Saturates, Aromatics, Resins And Asphaltenes Analysis Research Articles

Innovations in Crude-Oil Characterization: A Comprehensive Review of LF-NMR Applications

The advent of low-field nuclear magnetic resonance (LF-NMR) has revolutionized the petroleum industry by providing a swift and straightforward method for the spectroscopic characterization of crude oil. This review paper delves into the significant strides made in LF-NMR technology since its inception by Felix Bloch and Edward Purcell in 1946, particularly its application in determining the composition, viscosity, and water content of crude oil, alongside SARA (Saturates, Aromatics, Resins, and Asphaltenes) analysis. LF-NMR’s ability to noninvasively quantify the total water and oil content, differentiate between bound and mobile phases, and measure the SARA fractions underscores its superiority over traditional analysis methods, which often suffer from interference and lack of precision. This manuscript not only highlights LF-NMR’s pivotal role in enhancing crude-oil characterization but also reviews recent developments that solidify its position as an indispensable tool in the petroleum industry. The convergence of empirical studies and technological advancements points toward a pressing need for further research to fully exploit LF-NMR’s potential and refine its application, ensuring its continued contribution to the efficient and accurate analysis of petroleum products.

Molecular simulation and experimental analysis on co-aging behaviors of SBS modifier and asphalt in SBS-modified asphalt

ABSTRACT Styrene-butadiene-styrene block copolymer (SBS) is the most commonly used asphalt modifier. Studying the aging process of SBS-modified asphalt and clarifying the role of SBS and asphalt in the aging process can provide a basis for the targeted regeneration of SBS-modified asphalt. In this research, the physical and chemical changes of SBS and asphalt in the aging process were studied by FTIR (Fourier Transform Infrared Spectroscopy) analysis and SARA (Saturate, Aromatic, Resin, and Asphaltene) analysis. The effects of the thermal oxidation of asphalt and SBS on the viscosity and tensile properties of the SBS-modified asphalt were investigated by Brookfield Rotational Viscosity Test, force ductility test, and molecular dynamics simulation. Furthermore, the influence of asphalt and SBS aging on the adhesion property of the asphalt-aggregate interface was analyzed. The results show that the impact of SBS aging on the increase of viscosity and tensile yield stress was far less than that of asphalt aging. The adhesion energy of the modified asphalt-silica interface increases with both aging of SBS and asphalt. SBS and asphalt jointly influence the performance of modified asphalt in the aging process, but asphalt aging is the dominant factor.

Iron oxide nanoparticles impact on improving reservoir rock minerals catalytic effect on heavy oil aquathermolysis

The past decade has seen a renewed importance in developing heavy oil reserves due to the rapid raise in energy resources’ demand. The next decade is likely to witness a considerable rise in extracting these resources by thermally enhanced oil recovery methods. However, many hypotheses regarding the influence of reservoir mineral components on aquathermolysis reactions appear to be disputable. This paper outlines a new approach to model the aquathermolysis of Aschalcha’s reservoir rock heavy oil in the presence and absence of iron oxide nanoparticles combined with hydrogen donor in water steam atmosphere at 200, 250, and 300 °C using different physical and chemical methods. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) have showed adsorbed spherical magnetite (Fe3O4) nanoparticles with less than 100 nm size on the studied rock minerals in hydrothermal conditions. Moreover, SARA (Saturates, Aromatics, Resins and Asphaltenes) analysis, gas analysis, and gas chromatography–mass spectrometry (GC–MS) have revealed that the obtained iron oxide nanoparticles exhibit their highest catalytic activity at 250 °C comparing to 200 and 300 °C respectively. What’s more, the obtained data have indicated a considerable decrease in resins (from 19.6 to 8.9 wt%) and asphaltenes compounds (from 5.1 to 1.5 wt%) in the presence of iron oxide nanoparticles comparing to the non-catalytic aquathermolysis of reservoir rock heavy oil. Contrary to resins and asphaltenes’ content, it has been found that saturates’ content increases significantly from 41.1% to 61.7% wt%. On another hand, the viscosity of the extracted oil has decreased almost 30 times and the gas proportion has doubled more than twice from 0.2 g to 0.43 g per 100 g of the reservoir rock sample. Interestingly, these results have been obtained in the presence of iron oxide nanoparticles at 250 °C, meanwhile, the same results have been found for the non-catalytic experiments at 300 °C. These findings confirm the significant contribution (synergistic effect) of iron oxide nanoparticles to stimulate the catalytic activity of the reservoir rock minerals. What’s more, the evidence from this study suggests that the presence of iron oxide nanoparticles in hydrothermal conditions at higher temperatures leads to the formation and adsorption of heavy coke-like carbenes, carboides, needle coke as well as carbon nanotubes of 100 nm size on the surface of the reservoir rock heavy oil as confirmed by thermal analysis (TG-DSC), SEM, and drop shape analysis (DSA) data.

Microscopic experimental and numerical research on rejuvenators: A review

Prompting high content of reclaimed asphalt pavement (RAP) to be used in road building and maintenance has drawn great attention. The application of rejuvenators is an efficient way to ensure the performance of recycled asphalt mixtures. However, as various types of rejuvenators emerging, limited understanding about rejuvenation poses challenges to put effective ones into use. For precisely evaluating the performance of rejuvenators, plenty of studies were conducted to ascertain the fundamental mechanism of rejuvenating from the microscopic view. This paper provides an overview of studies focusing on the change inside asphalt after adding rejuvenators. Chemical compositions of rejuvenators were collected as basic information. Both laboratorial experiments and molecular dynamic simulations were investigated to not only compare the effectiveness of several rejuvenators but also explain the rejuvenating mechanism. Finally, functional groups of rejuvenator structures were comprehensively examined to provide global understanding about how chemical compositions influence the efficacy of rejuvenators. This review highlights that the essential capacity of a true rejuvenator is to disturb asphaltene agglomerations. Besides, the molecular structures of rejuvenators will not only affect their deagglomerating abilities but also the performances of diffusion and durability. It has been found that gel-permeation chromatography (GPC) analysis is effective in evaluating the performance of rejuvenators, while Fourier transform infrared spectroscopy (FT-IR) and SARA (saturates, aromatics, resins and asphaltenes) analysis are only suitable for assessing asphalt oxidization. In addition, comparing some tests can only detect changes, molecular dynamic simulation can reveal the mechanism both of data and vision. The results of this work can provide comprehensive knowledge for the evaluation and development of rejuvenators.

The Influence of Oil Composition, Rock Mineralogy, Aging Time, and Brine Pre-soak on Shale Wettability.

Experimental and field studies have indicated that surfactants enhance oil recovery (EOR) in unconventional reservoirs. Rock surface wettability plays an important role in determining the efficacy of this EOR method. In these reservoirs, the initial wettability of the rock surface is especially important due to the extremely low porosity, permeability, and resulting proximity of fluids to the solid surface. This study is designed to investigate the effect of oil components, rock mineralogy, and brine salinity on rock surface wettability in unconventional shale oil/brine/rock systems. Six crude oils, seven reservoir rocks, and seven reservoir brine samples were studied. These oil samples were obtained from various shale reservoirs (light Eagle Ford, heavy Eagle Ford, Wolfcamp, Middle Bakken, and Three Forks) in the US. SARA (saturates, aromatics, resins and asphaltenes) analysis was conducted for each of the crude oil samples. Additionally, this study also aims to provide a guideline to standardize the rock sample aging protocol for surfactant-related laboratory experiments on shale reservoir samples. The included shale reservoir systems were all found to be oil-wet. Oil composition and brine salinity showed a greater effect on wettability as compared to rock mineralogy. Oil with a greater amount of aromatic and resin components and higher salinity rendered the surface more oil-wet. Rock samples with a higher quartz content were also observed to increase the oil-wetness. The combination of aromatic/resin and the quartz interaction resulted in an even more oil-wet system. These observations are explained by a mutual solubility/polarity concept. The minimum aging time required to achieve a statistically stable wettability state was 35 days according to Tukey’s analysis performed on more than 1100 contact angle measurements. Pre-wetting the surface with its corresponding brine was observed to render the rock surface more oil-wet.

Full range temperature susceptibility of aged bitumen rejuvenated by polymer modified bio-derived rejuvenator

In this work, a polymer modified bio-derived rejuvenator consisting of bio-oil, polymer modifier, and other additives (plasticizer, cross-linking agent) was developed. Commercial rejuvenator (CR), bio-based rejuvenator (BR), and polymer modified bio-derived rejuvenator (PMBR) were applied to rejuvenate the aged base bitumen and styrene–butadiene–styrene (SBS) modified bitumen. The relationships between temperatures and properties of rejuvenated aged bitumen gained from Bending Beam Rheometer test (BBR), Dynamic Shear Rheometer test (DSR), and Rotational Viscosity test (RV) were utilized to evaluate the temperature susceptibility under full temperature range corresponding to various circumstances like preparation, construction, and service processes. Subsequently, the chemical fractioning of aged bitumen before and after rejuvenation were characterized via Saturates Aromatics Resins and Asphaltenes Analysis (SARA). The results showed that PMBR at proper dosages performed satisfactorily in rejuvenating the aged bitumen. However, PMBR presented better long-term performance on rejuvenating SBS modified and base bitumen compared with conventional rejuvenators. Moreover, the temperature susceptibility of PMBR rejuvenated bitumen was preferable to that of CR and BR rejuvenated bitumen in full temperature range. Finally, the SARA results showed that PMBR could readjust polar and non-polar fractions to make rejuvenated bitumen more like gel structure. This can explain the temperature susceptibility of PMBR rejuvenated bitumen.

Low-field NMR-relaxometry as fast and simple technique for in-situ determination of SARA-composition of crude oils

In this study a new, fast and simple method based on low field NMR-relaxometry for in-situ determination of SARA (saturates, aromatics, resins and asphaltenes) composition of crude oils was proposed. This method was tested on 22 samples of crude oils with a wide range of SARA-composition and API gravity values (4.6–42.0°), including extra-heavy, heavy, medium and light crude oils. Results obtained by low-field nuclear magnetic resonance (LF-NMR) were compared with conventional SARA analysis method (ASTM D 4124). Comparison shows good coincidence between SARA values determined by LF-NMR and conventional method data for heavy fractions of asphaltenes and resins (R2 is equal to 0.98 and 0.91, respectively) and for the sum of light fractions including saturates and aromatics (R2 = 0.96). However, comparison for saturated and aromatic compounds separately gave low correlation coefficients (R2 ≤ 0.61 and 0.27, respectively) and relatively soaring standard deviation for individual correlations for saturates and aromatics (8.18 and 9.20). Consequently, LF- NMR relaxation as an alternative method for studying the composition of crude oil allows the determination of asphaltenes, resins and the sum of light fractions (saturates and aromatics) without their extraction (in-situ), which greatly simplifies and accelerates conventional chromatographic analysis. This method can be successfully applied for different types of crude oils with a wide range of API gravity and viscosity values.

Genetic algorithm based support vector machine regression for prediction of SARA analysis in crude oil samples using ATR-FTIR spectroscopy.

In the current research, an analytical method was proposed for rapid quantitative determination of saturates, aromatics, resins and asphaltenes (SARA) fractions of crude oil samples. Rapid assessments of SARA analysis of crude oil samples are of substantial value in the oil industry. The conventional SARA analysis procedures were determined with the standards established by the American Society for Testing and Materials (ASTM). However, the standard test methods are time consuming, environmental nonfriendly, expensive, and require large amounts of the crude oil samples to be analyzed. Thus, it be would useful to approve some supportive approaches for rapid evaluation of the crude oils. The attenuated total reflection Fourier-transform infrared spectroscopy ATR-FTIR coupled with chemometric methods could be used as analytical method for crude oil analysis. A hybrid of genetic algorithm (GA) and support vector machine regression (SVM-R) model was applied to predict SARA analysis of crude oil samples from different Iranian oil field using ATR-FTIR spectroscopy. The result of GA-SVM-R model were compared with genetic algorithm-partial least square regression (GA-PLS-R) model. Correlation coefficient (R2) and root mean square error (RMSE) for calibration and prediction of samples were also calculated, in order to evaluate the calibration models for each component of SARA analysis in crude oil samples. The performance of GA-SVM-R is found to be reliably superior, so that it can be successfully applied as an alternative approach for the quantitative determination of the SARA analysis of crude oil samples.

Hydrogen donating capacity of water in catalytic and non-catalytic aquathermolysis of extra-heavy oil: Deuterium tracing study

The goal of this work is to try to figure out the role of water in catalytic and non-catalytic aquathermolysis by using isotope tracing techniques. For this purpose, heavy water (deuterium oxide, D2O) was used to replace the ordinary water (H2O) for catalytic and non-catalytic aquathermolysis processes of extra-heavy oil with high sulfur content in autoclave. The donating and upgrading performance of D2O were deeply investigated by analyzing the upgraded (deuterated) oil and their SARA (saturates, aromatics, resins and asphaltenes) fractions using different tracing techniques (FTIR, isotope and elemental analysis), evolved gases by GC, and change in physical-chemical properties of upgraded (deuterated) oils by viscosity measurement, SARA analysis, elemental analysis and GC, etc. The results proved the chemical role of water as a green and environmental hydrogen-donor solvent during aquathermolysis process, verified by considerable deuterium substitution (deuteration) obtained from isotope analysis both in upgraded oil and SARA fractions. The results are further supported by significant deuterium exchanges (deuteration) of aliphatic and aromatics parts in the initial and deuterated oil samples and their individual SARA fractions in FTIR spectra. Simultaneously, introducing Ni-tallate as an oil-soluble catalyst promoted the donating capacity of water, thus significantly improving the upgrading performance. The important finding about the role of water in catalytic and non-catalytic aquathermolysis not only enriches the theoretical basis in this area, but also provides a strong support for the use of catalysts in aquathermolysis for improving in-situ heavy oil upgrading performance.

Short- and Long-Term Epoxy Modification of Bitumen: Modification Kinetics, Rheological Properties, and Microstructure.

Aiming to gain knowledge in the epoxy-bitumen modification mechanisms, this work explores the effects that epoxy concentration and ambient curing exert on the physico-chemistry and thermo-rheological properties of epoxy-modified binders. Process rheokinetics of epoxy-bitumen blends indicates that binder short-term modification (i.e., during processing) is accelerated by epoxy concentration. Furthermore, a synergistic effect of epoxy concentration and ambient curing is found during long-term modification (i.e., during curing at ambient conditions). As a result, viscous and viscoelastic rheological properties of binders are enhanced at medium/high in-service temperatures, at least, after one month of curing. FTIR (Fourier Transform Infrared spectroscopy) tests and SARAs (Saturates, Aromatics, Resins and Asphaltenes) analysis confirm the existence of esterification/etherification reactions between epoxy oxirane groups and the carbonyl groups available in aromatic and resin molecules. Thus, the new high molecular weight compounds increase the asphaltenic fraction of modified bitumen. Likewise, nonreversing heat flow curves obtained by modulated calorimetry corroborate the formation of such highly structured domains responsible for the final binder performance.

Effect of different viscous rejuvenators on chemical and mechanical behavior of aged and recovered bitumen from RAP

Due to scarcity of virgin natural materials, the use of reclaimed asphalt pavement (RAP) has been promoted and encouraged in pavement engineering. However, note that the bituminous binder in RAP has been seriously aged due to long-term service exposure to the atmosphere. It is thus paramount to effectively restore properties of the RAP by adding proper rejuvenators. In this study, five rejuvenators were designed with different viscosities and applied to rejuvenate the aged binder. The changes in chemical compositions of bitumen caused by ageing and rejuvenating were evaluated by a SARA (Saturate, Aromatic, Resin and Asphaltene) analysis method. Brookfield viscosity, Dynamic Shear Rheometer (DSR) and Direct Tension (DT) were further conducted to evaluate the physical and mechanical properties of bituminous binders. Surface Free Energy test was applied to characterize the adhesion and moisture damage behavior of aged and rejuvenated binders. The experimental results showed that the ageing process increased resins and asphaltenes, which in turn improved the colloidal stability of the aged binder. The five rejuvenators designed in this research had a similar effect in restoring the rheological properties and stiffness of the aged bitumen to a similar level as that of the virgin binder. However, the viscosity level of rejuvenator has different impacts on tensile elongation at break, brittle fracture stress, adhesion property and moisture resistance of rejuvenated binders, in which the rejuvenator with an optimal viscosity may obtain the best rejuvenating performance.

Asphaltene Stability of Some Iraqi Dead Crude oils

Asphaltene is one of the fractions of the crude oil which is soluble in aromatics such as benzene or toluene and insoluble in alkane such as n-heptane, n-pentane or petroleum ether (mixture of alkane compounds). Asphaltene precipitation is one of the most common problems that sometimes occurs in both oil recovery and refinery processes as a result of changing in pressure, oil composition, or temperature. Therefore the stability of asphaltene in the crude oil must be studied to show the tendency of it for precipitating asphaltene to prevent it (Asphaltene precipitation and deposition problem) and eliminate the burden of high treatment costs.
 In the present study, saturate, aromatic, resin and asphaltene (SARA) analysis of the six dead crude oil samples from different Iraqi oil fields was conducted by using open column liquid chromatography after separating the asphaltene from them through filtration process. The asphaltene stability of dead crude oil samples was studied depending on changing the composition of them by adding the petroleum ether as an alkane and using colloidal instability index (CII) to determine the tendency of these crude oil samples to precipitate asphaltene depending on the SARA analysis results of these dead crude oils.
 All of dead crude oil samples showed the instability of asphaltene depending on this index and this means that all of them might precipitate asphaltene if the composition of these crude oil samples changed due to existing with the alkane in the live case in wells (Live oil is oil containing gas phase at reservoir conditions) such as injection of gas which has high ratio of alkane or the expanding the gas in the oil when the pressure decreases until reaches bubble point pressure.
 The refractive index of the dead crude oil samples was measured experimentally and calculated by two correlations which were Fan et al. correlation and Chamkalani correlation. The last one showed the best match between the experimental and calculated values of the refractive index of the dead crude oil samples.
 

Morphological insights into the catalytic aquathermolysis of crude oil with an easily prepared high-efficiency Fe3O4-containing catalyst

Elucidating the underlying structure-performance relationship of Fe3O4-containing catalysts for the aquathermolysis of crude oil is essential for the design of efficient heterogeneous catalysts. Therefore, recyclable Fe3O4 nanoparticles (NPs) with different morphology and particle size were first prepared and tested for catalytic aquathermolysis. The easily prepared Fe3O4 NPs with irregular morphology (L-Fe3O4) have larger intercrystalline mesopores than oleic acid-modified Fe3O4 NPs. This leads to enhanced mass transfer ability, more accessible active sites and thus better aquathermolysis performance. Moreover, these L-Fe3O4 NPs were loaded on a heulandite support by a scalable co-precipitation method, and this L-Fe3O4/heulandite catalyst showed very good performance in catalytic aquathermolysis, with a viscosity decrease of extra-heavy crude oil of 85.0%. The underlying structure-performance relationship was systematically investigated by XRD, HRTEM, EDX-mapping, FT-IR, elemental analysis, SARA (saturate, aromatic, resin and asphaltene) analysis and 1H NMR. The Fe3O4/heulandite catalyst broke C–S bonds and reduced the resin and asphaltene content of the oil. This work is important for the design of Fe3O4-containing catalysts in catalytic aquathermolysis.

What are the Alternatives of PG Plus Tests for Modified Asphalt Binders?

For characterizing the polymer modified binders, different state Departments of Transportation (DOTs) use different time consuming and empirical Performance Grade (PG) Plus test methods. Furthermore, the PG Plus tests are silent when asphalt binders are modified with chemicals such as polyphosphoric acid (PPA). But, the effects of the polymer are not accurately identified through these conventional tests such as Elastic Recovery (ER) and tenacity. The main goal of this study is to recommend alternative test method(s), which can possibly be pursued by using, a Dynamic Shear Rheometer (DSR). Thus, Multiple Stress Creep and Recovery (MSCR), ER-DSR, Frequency Sweep, and Binder Yield Energy Test (BYET) are being explored to find their effectiveness. Three PG binders (PG 64-22, PG 70-22 and PG 76-22) have been selected for this investigation. These binders have been prepared with styrene-butadiene-styrene (SBS) polymer, PPA, or a combination of both. Further, chemical tests such as SARA (Saturate, Aromatic, Resin, and Asphaltene) analysis and FTIR (Fourier-transform Infrared spectroscopy) are also being explored to fulfill the objectives. Preliminary findings suggest that the PG Plus tests deem to be obsolete. Also, a single test procedure is not sufficient to identify the presence and effectiveness of modifiers in the PG binders.

Catalytic Aquathermolysis of High-Viscosity Oil Using Iron, Cobalt, and Copper Tallates

The results of a study of the composition of active forms of the catalyst formed upon degradation of the precursor, based on the results of physical modeling of a sample of high-viscosity oil having high asphaltene and resin contents, are presented. Oil-soluble iron, cobalt, and copper tallates were used as the objects of the study. The composition of the separated powder of the active form of the catalyst was determined by X-ray diffraction analysis, and the catalyst particle size was determined by scanning electron microscopy. The SARA (saturate, aromatic, resin and asphaltene) analysis data revealed a marked decrease in high-molecular-weight oil components due to thermocatalytic cracking. The basic transformation mechanism is breakdown of the high-molecular-weight compounds along the sulfur-bearing bonds, as indicated by elemental CHNS (carbon, hydrogen, nitrogen and sulfur) analysis data. It is shown that the cobalt- and copper-based oil-soluble complexes turn are converted to sulfide forms and the iron-based complex is converted to the oxide form. According to the results of scanning electron microscopic analysis of the catalyst, the particle size is about 60 nm.

Evaluation of mechanical properties and aging index of 10-year field aged asphalt materials

Ten years’ field aged asphalt specimens have collected and being detailed studied. The aging index, viscoelastic behavior of aged binder recovered from the cored specimens, indirect tensile strength and residual fatigue life of the top layer and underneath layer were studied. Saturates, Aromatics, Resins and Asphaltenes (SARA) analysis and Fourier Transform Infrared Analysis (FTIR), viscoelastic analysis, Indirect Tensile (IDT) resilient modulus and fatigue test were performed.Both SARA, FTIR and viscoelastic analysis indicates that traffic loading does have positive degradation influence on asphalt binder. FTIR shows that traffic loading has limited influence on the chemic changes of SO compounds, while has positive contribution on degrading the CC bonds and hence promotes the oxidize aging. Although surface layer can protect underneath asphalt layer from aging, 10-year field aging would introduce significant deterioration onto the underneath layer. The effective aging depth can go as deep as to the second layer. Fatigue tests illustrate that 10-year service has resulted in very weak asphalt pavement surface. Its fatigue life is very sensitive to traffic loading.

Multiscale Investigation of Oxidative Aging in Biomodified Asphalt Binder

Oxidative aging causes major changes in asphalt binder’s physiochemical and rheological properties, giving rise to pavement distress and failure. Asphalt aging occurs due to two main processes: a loss of volatile components and a reduction of the malthene phase and oxidation of certain functional groups in asphalt, increasing the concentration of asphalt’s polar components. Performing SARA (saturate, aromatic, resin, and asphaltene) analysis and FTIR (Fourier transform infrared) spectroscopy on the crude oil shows that the ratio of polar components to nonpolar ones is higher in oxidized asphalt compared to virgin asphalt. However, when a biomodifier is introduced to virgin asphalt, the rate of carbonyl (as a polar functional) formation is reduced, which may indicate a delayed oxidation due to the presence of biomodifier molecules in the asphalt. To understand the fundamental origin of oxidative aging at the molecular level, this paper provides a comprehensive computational chemistry analysis conducted in ...

Chemical Aspects of Onshore Crude Oils from the Carmópolis Field, Sergipe-Alagoas Basin, Brazil: A Case Study on the Industrial Process for Water–Oil Separation

The importance of the Carmópolis field in Brazil for the exploration of onshore crude oil dates back to 1963. Currently still in operation, this is a major field, serving as a model for enhanced oil recovery tests. In this field, the differences in the physicochemical characteristics have awakened an interest in understanding the implications of the chemical composition of crude oils. Four blends of crude oil from this field were characterized using the SARA (saturates, aromatics, resins and asphaltenes) method and advanced methods such as energy dispersive X-ray fluorescence spectroscopy (EDX), laser desorption/ionization mass spectrometry (LDI-MS), infrared (IR), ultraviolet (UV), and thermogravimetric (TG) analysis. Of the four blends investigated, CEOL3 had the greatest affinity for water. The results for the SARA analysis did not reveal significant differences between the blends. The analysis of CEOL3 asphaltenes by IR spectroscopy revealed greater O–H stretching associated with water, and the TG indicated a more advanced state of thermal evolution compared with the other samples investigated in this study. Similarly, according to the EDX analysis, this oil sample had a greater affinity with produced water. Also, based on the UV analysis, the asphaltenes present in CEOL3 were of higher molecular mass compared with the other samples. Finally, the LDI-MS analysis of the blends showed a higher content of naphthenic acids and carbazoles in the CEOL3 sample which, together with the asphaltene content, is related to the stabilization of emulsions.

New method to detect asphaltene precipitation onset induced by CO2 injection

Carbon dioxide (CO2) flooding has been used as a commercial process for enhanced oil recovery since the 1970s. Significant amounts of residual oil can be recovered by this procedure. The application of carbon dioxide (CO2) to enhance oil recovery can induce precipitation and deposition of asphaltenes. The consequences generally include changes in reservoir wettability, formation damage, and wellbore and downhole facilities plugging, affecting the project budget due to production delays and costly clean up procedures. The amount of gas that can be dissolved in the oil before having asphaltene precipitation is an important parameter to consider in the design of the optimal gas injection scheme. The challenge of predicting asphaltene precipitation onset is attributed mainly to the difficulty of modeling the oil and the asphaltene molecules. As this behavior is very difficult to describe, the problem caused by this precipitation in all sectors of the oil industry is serious and complex. Therefore a simple method to predict the onset of precipitation would greatly benefit the oil exploration area. In this paper a new method is described which enables the detection of the conditions at which the onset of asphaltene deposition occurs. This approach is solely based on monitoring the difference between the asphaltene solubility parameter and the solubility parameter of the solvent containing the non-asphaltene liquid and CO2. To use this method only two parameters are fitted with the saturation pressure: the binary interaction parameters between the lightest and the heaviest components and the density of C7+ fraction. The experimental data required for the implementation of the method are the oil composition stops at C7+ fraction, the bubble point pressure at the reservoir temperature and the SARA (saturates, aromatics, resins and asphaltenes) analysis. The applicability of this method to predict asphaltene onset precipitation is demonstrated by extensive tests using data from literature. It corroborates the proposed approach which provides reasonably good predictive results. The examples shown not only validate the proposed method but pose an interesting alternative compared to the classic methods of determining asphaltene precipitation.

Prediction of the SARA analysis of Colombian crude oils using ATR–FTIR spectroscopy and chemometric methods

In this work eight chemometrics models to predict saturates, aromatics, resins and asphaltenes (SARA) composition of fifty Colombian crudes oils using Fourier transform infrared coupled to attenuated total reflectance (ATR–FTIR) spectra were developed. The samples were correlated by similarity using principal components analysis (PCA) with their ATR–FTIR spectra. The validation showed satisfactory results for the prediction of the SARA analysis of crude oils. For each SARA component, standard errors of prediction (SEP) for light samples were 1.9, 1.7, 1.3, and 0.4. For heavy samples SEP were 2.5, 1.7, 3.7, and 1.4. In all cases, the coefficients of correlation (R2) between the values of reference and those predicted by the models were superior to 0.95. The IR spectroscopy coupled with the ATR cell plus chemometric techniques provide an alternative way for the quantitative prediction of the wt% SARA group-types with minimal handling of the samples in a short period of time.