Asphaltene Aggregation Research Articles

Hydrate Agglomeration in Crude Oil Systems in Which the Asphaltene Aggregation State Is Artificially Modified

Summary Some crude oils contain naturally occurring surfactants that avoid hydrate agglomeration. Natural hydrate antiagglomeration has been linked to different crude oil fractions, including asphaltenes. Asphaltenes can promote the formation of stable water-in-oil (W/O) emulsions due to their amphiphilic properties. The surfactant-like behavior of asphaltenes is related to their aggregation state. Asphaltenes are strong emulsifying agents when in an aggregated state but weak emulsifying agents when either precipitated or well solubilized in the bulk oil phase. The asphaltene aggregation state may be artificially modified, changing its interfacial activity, by mixing crude oil with heptane–toluene mixtures. This work investigated the influence of the asphaltene aggregation state on gas hydrate agglomeration. Results show that the natural hydrate antiagglomerant properties of crude oils can be highly dependent on the artificially induced asphaltene aggregation state. For instance, if asphaltenes were induced to be solubilized into the bulk oil phase, the natural hydrate antiagglomerant behavior was diminished. However, when asphaltene aggregation was induced, gas hydrate agglomeration was avoided. These new findings could have significant implications for the implementation of novel hydrate management strategies that can reduce or eliminate the need for external interventions and hence minimize capital and operational expenditures by taking advantage of the intrinsic natural antiagglomerant properties of some crude oils.

Compositional Trends for Total Vanadium Content and Vanadyl Porphyrins in Gel Permeation Chromatography Fractions Reveal Correlations between Asphaltene Aggregation and Ion Production Efficiency in Atmospheric Pressure Photoionization

Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has exposed the ultracomplexity of fossil fuels, thereby validating the compositional trends that rule petroleum distillation...

Full factorial sensitivity analysis of asphaltene precipitation and deposition in CO2 and CH4 coreflooding

Modelling of asphaltene precipitation and deposition in petroleum reservoirs requires adjustable parameters and introduces uncertainty sources. To address the main sources of uncertainty, a two-level full factorial sensitivity analysis was applied to asphaltene precipitation and deposition. Six factors were critically evaluated in the models, three concerning the precipitation phenomenon and the others related to the asphaltene deposition: asphaltene molar content, binary interaction parameters, reference pressure, asphaltene molar volume, surface deposition rate coefficient and flocculation parameters. The effect of these factors on the average of permeability reduction is assessed and their relative importance and relevant interactions were analyzed. Curves of precipitated, flocculated and deposited asphaltene showed that asphaltene deposition caused permeability reduction. Results showed that thermodynamic sources of uncertainty have a more significant effect on the model performance compared to the kinetics parameters ones. This suggests that fitting deposition parameters using experimental permeability reduction data may jeopardize the applicability of these parameters in real field conditions. The aggregation of asphaltene precipitates to form larger particles is modelled using the Kohse and Nghiem flocculation model, one of the most used. Simulations for different conditions were also performed to improve the reliability of the findings. We conclude that reestimation of these model parameters using experimental data of kinetics of asphaltene aggregation is required to provide acceptable description of the aggregation phenomenon.

Fractionation and Characterization of Petroleum Asphaltene: Focus on Metalopetroleomics

Asphaltenes, as the heaviest and most polar fraction of petroleum, have been characterized by various analytical techniques. A variety of fractionation methods have been carried out to separate asphaltenes into multiple subfractions for further investigation, and some of them have important reference significance. The goal of the current review article is to offer insight into the multitudinous analytical techniques and fractionation methods of asphaltene analysis, following an introduction with regard to the morphologies of metals and heteroatoms in asphaltenes, as well their functions on asphaltene aggregation. Learned lessons and suggestions on possible future work conclude the present review article.

A review of nanomaterials as viscosity reducer for heavy oil

Heavy crude oil is one of the most potential fossil fuels at present and in the future. However, its high viscosity severely hinders its recovery from reservoir conditions. Heavy oil viscosity reduction is rather essential for its exploitation and transportation. Applying nanomaterials as viscosity reducer for heavy crude oil is an emerging research topic in petroleum industry. In this review, the recent progress about different nanomaterials that have been used in heavy oil viscosity reduction was summarized. These nanomaterials were roughly divided into four kinds: silicon oxide nanoparticles, metal oxide nanoparticles, carbon nanotubes, modified nanoparticles and nanocomposites. The properties of the nanomaterials, including chemical property, concentration and injection form, size and the operational conditions such as temperature, different heavy oil and field application were discussed. At the same time, the possible oil viscosity reduction mechanisms including asphaltenes adsorption, disruption of asphaltene aggregates and heavy oil viscoelastic network, recombination of hydrogen bonds for different nanoparticles were summarized. The challenges and future work for this technology are proposed at the end. Nanomaterials for heavy oil viscosity reduction are expected to make a huge impact on petroleum industry.

Bitumen fractionation: Contribution of the individual fractions to the mechanical behavior of road binders

Anticipation of alternative road binder to replace petroleum derived bitumen requires a deep understanding of relationships between the chemical composition of bitumen and their physical properties, especially rheological ones. The vast number of the different molecules constituting bitumen is too complicated to unravel, thus in this paper we propose to fractionate bitumen into four fractions and study their different physico-chemical properties. The melting temperature and the glass transition of each fractions was determined by DSC while their molecular weight distribution was determined by HS-SEC. Finally, their rheological properties were investigated by DSR. This study highlighted the importance of all bitumen phases: the less polar liquid phase driving the viscous behavior up to −50 °C, the more polar solid phase responsible of the thermal stability and the stiffness, and finally the intermediate viscous oily phases allowing the molecular weight distribution continuity and by consequence allowing to have, on a large temperature range, a viscous liquid behavior at high temperature or low frequency, and an elastic stiff behavior at low temperature. Crystallizable fractions and asphaltene aggregates seemed to act as key molecular structures in the continuous phase.

Imidazolium-based ionic liquids for asphaltene dispersion; experimental and computational studies

Heavy and bituminous crude oils containing asphaltene are expected to compensate for the decline of conventional oil production in the upcoming days. Asphaltene precipitation is detrimental to petroleum processing owing to blockage of the wellbores and formation of tough emulsions that diminishes the recovered oil amount. As a result, the petroleum industry resorts to asphaltene dispersants to overcome these challenges. In this regard, ionic liquids (ILs) can be utilized as a green chemistry alternative to the surfactants to prevent asphaltene aggregation in the petroleum feed stream. Ionic liquids are environmental, recyclable, and non-corrosive candidates, which destabilize or breakdown water in oil (W/O) or oil in water (O/W) emulsions through dispersing or replacing asphaltene molecules at the interface. Also, ionic liquids containing long alkyl chains can be effective asphaltene dispersants owing to the formation of hydrogen bonding and π-π∗ interactions with asphaltene aggregates. In this work, different ILs salts and their modified Lewis-acid structure were synthesized by mixing iron (III) chloride with different halogenated alkyl imidazolium salts with yield% of 73.56, 72.9, and 71.12% respectively. The thermogravimetric analysis indicates the thermal stability of the synthesized ILs to 463 °C. The critical micelle concentration (CMC) and interfacial tension (IFT) were investigated at simulated reservoir conditions of high-pressure high temperature (HPHT). ILs exhibited CMC values at 1000, 800, and 600 ppm, while IFT values lie in the range of 3–8 mN/m at 298 K. ILs efficiency as asphaltene dispersants were assessed experimentally through viscometric and spectroscopic methods using 1000 ppm of asphaltene extract. The viscometric method displays asphaltene onset precipitation at 65% n-heptane after the addition of [(-C4H9-IL) FeCl4−] dispersant, while spectroscopic method asphaltene onset precipitation at 55, 60 and 75% after the addition of [(-CH3-IL) FeCl4−], [(-C2H5-IL) FeCl4−] and [(-C4H9-IL) FeCl4−], respectively. Molecular dynamics (MD) simulation was carried out to investigate the compatibility of ionic liquids as a function of asphaltene and crude oil molecules. The asphaltene molecules modeled as a continental model involves a dominant polyaromatic nucleus linked to peripheral substituted side chains. The computational results are in great compliance with the experimental ones.

Изучение смеси нефти и газового конденсата для оценки эффективности ее применения в системе трубопроводного транспорта

With the development of reserves of oil and gas condensate fields, there is a need to study oil and gas condensate in order to assess the possibility of pumping them in the form of a combined mixture. To this end, laboratory studies and bench tests of oil and oil-gas condensate mixtures with different content of gas condensate in the composition have been carried out. Basing on the results of laboratory study, It is established that the increase gas condensate content in oil leads to changes in its physical properties and fire and explosion hazard indices. It is shown that the optimal gas condensate content is up to 10 wt. %. The results of the study of asphaltene aggregates stability has not reveal the incompatibility phenomenon when mixing oil and gas condensate. It`s been determined by bench tests that the addition of gas condensate to oil leads to reduce the hydraulic losses of flow specific energy and the rate of growth asphaltene-resin-paraffin deposits. Thus, the mixing of oil with a content gas condensate is practically useful in the operation of the main pipeline.

Molecular Interactions between Asphaltene and Surfactants in a Hydrocarbon Solvent: Application to Asphaltene Dispersion

Heavy oil and bitumen supply the vast majority of energy resources in Canada. Different methods can be implemented to produce oil from such unconventional resources. Surfactants are employed as an additive to water/steam to improve an injected fluid’s effectiveness and enhance oil recovery. One of the main fractions in bitumen is asphaltene, which is a non-symmetrical molecule. Studies of interactions between surfactants, anionic, and non-anionic, and asphaltene have been very limited in the literature. In this paper, we employed molecular dynamics (MD) simulation to theoretically focus on the interactions between surfactant molecules and different types of asphaltene molecules observed in real oil sands. Both non-anionic and anionic surfactants showed promising results in terms of dispersant efficiency; however, their performance depends on the asphaltene architecture. Moreover, a hydrogen/carbon (H/C) ratio of asphaltenes plays an inevitable role in asphaltene aggregation behavior. A higher H/C ratio resulted in decreasing asphaltene aggregation tendency. The results of these studies will give a deep understanding of the interactions between asphaltene and surfactant molecules.

Synthesis and characterization of imidazolium asphaltenes poly (ionic liquid) and application in asphaltene aggregation inhibition of heavy crude oil

New ionic liquids were synthesized from asphaltene colloids that aggregate in the petroleum sludge precipitated in the storage tanks and transportation petroleum pipeline. The alkyl side chains on the asphaltenes were oxidized to polynuclear aromatic carboxylic acids that catalyzed the formation of imidazolium ionic liquid cations. Heptylamine, glyoxal, and p-hydroxybenzaldehyde were used to prepare 1,3-diheptyl and 1,3-diheptyl-2-hydroxyphenyl imidazolium cations conjugated with asphaltenes carboxylate anions as AsIL and AHIL ionic liquids, respectively. The chemical structure, surface charges, particle sizes, thermal stability and thermal characteristics were assessed. The impact of AsIL and AHIL on the dispersion, solubilization, and inhibition precipitation of asphaltenes in the binary solvents and heavy crude oil was studied. The results demontrate that the prepared ionic liquid containing aromatic (AHIL) acts as an asphaltene dispersing and solubilizing agent to inhibit the asphaltene precipitation more than that containing AsIL.

Synthesis and evaluation of a hyperbranched copolymer as viscosity reducer for offshore heavy oil

As is well known, resin and asphaltene greatly increase the viscosity of the oil, which causes difficulty for heavy oil to flow and to be displaced. Therefore, reducing the viscosity of heavy oil effectively is the key to enhance oil recovery. A hyperbranched copolymer named as HVR grafted with hydrophilic surfactant monomers, was synthesized and evaluated in this paper as an alternative to reduce the offshore heavy oil viscosity. The synthesis method of HVR through free-radical copolymerizing using the third generation polyamidoamine dendrimer, acrylamide, acrylic acid and surfactant monomers in deionized water was detailed in this paper. Thereupon the characterization of HVR were described by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. The physical properties of HVR solution including apparent viscosity, oil viscosity reducing ability, interfacial tension were comprehensively studied. Otherwise the effect of HVR on sheet structure of asphaltene aggregate and asphaltene aggregation inhibition-dispersion activity were measured by X-ray diffraction and ultraviolet–visible spectrophotometer, respectively. The results indicate that apparent viscosities of HVR solution is relatively not high. For example, after shearing with a Waring blender at 3500 rpm for 20 s, the viscosity of 2500 ppm HVR solution is only 22.7 cP. However, the HVR solution has a relatively high viscosity remaining rate, which is approximately 58%. On the other hand, HVR solution has a good viscosity reducing ability on heavy oil. For the oil viscosities from 350 cP to 500 cP, the viscosity reduction rate of HVR at 2000 ppm is approximately 97% under the oil-water ratio of 3:7. In addition, the oil-water interfacial tension can be reduced by HVR solution at the concentration of 2500 ppm to 1.61 × 10−2 mN m−1. Comparing the asphaltene aggregates after interacting with HPAM and HVR, it illustrates that the layer spacing, interchain distance and diameter of the aromatic sheets are lager if interacting with HVR; meanwhile height of the aromatic clusters and effective number of aromatic sheets are smaller due to the reaction with HVR. In addition, if compared with the asphaltene treated by HPAM, with the increase of HVR concentration, the absorbance of asphaltene in toluene treated by HVR solution decreased significantly. Overall, this new hyperbranched copolymer shows potential for applications in heavy oil viscosity reduction.

Mechanistic Study of Effect of Ultrasonic Radiation on Asphaltenic Crude Oils

Ultrasonic irradiation is a new, economic, and environmentally friendly technique for treating asphaltene aggregation in petroleum industry. In this study, the effect of ultrasonic radiation on asphaltene formation is investigated using conventional optical microscopy, viscosity measurement, and Fourier-transform infrared spectroscopy (FTIR). To this end, five crude oil samples, collected from different reservoirs, are used, and the effect of ultrasonic radiation on the structure of the crude oils is investigated at various exposure times. The results show that, at an optimum radiation time, the ultrasonic waves can break the asphaltene clusters and shift the size distribution of the asphaltene aggregate to a smaller size. In addition, the FTIR analysis reveals structural changes in the composition of the crude oil after the ultrasonic irradiation. By increasing the ultrasound exposure time, the viscosity of the asphaltenic oil first decreases to a minimum before rising again. Moreover, the measurement of asphaltene and resin content of the crude oils indicates that at exposure times longer than the one leading to the minimum viscosity, resin molecules are broken upon exposure to ultrasound. This can be the main reason for the existence of an optimum time in the application of ultrasonic radiation, after which the percentage of asphaltene particles and the viscosity of the crude oils increase.

Theoretical Study on Disaggregation Strategies for Asphaltene Aggregates

Theoretical Study on Disaggregation Strategies for Asphaltene Aggregates

Study of Very High Molecular Weight Cluster Presence in THF Solution of Asphaltenes and Subfractions A1 and A2, by Gel Permeation Chromatography with Inductively Coupled Plasma Mass Spectrometry

Super high molecular weight (SHMW) asphaltenes aggregates, hereafter called asphaltenes clusters, have been observed for the first-time using gel permeation chromatography with inductively coupled ...

Hydrocracking of C5-Isolated Asphaltene and Its Fractions in Batch and Semi-Batch Reactors

Non-catalytic and catalytic hydrocracking of C5-isolated asphaltene and its subfractions were performed in batch and semi-batch reactors at various temperatures. Catalyst and H2 played an important role in the hydrocracking of asphaltenes. In the batch system, the catalyst enhanced asphaltene conversion to light liquid products and suppressed coke formation. The coke formation was controlled at a low reaction temperature, but the reaction rate was too low. Light liquid products were also formed at the beginning of the reaction even at high temperatures, but the coke formation was predominant as the reaction time went on due to the decrease in H2 amount in the reactor. To solve these problems, H2 was continuously supplied during the reaction using the semi-batch system. Sufficient supply of H2 improved the conversion of asphaltenes to light liquid products while inhibiting the coke formation. The lightest asphaltene fraction was easily cracked into light products by inhibiting the coke formation, while the heaviest fraction tends to form coke. The lightest asphaltene fraction prolonged the coke induction period of the heaviest fraction during the catalytic hydrocracking because the lightest fraction contained a significant amount of heavy resin close to that which could prevent aggregation of the heaviest asphaltenes.

A modified method for detection of interface and onset point in the asphaltenic fluids

ABSTRACT Asphaltene precipitation and deposition causes many serious problems to the petroleum industry from the reservoir to the surface facilities. Therefore, it is important to bring it under control by finding a method to accelerate or slow down its precipitation and deposition. For achieving this purpose two parameters play an important role; onset point of the precipitation and amount of the deposited phase. When asphaltene precipitates, it is capable of depositing in the solution. After the deposition, the solution split into two phases; asphaltene-rich and asphaltene-lean. Determining the amount of the deposited phase needs to distinguish the interface between two phases. In this study, a novel method has been developed for simultaneous detection of the onset point and the interface using a single IR beam at the standard pressure and temperature. The proposed method is based on the IR light absorption and scattering during precipitation and deposition of the asphaltene aggregates. The results of the paper show that the proposed method can properly measure the interface of the deposited phase (error <6%). Also, the measured onset point of the precipitation for the asphaltenic solution is in the acceptable range (0.4–0.5 volume fraction).

A Comparative investigation on Viscosity Reduction of Heavy Crude Oil Using Organic Solvents

The transport of heavy crude oil from the head-well to the refinery plants is an attractive factor as its production is currently increasing around the world. Though the higher viscosity increases trouble in the piping transportation and production from the reservoir, for these reasons, this study focuses on the dilution method to reduce its viscosity using toluene, dimethyl ketone (DMK) and a mixture of (50/50 vol. %) toluene/dimethyl ketone as a dilutes solvents with different weight fraction (0, 5, 10 and 15 wt. %) at 298.15 K. The heavy oil used collected from Amara oil field, south of Iraq. The viscosity was measured by Brookfield viscometer over a range of shear rates (0 - 42s-1). On another way to understand the effect of temperature, the better result for weight fraction of solvents in viscosity reduction of heavy oil was investigated under different temperatures (298.15, 308.15 and 318.15 K). The obtained results showed dilution of heavy oil samples with toluene, DMK and a mixture of (50/50 vol. %) toluene and DMK is an effective method for reducing the viscosity. Moreover, the temperature has a significant effect on the degree of viscosity reduction in the presence of the diluents. However, the higher DVR was noticed about 87.17 % at 15 wt.% of the mixture (50/50 vol. %) toluene + DMK at 318.15 K and shear rate 42 s-1. Tthe relevant results attribute to an aromatic characteristic of toluene which allows interferes in the asphaltene aggregation.

Developing a novel colloidal model for predicting asphaltene precipitation from crude oil by alkane dilution

This research aims to propose a thermodynamic model for predicting asphaltene precipitation upon diluting a crude oil with a paraffinic solvent. To this end, a thorough mathematical formulation was carried out to derive a novel micellization model based on the associative properties of asphaltenic compounds. It was assumed that asphaltenes exist in the oil both as monomeric molecules and aggregated cores; with stabilization latter by attachment of resin on its periphery. The aggregation equilibrium was established by taking into account asphaltene's lyophobic tendency, heat of resin adsorption, and interfacial tension between micelle and oil media which is the main driving factor contributing to Gibbs free energy of micellization. In this study, the mean diameter of asphaltene aggregates at different dilution ratios was incorporated into the framework of modeling approach, by measuring particle size distribution of asphaltenes at varying n-heptane fractions. The data density of pure asphaltene for an Iranian crude-oil sample was used in calculations. The proposed model favorably predicted the precipitation trend of the crude oil diluted at varying fractions of n-heptane. This model shows that taking into account the size of asphaltene aggregates can significantly improve the prediction accuracy of the micellization model, compared to the simple model, with normalized root-mean-square error of 9.4 and 28.7, respectively. A detailed sensitivity analysis was performed to gain insight into physical implication of the model parameters.

Experimental study and modeling of asphaltene deposition on metal surfaces via electrodeposition process: The role of ultrasonic radiation, asphaltene concentration and structure

Asphaltene deposition in the wellbore is considered as a major operational challenge while producing some crude oils. It has been claimed that, external fields, such as electric field and ultrasonic radiation, could help tackling this issue. Although the effect of electric field on the aggregation size and the aggregation rate of asphaltene particles has been investigated before, its correlation with asphaltene deposition in the presence and absence of ultrasonic radiation is not known. In this study, the asphaltene deposition on metal surfaces was first mimicked using an electrodeposition process, and then the effect of ultrasonic radiation on electrodeposition of asphaltene were measured and analysed. Our observations showed that the electric filed itself does not unstable the dissolved asphaltene, and the asphaltene deposition on electrodes, under the effect of DC electric filed, first requires the formation of asphaltene aggregates. The maximum deposition was generated at 2 kV/cm, the exposure time of 300 s to the electric field, and the weight ratio of toluene to heptane 4.2%. It was also found that the structure and composition of asphaltenes, especially their polarity and aromaticity, affect asphaltenes deposition. Among different adsorption kinetic models, the nth-order kinetics model was selected to estimate the amount of deposited asphaltene. Finally, simultaneous ultrasound radiation during the process of electrodeposition, reduced the deposition rate on the metal blades from an average of 65 wt % of the total asphaltene content to 10 wt%. The findings of this study highlight the role of composition and structural properties of asphaltene on its surface deposition in the wellbore. More importantly, simultaneous radiation of ultrasonic waves during electrodeposition process confirms the effectiveness of ultrasonic radiation, as a quite new asphatene remediation technique.

Precipitant Effects on Aggregates Structure of Asphaltene and Their Implications for Groundwater Remediation

Asphaltenes generally aggregate, then precipitate and deposit on the surfaces of environmental media (soil, sediment, aquifer, and aquitard). Previous studies have recognized the importance of asphaltene aggregates on the wettability of aquifer systems, which has long been regarded as a limiting factor that determines the feasibility and remediation efficiency of sites contaminated by heavy oils. However, the mechanisms/factors associated with precipitant effects on asphaltene aggregates structure, and how the precipitant effects influence the wettability of surfaces remain largely unknown. Here, we observe the particle-by-particle growth of asphaltene aggregates formed at different precipitant concentrations. Our results show that aggregates for all precipitant concentrations are highly polydisperse with self-similar structures. A higher precipitant concentration leads to a more compacted aggregates structure, while precipitant concentration near to onset point results in a less compact structure. The well-known Smoluchowski model is inadequate to describe the structural evolutions of asphaltene aggregates, even for aggregation scenarios induced by a precipitant concentration at the onset point where the Smoluchowski model is expected to explain the aggregate size distribution. It is suggested that aggregates with relative high fractal dimensions observed at high precipitant concentrations can be used to explain the relatively low Stokes settling velocities observed for large asphaltene aggregates. In addition, asphaltene aggregates with high fractal dimensions are likely to have high density of nanoscale roughness which could enhance the hydrophobicity of interfaces when they deposit on the sand surface. Findings obtained from this study advance our current understandings on the fate and transport of heavy oil contaminants in the subsurface environment, which will have important implications for designing and implementing more effective and efficient remediation technologies for contaminated sites.