Kinetic and rheological study of methane hydrate formation in water-in-oil emulsion: Effects of emulsion composition and silica sands

Gas hydrate blockage in the emulsifying crude oil poses security risks to the subsea multiphase flow transportation. The kinetic and rheological properties of methane gas hydrate in the water-in-oil emulsion were in situ characterized by experiments in a high-pressure rheometer with particular focus on the effects of emulsion composition and silica sands. Results demonstrated that the methane hydrate growth rate and yield stress increased with the surfactant concentration and water fraction, while the hydrate formation in the emulsion of pure light alkanes was faster than that in the mineral oil emulsion. Moreover, the presence of silica sands shortened the hydrate nucleation time, eliminated the stochasticity of nucleation, and induced the occurrence of hysteresis by affecting the transient and steady state viscosity of hydrate-in-oil slurry. Overall, this study was of added knowledge to the hydrate formation mechanisms in the water-in-oil emulsion, which highlighted the fact that the high emulsification degree, high water fraction, and the high concentration and large particle size of silica sands in the multiphase flow would increase the risks of hydrate blockage in the oil-gas transportation pipelines.