Methane hydrate formation behaviors in high water-cut oil-in-water systems with hydrate promoters

Hydrate slurry transport technology has become a focal point among worldwide researches, due to its high economic efficiency. However, the mechanism and law of hydrate growth kinetics in flow systems were still unclear, especially in high water-cut oil–water systems with hydrate promoters. On this basis, this paper conducted a series of growth kinetic experiments using a high-pressure transparent sapphire cell, and investigated systematically several influencing factors (such as initial pressure, the concentration of emulsifier, hydrate promoter, and the concentration of hydrate promoter) of growth kinetics, and obtained the quantitative relationship between these factors and gas consumption as well as the hydrate growth rate (gas consumption rate). It could be seen from the analysis of these influencing factors that the presence of hydrate promoters can promote hydrate nucleation rapidly and shorten the hydrate induction time, as compared with the (diesel oil + water) system. The concentration of emulsifier is positively correlated with the induction period of hydrate formation, whether it was sodium dodecyl sulfate (SDS) or l-leucine (l-l) systems. The SDS and l-l system could significantly improve the formation kinetics of methane hydrate in the emulsion system, while tetrabutylammonium bromide (TBAB) and polysorbate 80 (Tween80) significantly inhibited the nucleation and growth of methane hydrate in the emulsion. The kinetic curves of hydrate formation showed a trend of first increasing and then gradually decreasing, with the increase of SDS concentrations. However, the hydrate formation kinetics tended to increase gradually and reach equilibrium in the l-l system, with an increase in the concentration of l-l.