| dc.description.abstract | Asphaltenes represent the heaviest and the most polar fraction of crude oil. Asphaltenes precipitation within the reservoir pores or production flow lines can severely hamper petroleum extraction process. Although the effect of temperature and pressure on asphaltenes deposition is well known, how the oil composition affects the asphaltenes precipitation mechanism requires more clarity. Thus, interaction of asphaltenes with other crude oil fractions and reservoir elements like rock minerals, clays, and reservoir brines were investigated in this work and their impact on overall asphaltenes stability was assessed.
This dissertation analyzes the effect of solubility, electrical charges, and polarity of asphaltenes on its overall stability. Impact of each of these phenomena are described under three distinct sections of this study. In the first part, the effect of asphaltenes solubility and the mutual interaction between different crude oil fractions on asphaltenes stability were evaluated through elemental analysis and stability parameters (∆PS and Colloidal Instability Index) of 11 crude oil and bitumen samples. In the second part, presence of inorganic minerals originating from reservoir rocks, clays, and reservoir brines on asphaltenes surface was confirmed using Scanning Electron Microscopy (SEM) – Energy Dispersive Spectroscopy (EDS) analyses. The charge distribution on asphaltenes’ surface was also studied by measuring electrical properties of the asphaltenes-deionized water supernatant. Finally, in the third part, polarity of asphaltenes and other crude oil fractions were estimated indirectly through dielectric constant measurement using an in-house-built cylindrical capacitor.
It was observed that all three phenomena (solubility, electric charges, and polarity) contributes towards overall asphaltenes stability. However, combined assessment of solubility and polarity aspects yields better estimation of asphaltenes stability. Using the integrated approach, intermolecular forces acting between asphaltenes clusters and other crude oil fractions can be holistically understood. Moreover, strong electrostatic force between charge carrying inorganic minerals present on asphaltenes surface can also influence asphaltenes stability.
Through this dissertation, combined impact of asphaltenes solubility and polarity as well as the contribution of electrical charges induced by the inorganic mineral content of asphaltenes on overall asphaltenes stability are analyzed and described for the first time in literature. | |
