Existence of a critical carbon number in the aging of a wax-oil gel

A fundamental study, was carried out to understand the aging (or hardening) of the wax-oil gels formed in the subsea pipelines during the flow of crud e oil from offshore wells to shore. The aging process is a counterdiffusion phenomenon where there exists a critical carbon number (CCN), and wax mole cules with carbon numbers greater than the CCN diffuse into the gel matrice s and vice versa. Using a careful analysis of carbon number distributions o f gel deposits, collected from a cold finger after various deposition time intervals, the CCN for the wax-oil system was obtained. A mathematical mode l, based on a modified version of UNIQUAC model, was developed to predict t he CCN for wax-oil systems. The size of the interaction units for n-alkanes in the solid-phase UNIQUAC model was found to be a strong function of the mean carbon number in the solid phase.