Effects of Operating Conditions on Wax Deposit Carbon Number Distribution: Theory and Experiment

Wax deposition in subsea pipelines is a problem of enormous economic consequences. The carbon number distribution (CND) is an important characteristic of the deposit because it significantly affects the yield stress of wax deposit, which is important in the design of the remediation technique of pigging. In this study, the recent theories for wax thermodynamic modeling are coupled with heat and mass transport modeling to identify the critical factors that determine the carbon number distribution of wax deposits. It is found that the deposit carbon number distribution is closely related to the diffusion of different n-alkane components and their respective concentration driving forces. The impact of molecular diffusion of the multiple components on the evolution of deposit carbon number distribution is quantified by evaluating of the mass driving force for each n-paraffin component. In addition, the effects of operating conditions on the deposit carbon number distribution are investigated by modeling and are validated by series of flow-loop experiments.