Influence of Asphaltenes on Hydrate Formation and Decomposition in Water-in-Waxy Oil Emulsions

The formation of hydrate increases the uncertainty of the flow system in subsea multiphase transportation pipelines. Waxes and asphaltenes have been found to influence hydrate formation, but the detailed mechanism of their interaction remains unclear. A lab-scale high-pressure stirring reactor was used to analyze the influence of asphaltenes on CO2 hydrate evolution behavior in waxy water-in-oil (W/O) emulsions. Results demonstrated that waxes inhibited CO2 hydrate nucleation. The addition of asphaltenes promoted the inhibition effect of waxes, and the enhancement effect was nonmonotonic with the asphaltene contents increased. Based on microscopic observation and wax precipitation characteristics, this behavior could be interpreted as the competitive effect of increased adsorption of wax crystals on the surface of the droplets and reduced amount of wax precipitation. Moreover, asphaltenes were found to facilitate the decomposition process of CO2 hydrates in waxy systems by decreasing the wax precipitation amount and stabilizing the emulsion. This work can provide potential engineering guidance for flow assurance applications.