Kinetics of methane hydrate formation from stirred aqueous NaCl solutions

Abstract

We experimentally studied the kinetics of methane hydrate formation from stirred aqueous NaCl solutions. The studies were carried out with pure water and aqueous solutions in which the mass fractions of NaCl were 0.2%, 0.5%, 1.5%, 3.0%, 5.0%, and 7.0%. In all our kinetic experiments, there was the same initial mass of liquid water, a similar temperature, and a similar driving force for gas hydrate formation in terms of pressure. Under these conditions, the values of the rate of change in the mass of liquid water during the initial stage of methane hydrate formation from stirred aqueous NaCl solutions were determined. It has been found that if the mass fraction of NaCl in an aqueous solution is less than 1.0%, then methane hydrate is formed more rapidly from this solution compared to pure water, and if the mass fraction of NaCl in an aqueous solution is greater than 1.0%, then methane hydrate is formed more slowly from this solution compared to pure water. It has also been found that the presence of NaCl in an aqueous solution has little effect on the kinetics of methane hydrate formation from this solution. Additionally, we experimentally determined the phase equilibrium points for methane hydrate in the pure water–methane and 3.0 wt% NaCl solution–methane systems.