.

Dielectric spectroscopy is considered as an interesting method for determination quality parameters like density, viscosity and interfacial properties of petroleum fluids. In this paper are the mechanisms important for the dielectric properties of crude oils studied for development of new charaterising methods.     

Effect of Inorganic Solids,Wax to Asphaltene Ratio,and Water Cut on the Stability of Water-in-Crude Oil Emulsions

The formation of stable water-in-crude oil emulsions during petroleum production and refinery may create sever and costly separation problems. It is very important to understand the mechanism and factors contributing to the formation and stabilization of such emulsions for both great economic and environmental development. This article investigates some of the factors controlling the stability of water-in-crude oil emulsions formed in Burgan oil field in Kuwait. Water-in-crude oil emulsion samples collected from Burgan oil filed have been used to separate asphaltenes, resins, waxes, and crude oil fractions. These fractions were used to prepare emulsion samples to study the effect of solid particles (Fe₃O₄) on the stability of emulsions samples. Results indicate that high solid content lead to higher degree of emulsion stability. Stability of emulsion samples under various waxes to asphaltenes (W/A) ratios have also been tested. These tests showed that at low W/A content, the emulsions were very stable. While at a wax to asphaltene ratio above 1 to 1, the addition of wax reduced emulsion stability. Stability of emulsion samples with varying amount of water cut has also been investigated. Results indicated that stability and hence viscosity of emulsion increases as a function of increasing the water cut until it reaches the inversion point where a sharp decline in viscosity takes place. This inversion point was found to be approximately at 50% water cut for the crude oils considered in this study.