Phase inversion in water-oil emulsions with and without gas hydrates

In deepwater exploration and production, where long tieback multiphase pipelines are a preferred economic option, gas hydrate blockages pose serious problems for flow assurance to produce hydrocarbons with high water cuts because the traditional techniques, such as insulation, heating, or injection of thermodynamic inhibitors, often become economically and logistically impractical. The potential for transporting hydrate particles using antiagglomerant (AA) in high water cuts could be an attractive alternative to the traditional approaches. In high water cut systems, by converting some of the water phase into the hydrate particles, the behavior of the emulsion-hydrate mixture strongly depends on the water-oil emulsion which acts as a carrier fluid. Generally, AAs work as a surface active agent which influences the interface between water and oil and hence impacts the morphology of the hydrate-free emulsion (without hydrate particles) and emulsion during hydrate formation. However, information on the previous is still limited. In the present study, the phase inversion of water-oil emulsions was investigated in two types of experiments: hydrate free emulsions and emulsions during hydrate formation. Experiments were performed to examine the effect of existing natural surfactants in the liquid hydrocarbon phase, AA (quaternary ammonium salt) concentration, salt (NaCl), and hydrate particles on the phase inversion of emulsions. It was concluded that the type of emulsion before hydrate formation and the initial water cut are two important factors that determine the morphology of emulsion during hydrate formation. The results also revealed that in high water cut systems, water-oil emulsion, which is a binary system, is altered to a ternary water/oil/hydratesystem during the hydrate formation process. These findings could lead to a better understanding of the rheological properties of the hydrate slurry flows.