Nucleation of Methane Hydrate in Water-In-Oil Emulsions: Role of the Phase Boundary

Abstract

The processes of nucleation of the methane hydrate have been studied for water emulsions (50% (w/w)) in decane, toluene, oil, and their mixtures. The experimental data have been obtained by the polythermal technique under methane pressures of 12–13 MPa; each of the experiments has been carried out with a freshly prepared sample of the emulsion. The obtained data have been used to derive the survival curves of the samples describing the dependence of the probability N u / N 0 on temperature T, where N u is the number of samples lacking the hydrate on overcooling to a particular temperature T and N 0 is the total number of the samples. The observed curves constitute two families of similar nature: (1) emulsions in decane and toluene and (2) emulsions in oil and mixtures of the oil with decane or toluene. We suggest that the observed results are explained by adsorption of some components present in the systems (surfactant or heavy components of oil) at the interface between the water and organic phases and on the mineral particles present nearby. The result is the formation of a number of surfaces behaving as the centers of heterogeneous nucleation with similar activity in proximity to the water–organic interface (the region of the nucleation of the methane hydrate), thus explaining the similarity of the observed survival curves.