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 crude oil from offshore wells to shore. The aging process is a counterdiffusion phenomenon where there exists a ( ) critical carbon number CCN , and wax molecules with carbon numbers greater than the CCN diffuse into the gel matrices and ®ice ®ersa. Using a careful analysis of carbon number distributions of gel deposits, collected from a cold finger after ®arious deposition time inter®als, the CCN for the wax-oil system was obtained. A mathematical model, based on a modified ®ersion of UNIQUAC model, was de®eloped to predict the 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.