Studying asphaltene instability by capillary deposition

Abstract

Asphaltene deposition can occur during oil production and processing. It is necessary to understand the mechanism of asphaltene deposition in order to improve prediction and prevention of deposits. The capillary deposition technique was employed to study the asphaltene deposition process. The deposition apparatus has been developed to preserve the deposit. Scanning electron microscope (SEM) images of the asphaltene deposit generated confirm that proper mixing has been obtained in the deposition apparatus. To check for wide applicability of the results for Oil A, experiments were performed with an additional crude oil. Similar results were observed for both crude oils, showing that the deposit is roughly uniform and thinner at the outlet, suggesting proper mixing is obtained in the deposition system. In a parallel study, experiments were performed by flowing a previously precipitated asphaltene solution through a capillary. The results show that asphaltenes do not deposit in the capillary after they complete their growth (95 hr aging time) indicating that deposition occurs when the asphaltene nanoaggregates are in the process of aggregating.