The Effect of Surfactants on the Kinetics of Hydrate Formation

Abstract

AbstractDissociation of gas hydrates has been the primary concern of the oil and gas industry for flow assurance, primarily in an offshore environment. There is also a growing interest in the rapid formation of gas hydrates for gas storage, transport of natural gas and carbon sequestration.In this paper, we experimentally measure the kinetics of formation of methane hydrates and the effect of various anionic and cationic surfactants such as sodium dodecyl sulfate (SDS), cetyl trimethyl ammonium bromide (CTAB) and an alpha olefin sulfonate (AOS) on the association rate constants. The importance and necessity of micelle formation in these surfactants has been studied. The effect of foam generation on the rate of formation of these hydrates has also been measured.SDS was found to significantly increase the rate and decrease the induction time for hydrate formation. On the other hand, CTAB and AOS have an inhibiting effect. We observed a decrease in the induction time by a factor of ten when a low concentration of SDS was used instead of only de-ionized water and methane. There was an added decrease in the induction time when a foamed mixture of water and SDS was used. The contribution of some types of micelles towards promoting hydrate formation was demonstrated with a series of experiments using SDS and other surfactants. The micelles formed by these surfactants appear to serve as nucleation sites for the association of hydrates.New experimental data is presented to show that the use of some surfactants and the use of foam can significantly increase the rate of hydrate formation and decrease the induction time. Other surfactants are shown to act as inhibitors. An experimental setup, protocol and analysis method is presented that allows us to distinguish between surfactants that act as promoters and inhibitors for hydrate formation.