Investigation of Asphaltene Polydispersity, Stability, and Deposition on Steel Using XDLVO Theory

Abstract

The characterization and analysis of asphaltene particles are very crucial in the petroleum industry as the precipitation and subsequent deposition of asphaltenes cause formation damage and clogging of wellbore and production equipment, leading to production decline and operational drawbacks. In this study, the polydispersity of asphaltenes and the interaction between asphaltenes were probed by using the surface energy concept. Asphaltenes from three different oil fields in the Gulf of Mexico (GOM) were selected for this study. The results revealed that asphaltenes destabilized by different precipitants in the lab or from different assets in the field have distinctive surface energy values. Dispersive force was the dominant force of asphaltenes in oil systems. However, increasing polar forces appeared to increase the attractive interaction between asphaltenes which can in turn lead to higher aggregation and precipitation tendency. The magnitude of polar force is proportional to the content of heteroatoms and has a higher value for asphaltenes that were destabilized and then deposited by smaller alkanes. The stability of asphaltenes in oil from various fields and their deposition on steel were also investigated using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. The results showed that van der Waals and acid–base interactions, among other components of the surface energy, were dominant in promoting asphaltene aggregation and deposition by increasing the attractive force between similar asphaltenes and asphaltene-steel, respectively. These findings were further supported by the concept of works of cohesion and adhesion. The results showed that asphaltenes were unstable and had the tendency to deposit on the steel substrate. The total interaction energy between asphaltene and steel, obtained from the XDLVO theory, and the work of adhesion correlated well with the amounts of asphaltene deposition generated by experimental lab setups. Interfacial tension between asphaltene and steel can provide information about the bond stability and deposit persistence under shear.