Asphaltene Aggregation Research Articles

Relation between asphaltene adsorption on the nanoparticles surface and asphaltene precipitation inhibition during real crude oil natural depletion tests

Using nanoparticles for adsorbing asphaltene was known as one of efficient methods among researchers for upgrading of real oil samples in comparison to other expensive mechanical treatments or even solvents (such as n-pentane and n-heptane) and surfactants. In this study, Nickel zeolite oxide nanoparticles have been used for asphaltene adsorption and solving asphaltene precipitation problems. Although Nickel zeolite oxide nanoparticle used in previous studies as an asphaltene adsorbent, observing relation between asphaltene adsorption on its surface and asphaltene precipitation in the presence of nanoparticles was not covered. Series of experiments include FTIR, CO2-oil IFT tests, Langmuir and Freundlich isotherm models, and natural depletion tests were performed in the presence of Nickel zeolite oxide nanoparticles. Adsorption data was fitted well with the Langmuir model in comparison to the Freundlich model which shows that the adsorption occurs in a homogeneous surface with monolayer coverage. Based on the CO2-oil IFT results, there are two different slope forms in IFT readings as pressure increase from 150 Psi to 1650 Psi. Second slope (900 Psi-1650 Psi) is slower than the first one (150 Psi-900 Psi) which was due to aggregation of asphaltene. Three pressures of 1350 Psi, 1500 Psi, 1650 Psi and Nickel zeolite oxide nanoparticles at concentration of 30 ppm were selected for performing natural depletion tests and the basis of selection was high efficiency of adsorption in these points. As pressure decrease from 1650 Psi to 1350 Psi, asphaltene precipitation changes from 8.25 wt % to 10.52 wt % in the base case and it was 5.17 wt % to 7.54 wt % in the presence of Nickel zeolite oxide 30 ppm. Accordingly, Nickel zeolite oxide nanoparticles adsorbed asphaltene on its surface in proper way and the amount of asphaltene precipitation was decreased in the presence of Nickel zeolite oxide nanoparticles.

Synergetic adsorption of asphaltenes and oil displacement surfactants on the oil-water interface: Insights on stabilization mechanism of the interfacial film

This research focus on the interfacial stabilization mechanism of the asphaltene-rich oil-in-water emulsions that originated from the alkaline-surfactant-polymer (ASP) flooding produced water. Initially, we investigated the adsorption and aggregation behavior of asphaltenes and oil-displacement surfactants on the oil/water interface through molecular dynamics simulation. The interfacial formation energy for the composite asphaltenes-sodium dodecyl benzene sulfonate (SDBS) interfacial film system was calculated to be −3423.9 kJ/mol, which was much higher than that (−2499.9 kJ/mol) for the monolayer SDBS system. This enhanced interfacial film stability was attributed to the cross-linked aggregation of asphaltenes and SDBS molecules on the oil/water interface. Then, the interfacial properties of various interface systems were also obtained via interfacial adsorption thermodynamics, micromorphology, interfacial tension, and zeta potential analysis to further elucidate the stabilization mechanism. This composite asphaltenes-SDBS interfacial film with its pyknotic structure and high stability resulted in significant technical obstacles for oil-water separation of ASP flooding produced water.

Influence of ultrasonic treatment on kinetic of asphaltene aggregation in toluene/heptane mixture

This article illustrates the results of a study of ultrasonic dispersion’s influence on kinetic of asphaltene aggregation in a toluene/heptane mixture. The study was carried out by the method of dynamic light scattering. This optical method allows to measure the size of nano- and submicron particles in liquid medium. This method allows to measure the dependence of the average size of asphaltene aggregates during primary and secondary asphaltene aggregation. The primary aggregation was studied in a solution of asphaltenes in toluene and was initiated by the addition of heptane. Secondary aggregation of asphaltenes was initiated by ultrasonic dispersion of a mixture of toluene/heptane/asphaltene, in which primary aggregation finished and which contained asphaltene floccules. The effect of stabilization of asphaltene aggregates was experimentally detected after multiple ultrasonic dispersions.

Molecular Dynamics and Proton Hyperpolarization via Synthetic and Crude Oil Porphyrin Complexes in Solid and Solution States.

The use of vanadyl porphyrins either in synthetic compounds or naturally occurring in asphaltenes is investigated as a source of proton hyperpolarization via dynamic nuclear polarization (DNP) in nuclear magnetic resonance (NMR) experiments. The features of dynamics and location of the vanadyl VO2+ complex in aggregates within the oil asphaltene molecules are studied by means of DNP, electron paramagnetic resonance (EPR), and NMR field cycling relaxometry. Both the solid effect and Overhauser DNP were observed for the asphaltene solution in benzene, as well as in the solution and solid states for synthetic compounds. By comparison with a solution of synthetic vanadyl porphyrins, it is shown that vanadyl porphyrins in asphaltene aggregates are localized outside of the interface of the asphaltene aggregates and more exposed to the maltene molecules than "free" carbon-centered radicals associated with the core of asphaltene molecules. The perceptible contribution of scalar interaction is observed in solutions for both synthetic and asphaltene vanadyl porphyrins.

Monte Carlo Risk Assessment of Formation Damage Caused by Asphaltene Deposition

Summary Uncertainties regarding the factors that influence asphaltene deposition in porous media (e.g., those resulting from oil composition, rock properties, and rock/fluid interaction) strongly affect the prediction of important variables, such as oil production. Besides, some aspects of these predictions are stochastic processes, such as the aggregation phenomenon of asphaltene precipitates. For this reason, a well-defined output from an asphaltene-deposition model might not be feasible. Instead of this, obtaining the probability distribution of important outputs (e.g., permeability reduction and oil production) should be the objective of rigorous modeling of this phenomenon. This probability distribution would support the design of a risk-based policy for the prevention and mitigation of asphaltene deposition. In this paper we aim to present a new approach to assessing the risk of formation damage caused by asphaltene deposition using Monte Carlo simulations. Using this approach, the probability-distribution function of the permeability reduction was obtained. To connect this information to a parameter more related to economic concepts, the probability distribution of the damage ratio (DR) was also calculated, which is the fraction of production loss caused by formation damage. A hypothetical scenario involving a decision in the asphaltene-prevention policy is presented as an application of the method. A novel approach to model the prevention of asphaltene aggregation using inhibitors has been proposed and successfully applied in this scenario.

Impedance response of asphaltene solutions: Effect of solvation

The present work uses a combination of X-ray diffraction (XRD) analysis and dielectric spectroscopy (DES) to study asphaltene aggregation and interactions between these aggregate and maltene phases, with the variations in solvency power of the maltenes, at different asphaltene concentrations. The ability of the dielectric spectroscopy to quantify the interaction of the asphaltenes with the maltene phase lead to the development of a correlation with respect to the solution viscosity.It was seen that the combination of the data obtained from the XRD and DES accounted for differing asphaltene molecular structures, variations in the maltene phase with respect to its solvency power as well as the asphaltene concentration in the solution. This is the first step in developing the ability to predict solution viscosity, as well as eventually explaining rheological behavior, of asphaltene containing compositions.The future application of this work will be to assess if the findings of the methodology used in this paper,i.e. the combination of DES and XRD to predict asphaltene aggregation behavior and solvation, is applicable for asphaltenes from crude oils and heavy oil sands. In addition the use of the DES technique for online insitu monitoring of viscosity of crude oils/ refinery bitumen formulations will also be explored.

Experimental and DFT studies on the effect of carbon nanoparticles on asphaltene precipitation and aggregation phenomena

• CNPs were synthesized for controlling asphaltene precipitation and aggregation. • FESEM and FTIR demonstrate uniform adsorption of asphaltene on surface of CNPs. • DFT modeling proves the strong hydrogen interaction between CNPs and asphaltenes. • CNPs represent biocompatible and affordable asphaltene inhibitor-dispersant. In this study, a new class of carbon nanoparticles (CNPs) is synthesized for inhibition/dispersion of asphaltene precipitation and aggregation in unstable crude oil. The microscopy and asphaltene dispersant experiments are carried out to assess the effects of CNPs on asphaltene precipitation and aggregation. Also, density functional theory is applied to describe the mechanisms of asphaltene adsorption onto the CNPs surfaces. Experimental results demonstrate postponement of asphaltene onset of precipitation from 26 to 37 vol% n-C 7 in the presence of 400 ppm of the CNPs which is ascribed to the extra high specific surface area of the CNPs. DLS analysis shows the average size of asphaltene aggregates adsorbed onto the CNPs reduces from 1730 nm in the blank oil to 255 nm in treated oil with CNPs. The results of DFT modeling demonstrate the strong hydrogen interaction between functional groups of the CNPs and active sites of asphaltene. Also, π–π interactions occur between electron cloud of aromatic rings of asphaltene and CNPs with minimum equilibrium distance of 2.94 Å. The adsorption energy for the most stable complex of asphaltene and CNPs in the gas and solvent phases are −91.22 and −107.64 kJ/mol, respectively, confirming the strong chemisorption of asphaltene over the CNPs. This research reveals that synthesized CNPs with specific features such as high surface area, potential of covering the external shell with a wide variety of functional groups, low toxicity and cost, and environment-friendly can be successfully implemented as an efficient inhibitor and/or dispersant for asphaltene handling strategies.

Experimental and modeling investigations of temperature effect on chemical inhibitors of asphaltene aggregation

In this work, both experimental and theoretical procedures were performed to investigate the effect of temperature, ranging from 25 to 65 °C, on the performances of dodecyl benzene sulfonic acid (DBSA), benzoic acid (BA) and salicylic acid (SA) as chemical inhibitors of asphaltene aggregation in an undiluted dead crude oil. DBSA was found the most efficient inhibitor in size reduction of aggregates at all applied temperatures due to its acid-base interactions with asphaltenes. The size reduction by DBSA was 19% compared to free-additive oil at 65 °C. But SA increased asphaltene aggregates size by 2% at 65 °C. The temperature rise significantly accelerates the rate of asphaltene aggregation and so the effectiveness of inhibitors was reduced at high temperatures. The population balance modeling was employed in which a novel size-dependent relation was considered for collision efficiency. Fractal dimension, as an input of the model, was measured from experimental data at different temperatures and time intervals. Due to minor changes in fractal dimensions, an average value of 2.5 was considered for fractal dimension. The modeling results revealed that the collision efficiency is decreased by both efficient inhibitors and decrement of temperature. Considering a size-dependent collision efficiency halved the error of the model on average in comparison to a size-independent collision efficiency.

Effect of the heteroatom presence in different positions of the model asphaltene structure on the self-aggregation: MD and DFT study

In this study, a series of heteroatoms including nitrogen, oxygen, and sulfur were added to different positions of the model asphaltene structure to study the effect of the heteroatom presence in the self-aggregation of the model asphaltenes. Molecular Dynamics was used to calculate Solubility Parameters, Radial Distribution Function, and Relative Solubility Parameters. Additionally, Reactivity Parameters, Electrostatic Potential, Reduced Density Gradient, and Independent Gradient Model were calculated using the Density Functional Theory to further investigate the Molecular Dynamics results. This study indicated that heteroatoms' diversity and their positions in the model asphaltene structure had an essential role in forming the model asphaltene aggregates. Four different sites in the model asphaltene structure were selected to study the impact of the heteroatom position in the self-aggregation. The presence of heteroatoms in the aliphatic side-chain proved to be more effective in increasing the self-aggregation process in comparison to the aromatic ring position. The heteroatoms' presence in the terminal position of the aliphatic side-chain increased the self-aggregation strength more than other sites in the aliphatic side-chain based on the terminal heteroatoms' ability to perform hydrogen bond formation. Additionally, heteroatoms in the middle of the aliphatic side-chain increased the CH…C dispersion interaction by the carbons' polarization. The heteroatoms in the aliphatic side-chain sites, especially in the terminal position, decreased the asphaltenes' solubility in the heptane and toluene more than the aromatic ring position.

SiO2 Biogenic Nanoparticles and Asphaltenes: Interactions and Their Consequences Investigated by QCR and GPC-ICP-HR-MS

The processes in which crude oil asphaltene aggregates are adsorbed onto surfaces have been the subject of debate in recent years. Different thermodynamic, theoretical, and empirical models have be...

An Integrated Simulation Approach for Wellbore Blockage Considering Precipitation, Aggregation, and Deposition of Asphaltene Particles

Summary Asphaltene deposition triggers serious flow assurance issues and can significantly restrict the production capacity. Because of the complexity associated with asphaltene deposition that includes several mechanisms acting simultaneously, an accurate prediction of asphaltene blockage along the wellbore requires integration of asphaltene precipitation, aggregation, and deposition. In this work, an integrated simulation approach is proposed to predict the asphaltene deposition profile along the wellbore. The proposed approach is novel because it integrates various deposition patterns of particulate flow (which depends on hydrodynamics) with aggregation processes to investigate how the distribution of asphaltene particle size varies (governed by molecular dynamics) after being precipitated out of the oil phase (controlled by thermodynamics). To improve the predictability capability of simulations, a direct input from the wellbore flow simulator is used to update the velocity profile after the wellbore radius changes beyond a certain predefined threshold. The fraction of asphaltene precipitation is determined using the asphaltene solubility model and combined with aggregation models to feed into deposition calculations. Wellbore blockage was examined for two cases with and without the aggregation mechanism included. A sensitivity analysis was carried out to study parameters that affect the severity of blockage, such as range of pressure-temperature along the wellbore, flow velocity, and radial distribution of asphaltene particles. The simulation approach proposed in this paper provides an in-depth understanding of the wellbore flow assurance issues caused by asphaltene deposition and thus provides useful insights for improving the predictions of production performance.

Microstructure and dynamic mechanical properties epoxy/asphaltene composites

Asphaltenes tend to aggregate to nanoparticles or clusters in crude oil and solvents over a wide concentration and temperature range. In the present paper, asphaltenes extracted from the base asphalt was used as a filler to introduce into epoxy resin. The microstructure and evolution of asphaltenes aggregation in the epoxy resin were observed using laser scanning confocal microscopy. Furthermore, the effect of asphaltenes on the viscosity, dynamic mechanical behavior, thermostability, mechanical properties of epoxy resin was evaluated by Brookfield rotational viscometer, dynamic mechanical analysis, thermogravimetric analysis and universal testing machine. The presence of asphaltenes increased the viscosity of the neat epoxy during all stages of cure reaction. The viscosity of epoxy/asphaltenes composites increased with the filler concentration. Fractal asphaltenes aggregation formed in the composites with 1 mass% asphaltenes. Network microstructures of asphaltenes aggregation appeared in the epoxy phase with a further increase of asphaltenes content. Moreover, the increase of asphaltenes loading resulted in denser network microstructures in the epoxy matrix. Aggregation evolution revealed that asphaltenes particles redispersed evenly in the epoxy resin in the form of some aggregates at the beginning of curing. During the cure reaction of epoxy, asphaltenes aggregates started to agglomerate and grow to network microstructures. The presence of asphaltenes led to the enhancement of the storage modulus of the neat epoxy at the rubbery stage. The glass transition temperature (Tg) of the epoxy composites slightly increased with the increase of asphaltenes loading. The epoxy composite with 5 mass% asphaltenes had higher Tg than the neat epoxy. The inclusion of asphaltenes had a negligible effect on the damping properties and thermal stability of the neat epoxy. The aggregation and heterogeneous dispersion of asphaltenes resulted in the decrease of the tensile strength and elongation at break of the neat epoxy. However, the inclusion of asphaltenes significantly enhanced Young’s modulus of the neat epoxy. Young’s modulus of the neat epoxy was increased by more than fourfold with the addition of 5 mass% asphaltenes.

Synthesize of MWCNT-Fe2O3 nanocomposite for controlling formation and growth of asphaltene particles in unstable crude oil

In this study, synthesized Fe2O3 nanoparticles were successfully loaded on multi-walled carbon nanotubes (MWCNTs) to obtain MWCNT-Fe2O3 nanocomposite for controlling the asphaltene precipitation and aggregation in a medium-heavy crude oil. The microscopy experiments were conducted to evaluate the performance of synthesized nanocomposite for inhibition and dispersion of asphaltene precipitation. The synthesized nanoparticles and adsorbed asphaltenes onto the surface of nanoparticles were fully characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscopy (FESEM) and Brunauer-Emmett-Teller (BET) techniques. Microscopy results showed that in presence of nanoparticles at concentration of 400 ppm the asphaltene onset of precipitation increased from 29 vol% in blank crude oil to 34 and 39 vol% for MWCNTs and MWCNT-Fe2O3, respectively. In addition, treating the blank crude oil with nanoparticles lessened the average size of asphaltenes and the rate of asphaltene aggregation. According to the TGA and BET results, the mass of adsorbed asphaltene per unit surface area of MWCNTs and MWCNT-Fe2O3 nanoparticles are 0.0065 and 0.0202 (gasp/ mnano2), respectively. Decorating of MWCNTs by Fe2O3 improves the ability of carbon nanotubes for inhibition and controlling of asphaltene precipitation and aggregation phenomena. Findings of this work reveal that the synthesized MWCNT-Fe2O3 nanocomposite has high potential applications for handling of asphaltene-induced issues in petroleum industry.

A mechanistic study toward the effect of single-walled carbon nanotubes on asphaltene precipitation and aggregation in unstable crude oil

Despite the numerous works devoted to using of different types of nanoparticles for treatment of asphaltene related issues, the potential applications of carbon nanostructures for controlling of asphaltene precipitation have not been addressed in the literature. Here, single-walled carbon nanotubes (SWCNTs) are synthesized and characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) techniques. The viscometry, asphaltene dispersant tests, and microscopy experiments are performed to investigate the effects of synthesized carbon nanotubes at different dosages on asphaltene precipitation and the size-growth of asphaltene particles in an unstable crude oil. Results of different experiments indicate that the synthesized carbon nanotubes considerably postpone the asphaltene onset of precipitation. In addition, SWCNTs adsorb asphaltenes and lead to a slower asphaltene aggregation process, and hence smaller asphaltene aggregates size distribution. Experiments performed at different concentrations of SWCNTs reveal that the highest performance of SWCNTs can be achieved at concentration of 100 ppm with dispersion efficiency value of 93.5% via asphaltene dispersant tests (ADTs). The large surface area of synthesized carbon nanotubes and strong π − π interactions between carbon nanotubes and asphaltenes are responsible for efficient controlling of asphaltene precipitation/aggregation by SWCNTs. Results of this work demonstrate that the synthesized SWCNTs can be utilized as cost-efficient and environmentally friendly asphaltene inhibitor and dispersant for oilfield applications. Also, using of SWCNTs can eliminate the weaknesses of other types of nanoparticles and tackles the induced problems by asphaltene precipitation and deposition.

An Integrated Simulation Approach To Predict Permeability Impairment under Simultaneous Aggregation and Deposition of Asphaltene Particles

Summary Formation damage mechanisms in general lower the quality of the near wellbore, often manifested in the form of permeability reduction, and thus reducing the productivity of production wells and injectivity of injection wells. Asphaltene deposition, as one of the important causes, can trigger serious formation damage issues and significantly restrict the production capacity of oil wells. Several mechanisms acting simultaneously contribute to the complexity associated with prediction of permeability impairment owing to asphaltene deposition; thus, integration of modeling efforts for asphaltene aggregation and deposition mechanisms seems inevitable for improved predictability. In this work, an integrated simulation approach is proposed to predict permeability impairment in porous medium. The proposed approach is novel because it integrates various mathematical models to study permeability impairment considering porosity reduction, particle aggregation, and pore connectivity loss caused by asphaltene deposition. To improve the accuracy of simulation results, porous media is considered as a bundle (different size) of capillary tubes with dynamic interconnectivity. The total volume change of interconnected tubes will directly represent permeability reduction realized in porous media. The prediction of asphaltene deposition in porous media is improved in this paper via integration of the particle aggregation model into calculation. The simulation results were verified by comparing with existing experimental data sets. After that, a sensitivity analysis was performed to study parameters that affect permeability impairment. The simulation results show that our permeability impairment model—considering asphaltene deposition, aggregation, and pore connectivity loss—can accurately reproduce the experimental results with fewer fitting or empirical parameters needed. The sensitivity analysis shows that longer aggregation time, higher flow velocity, and bigger precipitation concentration will lead to a faster permeability reduction. The findings of this study can help provide better understanding of the permeability impairment caused by asphaltene deposition and pore blockage, which provides useful insights for prediction of production performance of oil wells.

Studying the effect of carbon dioxide oil solubility on asphaltene aggregation under conditions of the Bashkortostan Republic fields

The purpose of this work is to study the effect of carbon dioxide oil solubility on the aggregation of asphaltene associates and decrease of oil permeability of sandstones. Consideration is given to the interaction variants of oil and carbon dioxide in a free volume before being injected into a porous medium and immediately in the porous medium. The influence of oil composition on the aggregation of asphaltene associates is studied. The effect of the dissolved carbon dioxide on associate dispersion in oil is examined through oil filtering in sandstones. If asphaltene aggregation occurs in a porous medium it causes pore plugging leading to reduced permeability, complicates the development of carbon dioxide injection wells and, as a result, prevents from achieving the planned indicators of oil production and oil recovery. It is found that in the case when oil interacts with carbon dioxide in the free volume before being injected into a porous medium, the increase in the volume of filtered oil and the concentration of carbon dioxide dissolved in oil, and decrease in sandstone permeability reduce the relative mobility of oil with the dissolved carbon dioxide. The significant influence of sandstone permeability on the experimental results indicates that the sizes of asphaltene aggregates are comparable to the sizes of small pores. We have not observed complete attenuation of filtration after passing of oil with dissolved carbon dioxide through sandstones. Based on the analysis of changes in oil composition and properties carried out in the laboratory experiments on oil displacement by carbon dioxide rims, it has been determined that aggregation of asphaltene associates takes place under immediate contact of oil and carbon dioxide in a porous medium. The higher the asphaltene content in oil, the lower the formation permeability, whereas tight formations feature a more significant decrease in permeability.

Features of the Composition of Compounds Trapped in Asphaltenes of Oils and Bitumens of the Bavly Oil Field

The asphaltene aggregates are made of a well-packed and stable in benzene (toluene) solution core and a loose-packed periphery, which can respectively occlude and adsorb the other oil fractions. Pr...

Synthesis and characterization of tannic acid esters and their performances as asphaltenes dispersants

Asphaltene aggregation and flocculation in upstream and downstream industries cause severe problems due to phase separation and asphaltene particle growth. This work aims to esterify tannic acid (TA) at different molar ratios of heptanoyl chloride (HC) 1:3, 1:6, and 1:9, producing species TA-HC3, TA-HC6, and TA-HC9, respectively. The synthesized esters were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), and thermal analyses. Their performances as asphaltene dispersants of Arabian heavy crude oil were assessed by dynamic light scattering (DLS), ultraviolet–visible (UV–Vis) spectroscopy, and viscosity measurements. All specimens (TA-HC3, TA-HC6, and TA-HC9) dispersed asphaltene, and their dispersal abilities increased with increasing number of alkyl chains (i.e., TA-HC3 > TA-HC6 > TA-HC9).

Molecular dynamics simulation to investigate the effect of polythiophene-coated Fe3O4 nanoparticles on asphaltene precipitation

Asphaltene precipitation is one of crucial problems in oil industry that negatively affects oil production, transportation, and processing, imposing high costs. In recent years, numerous experimental studies have been conducted to analyze inhibition of asphaltene precipitation using nanoparticles. In this study, molecular dynamics simulations are employed for the first time to investigate the effect of Fe3O4 and polythiophene-coated Fe3O4 nanoparticles on asphaltene aggregation phenomena. In addition, the structure of asphaltene is determined based on elemental analysis, 1HNMR, 13CNMR, and FTIR. The number of molecules and average size of asphaltene aggregates in the presence of nanoparticles show a considerable decrease in aggregation, compared to the case without nanoparticles due to delay in growth of asphaltene aggregates. Asphaltenes tend to adsorb on surface of nanoparticles as a result of interaction forces. Consequently, smaller and/or fewer aggregates of asphaltene precipitate on the quartz surface. The simulation results show a good match with the experimental data.

Investigation of asphaltene aggregate size: influence of Fe3O4 nanoparticles, asphaltene type, and flocculant

Investigation of asphaltene aggregate size: influence of Fe3O4 nanoparticles, asphaltene type, and flocculant