Asphaltene Aggregation in Crude Oils during Supercritical Gas Injection

Abstract

This paper presents the aggregation of asphaltenic materials in three dead crude oils, including two heavy samples from Hokkaido (Japan) and an extra heavy sample from Canada. In this study, a modified ASTM D3279 method and PVT test were used to estimate the amount of precipitated asphaltene and the experimental bubble-point pressures of the samples, respectively. Upon which, a crude oil characterization was performed following pseudocomponent approach with the use of molecular weight and specific gravity of single carbon number from oil assay data as distribution variables. A simplified thermodynamic model, derived from the solubility model, was used to correlate the maximum asphaltene soluble with the aggregated amount. This study has highlighted that oil precipitation, during its titration, occurs as a function of both the molecular weight of the titrant and the carbon-to-hydrogen ratio in the asphaltene phase. Furthermore, the kinetics and the stability of intermolecular forces, developed during the miscibility process, are believed to alter oil polarity and gas solubility. More specifically, pressurization of the system [oil-supercritical gas] decreases the solubility parameters of the asphaltene fraction and increases the solvating strength of gas. Both effects were found to occur concurrently. This study has also demonstrated that asphaltenes are less soluble in impure gases compared to the pure one. At/near the bubble-point pressure, the supercritical gas, in contact with the oil, develops a potential as either a flocculant or coagulant. The increase in pseudo equilibrium temperature attained after gas injection was found also to alter asphaltene aggregation.

Mechanism of asphaltene aggregation induced by supercritical CO2: insights from molecular dynamics simulation

“…This result is in agreement with experiments. 13,14,53,54 To supply information regarding the Z-direction, the radial distribution functions between oil components and CO 2 from further quantitative testing are reported in Fig. S3.…”

“…This may cause pore throat plugging, permeability reduction, and wettability alteration in reservoirs, further resulting in a reduction in the recovery factor. 7 In addition, deposited asphaltenes can also lead to severe plugging of the wellbore, tubing, and pumps, which must be remediated by constant washing and scrapping. 8 Consequently, this will generate a considerable increase in maintenance costs in the petroleum industry.…”

Nanocomposite and Nanofluids: Towards a Sustainable Carbon Capture, Utilization, and Storage

“…During a gas-EOR, the injected gas dissolves into the oil after a first (or multiple) contact leading to a foamy oil, whose viscosity is lower than that of the original oil [55]. Often, gas-EOR is challenged, in part by, the deposition of heavy fractions [56][57][58].…”

Role of Polymer-Based Nanofluids on Asphaltene Adsorption during Carbon Dioxide (CO2) Injection

“…9 Such phenomenon could be triggered by either a change in the thermodynamic conditions (temperature, pressure, etc.) 12,14 or the addition of foreign material (CO 2 for example). 15 that the precipitation occurs after a destabilization of dispersed monomers, which promotes in turn the formation of nanoaggregates (2−5 nm).…”

“…Asphaltenes are defined as organic molecules consisting of large aromatic cores with a variable amount in heteroatoms, which are soluble in aromatic solvents and insoluble in paraffin. − Known to contribute to severe issues during CO 2 -EOR, asphaltene precipitation has been covered extensively over the past few decades as evidenced by the wealth of review and research papers addressing the topic. ,− Asphaltenes are dispersed in the crude oil as monomers, which are stable because the balance between the intramolecular forces (e.g., π–π stacking) and intermolecular forces (e.g., hydrogen bonding). − In other words, any phenomenon that unbalances these forces could theoretically lead to asphaltene precipitation …”