A detailed morphology investigation on the effects of mixed anionic and nonionic surfactants on methane hydrate formation and dissociation

Foam generation from the presence of sodium dodecyl sulfate (SDS) as a kinetic promoter in methane hydrate formation can be potentially reduced by using mixed surfactants. Mixtures of SDS with nonionic surfactants were proposed to solve this problem. Polyoxyethylene (n) lauryl ether (EO3 and EO5) and alkyl poly glycol ether (APG) were chosen to mix with SDS in different concentrations at 8 MPa and 4 ?C in the quiescent system for both kinetics and morphology studies. The result showed that the addition of EO3 resulted in the slight increase for the induction time but no change in the formation rate. Adding EO5 showed the stochastic phenomenon on hydrate formation kinetics. In the presence of APG, the induction time increased up to ten times and lowered the hydrate formation rate compared to only 0.25 wt% SDS. The methane uptakes were about the same with all conditions. The morphology showed similar hydrate formation and dissociation patterns with all investigated solutions. Interestingly, the mixture of nonionic surfactants with SDS decreased the foam formation compared with the system with only SDS. The addition EO3 showed the gradual decrease in the foam height with the higher concentration of EO3. Adding the highest EO5 concentration showed the optimum foam reduction compared with all conditions. Moreover, the presence of APG showed the similar effects of foam reduction with EO5.

Automated summary

Mixing nonionic surfactants with SDS can reduce foam generation in methane hydrate formation, with the highest EO5 concentration showing the best foam reduction effect, and APG also reducing foam generation.