Saturates, Aromatics, Resins, Asphaltenes Research Articles

Chemical Kinetics of SARA fractions pyrolysis: Saturates and Aromatics

This manuscript focuses on presenting a predictive and widely applicable model for describing the pyrolysis of saturates and aromatics, two of the so called SARA (Saturates, Aromatics, Resins, Asphaltenes) fractions. The fractions extracted from two different oil samples, a typical Heavy Fuel Oil 380 and a typical Vacuum Residue Oil, were thoroughly investigated. Different experimental methods elucidated the elemental composition, chemical structure, thermal degradation behavior, and characterized the products released during the pyrolysis of these two oils. Finally, a model to describe the pyrolysis of saturates and aromatics was developed. The model is comprehensive of methodology for the definition of a surrogate and a kinetic mechanism to describe its pyrolysis. The surrogate is defined using a certain number of pseudo-components, whose mass fraction in the mixture is defined to match the chemical properties of the actual fuel. A kinetic mechanism was defined by pairing each pseudo-component with a reaction to describe its thermal decomposition. The model was then validated against literature data and demonstrated to be predictive in describing the pyrolysis of different samples.

Cost-effective enhancement of high viscosity modified bitumen anti-aging properties using organic layered double hydroxide/fume silica nanoparticles composite nanomaterials

High-viscosity modified bitumen (HVMB) is prone to thermal-oxidative and photooxidative aging, resulting in pavement diseases. The use of conventional Nano-modifiers to enhance the aging resistance of bitumen is often hindered by high costs, limiting their adoption in widespread applications. This study aims to evaluate the impact of a cost-effective Multi-Dimensional Nano-Composite (MDNC) modifier on the durability of HVMB, which includes organically modified Layered Double Hydroxides (OLDHs) and Fumed Silica Nanoparticles (FSNPs). Additionally, Zero-Dimensional Nanomaterials (ZDNs) such as FSNPs, Nano-SiO2, or Nano-TiO2, in combination with various MDNC modifiers consisting of OLDHs and ZDNs, were also utilized as comparative anti-aging modifiers for HVMB binders. FTIR, XRD, and contact angle tests indicate that LDHs modified with KH560 (OLDHs) exhibit improved hydrophobicity and increased interlayer distance. The temperature sweep test of the unaged binders and the FESEM test of the Nano-modifier indicate that the branched network structure of the FSNPs significantly enhances the high-temperature elasticity of the HVMB binders. Rheological test results have shown that both ZDNs and MDNC modifiers can delay the changes in rheological parameters after aging. Combining FTIR and SARA (Saturates, Aromatics, Resins, Asphaltenes) results, it was found that the combination of OLDHs/FSNPs synergistically inhibited the increase in the content of heavy components in bitumen during thermal oxygen and ultraviolet aging. The enhancement of the HVMB's thermal oxidation aging resistance by OLDHs/FSNPs composite modifiers is primarily due to the multidimensional structure of the composite nanomaterial, which effectively prevents the penetration of oxygen molecules. Meanwhile, the improvement in resistance to ultraviolet aging is mainly due to the absorption and scattering characteristics of FSNPs. Therefore, OLDHs/FSNPs are demonstrated to be a cost-effective multidimensional nano-modifier.

Organic petrography and geochemistry of the Fu 2 member of the Paleocene Funing formation, Gaoyou Depression, Subei Basin, Eastern China: Implications for shale oil potential

The Fu 2 Member of the Paleocene Funing Formation in the Gaoyou Depression, Subei Basin is an organic matter-rich formation, and has a high potential for shale oil exploration and exploitation. Total organic carbon (TOC), organic petrography, Rock-Eval pyrolysis, chloroform bitumen “A” extraction, and SARA (saturates/aromatics/resins/asphaltenes) composition analyses of shale samples from one drill core in the studied area spanning a thickness of 257 m were conducted to study the organic matter (OM) richness, kerogen type, maceral composition, hydrocarbon generation potential, and oil content of the Fu 2 Member. Results show that the Fu 2 Member shales in the study area have a Ro of 0.87%, in the peak oil window, suggesting a high potential for hydrocarbon generation. The studied OM in shales mainly belongs to kerogen Type II, with a minor portion of Type I and Type III. Under microscopic observation, macerals in the studied shales are mainly composed of vitrinite, inertinite, alginite, and solid bitumen. The studied shales have an average TOC content of 1.41 wt%, indicating good petroleum potential. The variations of maceral compositions could affect the reliability when the Tmax is used as an indicator of thermal maturity. The lower Shale 4 and upper Shale 5 interval (3650–3700 m), with high TOC and high oil saturation index, is identified as the sweet-spot interval of the Fu 2 Member for shale oil exploration.

Adsorbing Volatile Organic Compounds within Bitumen Improves Colloidal Stability and Air Quality

The mass loss of bitumen due to volatilization is one of the deterioration mechanisms through which the chemical composition of bitumen deviates from its original condition, leading to change in the physical and rheological properties of bitumen. The emissions from bitumen not only accelerate its aging but also negatively impact air quality and consequently human health. Here, we characterized the molecular compositions of the volatiles emitted from bitumen in an isothermal aging process (150 °C for 24 h). We also investigated the impact of losing these compounds on the association behavior of asphaltene stacks. Based on the GC-MS results, the main mass loss of SARA (saturates, aromatics, resins, asphaltenes) fractions is attributed to the emission of lightweight nonpolar aromatic and aliphatic compounds. The most dominant volatiles are single-ring aromatics carrying short side chains, followed by saturated and unsaturated aliphatic compounds including short-chain n-alkanes, iso-alkanes, cyclic alkenes, alkenes, and dienes. Using molecular modeling in the framework of density functional theory (DFT), we showed how the reduction in aromatics and saturates can impact the colloidal stability of asphaltenes in the matrix of bitumen. Based on the DFT results, the surface adsorption of aromatics and saturates on asphaltene planes provides the steric repulsion required to maintain the asphaltene planes at a distance sufficient to inhibit their agglomeration. In addition, aromatic molecules with the least hindrance repulsion can disturb the π–π interfacial interactions between asphaltene planes, facilitating their deagglomeration. Therefore, a direct consequence of the mass loss of bitumen due to volatilization is disturbing the asphaltene distribution within the bitumen and stimulating the aggregation of asphaltenes. We also studied the merits of incorporating biochar into the bitumen surface to reduce bitumen’s mass loss. Modification of bitumen separately with each of six biochars derived from biomass feedstocks (walnut shell, peanut shell, Douglas fir, pine bark, birch, and algae) showed the efficacy of each biochar to reduce the volatiles emitted from bitumen, thereby reducing the changes in the composition of maltene with consequent colloidal stability losses. The study outcomes highlight the importance of reducing emissions from bitumen to delay its aging and minimize negative impacts on air quality and human health.

Investigation of changing SARA and fatigue properties of asphalt bitumen under ageing and analysis of their relation based upon the BP neural network

Thermal oxidation has a significant effect on asphalt binders’ saturates, aromatics, resins, asphaltenes (SARA) fractions and fatigue properties, but its effect on the SARA of different asphalt binders and the relation between SARA and the fatigue performance is not clear. In this study, thin layer chromatography/flame ionization detection (TLC/FID) was applied to analyze the SARA of the 36 specimens of original, short-term aged, and long-term aged asphalt binders. And then the viscoelastic continuum damage (VECD) model was applied to analyze these asphalt binders’ fatigue. Finally, the relation between SARA and the binders’ fatigue was determined by back-propagation (BP) neural network. The results showed that asphalt ageing can be considered to be the conversion of the light constituents to heavy constituents but the conversion ratios differed significantly for different asphalt binders. Asphalt binders of the same grade but different origins may have completely different mechanical properties and exhibit an entirely different composition conversion during ageing. Saturates can be considered the most inert constituent in asphalt. The oil source is the critical factor that determines the SARA and its degree of change during ageing. Ageing increased all of the asphalt binders’ fatigue life under a low strain level, but decreased it under high strain. The fatigue performance of asphalt binders with the same oil origin and grade but different manufacturers, did not differ significantly, either in the original or the aged states. Further, training the BP neural network showed that asphaltenes had the most significant effect on the asphalt’s fatigue behavior, followed by the resins and saturates, while aromatics had a minimal effect. And the BP neural network can forecast asphalt binders’ fatigue performance accurately based upon the SARA.

Low-field NMR investigations on dynamics of crude oil confined into nanoporous silica rods and white powder.

In the present study, to mimic the natural confinement of crude oils, model experiments are conducted with crude oils having different physical properties and maltenes of parent crude oils without asphaltenes confined into engineered nanoporous silica rods with pore diameters of 2.5 and 10.0nm and white powdered nanoporous silica with pore diameters of 2.5 and 4.0nm. This will help with suggesting potential treatments for enhancing crude oil recovery. Low-field nuclear magnetic resonance (LF-NMR) relaxometry has been applied to achieve this goal. The nanoporous proxies resemble real-life nanoporous rocks of reservoirs. The dynamics of confined crude oils with different oAPI gravity deviate from bulk dynamics, and deviation changes depending on the oAPI gravity. This suggests that treatments must be decided appropriately before crude oil production. Similar treatments could be applied for light and medium-heavy crude oils. Mathematical analysis of NMR relaxation curves of confined crude oils with different fractions of SARA (saturates, aromatics, resins, asphaltenes) indicates that the conventional SARA approach needs a better definition for the confined state of matter. The NMR relaxation behavior of confined maltenes shows that resin molecules might act like saturates in natural confinement with various scale pores from nano to micro and even macro, or aromatics might show resin-like behaviors. Confinement of brine and a light crude oil into white powdered nanoporous silica proxies demonstrates that brine could be utilized along with some additives such as nanoparticles for oil recovery. Therefore, these issues must be evaluated in deciding the proper treatments for crude oil production.

SARA-based kinetic model for non-catalytic aquathermolysis of heavy crude oil

A new kinetic model based on SARA (Saturates, Aromatics, Resins, Asphaltenes) fractions for the non-catalytic aquathermolysis of heavy crude oil is proposed. The aquathermolysis experiments were carried out with Ashal'cha heavy oil in batch reactor at different reaction times (12–72 h) and temperatures (250 and 300 °C). Different reactions in series and in parallel were considered in the model. The optimal values of estimated kinetic parameters were verified by sensitivity analysis. Residual analysis, parity plot, and average absolute error (less than 5%) demonstrated that the proposed kinetic model for the non-catalytic aquathermolysis of heavy crude oil fits well the experimental data.

Effect of solvent on the adsorption behavior of asphaltene on silica surface: A molecular dynamic simulation study

In recent years, the hybrid thermal-solvent process has been widely applied to improve the recovery performance of steam injection processes in heavy oil reservoirs. In this paper, the method of Molecular Dynamics (MD) simulation is employed to illuminate the asphaltenes adsorption behavior in the thermal-solvent recovery process. Three different solvent molecules (CO2, C3H8, and nC4H10) and SARA (Saturates, Aromatics, Resins, Asphaltenes) simulated heavy oil model are constructed as the basic simulation model. A series of MD simulations at different temperature conditions are performed. Results show that for the SARA model, the asphaltene molecules can interact with the silica by a T-shape stacking, finally forming the asphaltene dense aggregates as a basic heavy oil occurrence state. The steric hindrance effect of other SARA components can also contribute to this configuration. Temperature significantly affects the adsorption configuration of asphaltenes by disassembling the dense core and loosening the structure of the aggregates. For the SARA model in three solvent atmospheres, the increasing temperature can benefit the extraction of light components. CO2 can only extract saturates, while nC4H10 and C3H8 can simultaneously extract the saturates and aromatics. Besides, asphaltenes re-precipitation behavior can be observed in the 393 K CO2 atmosphere. Both nC4H10 and C3H8 have mutual solubility with the heavy oil system. No apparent precipitation of asphaltenes occurs in the above two atmospheres. Comparing the performance of extraction capability and diffusion capability in all MD simulations, the nC4H10 can both extract light oil components and control the asphaltenes precipitation. It further reveals that nC4H10 can recover heavy oil more efficiently at a microcosm level. Among the three different solvents, nC4H10 is the optimal solvent for hybrid thermal-solvent processes in heavy oil reservoirs.

Performance evaluation and improvement of PC-SAFT equation of state for the asphaltene precipitation modeling during mixing with various fluid types

One of the significant problems of the upstream flow assurance community is precipitation or deposition of asphaltene that leads to affect the economics of oil production seriously. Knowledge of asphaltene onset pressure (AOP) and amount of asphaltene precipitation in the change of temperature, pressure, and composition is the essential information for preventing this problem. Recent studies have shown that thermodynamic models based on the solubility nature of asphaltenes using an equation of state (EOS) are the most effective approach to asphaltene behavior modeling. In this research, the common version of the SAFT equation, known as the Perturbed Chain form of Statistical Association Fluid Theory (PC-SAFT) EOS without using association terms, has been employed and evaluated during the pure gas and other fluid types injection or mixing. In the case of pure gas injection (single components, for instance, N2 or CO2 injection), the model results have shown that using the reference values of the PC-SAFT parameters (m, σ, ε/k), those are reported in the literature, may not predict the weight percentage of the asphaltene precipitation accurately. It will be shown that considering these parameters as the adjustable variables can improve the model prediction for the asphaltene precipitation behavior. Furthermore, a new methodology has been suggested to characterize the injection fluid while its SARA (Saturates-Aromatics-Resins-Asphaltenes) analysis is not reported. This methodology is established in accordant with the material balance concept; in fact, the distribution of SARA fractions for the injection fluid will be estimated from the characterized crude oil. Six systems of crude oil and injection fluid, including pure N2, pure methane, pure CO2, wet gas, and liquid condensate, have been taken under study to evaluate the accuracy and flexibility of the proposed methodology by comparing to the available asphaltene experimental data.

SARA-Based Correlation To Describe the Effect of Polar/Nonpolar Interaction, Salinity, and Temperature for Interfacial Tension of Low-Asphaltene Crude Oils Characteristic of Unconventional Shale Reservoirs

Summary Oil/water interfacial tension (IFT) is an important parameter in petroleum engineering, especially for enhanced-oil-recovery (EOR) techniques. Surfactant and low-salinity EOR target IFT reduction to improve oil recovery. IFT values can be determined by empirical correlation, but widely used thermodynamic-based correlations do not account for the surface-activities characteristic of the polar/nonpolar interactions caused by naturally existing components in the crude oil. In addition, most crude oils included in these correlations come from conventional reservoirs, which are often dissimilar to the low-asphaltene crude oils produced from shale reservoirs. This study presents a novel oil-composition-based IFT correlation that can be applied to shale-crude-oil samples. The correlation is dependent on the saturates/aromatics/resins/asphaltenes (SARA) analysis of the oil samples. We show that the crude oil produced from most unconventional reservoirs contains little to no asphaltic material. In addition, a more thorough investigation of the effect of oil components, salinity, temperature, and their interactions on the oil/water IFT is provided and explained using the mutual polarity/solubility concept. Fifteen crude-oil samples from prominent US shale plays (i.e., Eagle Ford, Middle Bakken, and Wolfcamp) are included in this study. IFT was measured in systems with salinity from 0 to 24% and temperatures up to 195°F.

Surfactants Enhanced Heavy Oil-Solid Separation from Carbonate Asphalt Rocks-Experiment and Molecular Dynamic Simulation.

In this study, surfactants were used to enhance heavy oil–solid separation, and a detailed mechanism was explored by SARA (saturates, aromatics, resins, asphaltenes) analysis, element analysis, AFM measurement, and molecular dynamic simulation. Surfactants could effectively decrease oil/solid interaction force and then oil–solid separation would be enhanced. The oil–solid interactive force was in relation to surfactants concentration, pH value, asphaltene content, and salinity. The molecular dynamics simulation results show that the dissociation of saturated hydrocarbon, aromatic hydrocarbon, resin, and asphaltene (SARA) on carbonate minerals is gradually weakened for all surfactants. In the process of molecular dynamics simulation of surfactant stripping SARA, firstly, the surfactant molecules adsorb on the surface of SARA molecules. After that, the surfactant peels SARA molecules off the surface of calcite under the influence of molecular thermal motion. In this process, surfactant molecules will not be directly adsorbed on the surface of trace minerals. The results of energy/temperature balance indicated that saturates, aromatics and resins could remain stable when the molecular dynamics simulation time reached 2000 ps with the phenomenon that saturates, aromatics could liberate from minerals totally within 2000 ps. The molecular dynamics simulation of asphaltenes will not liberate from calcite surface within 6000 ps, meanwhile, they could not reach the energy balance/energy balance within 6000 ps. The functional groups of surfactant molecules would have interactions with the SARA functional group, resulting in different dissociation effects of SARA. The results of molecular dynamics simulation are consistent with the experiment results. The separation effect of saturated hydrocarbon, aromatic hydrocarbon, resin, and asphaltene in five kinds of surfactants were different. The molecular dynamic simulation results were in accordance with the SARA analysis.

Characterization, fate and impact of ISB products from different types of crude oils: Literature review and experimental study for ISB predictive modelling and SIMA process

In situ burning (ISB) is an OSR (Oil Spill Response) technique generally not accepted as a “standard” response by most regulators. Main reluctance generally comes from the occurrence of large and dark smokes plumes as well as possible heavy burn residues likely to sink and reach the seafloor. However, ISB has been widely used during the Macondo oil spill in 2010 and highlighted as a promising operational technique. Additionally, standard OSR modeling tools do not consider ISB, as there is a lack of knowledge in the capacity to predict accurately the physico-chemical characteristics, fate and ecotoxicity, of the burn products from large varieties of crude oils. In order to provide dispassionate arguments, we have conducted a study to gain knowledge and try to develop predictive capabilities to infer composition and fate of burn products from characteristics of starting crude oils. The study comprises both large literature review and experimental work where six crude oils of different types (along with corresponding weathered oils) were burnt, and all products quantified and analyzed (physico-chemistry), at both laboratory scale (burning bench) and pilot scale (fire platform). Additionally, ecotoxicity testing on Vibrio fischeri bacteria and Phaeodactylum tricornutum algae were conducted on crude and weathered oils, burn residues, water and soot. The fate of burn residues was also investigated through dispersibility, emulsification and biodegradability testing. The experimental work led to a very large set of data which was subject to multivariate regression statistical treatments to build predictive models. Main data investigated were burn efficiency, density, viscosity, SARA (Saturates, Aromatics, Resins, Asphaltenes) composition, n-alkanes and PAHs (polycyclic aromatic hydrocarbons) distributions in burn residues, gas emissions composition, soot' PAHs distribution in the smokes, and ecotoxicity data of burn residues, soot and water. The paper describes the main results of this study, with promising outcomes to develop predictive ISB modeling and help addressing objectively the relative impact of ISB within the SIMA process in comparison with other cleaning responses.

Accurate prediction of the viscosity of light crude oils using one-parameter friction theory: Effect of crude oil characterization methods and property correlations

The one-parameter friction theory framework using the Peng-Robinson equation of state (PR FT) (Quiñones-Cisneros et al., Fluid Phase Equilibria, 2001) is applied for the viscosity modeling of light, crude oils. Three different methods have been implemented to characterize and determine the composition of these fluids: SARA-based method using the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT) EoS (Punnapala and Vargas, Fuel, 2013), SARA-based method using the PR EoS (Abutaqiya et al., Energy & Fuels, 2020), and Single Carbon Number (SCN) method using the PR EoS (Pedersen and Christensen, Taylor & Francis Group, 2007). Both SARA-based methods use the Saturates-Aromatics-Resins-Asphaltenes (SARA) content analysis. Additionally, two different property correlation sets have been used with each characterization method to estimate the critical properties of the generated pseudo-components: Evangelista and Vargas (EV) correlations (Evangelista and Vargas, Fluid Phase Equilibria, 2018) and Pedersen correlations (Pedersen and Christensen, Taylor & Francis Group, 2007). The predictive capabilities of the different modeling schemes are tested against experimental viscosity data for 10 light crude oils from the Middle East after fitting the friction theory parameters to a single viscosity data point at saturation condition. A systematic comparison of the characterization methods revealed that the SARA-based methods with either EoS predict viscosity with higher accuracy (below 5% AAPD) than the SCN method (above 5% AAPD), irrespective of the correlations used. Despite using the relatively simpler PR EoS with SARA-based method, the viscosity predictions are as good as the predictions obtained using the highly advanced PC-SAFT EoS.

A Detailed Look at the Saturate Fractions of Different Crude Oils Using Direct Analysis by Ultrahigh Resolution Mass Spectrometry (UHRMS)

SARA (Saturates, Aromatics, Resins, Asphaltenes) fractionation is a common simplification technique used for decades in petrochemical analysis. A large number of studies are dealing with the different fractions, but overall, the saturate fraction is strongly neglected. Of the very few available studies on the saturates fraction, almost all have been performed using gas chromatographic (GC) techniques. This discriminates the results of the saturate fraction especially since non-volatile, high molecular weight and polar constituents are mostly excluded. Here, for the first time, saturate fractions of different crude oils from different origins are analyzed using direct infusion ultrahigh resolution mass spectrometry (UHRMS), to study the compositions on a molecular level. Electrospray (ESI), atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) are used in positive mode. The observed results show the presence of different heteroatom containing classes, with different chemical identities (i.e., presence of thiophenes, mercaptans and cyclic-sulfides in case of S-containing compounds). These results show the high affinity of some specific compounds towards different ionization techniques. Finally, the saturate fraction is shown to include much more than only volatile, saturated and aliphatic compounds. The detected compounds in this fraction present a very wide variety, not only in terms of their carbon atoms per molecule and their aromaticity, but also with regard to their functional groups and structural arrangements.

On the Optimum Aging Time: Magnetic Resonance Study of Asphaltene Adsorption Dynamics in Sandstone Rock

Wettability is a key factor defining ultimate hydrocarbon recovery. Extensive experimentation is required to replicate the wetting state of reservoir rocks. This involves a rock sample wettability restoration procedure, including an aging step and a concept of an optimum aging time, in which asphaltene chemistry plays a major role. There are numerous reports on significance of various crude oil components and elements of asphaltene structure to their tendency to interact with the solid phase, though subject evidence is contradictory. We investigate a possible relationship between the composition of oil, kinetics of an aging process, and a change of sandstone rock wettability. Wettability state of the cores was monitored using low-field NMR relaxometry. The composition and key components of accumulated deposits were established by matching 1H solution-state NMR and X-band EPR spectra of deposits to the spectra of SARA (saturates-aromatics-resins-asphaltenes) fractions of aging fluids. We determined adsorpt...

Integrative Investigation of Low-Temperature Oxidation Characteristics and Mechanisms of Heavy Crude Oil

During an in situ combustion (ISC) process, low-temperature oxidation (LTO) is of vital significance for the follow-up oxidation reactions and oil recovery. Herein, this work is intended to carry out in-depth investigations regarding LTO of heavy crude oil. Alterations of evolved gas compositions and oil properties caused by LTO were first examined. Then the particular focus was placed on the analyses of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) of oxidized oil samples. The results indicated that the LTO degree was intensified with the oxidation temperature, during which produced gas compositions and the contents of element, saturates–aromatics–resins–asphaltenes (SARA) fractions, free radicals, and hydrogen groups of oils changed obviously. Furthermore, part of the main LTO reactions are given in this paper. On the basis of these reactions and experimental results obtained, some aspects of LTO mechanisms of the oil are stated, which were highly valuable for ISC field appl...

A theoretically modified PC-SAFT equation of state for predicting asphaltene onset pressures at low temperatures

This paper presents a modified perturbed chain-statistical association fluid theory (mod-PC-SAFT EoS) obtained by including into PC-SAFT the second-order dispersion term developed originally by Zhang [Fluid Phase Equilibria, 154 (1999) 1–10] for pure components. This version of PC-SAFT was then used to predict asphaltene onset pressures (AOPs) for nine petroleum reservoir fluids with asphaltene contents, based on saturates-aromatics-resins-asphaltenes (SARA) analyses, varying from 0.80 to 16 wt%. In all modeled cases, this new version predicted less accelerated AOPs at low temperatures than the original PC-SAFT, and then the well-known and widely discussed tendency of PC-SAFT of predicting very high AOPs at these conditions was corrected. The new model also reduced or eliminated the crossover temperatures predicted by PC-SAFT when a reservoir fluid, prone to precipitate asphaltenes, was enriched with CO2.

Establishment of Wax Deposition Index from Saturates, Aromatics, Resins, Asphaltenes Analysis

Saturates, aromatics, resins, asphaltenes (SARA) analysis is one method of characterizing crude oils. It is versatile because it can apply to many components of the crude oil. SARA analysis furnishes one with the composition of any crude and ultimately gives an idea of the potential of the crude oil to precipitate and deposit wax. This analysis method usually breaks crude oil down into four components (saturates, aromatics, resins and asphaltenes) according their solubility and polarity. SARA analysis results are always reported in terms of these four components and may not easily be understood by most decision makers at a glance without some explanation from laboratory analysts. Most importantly SARA analysis plays a vital role in providing information on whether or not a particular crude oil is waxy, a role that is not always obvious. Wax deposition index (WDI) bridges this gap by providing a single number from SARA analysis that captures the waxing potential of the crude as well as the degree of the waxicity. In this study, WDI was tested using a wide variety of SARA results from across the globe and has been found to be consistent. WDI could therefore be combined with other methods to determine the frequency of wax removal operations. Keywords: SARA analysis, wax deposition index, waxicity

Effect of ageing on the microstructure of reclaimed asphalt binder with bio-based rejuvenators

Reclaimed asphalt pavement (RAP) has become an important source in asphalt pavement production for energy and cost savings. In this work, three different bio-based rejuvenators were added to the RAP binder: a vegetable oil, a cashew nut shell-based oil and a tall-based oil. Saturates-aromatics-resins-asphaltenes (SARA) analysis was performed to observe the evolution of different chemical fractions before and after ageing. Results suggested changes in chemical fractions after the addition of the rejuvenators; specifically a decrease of polar compounds. To better understand the binders’ morphology, atomic force microscopy (AFM) was used for topography investigation and phase detection. RAP binder morphology was significantly affected by the addition of rejuvenators. Furthermore, ageing had an effect not only at polar and non-polar fractions level but also at microstructural level. Aim of this work was to show how the addition of rejuvenators affected both the microstructure and the chemical fractions of RAP binder before and after ageing. Such evaluation can help developing guidelines for evaluating the rejuvenating effect in the RAP binder.

Phase-Behavior Modeling of Oils in Terms of Saturates/Aromatics/Resins/Asphaltenes Fractions

Summary One of the key steps toward improving the predictability of air-injection-based processes relies on the development of accurate phase-behavior models of the oil. Historically, for in-situ combustion (ISC) in heavy oils and bitumens, phase behavior was often ignored because the physical aspects of the process (e.g., distillation) were not considered to be as significant as the oxidation reactions. However, this step is important for several reasons. First, the compositional model should reflect the phase behavior of the original fluids. Second, reaction rates are dependent on the concentrations of the reactants, which in turn are affected by the volatility of the components. This is particularly important for lighter oils (but not unimportant for heavier oils), where the phase equilibrium between the liquid and vapor can have a significant effect on the flammability range for vapor-phase combustion at given temperature and pressure conditions. Finally, for the case of lighter oils, a good phase-behavior model is required to capture the compositional effects of the resulting flue-gas drive. This study presents a practical work flow to develop a phase-behavior model in terms of saturates/aromatics/resins/asphaltenes (SARA) fractions that is aligned with the reaction-modeling approach used in most kinetic models. The methodology requires conventional-oil-characterization (i.e., dependent on distillation cuts) and conventional-phase-behavior experiments (e.g., differential liberation), as well as oil characterization in terms of SARA fractions. The first step of the method consists of splitting the heaviest oil fraction (i.e., plus fraction), followed by lumping all of the single-carbon-number (SCN) components, in such a way that the new oil characterization honors the SARA data available, such as composition and the physical properties of each fraction (e.g., molecular weight). In addition, the gas components (e.g., methane) would be treated as additional components as necessary. The second step is to tune an equation of state (EOS), in terms of the SARA-based model, to match the relevant laboratory experiments. Finally, the tuned EOS would be used to export the equilibrium constants (K-value tables) to the thermal numerical simulator. Different examples on the application of the phase-behavior-modeling work flow are presented and discussed in detail for heavy and light oils. This work opens up opportunities to model the ISC process for any oil (i.e., light or heavy) using the currently available kinetic models, which in turn is an important step toward improving the predictability of ISC processes using reservoir simulation.