Separate Asphaltene Research Articles

Surfactant flooding for enhanced oil recovery – Insights on oil solubilization through optical spectroscopic approach

Surfactant flooding is a proven method employed to improve the recovery of crude oil from subsurface reservoirs but the knowledge about microemulsion formation, factors related to their stability, and the trapping mechanism of crude oil components in a microemulsion is still not clear for designing of injection fluid for specific crude type. The interaction mechanisms of four crude oils with surfactant-brine solutions were studied in this work for better insight into the molecular level mechanisms during surfactant flooding. UV–visible absorption and fluorescence spectra of the separated maltene and asphaltene fractions indicate the structural difference of the components in the molecular level, particularly, the size of the fused aromatic rings (FAR) present within individual bulk crude sample. Moreover, the FTIR spectra of the separated asphaltenes from the crude samples clearly showed the subtle difference in the functional groups present in respective FAR structures. Well-characterized compositionally different crude oils were mixed with four different surfactant-brine solutions (anionic – SDS, AOS, cationic - CTAB, and neutral - TX-100) and examined using UV–visible absorption and fluorescence spectroscopic approach. Detailed analysis of the acquired absorption and fluorescence spectra of the crude oil-surfactant-brine solutions distinctly demonstrate the entrapment of different crude oil components within the micelles formed by surfactants of different charges while the synchronous fluorescence spectra show the entrapment of specific size FARs within the specific micellar microenvironment. The results exhibit that the anionic surfactant entraps the smaller size (2–4) FARs whereas cationic and neutral surfactants entrap small as well as medium size (2–6) FARs within the formed micelles in the microemulsions. The present spectroscopic study signifies the importance of molecular-level interaction mechanisms for customized designing of surfactant solutions for maximizing crude oil recovery from petroleum reservoirs.

Rheological Modification for Asphaltic Materials Using a Mixture (Poly carbonate: Poly Methyl Methacrylate) and Microwave Radiation

Obtaining asphalt that suits the nature of the countries it is used in, is of great importance. Asphalt constitutes an important component in the paving of roads, mastic and flattening substance. This study was included the modification of the asphaltic material by the use of a mixture of polycarbonate and polymethyl methacrylate after crushed to obtain low molecular weight. The study included two paths: In the first asphaltic materials was treated with different percentages of a mixture in the presence of anhydrous aluminium chloride (0.06%of weight) as a catalyst for this reaction. The mixture was heated at 150° for 30 minutes. In the second path, the process of mixing was performed with the existence of a 360 watt microwave radiation for 15 minutes. The process of mixing was repeated in the presence of sulphur (1% of weight) instead of anhydrous aluminium chloride and under the same conditions. Properties of the original and modified asphalts were determined, and this included the measurement of ductility, penetration, softening point, penetration index and calculating the percentage of separated asphaltenes. Additionally, Marshal test, chemical Immersion test and aging were measured for some of the samples. Good samples that can suit Iraq's climate were obtained from this study.

Recent advances in characterizing the \u201cbee\u201d structures and asphaltene particles in asphalt binders

The microscopic surface features of asphalt binders are extensively reported in existing literature, but relatively fewer studies are performed on the morphology of asphaltene microstructures and cross-examination between the surface features and asphaltenes. This paper reports the findings of investigating six types of asphalt binders at the nanoscale, assisted with atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM). The surface features of the asphalt binders were examined by using AFM before and after being repetitively peeled by a tape. Variations in infrared (IR) absorbance at the wavenumber around 1700 cm−1, which corresponds to ketones, were examined by using an infrared s-SNOM instrument (scattering-type scanning near-field optical microscope). Thin films of asphalt binders were examined by using STEM, and separate asphaltene particles were cross-examined by using both STEM and AFM. In addition, connections between the microstructures and binder’s physicochemical properties were evaluated. The use of both microscopy techniques provide comprehensive and complementary information on the microscopic nature of asphalt binders. It was found that the dynamic viscosities of asphalt binders are predominantly determined by the zero shear viscosity of the corresponding maltenes and asphaltene content. Limited samples also suggest that the unique bee structures are likely related to the growth of asphaltene content during asphalt binder aging process, but more asphalt binders from different crude sources are needed to verify this finding.

EVALUATION OF THE CHEMICAL COMPOSITION AND STRUCTURE OF ASPHALTENES FROM THREE OFFSHORE BRAZILIAN BIODEGRADED HEAVY OILS

Asphaltenes fractions were extracted and purified from three heavy Brazilian oils. Their mass compositions of C, H, N, Ni and V were obtained from elemental analysis and S and O atomic percentages from EDS. The H/C ratios showed high degree of unsaturation, while the O atomic percentages indicated more pronounced biodegradation effects on two samples. Quantitative data on N, Ni, and V and semi-quantitative data on S were related to oils origins. The structural data of asphaltenes were explored by combining Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1 H NMR). The oil with the lower degree of biodegradation contained asphaltenes with a lower level of condensed aromatic rings and longer aliphatic chain substituents. The asphaltenes obtained from the two most biodegraded oils showed similarities of polar groups and the presence of carboxylic functions, as well as lower contents of aliphatic substituents. The quality and quantity of occluded hydrocarbons were assessed after the mild oxidation of the separated asphaltenes fractions. It was suggested that the severe biodegradation which altered these structures may also be responsible to affect their occluded hydrocarbons.

Effect of Alkyl Chain Length of Ionic Surfactants on Selective Removal of Asphaltene from Oil Sand Bitumen

In an attempt to find a more effective way to separate asphaltene from bitumen froth or bitumen emulsion by utilizing solvents, we added four different types of cationic (pyridinium series) and anionic (sulfate series) surfactants having different alkyl chain lengths and then compared the results. The data of the experiments showed that at given conditions (n-heptane at 50 °C, solvent-to-bitumen ratio of 3, and 20% water) and based on feedstock treated with 0.4 mmol of surfactant, asphaltene–resin particles (colloid) with an initial negative charge showed different characteristics of adsorption of surfactants and aggregation of asphaltenes depending on the charge of the surfactants (cationic or anionic) and the alkyl chain length. Ultimately, the results showed that when methyl-pyridinium chloride (which is cationic and has the shortest alkyl chain) is added that the colloidal instability of asphaltene became the highest so that asphaltene removal increased by up to about 10% compared to treatments withou...

New Multiway Model for Identification of Crude Oil and Asphaltene Origin Based on Diffusion-Ordered Nuclear Magnetic Resonance Spectroscopy

Identification and characterization of asphaltenes, the most polar and predominantly aromatic components of crude oil, still post a challenge for researchers in the oil industry, owing to their complex molecular architecture. Recently, much effort has been devoted to understanding their structure and physicochemical properties. In this paper, a combination of diffusion-ordered NMR spectroscopy (DOSY) and statistical multiway methods was used to investigate petroleum samples and asphaltenes of different origin. Such multiway TUCKER3 decomposition has been used for the first time to analyze the two-dimensional matrix of complex nuclear magnetic resonance (NMR) data for petroleum samples. DOSY NMR spectra of 50 samples (45 for establishing the statistical model and 5 for its validation) were recorded and evaluated by an in-house-developed code incorporating multiway analysis to set up a tool for predicting their identity and origin. A statistical model was developed that can identify and separate asphaltene ...

Effect of temperature on the analysis of asphaltenes by the on-column filtration/redissolution method

The study of the effect of temperature on the analysis of asphaltenes by the on-column filtration/redissolution method is presented. The goal of this work is the prediction and early detection of asphaltene/solid precipitation at reservoir and refining conditions using simple, fast and reliable analytical techniques. A description of the new experimental methodology is introduced followed by the results of the analysis of n-heptane asphaltenes and virgin, vacuum residue (VR), visbroken and hydroprocessed petroleum samples in the temperature range 35–195°C. Mass balances were effectively carried out and the presence of adsorbed species on the column surface was found. Consistent with gravimetrically separated asphaltenes, the new method showed that asphaltene contents are reduced as the temperature is raised whereas the maltene contents increased. Similar behavior was found for separated asphaltenes and whole virgin, VR or whole hydroprocessed samples. In general, it was observed that the amount of adsorbed species seems to increase with the temperature.

Heavy oil upgrading at moderate pressure using dispersed catalysts: Effects of temperature, pressure and catalytic precursor

A study of the influence of reaction parameters (reaction temperature, pressure and catalytic precursor) on the upgrading of Maya heavy oil under low pressure and moderate temperature under slurry conditions is presented. The behavior of the purely thermal hydrotreating system was first characterized to have a basis for distinguishing the effect of incorporating a catalyst in further hydrotreatings. The distillation curves of liquid product were obtained by thermo gravimetric analysis (TGA), ASTM standards were used for evaluation of API gravity and content of asphaltenes and carbenes–carboids. The separated asphaltenes were analyzed by XRD and C13 NMR techniques. The effect of temperature, catalytic precursor and pressure (800 and 960psi) of process were studied. The study of thermal hydrotreating showed that 390°C and 400°C were promising temperatures for catalytic hydroprocessing and increasing pressure approximately 100psi promoted the improvement of light liquid fractions at the expense of the heavy and residua fractions. The use of catalytic precursors at 400°C in concentrations of 330ppm of Mo increased gasoline production without producing more solids but did not result in the improvement of the liquid yield in comparison to the homologous thermal hydrotreatment. The liquid yield was improved either hydrotreating at 390°C or at 400°C with 1000ppm Mo as catalyst.

Correlating the chemical and physical properties of a set of heavy oils from around the world

Variations in the viscosity and other physical properties of heavy oils are poorly understood. The viscosities measured for different heavy oils can vary by orders of magnitude even at the same API gravity, which is the standard metric for lighter oils. Heavy oils are viscoelastic materials, and the shear modulus and the viscosity are coupled. Understanding what controls heavy oil viscosity will provide insight into what controls heavy oil shear modulus. Therefore, using rheology, ultrasonic measurements and molecular beam mass spectroscopy (MBMS) the physical and chemical properties of seven heavy oils from around the globe are explored. The viscoelastic nature of the oils is quantified as a function of temperature. Overall, the heavy oil samples show little correlation between the viscosity or shear modulus and the API gravity, separate resin content or separate asphaltene content as measured from SARA analysis. However, the total resin plus asphaltene content collapses the viscosity and modulus values to provide empirical relations between these quantities. Also, a partial least squares regression analysis provides tight correlations for the chemical signatures from the MBMS. The rapid and quantitative nature of the MBMS make it an attractive substitute for the inconsistencies endemic to SARA analysis.

Experimental measurement of the mass distribution of petroleum asphaltene aggregates using ultracentrifugation and small-angle X-ray scattering

Fractionation of petroleum asphaltene in toluene has been carried out using ultracentrifugation. The separated asphaltenes are examined by small-angle X-ray scattering (SAXS). The radii of gyration and molar mass of the separated asphaltenes range over a wide scale that provides a good indication of the self-similar structure of asphaltene aggregates. The relations between mass and radius of gyration ( M∝ R G D ) and between scattered intensity and wave vector ( I( q)∝ q − d ) were studied. Values of both D (=1.99) and d (=2.06) show a fractal dimension D f of the asphaltene structure close to 2. The mass distribution of these aggregates can be calculated from the knowledge of both the quantity of separated fractions and the mass M of every fraction. We found experimentally a mass distribution with a power-law shape ( N( M)∝ M − τ ) with exponent τ=1.66. The fractal dimension values and the mass distributions of asphaltene aggregates are similar to those predicted by the RLCA model.

RESID HYDROTREATING CHEMISTRY Analyses of Hondo Feed and Product Fractions

Abstract The chemistry of resid upgrading was studied by following the changes caused by hydrotreatment of Hondo 450°F+ resid, its separated asphaltenes and maltenes, and polar, aromatic, and saturate fractions. Both continuous and batch hydrogenations were studied, using two commercial resid hydrotreating catalysts. At low reactor temperatures, the most important reactions are saturation of aromatics and removal of reactive heteroatoms. Increasing the temperature adds cracking reactions. Detailed results can he explained by arbitrarily assigning to resid cuts the ranking: saturates > aromatics > polar compounds > asphaltenes and assuming that hydrotreating moves materials upward in the hierarchy. Each cut can form products only at or above its ranking. Only asphaltenes can give rise to asphaltenes in the products. Asphaltenes are the most difficult resid fraction to treat, and they reduce the catalyst's activity for treating other fractions, possibly by blocking pores or adsorbing strongly on the catalys...