Increase In Asphaltene Content Research Articles

Experimental Study on the Influence of Asphaltenes with Small Dosage on the Rheological and Gelation Behavior of Waxy Mixtures

Asphaltene, the heaviest and most polar non-hydrocarbon component in crude oil, may interact with waxes and affect the flow and gelation behavior of waxy oils. To further study the effect of asphaltene on the flow and gelation behavior of waxy oils, five wax-containing simulated oils with small dosage asphaltene content were prepared. Through pour point and rheometer test, it is found that asphaltenes can improve the low-temperature rheology of waxy oil. There is no critical turning point above which the low-temperature flowability improved. With an increase in asphaltene content from 0 wt% to 0.1 wt%, notable changes were observed in the properties of the waxy oil. The pour point, which measures the temperature at which the oil becomes too viscous to flow freely, exhibited a decrease from 25 ℃ to 13 ℃. Similarly, the gelation temperature, indicating the temperature at which the oil starts forming a gel-like consistency, also decreased from 29.0 ℃ to 27.1 ℃. These modifications can be attributed to the presence of asphaltene in the oil sample. This outcome can be attributed to the interference caused by the presence of asphaltenes, which disrupts the gel network structure of the waxy oil and consequently hinders its gelation process. Simultaneously, within the low asphaltene content range, an increase in asphaltene content resulted in a considerable decrease in the viscosity of the waxy oil at 10°C, reducing it from 531.5 mPa·s to 14 mPa·s.

Integrated investigation on the nucleation and growing process of hydrate in W/O emulsion containing asphaltene

During the production and transportation of deep-water oil and gas, the low-temperature and high-pressure operating environment might induce hydrate formation and eventual blockage, which poses a serious threat to the flow assurance. Furthermore, the formation, aggregation and deposition characteristics of hydrate would become more complicated in the presence of asphaltene. Consequently, clarifying the effect of asphaltene on hydrate nucleation and growing process plays an important role in the safety production and flow assurance of deep-water oil and gas field. The kinetic characterizations of hydrate nucleation and growth in W/O systems containing asphaltene were investigated via experimental research, molecular dynamics simulations and mathematical modeling. Results revealed that the hydrate nucleation induction time increased with the increase of asphaltene content. The inhibition of hydrate nucleation by asphaltene in high-pressure (5 MPa) experiments was more pronounced than that in low-pressure (3 MPa). On the other hand, asphaltene restrained hydrate formation and the total gas consumption decreased with the increase of asphaltene content. The dynamic adsorption process of asphaltene at oil–water interface and the evolution of the surface coverage with time were elucidated by jointly solving the Ward-Tordai and Langmuir equation. Combined with the above aspects, the induction time model containing asphaltene was developed, which could provide a new perspective and methodology for deep-water flow assurance

Study on pavement performance of cotton straw cellulose modified asphalt

To improve the pavement performance of heavy traffic asphalt pavement, two modifiers, cotton straw powder and cotton straw cellulose, were added to matrix asphalt. Through the tenacity test, dynamic shear rheological test, multi-stress creep recovery test and bending beam rheological test of asphalt, the tenacity, high temperature properties, viscoelastic properties and low temperature properties of three kinds of asphalt, including matrix asphalt, cotton straw powder modified asphalt and cotton straw cellulose modified asphalt, were evaluated. Scanning electron microscopy and synchronous thermal analyzer were used to analyze the microstructure and thermal stability of modified asphalt. The results show that both cotton stalk powder and cotton stalk cellulose can effectively improve the tenacity, temperature sensitivity and rheological properties of asphalt. The comprehensive improvement effect of 1% cotton straw cellulose is the best, but its low temperature performance has not been improved significantly. Cotton straw cellulose and asphalt form a more stable system, thereby improving the stability of asphalt. The increase of asphaltene content and the decrease of aromatic content are due to the good oil absorption of cotton straw cellulose, and the high temperature performance of asphalt is improved.

Modification Mechanism of Asphalt Modified with Rock Asphalt and Styrene-Butadiene Rubber (SBR)

High-performance asphalt binder plays an important role in the durable asphalt pavement. Asphalt modified by rock asphalt (RA) is one of the high-performance modified asphalt materials. It was used in road engineering as a relatively environmentally friendly material, because rock asphalt takes some advantages of large reserves, easy treatment, and efficient modification. Moreover, the main component of rock asphalt is bitumen, which enables it to substitute part of the binder used in asphalt mixtures. On the other hand, the negative low-temperature performance of RA modified asphalt impeded its application in cold regions. The object of this paper is to improve the low-temperature performance of RA modified asphalt by compound modified with styrene-butadiene rubber (SBR). The 70-penetration grade binder and the RA modified asphalt with 15% RA by weight were applied as the base binder. Five types of RA-SBR modified asphalt were prepared, and the content of SBR was 2%, 4%, 5%, 6% and 8% by weight of BRA modified binder. The Fourier transform infrared spectroscopy (FTIR) tests were utilized to illustrate the reasons for the poor low-temperature performance of BRA modified asphalt and reveal the compound modification mechanism of BRA-SBR modified asphalt. The Brookfield viscosity test, dynamic shear rheometer test, and bending beam rheometer test were adopted to reveal the variation patterns of rheological behavior and low-temperature performance with mass contents of SBR. The test results indicated that the worse of low-temperature performance was caused by the increase of asphaltene content and the stress concentration due to ash in RA modified asphalt. And the compound modification is a physical process. The addition of SBR has improved the low-temperature performance of RA modified asphalt dramatically. And based on the rheological behaviors and low-temperature performance of RA-SBR compound modified asphalt, the optimum content of SBR was determined, which is about 4%∼5%.

Thermodynamic Properties Investigation of Process Volatile Organic Compounds (VOCs) and Its Transport Impact Factor in Oil Sands Management

This paper presents a new approach for the determination of volatile organic compounds (VOCs) characteristics and their migration influencing factors in oil sands management processes and reveals the relationship between different asphaltene content and different solvents. Specifically, thermodynamic (i.e., partitioning coefficients, Kr, specific retention volume, Vg, the activity coefficients, γ and enthalpy of solution, ΔH0) and their impact factors are discussed. Gas-liquid chromatography (GLC) experimental measurements were used as the test data. A range of solvents (nC5, iC5, nC6, nC7, and Toluene) has been tested in different asphalt contents (0, 2.56, 9.93, 36.86, 53.67 wt%). There are temperatures in the range of 333.2–393.2 K (with 10 K increase) were conducted, respectively. The dynamics properties of asphalt mixture are calculated, and the relation between dynamics properties of asphalt mixture and absolute temperature, asphalt content and solvent type is discussed. The results show that within the acceptable error range, partitioning coefficients, Kr, specific retention volume, Vg, and enthalpy of solution, ΔH0 and other thermodynamic properties have a good tendency to predict, they decrease with the increase in asphaltene content and temperature and increase with the increase in solute carbon number.

Effect of Asphaltene on Threshold Pressure Gradient of Heavy Oil in Porous Media

Many studies have shown that heavy oil with high asphaltene content has a yield stress. Coupled with the solid-liquid interaction between porous media and heavy oil, there is a threshold pressure gradient when heavy oil flows in porous media. Meanwhile, some previous research has indicated that the high viscosity of heavy oil is the decisive factor for its threshold pressure gradient. Hence, this concept needs more clarification, especially because its accuracy is questionable. In this research, different oil samples with the same viscosity and also different asphaltene contents heavy oil samples were prepared. The viscosity of the different heavy oil samples was measured. Threshold pressure gradient experiments under different permeabilities and temperatures were also conducted on heavy oils. The results proved that the viscosity was not directly related to threshold pressure gradient of heavy oil. They also suggested that the heavy oil viscosity increased with the increase of asphaltene content. Moreover, the formula of the factors affecting threshold pressure gradient was regressed, and also its applicability was verified. As the temperature and core permeability increase, the threshold pressure gradient was also proven to decrease significantly. Furthermore, it was found that the threshold pressure gradient increased significantly with the increase of asphaltene content. Therefore, the heavy oil threshold pressure gradient could be characterized as a function of temperature, permeability, and asphaltene content. This study provided some theoretical support for the research attempts on the reduction of threshold pressure gradient and also on the effective development of heavy oil reservoirs.

Evaluation of weathering aging on resistance of high viscosity modified asphalt to permanent deformation and fatigue damage

Currently, high viscosity modified asphalt (HVMA) has broad application prospects in permeable asphalt pavement. However, the large-void structure of permeable asphalt pavement makes HVMA excessively exposed to extremely adverse coupling aging of solar radiation, heat, and moisture, which accelerates the performance deterioration of HVMA. In order to investigate the effect of weathering aging on the permanent deformation and fatigue resistance of HVMA during the long-term service period, an accelerated weathering aging tester considering solar radiation, heat, and moisture was used in this study to simulate different weathering aging environment. Dynamic shear rheometer and multiple stress creep recovery test were conducted to investigate the high-temperature rheology property of HVMA at different weathering aging stages. Linear amplitude sweep test was applied to evaluate the effect of weathering aging on the fatigue resistance of HVMA. Besides, gel permeation chromatography test and fluorescence microscopic observation were used to study the molecular weight distribution and surface micromorphology of HVMA during weathering aging, respectively. The results showed that the effect of weathering aging led to an increasing rutting factor and a decreasing non-recoverable creep compliance of HVMA. The strain recovery of HVMA decreased initially and then increased with the process of weathering aging. At 50 °C weathering aging condition, the decrease in the fatigue resistance of HVMA was not significant. However, the fatigue resistance of HVMA showed a significantly decreasing trend with the process of 70 °C weathering aging. After 12d of 70 °C weathering aging, the Nf2.5% (fatigue life at 2.5% strain) of HVMA decreased from 455,035 cycle numbers to 1908 cycle numbers sharply. The degradation of polymers, the increase of asphaltene content, and the extension of surface microcracks were the main reasons for the deteriorated fatigue resistance of HVMA after long-term weathering aging.

Effects of SARA fractions on low temperature properties of asphalt binders

Effects of the chemical fraction on the low temperature rheological behaviours of asphalt binders were explored in this study. Four fractions, namely saturate, aromatic, resin and asphaltene (SARA), were obtained from eleven asphalt binders by a novel column chromatography separation method. In addition, the viscoelastic master curves for binders and their subsets were characterised by dynamic shear rheometer (DSR) at high frequencies (low temperatures). The results showed that the complex modulus and phase angle of asphalt binders were closely related to the changes of SARA fractions. Moreover, low temperature properties of asphalt binders characterised by the creep stiffness modulus and m-value were measured using bending beam rheometer (BBR) test. The increases of asphaltene in asphalt binder resulted in the decreases of creep stiffness modulus of asphalt as well as m-value. Further, the glass transition temperature (Tg) of resins, asphaltenes and asphalt binders were measured by differential scanning calorimetry (DSC) test. The results showed that the Tg values of asphalt binders were mainly determined by saturates and aromatics fractions. However, the Tg values of the asphalt binder would increase with the increase of asphaltene content. Finally, significant relationships between SARA fractions and low temperature parameters of asphalt binder specimens were found and conducted using linear regression analysis, indicating that the SARA fractions would perform significant effects on the low temperature properties of asphalt binders.

Peculiarities of Hydrocarbon Generation in Procsses of Transformation of Organic Matter of Domanikovian Rocks in Various Media of Hydrothermal System

The influence of various media on the degree of transformation of kerogen of Domanikovian rocks in hydrothermal processes was studied in model experiments. Autoclave experiments were conducted with debituminized rock in inert, hydrogen, and carbon dioxide media. A common mechanism was observed for all the reaction media under the influence of hydrothermal factors: the kerogen content in the rocks decreases and the yield of free hydrocarbons extractable from the rocks by organic solvents increases. The saturated hydrocarbon content is higher in the group composition of the experiment products compared to the original extract due to decrease in resin and aromatic hydrocarbon content. In the original extract from the Domanikovian rock, as well as in the experiment products, there are two solid dispersed phases, namely, asphaltenes soluble in aromatic solvents and their modified structures of the type of carbenes and carboids insoluble in toluene due to their more condensed structure with a smaller number of aliphatic substituents. The most pronounced decrease in resin content is observed in carbon dioxide medium with a marked increase in asphaltene content in the experiment products relative to the original extract. In hydrogen medium, on the other hand, asphaltene content decreases in the experiment products, but, in comparison with the carbon dioxide medium, carbenes and carboids are formed more intensely due to decomposition of the kerogen structure. Asphaltenes and carbenes-carboids were found to differ in structure and paramagnetic properties.

Asphaltene Grading and Tar Mats in Oil Reservoirs

Advances in asphaltene science and a new generation of downhole fluid analysis (DFA) technology have been combined to yield powerful new insights to reservoir tar mats. The asphaltene nanoscience model, the modified Yen model, also known as the Yen–Mullins model, has enabled development of the industry’s first predictive equation of state for asphaltene concentration gradients. This equation of state (EOS) is a modified Flory–Huggins regular solution model for the asphaltene part that has been referred to as the Flory–Huggins–Zuo (FHZ) EOS for asphaltene concentration gradients in oil reservoirs. Measurement of these gradients using “downhole fluid analysis” coupled with analysis using the FHZ EOS has successfully addressed a variety of reservoir concerns including reservoir connectivity, viscosity gradients, and fluid disequilibrium. The EOS model shows that asphaltene concentration gradients can be large owing to both the gravity term and gas/oil ratio (GOR) gradients. The FHZ EOS is reduced to a very simple form—the gravity term only for low GOR black oils and heavy oils—and heavy oils are shown to exhibit enormous asphaltene concentration gradients in contrast to predictions from conventional models. In this paper, the FHZ EOS has been applied not only to calculate asphaltene concentration gradients but also to predict asphaltene phase instability in oil reservoirs. Two types of tar mats are discussed: one with a large discontinuous increase in asphaltene concentration versus depth typically at the base of an oil column (corresponding to asphaltene phase transition); the second with a continuous increase in asphaltene content at the base of a heavy oil column due to an exponential increase in viscosity with asphaltene content. Both types of tar mats are consistent with the Yen–Mullins model of asphaltenes within the FHZ EOS analysis discussed herein. The predictions are in good agreement with the laboratory and field observations, and the mechanisms of forming these two kinds of tar mats are also discussed. This methodology establishes a powerful new approach for conducting the analyses of asphaltene concentration grading and tar mat formation in oil reservoirs by integrating the Yen–Mullins model and the FHZ EOS with DFA technology.

Physico-chemical analysis of five hard bitumens: Identification of chemical species and molecular organization before and after artificial aging

The present paper focuses on a physico-chemical analysis of five different types of bitumens, both before and after aging. These bitumen samples were chosen based on: the original crude oil (straight-run bitumens with different asphaltene and crystallized fraction contents), mode of refining (straight-run vs. half-blown bitumen), and modifier characteristics (straight-run vs. polyphosphoric acid (PPA)-modified bitumen). The aim of this study is to determine both the aging effect on chemical species and the chemical organization as a function of the type of bitumen sample. In order to obtain information on bitumen chemistry, n-heptane precipitation (Standard NF EN 12591), IATROSCAN chromatography (coupling between a thin-layer liquid chromatography on a silica gel and a flame ionization detector), FTIR spectroscopy and differential scanning calorimetry (DSC) have all been used. Size exclusion chromatography under “high-speed” conditions (HS-SEC), which yields information relative to asphaltene associations, was also introduced. Several years of road aging were simulated through 25 h of a pressure aging vessel (PAV) test. The coupling of IATROSCAN chromatography and n-heptane precipitation made it possible to identify and quantify polar resins. In accordance with previous studies, the use of HS-SEC combined with IATROSCAN chromatography indicates that a modification by PPA leads to an increase in asphaltene content and a more dispersed asphaltene structure than that found in pure bitumen. This same conclusion can be drawn from observations of the half-blown bitumen sample. The half-blown bitumen actually contains less asphaltene than one of the straight-run bitumens in the study; furthermore, its asphaltenes are more highly agglomerated. These results demonstrate that asphaltene association does not systematically depend on quantity alone, as its chemical type also enters into play. Moreover, during aging, even though asphaltene content is increasing for all bitumen samples, its agglomeration is still highly dependent on the type of bitumen. It would therefore appear that the presence of crystallized fractions exerts a major influence on this process.

Investigation of the Demulsification Efficiency of Some Ethoxylated Polyalkylphenol Formaldehydes Based on Locally Obtained Materials to Resolve Water-in-Oil Emulsions

Fourteen ethoxylated polyalkylphenol formaldehyde surfactants were prepared from locally sourced raw materials. These surfactants were used as demulsifiers to resolve asphltenic crude oil emulsions. Different factors affecting demulsification efficiency such as water:oil ratios, surfactant concentration, surfactant molecular weight, ethylene oxide content, alkyl chain length, and asphaltene content were investigated. From the data obtained it was found that the demulsification efficiency increases by increasing the concentration, alkyl chain length and water content in the emulsion. Also it was found that the increase of asphaltene content in the crude oil impeded the demulsification efficiency. The effect of molecular weight was studied and it was found that the demulsification efficiency was controlled by an optimum range of molecular weight between 3640 to 3810 for the family of demulsifiers studied. Regarding the effect of ethylene oxide content in the demulsifier structure, it was found that the maximum demulsification efficiency was obtaind at 40 units ethylene oxide. The maximum demulsification efficiency was obtained by TND5 (m.wt. = 3800, eo = 40 units). With this demulsifier 100% water separation was exhibited after 35 minutes at 150 ppm demulsifier concentration and 50% w/o emulsion. The surface, interfacial tension, and hydrophilic lipophilic balance (HLB) of the invistigated demulsifers were studied. The obtained results justified that they are strongly related to the demulsification effeciency.

Age Hardening Potential of Tall Oil Pitch Modified Bitumen

ABSTRACT The long-term ageing characteristics of bitumen modified using tall oil pitch (TOP) were investigated. Bitumen containing various proportions of TOP was aged as 1 mm thick films at 60°C for 3024 hours. The TOP modified bitumens displayed an increased ageing index and viscoelastic modulus after ageing indicating that they are more susceptible to oxidative ageing than conventional bitumen. Determination of the Heithaus parameters of aged samples showed that an increase in the TOP content caused a reduction in the asphaltene dispersability (Pa), an increase in solvent power (Po) of the maltene phase and an overall improvement in compatibility (P) of the bitumen. A significant increase in asphaltene content with increasing TOP content also occurred after ageing. The acid number of the bitumen increased in proportion to the TOP content, but did not change after ageing. It is postulated that unsaturated carboxylic acids in the TOP are susceptible to oxidative polymerisation, which leads to the creation of large, highly polar, asphaltene-like molecules. It is these oxidised carboxylic acids, which cause the bitumen to harden more as it ages.

96/05947 Effect of coal preoxidation on the development of microporosity in activated carbons

The structure and carbonization behavior of the pitches from the products of gas-coking coal hydrogenation performed at 420°C and 455°C in a continuous bench scale unit were estimated. The pitches, prepared as residues from vacuum distillation of purified hydrogenation products, were characterized y elemental analysis, solvent fractionation, IR and 1H NMR spectroscopy. The mesophase formation on isothermal carbonization at 450°C and the optical texture of resultant semicokes were studied by polarized-light optical microscopy. The most pronounced effect of hydrogenation temperature rise was an increase in asphaltene content at the expense of preasphaltenes and a decrease of heteroatom content and reactivity of resultant pitch. This alteration of pitch nature resulted in distinctly different carbonization behavior of both materials. The transformation of the low temperature (420°C) hydrogenation pitch occurred at a high rate leading to the coke of small size optical texture. The high temperature (455°C) hydrogenation pitch produced on carbonization large, easily deformable anisotropic units, and the optical texture of resultant semicoke was comparable to that observed in the cokes from petroleum pitch or QI free coal tar pitch.

Kinetics and mechanism of carbonization of QI free products from gas-coking coal hydrogenation—I: The structure and carbonization behavior of pitches produced by the coal hydrogenation at 420°C AND 455°C

The structure and carbonization behavior of the pitches from the products of gas-coking coal hydrogenation performed at 420°C and 455°C in a continuous bench scale unit were estimated. The pitches, prepared as residues from vacuum distillation of purified hydrogenation products, were characterized y elemental analysis, solvent fractionation, IR and 1H NMR spectroscopy. The mesophase formation on isothermal carbonization at 450°C and the optical texture of resultant semicokes were studied by polarized-light optical microscopy. The most pronounced effect of hydrogenation temperature rise was an increase in asphaltene content at the expense of preasphaltenes and a decrease of heteroatom content and reactivity of resultant pitch. This alteration of pitch nature resulted in distinctly different carbonization behavior of both materials. The transformation of the low temperature (420°C) hydrogenation pitch occurred at a high rate leading to the coke of small size optical texture. The high temperature (455°C) hydrogenation pitch produced on carbonization large, easily deformable anisotropic units, and the optical texture of resultant semicoke was comparable to that observed in the cokes from petroleum pitch or QI free coal tar pitch.

Modification of Asphalt and Asphalt Paving Mixtures by Sulfur Additives

Five series of investigations have been undertaken to evaluate the rheological, durability, and chemical effects of sulfur addition to asphalts and asphalt paving mixtures. Sulfur was added to asphalt or asphalt concrete at normal mixing temperature of 150 DEG C. The original and aged (both laboratory and natural) sulfur asphalts, at sulfur-asphalt weight ratios of 0.02 to 1.80, were tested for penetration, ductility, softening point, percent asphaltene, percent total and free sulfur, mixture stability, and hydrogen sulfide evolution. The addition of sulfur to asphalt at working temperature of 150 DEG C resulted in an increase in asphaltene content, percent bonded sulfur, and evolution of hydrogen sulfide. Data also indicated the existence of optimum sulfur concentration for sulfur modification and sulfur-asphalt concrete stability. /Author/