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Scott H Fogler - One of the best experts on this subject based on the ideXlab platform.
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revisiting the flocculation kinetics of destabilized Asphaltenes
Advances in Colloid and Interface Science, 2017Co-Authors: Claudio Vilas Boas Favero, Nasim Hajiakbari, Michael P Hoepfner, Tabish Maqbool, Scott H FoglerAbstract:A comprehensive review of the recently published work on asphaltene destabilization and flocculation kinetics is presented. Four different experimental techniques were used to study Asphaltenes undergoing flocculation process in crude oils and model oils. The Asphaltenes were destabilized by different n-alkanes and a geometric population balance with the Smoluchowski collision kernel was used to model the asphaltene aggregation process. Additionally, by postulating a relation between the aggregation collision efficiency and the solubility parameter of Asphaltenes and the solution, a unified model of asphaltene aggregation model was developed. When the aggregation model is applied to the experimental data obtained from several different crude oil and model oils, the detection time curves collapsed onto a universal single line, indicating that the model successfully captures the underlying physics of the observed process.
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mechanistic investigation of asphaltene deposition
Energy & Fuels, 2016Co-Authors: Claudio Vilas Boas Favero, Apirak Hanpan, Pantid Phichphimok, Krittin Binabdullah, Scott H FoglerAbstract:Asphaltenes are the most polar molecules in crude oil and are responsible for a large number of deposition and fouling problems in the oil industry. The mechanisms by which Asphaltenes deposit have not been fully elucidated, and the goal of this investigation is to reveal the underlying physics of the asphaltene deposition process. A new deposition apparatus was designed and constructed to investigate asphaltene deposition. The apparatus consists of a packed bed of stainless steel beads over which a mixture of oil and heptane is passed at a specified flow rate and run-time. The asphaltene deposition rate and the mass of deposit can be obtained along the packed bed. The dependency of the asphaltene deposition rate on concentration of unstable Asphaltenes and on fluid flow velocity was studied. Experimental results show that a mass-transfer limited deposition model can explain the asphaltene deposition of nanometer-sized unstable Asphaltenes in the viscous flow regime. This investigation sheds light on the ...
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combined asphaltene aggregation and deposition investigation
Energy & Fuels, 2016Co-Authors: Wattana Chaisoontornyotin, Nasim Hajiakbari, Scott H Fogler, Michael P HoepfnerAbstract:This study discusses experimental and modeling results of asphaltene aggregation and deposition using various n-alkanes as precipitants to destabilize Asphaltenes from a crude oil. The amount of Asphaltenes precipitated as a function of precipitant carbon number and concentration was obtained after monitoring the slow kinetic aggregation process. A geometric population balance was used to estimate the asphaltene–asphaltene collision efficiency during bulk aggregation. The results revealed that, for a fixed volume fraction of precipitant, the collision efficiency decreases with increasing precipitant carbon number, resulting in slower aggregation. The tendency for Asphaltenes to deposit was measured using capillary flow experiments under similar conditions. Similar asphaltene deposition behavior was obtained when the results were normalized by the asphaltene solubility and other experimental factors. A modified aggregation model was applied to the results and revealed that the difference between the asphal...
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effect of asphaltene concentration on the aggregation and precipitation tendency of Asphaltenes
Energy & Fuels, 2014Co-Authors: Nasim Hajiakbari, Phitsanu Teeraphapkul, Scott H FoglerAbstract:Destabilized Asphaltenes can easily adhere to the oil well production equipment, the transportation pipelines, and also the refining and storage facilities, resulting in significant remediation costs. Therefore, it is of great importance to the energy industry to understand the factors that govern the kinetics of asphaltene aggregation and precipitation. In this study, the effect of asphaltene concentration on their aggregation and precipitation tendencies after their destabilization with heptane is investigated for three different types of Asphaltenes. It is intuitively expected that any increase in asphaltene concentration will accelerate the precipitation kinetics after heptane addition. For asphaltene concentrations below 1 wt % in toluene, this expected trend is indeed experimentally confirmed. However, for asphaltene concentrations above 1 wt %, an increase in concentration leads to slower aggregation instead. We believe that this counterintuitive decline in the aggregation rate is due to the stabil...
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the fractal aggregation of Asphaltenes
Langmuir, 2013Co-Authors: Michael P Hoepfner, Claudio Vilas Boas Favero, Nasim Hajiakbari, Scott H FoglerAbstract:This paper discusses time-resolved small-angle neutron scattering results that were used to investigate asphaltene structure and stability with and without a precipitant added in both crude oil and model oil. A novel approach was used to isolate the scattering from Asphaltenes that are insoluble and in the process of aggregating from those that are soluble. It was found that both soluble and insoluble Asphaltenes form fractal clusters in crude oil and the fractal dimension of the insoluble asphaltene clusters is higher than that of the soluble clusters. Adding heptane also increases the size of soluble asphaltene clusters without modifying the fractal dimension. Understanding the process of insoluble Asphaltenes forming fractals with higher fractal dimensions will potentially reveal the microscopic asphaltene destabilization mechanism (i.e., how a precipitant modifies asphaltene-asphaltene interactions). It was concluded that because of the polydisperse nature of Asphaltenes, no well-defined asphaltene ph...
Oliver C. Mullins - One of the best experts on this subject based on the ideXlab platform.
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advances in the flory huggins zuo equation of state for asphaltene gradients and formation evaluation
Energy & Fuels, 2013Co-Authors: Oliver C. Mullins, Denise E Freed, Hani Elshahawi, Chengli Dong, Douglas J SeifertAbstract:Recent advances in the understanding of the molecular and colloidal structure of Asphaltenes in crude oils are codified in the Yen–Mullins model of Asphaltenes. The Yen–Mullins model has enabled the development of the industry’s first asphaltene equation of state for predicting asphaltene concentration gradients in oil reservoirs, the Flory–Huggins–Zuo equation of state (FHZ EOS). The FHZ EOS is built by adding gravitational forces onto the existing Flory–Huggins regular solution model that has been used widely to model the phase behavior of asphaltene precipitation in the oil and gas industry. For reservoir crude oils with a low gas/oil ratio (GOR), the FHZ EOS reduces predominantly to a simple form, the gravity term only, and for mobile heavy oil, the gravity term simply uses asphaltene clusters. The FHZ EOS has successfully been employed to estimate the concentration gradients of Asphaltenes and/or heavy ends in different crude oil columns around the world, thus evaluating the reservoir connectivity, w...
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comparison of coal derived and petroleum Asphaltenes by 13c nuclear magnetic resonance dept and xrs
Energy & Fuels, 2011Co-Authors: Ballard A Andrews, Oliver C. Mullins, John C Edwards, Andrew E Pomerantz, Dennis Nordlund, Koyo NorinagaAbstract:The molecular architecture of Asphaltenes is still a matter of debate. Some literature reports provide evidence that the contrast of petroleum Asphaltenes versus coal-derived Asphaltenes is useful for understanding the governing principles of asphaltene identity. Coal-derived Asphaltenes provide an excellent test for understanding the relationship of asphaltene molecular architecture with asphaltene properties. Diffusion measurements have shown that coal-derived Asphaltenes are half the size of many crude oil Asphaltenes, but there are relatively few studies comparing coal-derived and petroleum Asphaltenes using liquid state 13C NMR. 13C NMR confirms that the molecular sizes of these coal-derived Asphaltenes are smaller than virgin petroleum Asphaltenes. DEPT-45 experiments were performed in order to determine the relative amount of nonprotonated and protonated carbon in the aromatic region of the spectrum. In contrast to previous NMR work on Asphaltenes that ignored interior bridgehead carbon, we show th...
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asphaltene nanoaggregates studied by centrifugation
Energy & Fuels, 2009Co-Authors: Farshid Mostowfi, Kentaro Indo, Oliver C. Mullins, Richard McfarlaneAbstract:The colloidal structure of Asphaltenes impacts various physical properties and is important to characterize. Previously, in both laboratory and oilfield studies, Asphaltenes have been shown to form nanoaggregates. In addition, previous work has shown that Asphaltenes exhibit a critical nanoaggregate concentration (CNAC) in toluene in the range of 50−150 mg/L. In this study, centrifugation is used to prove a major change of asphaltene aggregation at the CNAC concentration, thereby corroborating previous results. Collection of these nanoaggregates by centrifugation validates there existence. The nanoaggregate size is found to be ∼2.5 nm, which is compatible with corresponding previous determinations from gravitational gradients. Asphaltene monomers are seen to be small (<1.5 nm), confirming previous diffusion measurements and corroborating the now common view that asphaltene molecular size is rather small. A two-component, monomer and nanoaggregate, phase equilibrium model is shown to treat the primary feat...
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polycyclic aromatic hydrocarbons of Asphaltenes analyzed by molecular orbital calculations with optical spectroscopy
Energy & Fuels, 2007Co-Authors: Yosadara Ruizmorales, Oliver C. MullinsAbstract:The number and geometry of the rings in polycyclic aromatic hydrocarbons (PAHs) in petroleum asphaltene has remained unresolved for many years. Many sophisticated imaging and spectroscopic methods have been utilized to narrow the list of candidate structures for asphaltene PAHs. Here, we exploit a canonical property of petroleum Asphaltenes, their color, along with their fluorescence emission properties. These universal spectral properties are analyzed through the lens of molecular orbital (MO) calculations, thereby providing quantitative bounds on asphaltene PAH systems. Energetic considerations mandate that these fused aromatic ring systems are predominantly aromatic sextet carbon (within the Clar representation) but not entirely sextet carbon. Matching the ubiquitous asphaltene spectral data with MO calculations shows that asphaltene ring systems predominantly consist of 4−10 rings. PAHs with 6−8 rings are most predominant in petroleum Asphaltenes. Not surprisingly, polydispersity is implied in this an...
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molecular size and weight of asphaltene and asphaltene solubility fractions from coals crude oils and bitumen
Fuel, 2006Co-Authors: Sophie Adre, Cristiane Carla Goncalves, Koyo Norinaga, Gale Gustavso, Oliver C. MullinsAbstract:Abstract The molecular weight of Asphaltenes has been a controversy for several decades. In recent years, several techniques have converged on the size of the fused ring system; indicating that chromophores in virgin crude oil Asphaltenes typically have 4–10 fused rings. Consequently, the molecular weight debate is equivalent to determining whether Asphaltenes are monomeric (one fused-ring system per molecule) or whether they are polymeric. Time-resolved fluorescence depolarization (FD) is employed here to interrogate the absolute size of asphaltene molecules and to determine the relation of the size of the fused ring system to that of the corresponding molecule. Coal, petroleum and bitumen Asphaltenes are compared. Molecular size of coal Asphaltenes obtained here by FD-determined rotational diffusion match closely with Taylor-dispersion-derived translational diffusion measurements with UV absorption [1] . Coal Asphaltenes are smaller than petroleum Asphaltenes. N-methyl pyrrolidinone (NMP) soluble and insoluble fractions are examined. NMP soluble and insoluble fractions of Asphaltenes are monomeric. It is suggested that the ‘giant’ asphaltene molecules reported from SEC studies using NMP as the eluting solvent may actually be the expected flocs of asphaltene which are not soluble in NMP. Data is presented that intramolecular electronic relaxation in Asphaltenes does not perturb FD results.
Yansong Zhao - One of the best experts on this subject based on the ideXlab platform.
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ethylene vinyl acetate copolymer and resin stabilized Asphaltenes synergistically improve the flow behavior of model waxy oils 2 effect of asphaltene content
Energy & Fuels, 2018Co-Authors: Bo Yao, Fei Yang, Xiaoping Zhang, Guangyu Sun, Gang Liu, Yansong ZhaoAbstract:In part 1 (10.1021/acs.energyfuels.7b03657), the synergistic effect of ethylene–vinyl acetate copolymer (EVA) pour point depressant (PPD) and rensin-stabilized Asphaltenes on improving the flowability of synthetic waxy oil has been verified. This paper is a continuous work studying the effect of the asphaltene content (0.01–3 wt %) on the synergistic effect between EVA PPD and resin-stabilized Asphaltenes. The results showed that, in the absence of EVA and with the increase of the asphaltene content, the precipitated wax crystals of the waxy oil tend to grow gradually from initial big needle-like to smaller and more regular (spherical-like) particles with a larger amount; therefore, adding aphaltenes can only decrease the apparent viscosity of waxy oil at the temperature range slightly lower than the wax precipitation temperature (WPT) (the precipitated wax crystal amount is low), and the temperature range is broadened by increasing the asphaltene content. When the temperature is decreased far below the W...
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Ethylene–Vinyl Acetate Copolymer and Resin-Stabilized Asphaltenes Synergistically Improve the Flow Behavior of Model Waxy Oils. 2. Effect of Asphaltene Content
2018Co-Authors: Bo Yao, Fei Yang, Xiaoping Zhang, Guangyu Sun, Gang Liu, Yansong ZhaoAbstract:In part 1 (10.1021/acs.energyfuels.7b03657), the synergistic effect of ethylene–vinyl acetate copolymer (EVA) pour point depressant (PPD) and rensin-stabilized Asphaltenes on improving the flowability of synthetic waxy oil has been verified. This paper is a continuous work studying the effect of the asphaltene content (0.01–3 wt %) on the synergistic effect between EVA PPD and resin-stabilized Asphaltenes. The results showed that, in the absence of EVA and with the increase of the asphaltene content, the precipitated wax crystals of the waxy oil tend to grow gradually from initial big needle-like to smaller and more regular (spherical-like) particles with a larger amount; therefore, adding aphaltenes can only decrease the apparent viscosity of waxy oil at the temperature range slightly lower than the wax precipitation temperature (WPT) (the precipitated wax crystal amount is low), and the temperature range is broadened by increasing the asphaltene content. When the temperature is decreased far below the WPT of the oil, however, the apparent viscosity of oil rises up with increasing the aphaltene content as a result of the large amount of wax crystals and Asphaltenes. In addition, only a part of the Asphaltenes participates in the wax precipitation process, and the rest of the Asphaltenes disperses in the oil phase as asphaltene aggregates, which could adhere or adsorb on the existing wax crystal flocs, strengthening the interactions between wax flocs. After Asphaltenes are added together with EVA, EVA molecules can adsorb onto the asphaltene aggregates to generate the formation of the EVA/asphaltene composite particles, and the synergistic effect of the EVA/asphaltene composite particles on the flowability of waxy oil improves first with the increase of the asphaltene content and then somewhat deteriorates at a higher asphaltene content (3 wt %). When the asphaltene content is low, the wax crystal modification by the composite particles is insufficient and the formed large wax flocs have a very loose structure, which favor the wax crystal structure building. When the asphaltene content is too high (3 wt %), EVA/asphaltene composite particles disperse the precipitated wax flocs into relatively small spherical-like wax flocs with a larger amount. Although the structure of the wax flocs is compact, the large amounts of wax flocs and asphaltene aggregates in the oil phase lead to somewhat deterioration of the synergistic performance of EVA and Asphaltenes. At the middle contents of Asphaltenes (0.75–1.5 wt %), EVA/asphaltene composite particles cause the formation of relatively large spherical-like wax flocs with a compact structure and the asphaltene content is moderate, both of which greatly promote the flow behavior improvement of the oil
H. Scott Fogler - One of the best experts on this subject based on the ideXlab platform.
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Effect of Temperature on the Precipitation Kinetics of Asphaltenes
Energy & Fuels, 2011Co-Authors: Tabish Maqbool, Perapat Srikiratiwong, H. Scott FoglerAbstract:Asphaltene precipitation is a challenging problem for the petroleum industry. Changes in pressure, temperature, and composition are key factors that influence asphaltene stability in crude oils. We have previously shown that the time required to precipitate Asphaltenes can actually vary from a few minutes to several months, depending on the precipitant concentration used and that no single concentration can be identified as the critical precipitant concentration for asphaltene precipitation. Both upstream and downstream processes involve temperature variations, which can cause the precipitation of Asphaltenes and can lead to deposition and fouling problems during the production, transportation, and processing of crude oils. In the present work, we extend the findings of the previous research to incorporate the effect of temperature on the precipitation kinetics of Asphaltenes. The effect of temperature on asphaltene stability can be complex and various competing effects can be identified. We demonstrate t...
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Stabilization of Asphaltenes in Aliphatic Solvents Using Alkylbenzene-Derived Amphiphiles. 2. Study of the Asphaltene-Amphiphile Interactions and Structures Using Fourier Transform Infrared Spectroscopy and Small-Angle X-ray Scattering Techniques
Langmuir, 1994Co-Authors: Chia Lu Chang, H. Scott FoglerAbstract:In the preceding paper in this issue, the influence of the chemical structure of a series of alkylbenzene-derived amphiphiles on the stabilization of Asphaltenes was described. In this paper, we present the results of using Fourier transform infrared (FTIR) spectroscopy and small-angle X-ray scattering (SAXS) techniques to study the interaction between Asphaltenes and two alkylbenzene-derived amphiphiles, p-alkylphenol and p-alkylbenzenesulfonic acid. FTIR spectroscopy was used to characterize and quantify the acid-base interactions between Asphaltenes and amphiphiles. It was found that Asphaltenes could hydrogen-bond to p-dodecylphenol amphiphiles. The hydrogen-bonding capacity of Asphaltenes was estimated to be 1.6-2.0 mmol/g of asphaltene. On the other hand, the FTIR spectroscopic study indicated that Asphaltenes had a complicated acid-base interaction with p-dodecylbenzenesulfonic acid (DBSA) amphiphiles with a stoichiometry of about 1.8 mmol of DBSA/g of asphaltene. The UV/vis spectroscopic study suggested that Asphaltenes and DBSA could associate into large electronic conjugated complexes. Physical evidence of the association between Asphaltenes and amphiphiles was obtained by SAXS measurements. 27 refs., 10 figs.
Michael P Hoepfner - One of the best experts on this subject based on the ideXlab platform.
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Solvent Effects on the Structure of Petroleum Asphaltenes
'American Chemical Society (ACS)', 2021Co-Authors: Yuan Yang, Thomas F. Headen, Jingzhou Zhang, Michael P HoepfnerAbstract:Neutron total scattering was employed to study the impact of a solvent on the behavior of Asphaltenes by comparing structural interpretations of solid phase samples to those dispersed in 1-methylnaphthalene (1-MN) as a function of temperature and asphaltene solubility. This powerful technique enables structural interpretation on length scales ranging from local molecular order to the formation of nanoaggregates and/or fractal clusters in a single experiment. We observed that more unstable Asphaltenes exhibit greater aromatic stacking on the local molecular length scale and also produce more frequent nanometer-sized associations. However, when the temperature was elevated, the breakup of larger asphaltene clusters was correlated to a reduction in the extent of asphaltene side-chain interactions. Additionally, dispersed Asphaltenes demonstrated an increase in aromatic stacking as the temperature was increased, suggesting an entropic driving force for assembly driven by solvent depletion interactions. This observation is novel in asphaltene science and serves as a pathway to assess the impact of local solvent composition on both enthalpic and entropic assembly pathways. The results suggest that while more unstable Asphaltenes exhibit greater aromatic stacking, further association may be assisted by an increase in the disordered side-chain interactions. The experimental results also serve as a useful benchmark to validate simulation predictions of asphaltene structure
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structure of Asphaltenes during precipitation investigated by ultra small angle x ray scattering
Langmuir, 2018Co-Authors: Yuan Yang, Wattana Chaisoontornyotin, Michael P HoepfnerAbstract:Time-resolved size and structure measurements of Asphaltenes while in the process of precipitating were monitored for the first time using ultra-small-angle X-ray scattering. The results revealed that Asphaltenes precipitating from a heptane–toluene mixture demonstrate a hierarchical structure of an asphaltene-rich phase (e.g., droplet) that further agglomerates into fractal flocs. The fractal flocs that form by the agglomeration of the asphaltene-rich phase are what is commonly detected by optical microscopy above the precipitation detection point. The surface of the asphaltene-rich phase is initially rough and transitions to a smooth interface, as would be expected for a highly viscous liquid. Simultaneous small-angle X-ray scattering measurements were also performed to investigate the structure of soluble Asphaltenes, providing comprehensive structural characterization from the nanometer- to micrometer-length scales as a function of time. Further, the results demonstrate that the size and concentration...
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revisiting the flocculation kinetics of destabilized Asphaltenes
Advances in Colloid and Interface Science, 2017Co-Authors: Claudio Vilas Boas Favero, Nasim Hajiakbari, Michael P Hoepfner, Tabish Maqbool, Scott H FoglerAbstract:A comprehensive review of the recently published work on asphaltene destabilization and flocculation kinetics is presented. Four different experimental techniques were used to study Asphaltenes undergoing flocculation process in crude oils and model oils. The Asphaltenes were destabilized by different n-alkanes and a geometric population balance with the Smoluchowski collision kernel was used to model the asphaltene aggregation process. Additionally, by postulating a relation between the aggregation collision efficiency and the solubility parameter of Asphaltenes and the solution, a unified model of asphaltene aggregation model was developed. When the aggregation model is applied to the experimental data obtained from several different crude oil and model oils, the detection time curves collapsed onto a universal single line, indicating that the model successfully captures the underlying physics of the observed process.
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combined asphaltene aggregation and deposition investigation
Energy & Fuels, 2016Co-Authors: Wattana Chaisoontornyotin, Nasim Hajiakbari, Scott H Fogler, Michael P HoepfnerAbstract:This study discusses experimental and modeling results of asphaltene aggregation and deposition using various n-alkanes as precipitants to destabilize Asphaltenes from a crude oil. The amount of Asphaltenes precipitated as a function of precipitant carbon number and concentration was obtained after monitoring the slow kinetic aggregation process. A geometric population balance was used to estimate the asphaltene–asphaltene collision efficiency during bulk aggregation. The results revealed that, for a fixed volume fraction of precipitant, the collision efficiency decreases with increasing precipitant carbon number, resulting in slower aggregation. The tendency for Asphaltenes to deposit was measured using capillary flow experiments under similar conditions. Similar asphaltene deposition behavior was obtained when the results were normalized by the asphaltene solubility and other experimental factors. A modified aggregation model was applied to the results and revealed that the difference between the asphal...
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the fractal aggregation of Asphaltenes
Langmuir, 2013Co-Authors: Michael P Hoepfner, Claudio Vilas Boas Favero, Nasim Hajiakbari, Scott H FoglerAbstract:This paper discusses time-resolved small-angle neutron scattering results that were used to investigate asphaltene structure and stability with and without a precipitant added in both crude oil and model oil. A novel approach was used to isolate the scattering from Asphaltenes that are insoluble and in the process of aggregating from those that are soluble. It was found that both soluble and insoluble Asphaltenes form fractal clusters in crude oil and the fractal dimension of the insoluble asphaltene clusters is higher than that of the soluble clusters. Adding heptane also increases the size of soluble asphaltene clusters without modifying the fractal dimension. Understanding the process of insoluble Asphaltenes forming fractals with higher fractal dimensions will potentially reveal the microscopic asphaltene destabilization mechanism (i.e., how a precipitant modifies asphaltene-asphaltene interactions). It was concluded that because of the polydisperse nature of Asphaltenes, no well-defined asphaltene ph...
