The Study On The Influence Of Hydrate On Wax Appearance In Subsea Multiphase Pipeline

Wax and hydrate could occur in the subsea multi-phase pipelines, which works at the lower environmental temperature .It can block the pipelines and lead to serious security problems and huge economic losses. So it is particularly important for us to investigate the formation of wax and hydrate in subsea multi-phase pipeline. However, these two solid depositions were mostly studied independently in previous work without considering the interaction between them. Actually, the formation of hydrate or wax will change the composition of the fluid, which could affect thermodynamics behavior of the other.To study the relationship of them, this paper did the work on the precipitation of wax with the existence of hydrate in thermodynamics ways. Phase equilibrium theory and numerical algorithm of the model were discussed. We did selection and optimization on the basis of previous wax models .A procedure was present for simulate phase equilibrium of wax. It was tested for a large number systems comparing with the experimental results ,which lead to a good representation .We adopted hydrates module of simulation software to simulate hydrates phase balance calculation.The simulations were carried on for the formation of hydrate and the appearance of wax individually for one system. If hydrate form first, the hydrate flash calculation was done to update the fluid composition after the formation of hydrate. Then the wax phase boundaries were calculated again. Compare the variation of wax appearance temperature with and without hydrate. It is shown that the influence of hydrate formation on the wax precipitation mainly depends on the variation of the light component which caused by hydrate formed. The more the content of light component changed, the more influences on the wax formation,Vice versa. For this study, the formation of hydrate didn't affect the wax greatly.