Asphaltene Interactions Research Articles

Probing the interactions between asphaltenes and a PEO-PPO demulsifier at oil–water interface: Effect of temperature

HypothesisAsphaltenes are primary stabilizers in water-in-oil (W/O) emulsions that cause corrosion and fouling issues. In oil sands industry, oil/water separation processes are generally conducted at high temperatures. A high temperature is expected to impact the interactions between asphaltenes and emulsion breakers (EBs), consequently influencing demulsification performance. ExperimentsThe adsorption and interactions of asphaltenes and a PEO-PPO type EB (Pluronic F68) at the oil–water interface were investigated at various temperatures, using tensiometer, quartz crystal microbalance with energy dissipation (QCM-D), and atomic force microscopy (AFM). The effect of temperature on EB’s demulsification performance was explored through bottle tests. Additionally, demulsification mechanisms were studied using direct force measurements with the droplet probe AFM technique. FindingsDynamic interfacial tension and QCM-D results demonstrate that the PEO-PPO type EB exhibits higher interfacial activity than asphaltenes and can disrupt rigid asphaltene films at the oil–water interfaces. Elevated temperatures accelerate the displacement of adsorbed asphaltenes by EB molecules, leading to sparse interfacial films, rapid droplet coalescence, and improved demulsification efficiency (supported by AFM and bottle test results). This work provides valuable insights into interfacial interactions between asphaltenes and EB at different temperatures, enhancing the understanding of demulsification mechanisms and offering useful implications for the development of efficient EBs to enhance oil/water separation performance.

The influence mechanism of bitumen components on its macroscopic and microscopic properties: Analysis based on polyphosphoric acid modification

In order to investigate the impact of bitumen components on its overall properties, various modified bitumen with 1.0 %PPA or 2.0 %SBS/SBR + 0.6 %PPA were prepared. The influence of PPA dosage on bitumen’s physical properties were evaluated, and the macroscopic and microscopic properties of each bitumen sample were characterized by DSR, BBR and atomic force microscopy observation. The components of bitumen were separated through SARA test, and the infrared spectroscopy of asphaltenes was further analyzed. The findings suggest a significant impact on bitumen with PPA incorporation, the elastic recovery properties of bitumen at high temperatures were enhanced due to a more stable colloidal structure was formed by the dispersion and interaction of macromolecular asphaltenes. However, the low-temperature rheological properties of bitumen were impaired by reason of a relatively reduced flowable lightweight component. Specifically, the large asphaltenes clusters were dispersed cause PPA reacted with the –OH bonds of alcohols in bitumen by phosphorylation. By modeling the correlation between bitumen component contents and its microscopic surface parameters, the asphaltenes decomposition was demonstrated to be an important factor on the microscopic morphology, which was also related to the content of saturates and aromatics. Thus, a method for deconstructing bitumen from a compositional perspective is proposed.

Density functional theory assessed molecular insights into asphaltene interactions within silica and calcium carbonate surface with deep eutectic solvents

Deep Eutectic Solvents (DES) have gained recent attention as asphaltene solvents due to their low cost and eco-friendliness. However, identifying the intermolecular behavior of asphaltene with different DESs using experimental methods is costly and time-consuming. Therefore, this study investigates the intermolecular interactions and electronic properties of DESs with model asphaltene in the presence of sandstone (SiO2) and carbonate (CaCO3) surfaces using Density Functional Theory (DFT) calculations. The study focuses on understanding the binding energies, interaction energies, band gap, and intermolecular mechanism between SiO2 surface, asphaltene, and DESs (SiO2-Asp-DESs systems) and CaCO3 surface, asphaltene, and DESs (CaCO3-Asp-DESs systems). The investigation yields valuable insights into the interactions, stability, and affinity of the asphaltene and DES in the overall system, enhancing understanding of asphaltene behavior in solvent environments. The study shows that DES containing choline chloride as a hydrogen bond acceptor (HBA) outperforms in the presence of both surfaces (SiO2 and CaCO3) with asphaltene. For the SiO2-Asp-DES system, which contains DES as choline chloride and ethylene glycol, a higher intermolecular interaction energy of − 747.174 kJ/mol is observed. In contrast, for the CaCO3-Asp-DES system, DES as choline chloride and glycerol show higher intermolecular interaction energy of − 259.154 kJ/mol. Variations in interaction and binding energies for the systems further show that the effectiveness of DES with asphaltene varies depending on the type of surface (SiO2/CaCO3). As for the overall reactivity, CaCO3-Asp-DESs systems show comparatively less reactivity than SiO2-Asp-DESs systems that show smaller band gaps.

Interfacial tension of smart water and various crude oils

The utilization of smart water in EOR (enhanced oil recovery) operations has drawn increased attention in recent years. Nevertheless, the variety and complexity of mechanisms during smart water injection require more research endeavors. In this study, interfacial tension (IFT) for the smart water/crude oil interacting system has been investigated. The investigated parameters included various salts with different salinity, pH, asphaltene type, and aged smart water with two crude oil samples. The results showed that the hydration of ions in smart water would play a key role to discern the primary mechanism of smart water. The interaction of acidic and basic asphaltene with hydration shell of different ions can be considered as primary mechanism for efficacy of smart water. Acidic and basic asphaltenes serve as intrinsic surfactants due to their interaction with OH− in the anion hydration shell and H+ in the cation hydration shell, respectively. The propensity of acidic asphaltene to interact with anions with high hydration energy and the tendency of basic asphaltene to interact with cations with high hydration energy led to an IFT of 0.2 mN/m and 11.3 mN/m for acidic and basic oils, respectively. The impact of pH also revealed that acidic and basic asphaltenes would have lower IFT in alkaline and acidic environments. Finally, it was found that changes in IFT for the aged smart water with crude oil depend on the asphaltene type as well as salt and salinity.

Evaluating the effects of oxidation and the deagglomerating potential of selected additives on asphaltene aggregation via computational modeling

Economic and environmental sustainability has been a significant stimulus to the use of recycled asphalt materials in the pavement industry. In this practice, rejuvenators are usually required to treat the oxidized asphalts with the aim to restore the physical properties and engineering performance. A critical function required for rejuvenators is that they can deagglomerate the asphaltene aggregates by effectively interacting with them. This study employed the techniques of molecular dynamics simulations and quantum chemical calculations, and investigated the impacts of oxidation on asphaltenes and the deagglomerating potential of three selected additives with different molecular structures and polarities, i.e., tributyl citrate (TBC), limonene, and myristamide. Analyses based on the aggregation number, orientational order parameter, and decomposition of the interaction energy indicated that oxidation strengthened the binding between the asphaltenes and thus promoted their aggregation behaviors. Among the three additives, TBC exhibited the highest rejuvenating effectiveness as it restrained the formation of large asphaltene aggregates and improved the orientational randomness of the aromatic cores. This capability was attributed to the highest number of polar sites in TBC and its three-dimensional spatial structure, which enhanced the compatibility and interactions with the aged asphaltenes. Based on the independent gradient model (IGM) method, the asphaltene aggregation is driven by the π-π interactions dominated by dispersion forces between the fused aromatic cores. The additives weakened the asphaltene interactions to different degrees, but the reversing effects were limited compared to the unaged state.

Effect of clay minerals on asphaltene deposition in reservoir rock: Insights from experimental investigations

This study investigated the effect of crude oil characteristics and the presence of clays on the interaction and precipitation tendency of asphaltenes during solvent washing. As solvent n-pentane was used, hence, in this study, the behavior of n-pentane insoluble asphaltenes was investigated. The asphaltenes precipitation tendency and consequently its impact on formation damage were investigated with several experiments performed on sand samples mixed with two different crude oils, with and without added clays. The samples were then analyzed using various techniques including Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and porosity measurements. The results showed that the presence of clays increased the affinity of asphaltenes towards adsorption onto the clay surfaces, resulting in the plugging of pore spaces and inducing higher asphaltenes precipitation. The surface elemental composition of the samples indicated that the asphaltenes of one crude oil (Oil 1) had a higher concentration of aluminum (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), and silicon (Si), while the asphaltenes of the other crude oil (Oil 2) had a higher concentration of sulfur (S) and vanadium (V). These differences in elemental composition led to different precipitation tendencies and porosity reductions. Accordingly, the interactions of asphaltenes with reservoir rock found more for Oil 1 to Oil 2. The findings of this study provide insights into the factors that influence asphaltene precipitation during solvent washing, which can have implications for oil production and processing.

Molecular dynamics investigation of the asphaltene-kaolinite interactions in water, toluene, and water-toluene mixtures.

Understanding the interactions of petroleum asphaltenes with mineral surfaces is important for diluted bitumen spill response and modeling. In this study, molecular dynamics and umbrella sampling simulations are performed using interfacially active and non-interfacially active asphaltene model compounds individually positioned near each of the surfaces of kaolinite in the presence of explicit solvent environments containing water, toluene, and mixtures of toluene and water in varying proportions. The interfacially active asphaltene bonds the strongest to the silicon oxide surface of kaolinite in pure water and the bonding weakens to nearly zero in toluene-water mixtures. The non-interfacially active asphaltenes bond to kaolinites silicon oxide surface in water about half as strongly as the interfacially active one in water and the bonding weakens in the presence of toluene. The number of non-hydrogen bonded contacts between the interfacially active asphaltene and the aluminum hydroxide surface of kaolinite increases as the proportion of toluene is increased and the contacts with water are decreased. In these conditions, the non-interfacially active asphaltenes do not form non-hydrogen bonded contacts with kaolinite. On the silicon oxide surface, the number of non-hydrogen bonded contacts of all asphaltenes with kaolinite tends to decrease as the proportion of toluene is increased and the contacts with water are decreased. The number of hydrogen bonds of the interfacially active asphaltene with water decreases as the proportion of toluene is increased. The radii of gyration indicate that the interfacially active asphaltene is extended in water and when adsorbed on kaolinite, and becomes compact as the proportion of toluene is increased. The simulation results highlight the competitive interfacial interactions in the complex scenario of diluted bitumen spills in the presence of water and clay minerals.

Applicability and structural relevance of Hansen solubility parameters for asphaltenes

The Hansen solubility parameters of different asphaltenes were determined, and the combination of experimental and different characterization methods, such as the modified Brown-Lander method, X-ray diffraction, in situ infrared, dipole moment measurements, and X-ray photoelectron spectroscopy, confirmed that the Hansen solubility parameters can well reveal the strength of the interactions of asphaltenes, which are mixtures of condensed aromatic macromolecules, and indicated the applicability of using Hansen solubility parameters to study systems involving asphaltenes. By analyzing the relationship between the composition of asphaltenes and their interaction strengths, it was obtained that the strength of polar interaction is positively correlated with the condensation degree and the number of unit sheets; while the most influential factor on the strength of dispersion is the number of aromatic rings of asphaltenes; besides, the strength of hydrogen bond interaction increases with the heteroatomic content, while the different heteroatomic functional groups also have a great influence.

Lattice-Gas Model for Asphaltene Interactions Observed at Interfaces in the Context of the Yen-Mullins Model

Lattice-Gas Model for Asphaltene Interactions Observed at Interfaces in the Context of the Yen-Mullins Model

Critical Review of Underlying Mechanisms of Interactions of Asphaltenes with Oil and Aqueous Phases in the Presence of Ions

Asphaltene studies have been a prime focus topic for many decades. However, the underlying interaction mechanisms between water, oil, and asphaltenes requires more attention. Water is involved in all production parts (reservoir, tubing, surface facilities, and refinery), posing comprehensive research about the issues and operating conditions. According to the available literature, there are contradictory opinions regarding the effect of salinity on the aqueous phase and the oil phase interfacial characteristics. This review provides a critical summary of asphaltene’s role in the stability of the aqueous phase emulsions in an oil phase. We reviewed the effect of temperature, pressure, asphaltene concentration, bulk phase components, different salinity, types of ions, and pH on emulsion stability regarding the low salinity water injection aspects. Moreover, the studied cases investigating emulsion stability in the presence of asphaltenes and other species were collected, compared, and categorized. Furthermore, the interfacial and rheological characteristics of the brine–oil interface composed of asphaltenes and other species were compared. We found that the effect of some parameters requires an in-depth study as there are not many related works. For example, the effect of pressure on the rheological characteristics of emulsions and, at the same time, on the aggregation, precipitation, and deposition using visual devices (high pressure–high temperature microfluidic) is missing from the literature. Therefore, we recommend a specific study of each crude oil’s combined effects of temperature, pressure, and salinity. Low salinity water injection is a newly developed enhanced oil recovery method that employs the results of emulsion studies in the presence of different ions and reservoir conditions (high pressure and high temperature).

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.

Study on the Kinetic Process of Asphaltene Precipitation during Crude Oil Mixing and Its Effect on the Wax Behavior of Crude Oil.

As an important component of crude oil, asphaltene precipitation and deposition are harmful to petroleum production and processing. In previous research, the impacts of asphaltene precipitation on crude oil characteristics were preliminarily explored. In this paper, by mixing different types of crude oil, the dynamic process of asphaltene precipitation and its effect on the crystallization and gelation behaviors of mixed crude oil were in-depth analyzed and discussed using the high-speed centrifugation technique, microscopic observation, differential scanning calorimetry (DSC) thermal analysis, and rheological test. The results showed that the asphaltene precipitation mainly occurred in the early stage of crude oil mixing and was influenced by crude oil composition. As the precipitation time increased, the driving force for asphaltene precipitation was gradually weakened until a dynamic equilibrium between asphaltene precipitation and dissolution was reached. Meanwhile, once the asphaltene precipitation occurred, the crystallization and gelation processes of crude oil were significantly affected. It was discovered that the change in the existing state of asphaltenes due to their precipitation is an important factor affecting the interaction of asphaltenes and waxes, which is critical for the technological development of oil and gas flow assurance.

Comprehensive molecular scale modeling of anionic surfactant-asphaltene interactions

Asphaltene is the heaviest fraction of oil sands/bitumen, which is also the leading cause of these oil resources' high viscosity value. Nowadays, steam with additives is used to make oil sands/bitumen mobile through a reservoir by lowering their viscosity. Additives can be air, solvent, non-condensable gas (NCG), and surfactants. Surfactants can be used not only as a chemical additive in thermal oil recovery but also as an asphaltene inhibitor or dispersant. Formulating surfactants needs thorough and reliable knowledge about molecular interactions between asphaltene and surfactants. This paper has used molecular dynamics (MD) simulation to evaluate these interactions at thermodynamic conditions close to thermal-based oil recovery conditions. Three different asphaltene architectures observed in Athabasca oil-sands are used to examine the molecular interactions between asphaltenes and anionic surfactants.Moreover, the effect of a benzene ring on inter-molecular interactions at different temperatures is thoroughly investigated. Various analyses, including a radial distribution function (RDF), hydrogen bonds, and interaction energies, are employed to support the outcomes. Based on MD simulation results, the presence of a benzene ring in a surfactant structure can increase the interactions, especially van der Waals interactions. Moreover, the position and number of heteroatoms in asphaltene architecture play a vital role in asphaltene behavior in a solution. Results of this work give solid knowledge regarding asphaltene and surfactant interactions and provide helpful information for formulating surfactants, whether as an asphaltene inhibitor/dispersant or a steam additive for in-situ bitumen recovery.

Intermolecular Interaction between Heavy Crude Oils and Surfactants during Surfactant-Steam Flooding Process.

The objective of this study is to investigate the intermolecular interactions between the surfactants and the fractions of heavy crude oils. Two possible interactions were considered; polar and ionic interactions for two heavy crude oil–surfactant systems, and 20 surfactant-steam flooding tests were conducted on these crudes by testing nine surfactants (three anionic, three cationic, and three nonionic) with different tail lengths and charged head groups. The performance differences observed in each core flood were discussed through the additional analyses. To explain polar interactions, the pseudo blends of crude oil fractions (fractionation of saturates, aromatics, resins, and asphaltenes) were exposed to the surfactant solutions under vapor and liquid water conditions and their mutual interactions were visualized under an optical microscope. To explain ionic interactions, the charges on asphaltene surfaces were analyzed by zeta potential measurements before and after core flood tests on both the produced and the residual oil asphaltenes. The addition of surfactants improved the oil recovery when compared to steam injection alone. However, different oil recoveries were obtained with different surfactants. Further analyses showed that asphaltenes are key and the interaction of asphaltenes with other crude oil fractions or surfactants determines the success of surfactant-steam processes. The polar interactions favor the emulsion formation more; hence, if the polar interactions are more dominant than the ion interactions in the overall crude oil–surfactant system, the surfactant flooding process into heavy oil reservoir became more successful.

Investigating molecular interaction between wax and asphaltene: Accounting for wax appearance temperature and crystallization

Three modes will improve the interaction of the wax-asphaltene molecules that eventually increase wax appearance temperature (WAT) within crude oil. The first mode takes place when the wax is composed of long-chain alkanes, and its aromatic compounds are low, and adjacent hydrogens in its constituent aromatic rings are substituted with long-chain paraffin. The second condition is when the wax is formed from low carbon number alkanes. In this case, the lower the asphaltene aromaticity and the carbon number of side alkyl chain, the higher its interaction with wax would be. The third approach occurs if naphthenic or aromatic structures exist in wax, and asphaltene aromatic rings are arranged as peri-condenses. Higher interaction of wax and asphaltene reduces wax crystals’ size. The presence of polar compounds in the molecular structure of the wax and asphaltene does not affect WAT, but the size and morphology of crystals alter in microscopic images.

Effects of Waxes and the Related Chemicals on Asphaltene Aggregation and Deposition Phenomena: Experimental and Modeling Studies.

Solid deposition during production, transport, and storage of crude oils leads to significant technical problems and economic losses for the oil and gas industry. The thermodynamic equilibrium between high-molecular-weight components of crude oil, such as asphaltenes, resins, and waxes, is an important parameter for the stability of crude oil. Once the equilibrium is disturbed due to variations in temperature, pressure, and oil composition during production, the solubility of high-molecular-weight waxes decreases. This results in a decrease in the wax appearance temperature (WAT) and the deposit of wax onto solid surfaces. On the other hand, under these conditions, asphaltenes do not interact sufficiently with the resins/waxes and tend to flocculate among themselves and form asphaltene nanoaggregates. The role of waxes during the asphaltene aggregation and deposition has not been appropriately explained yet. The objective of this research study is to describe the interaction of asphaltenes and waxes and subsequently address the specific example of an asphaltenic oil commingled with a wax inhibitor-containing oil during the combination of different oil streams. It is a crucial building block for the development of a suitable and cost-effective strategy for the handling of wax/asphaltene associated flow assurance problems. In this work, the quartz crystal microbalance (QCM) technique has been used for the first time to investigate the effect of waxes and related chemicals, which are used to mitigate wax deposition, on asphaltene aggregation and deposition phenomena. Asphaltene onset point and asphaltene deposition rate have been monitored using QCM at high pressure–high temperature (HPHT) conditions. This study confirms that the different wax inhibitor chemistries result in significant differences in the pour point decrease and viscosity profiles in crude oil. Different wax inhibitors also showed different outcomes regarding the asphaltene deposition tendency. A comprehensive modeling study has also been conducted for mechanistic investigation of experimental results. In this regard, the perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) was utilized to model the systems.

New insights into the interactions between asphaltene and a low surface energy anionic surfactant under low and high brine salinity

Hypothesis: The hyperbranched chains on the tail of low surface energy surfactants (LSES) causes lowering of surface free energy and rock wettability alteration, offering significant improvement in oil recovery in asphaltene oil reservoirs.Experiments: Oil sweep efficiency was determined by fluid displacement in pure brine and LSES-brine solutions in a microfluidic pattern that was representative of a sandstone cross-section. Interfacial tension (IFT), wettability alteration, Raman and X-ray photoelectron spectroscopy (XPS) were used to measure the changes of asphaltene interactions with oil-aged substrate after surface treating with brine and surfactant-brine solutions.Findings: The hyperbranched LSES yielded a significant increase in the original-oil-in-place (OOIP) recovery (58%) relative to brine flooding (25%), even in the presence of asphaltene. Raman spectra showed the LSES-brine solutions to be capable of causing change to the asphaltene aggregate size after centrifugation treatment.

Surface interaction of crude oil, maltenes, and asphaltenes with calcite: An atomic force microscopy perspective of incipient wettability change

Close examination of surface interactions between calcite and crude oil is relevant to better understand the mechanisms that lead to wettability changes in petroleum reservoirs. Mineral surface wettability is a determinant factor in petroleum production and recovery, and the surface-active compounds in crude oil, typically concentrated in its asphaltene fraction, are mainly responsible for these wettability changes. Here, we use atomic force microscopy (AFM) to examine the incipient interactions between calcite {101‾4} surfaces and the Kuwait UG8 crude oil, and its asphaltene and maltene (i.e., crude oil after asphaltene has been extracted) fractions. The resulting adsorbates are interpreted on the basis of coverage, size, shape, and distribution. Adsorbates from crude oil are equally-spaced hemispheroidal droplets occurring predominantly at [4‾41] and [481‾] surface steps with a separation of about 550 nm between centers of adjacent adsorbates. Adsorbates from asphaltenes are irregularly spaced droplets or continuously cover the steps along the edges of dissolution pits. The average and standard deviation of diameter and height of 10–16 representative adsorbates from the selected images highlight the contrast among samples. Crude oil adsorbates average about (240 ± 120) nm in diameter and (60 ± 30) nm in height. Diameters of isolated adsorbates and lateral dimension of elongated adsorbates of asphaltene average (100 ± 20) nm and (150 ± 40) nm, respectively, and about (30 ± 10) nm in height overall. Isolated non-periodic smaller adsorbates (average diameter (20 ± 5) nm and height (7 ± 3) nm) occur from the maltene fraction and are mostly restricted to steps surrounding dissolution pits. Adsorbates from maltenes are most likely produced by resins that remain in this fraction after extracting the asphaltenes. Adsorption from crude oil involves the greatest surface area compared to asphaltenes and maltenes. Based on the sizes and heights of adsorbates reported here, we infer that, unlike resins, asphaltenes in crude oils act as anchors for increased oil adsorption and help enhance the change of an original water-wet surface to an oil-wet one. Differences in average height and architecture between adsorbates from oil and asphaltenes (i.e., isolated vs. continuous) may in part be associated to increased aggregation in toluene, which will intensify colloidal interactions before adsorption. We argue that asphaltenes in crude oil help stabilize larger, almost periodically spaced adsorbates all throughout the calcite surface and not only along the deeper steps that border large dissolution pits. The computational model of a chosen specific asphaltene molecule attached to a calcite surface shows strong interactions between hydroxyl groups and Ca2+ cations on the calcite surface in addition to weaker interactions of the negatively charged π orbitals of the polycyclic aromatic hydrocarbon (PAH) center and the surface cations, which is in agreement with the notion of establishing asphaltene anchors on calcite. Along with basic chemical information, systematic AFM imaging of a variety of crudes may become part of a practical strategy to evaluate surface-active compounds in oil and to predict their likely molecular structure and participating functional groups.

Experimental investigation on the interactions of asphaltenes and ethylene–vinyl acetate (EVA) copolymeric flow improvers at the interface between brine water and model oil

In oil fields, ethylene–vinyl acetate copolymers (EVA) are often added to the produced fluid as flow improvers. Asphaltenes in the crude oil and EVA can both adsorb at the interface and form a protective interfacial layer, affecting the emulsion stability of produced fluid. In this study, the effects of the interactions between asphaltenes and EVAs with different VA contents on the oil/water interfacial properties are investigated. To explore the adsorption behavior of asphaltenes and EVAs, the dynamic interfacial tension is firstly measured with droplet shape analysis method. The effects of the interactions between asphaltenes and EVAs are observed by analyzing the dynamic interfacial tension of the binary system and that of the single system. The added EVAs participate in the formation of interfacial layer and motivate the interfacial activity of asphaltenes to different degrees by influencing the dispersion state of asphaltenes in the model oil. The dilational modulus is then obtained by interfacial small-amplitude oscillation method. The addition of EVAs decreases the modulus, weakening the structure of interfacial layer. The conductivity experiment, asphaltene precipitation experiment and dynamic lighting scattering experiment are combined to explore the effect of EVAs on the dispersion state of asphaltenes. The polar moieties of EVAs interact with asphaltenes and form composite particles with peripheral nonpolar moieties, thus inhibiting asphaltenes from aggregation and improving the dispersion state. Among all the EVAs in this study, the EVA with 30% VA content has the strongest influence on the dispersion state of asphaltenes.

An Overview on the Recent Techniques for Improving the Flowability of Crude Oil in Pipelines

Crude oil is considered as a major source of energy all over the world. Midstream refers to the various methods of transportation. Important issues that oil transportation methods face are spills and inadvertent emissions. Therefore, most of the technology developments in transportation methods are aimed at reducing emissions, increasing efficiency, or preventing spills and leaks. Piping systems are the safest and most efficient and cost-effective way for crude oil transportation. The process suffers from serious problems such as: asphaltene and paraffin structures interactions, pipes pressure drop, and high pumping energy consumption. One of the economical important challenges in oil pipeline transportation is to keep the flowability and reduce the pressure drop along the pipe. The current review highlights the recent and most development techniques which have been used to enhance the fluidity of crude oil in pipelines.