Work of Adhesion Concept to Predict Asphaltene Stability in Crude Oil

Abstract Asphaltene deposition can clog wellbores, pipelines, and decrease oil production, leading to economic and operational losses. Since remediation/intervention efforts are often costly in terms of equipment and production downtime, prevention/minimization of asphaltene deposition is highly preferred. This can be achieved by using asphaltene control chemicals (ACCs). The industry has many laboratory test methods for investigating the asphaltene deposition risk for a production system and measuring the performance of ACCs, ranging from the simplest precipitation-based tests to more elaborate and complex tests that involve high temperature, pressure and shear rates. In this study, we investigate the performance of ACCs theoretically by using the concept of surface energy, which is the sum of the dispersive and polar intermolecular forces. Essentially, surface energy determination can be applied to understand the strength of a material adhered to a substrate and how an applied chemical treatment can be used to reduce the adhesion forces and thus mitigate deposition. Using a selection of laboratory generated asphaltenic deposits together with those collected from various locations in the real production system, we demonstrate that an effective ACC lowers the work of adhesion between asphaltene and the steel substrate. Interfacial tension measurements have shown that the bond strength between an asphaltene particle and effective ACC is lower than that with an ineffective one. Additionally, it was observed through surface energy and work of adhesion studies that an effective ACC interacts with asphaltene particles while having a lower affinity towards itself, thus suppressing the aggregation of ACC molecules in crude oil. Therefore, the addition of an effective ACC to crude oil could retard cohesion of asphaltene particles, thereby minimizing aggregation and subsequent deposition on the steel substrate. These findings could potentially aid in predicting deposition tendencies of oils and the right selection of ACCs to mitigate asphaltenic deposition via a simple set of surface energy measurements. Results obtained during this study best align with a thermodynamic adhesion model, which helps gain insight as to why and through what mechanism ACCs perform.