Asphaltene

Direct liquefaction of low-rank Malaysian coal from the Mukah Balingian (MB) area was successfully carried out in a 1000 ml high-temperature (360–450°C) high-pressure (4–13 MPa) batch-wise reactor system using tetralin as hydrogen donor solvent. The results indicated that the percent coal conversion obtained were in the range of 31–90%. At optimum conditions of 450°C and 4 MPa, the oil + gas, asphaltene and preasphaltene of the coal extract were 80%, 7%, and 2%, respectively. It was observed that heat plays an important role in comparison to pressure in contributing to high coal conversion, oil yield, and organic properties of the residues. The high coal conversion and oil yield correlate well with the high content of reactive macerals, i.e., vitrinite and exinite, in the coal. Other parameters that were also investigated include the effect of reaction time (0–120 min) and coal-to-solvent ratio. A high yield of asphaltene and preasphaltene was obtained at the longest reaction time (i.e., 120 min). Coal conversion and oil yield increase with increasing in coal-to-solvent ratio, with the optimal ratio being 1:5.

Asphaltene is a component of crude oil that has been reported to cause severe problems during production and transportation of the oil from the reservoir. It is a solid component of the oil that has different structures and molecular makeup which makes it one of the most complex components of the oil. This research provides a detailed review of asphaltene properties, characteristics, and previous studies to construct a guideline to asphaltene and its impact on oil recovery. The research begins with an explanation of the main components of crude oil and their relation to asphaltene. The method by which asphaltene is quantified in the crude oil is then explained. Due to its different structures, asphaltene has been modeled using different models all of which are then discussed. All chemical analysis methods that have been used to characterize and study asphaltene are then mentioned and the most commonly used method is shown. Asphaltene will pass through several phases in the reservoir...

New experimental data show that previously reported UV/vis spectra of asphaltenes/crude oils may have been strongly distorted by artifacts, affecting not only quantitative parameters (spectra’s slopes), but also qualitative features (a presence of strong UV peaks). In a popular revised “amorphous semiconductor” (AS) model, the properties of UV/vis spectra are defined by population distribution of higher aromatics. This interpretation is obviously incompatible with the newly observed concentration effects in toluene solutions. Some specific features of UV/vis absorbance in asphaltenes/crude oils may be better described by the traditional AS model, taking into account the distribution of defects in chromophore carriers, e.g. nanosized carbonaceous species of the graphene family.

Asphaltene-based correlations of crude oil properties were analysed for more than 390 recovered (dead) crudes from a new database of the oils of the former USSR, as well as from databases by other authors. For densities, viscosities and pour points the analysis revealed a definite absence of frequently quoted strong linear correlations with asphaltene content and a persistent occurrence of non-linear anomalies for oils with <2.5–3 wt.% asphaltenes. As shown by selective filtering of databases, these anomalies most probably are due to the existence of two distinct types of world’s crude oils, as classified with respect to their asphaltene-based correlations. Two separate branches also are observed in most correlations for SARA components, for contents of N, S, O, V and Ni. The analysed correlations show definite imprints of biodegradation and of source types. However, a review of various oil alteration processes shows that an apparent subdivision of crudes into two types is most probably due to deasphalting via a natural geochromatography of oils in course of migration, resulting in a selective removal of a well-defined polar asphaltene fraction, distinguished by its low solubility.

The effects of visible and UV light on the characteristics and properties of Prudhoe Bay (PB) and South Louisiana (SL) emulsions were investigated to better understand the role of sunlight on the fate of spilled crude oils that form emulsions with a dispersant in the aquatic environment. Before irradiation, crude oil emulsions showed the presence of dispersed crude oil micelles in a continuous water phase and crude oil components floating on the surface. The crude oil micelles decreased in size with irradiation, but emulsions retained their high degree of polydispersity. UV irradiation reduced the stability of emulsions more effectively than visible light. The reduction of micelles size caused the viscosity of emulsions to increase and melting point to decrease. Further, irradiation increased acid concentrations and induced ion formation which lowered the pH and increased the conductivity of emulsions, respectively. Ni and Fe in PB emulsions were extracted from crude oil with UV irradiation, which may provide an efficient process for metal removal. The emulsions were stable toward freeze/thaw cycles and their melting temperatures generally decreased with irradiation. Evidence of ˙OH production existed when emulsions were exposed to UV but not to visible light. The presence of H2O2 enhanced the photodegradation of crude oil. Overall, the changes in emulsion properties were attributed to direct photodegradation and photooxidation of crude oil components.

... Characterization of the rock-fluid system: (1) Measure the initial effective porosity of the core. (2) Determine the liquid or absolute permeability using Darcy&amp;#x27;s law (the Klinkenberg effect, ie, variation in gas permeability with mean pressure and type of gas). ...

In this study, experimental data on the amount of asphalt and asphaltene precipitation due to addition of solvents to West Sak crude were gathered. The first set of tests were conducted for two types of West Sak stock tank oils. Solvents used include: ethane, carbon dioxide, propane, n-butane, n-pentane, n-heptane, Prudhoe Bay natural gas (PBG) and natural gas liquids (NGL). Effect of solvent to oil dilution ratio on the amount of precipitation was studied. Alteration of crude oil composition due to asphalt precipitation was measured using gas-liquid chromatography. A second set of experiments were conducted to measure asphaltene precipitation due to addition of CO{sub 2} to live (recombined) West Sak crude.

Comparative analysis of previously available and new experimental data reveals a complex structure of ambient pressure T-C phase diagram of asphaltenes in solutions, as well as in native petroleum. One of the characteristic properties of the diagram is an apparent series of temperature-controlled transitions between structural states in primary asphaltene nanoaggregates, presumably related to different types of intermolecular bonding. Hence, various earlier models of primary aggregates may be more closely related, than conventionally believed.