Gas hydrate nucleation and growth in a micro-reactor: Effect of individual component separated from the crude oil in the South China Sea

Abstract

Gas hydrate has been a major problem for flow assurance due to its potential to cause pipelines clogging inside subsea multiphase transportation systems. Of special interest is that polar components in crude oil should play a significant role in the hydrate formation kinetics, but the detailed understanding of their interaction remains unclear. Here, the individual component in the crude oil collected from the South China Sea was for the first time separated through the saturates, aromatics, resins, and asphaltenes (SARA) fractionation method. The promotion effect of saturates on hydrate nucleation and growth, and the surprising inhibition effect of aromatics and resins were discovered. Specifically, the average induction time was shortened by 45.13 % with the addition of the saturates; while the aromatics and resins would prolong the induction time by 2.20 and 20.83 times, respectively. Results also indicated that gas flow direction determined the behavior of hydrate growth; hydrates preferentially nucleated at the cell walls with a higher subcooling. It was further illustrated that the average growth rate of hydrate films was enhanced by 32.65 % with the addition of the saturates; while it was reduced by 54.01 % and 84.52 % with aromatics and resins, respectively. Our findings provided the first knowledge on the effect of single polar component in crude oil on hydrate formation kinetics; natural fraction such as resins was also suggested for a potential application in preventing hydrates plugging in pipelines.