Effect of different kinds of hydrate promoters on the kinetics of methane hydrate formation in methane-water-oil system

Abstract

In this work, the effect of hydrate promoters on methane hydrate formation in methane-water-oil system with different initial watercuts from 20 vol% to 100 vol% were studied. For comparison, four promoters based on different promotion mechanisms, sodium dodecyl sulfate (SDS), L-leucine (L-l), tetrabutylammonium bromide (TBAB) and polysorbate 80 (Tween 80) were used. The experimental results show that four hydrate promoters did inhibit the nucleation of methane hydrate in 100 vol% watercut system, but the growth kinetic of methane hydrate was effectively improved compared with the system without hydrate promoter. The induction time decreasesd with the increase of initial watercut under the same concentration of hydrate promoter for the methane-water-oil system, and the total methane consumption used for hydrate formation gradually increased with increasing initial watercut (except Tween80). But the current results also show significant improvement in normalized gas consumption per unit water content with the increase of oil phase volume fraction due to that upon addition of oil phase the methane dissolution and mass transfer rate in the methane-water-oil system improves further, meaning that the formation rate of methane hydrate is enhanced. Because of the emulsifying property of Tween 80, the emulsion structure of the systems within Tween 80 hindered the hydrate growth process to some extent. Out of the four hydrate promoters used in this study, SDS was found to be most effective in enhancing the formation kinetic of methane hydrate as well as reducing the induction time in methane-water-oil system under similar conditions.