Effect of asphaltenes on growth behavior of methane hydrate film at the oil-water interface

Abstract

Investigation of the effect of asphaltenes, the natural surfactant in crude oil, on the methane hydrate formation is crucial for flow assurance in deep-water oil and gas field. However, most of recent studies on hydrate growth mainly focused on the impact of artificial and commercial surfactants. Limited attention has been given to the effect of the important natural surfactants presented in crude oil on hydrate film growth, such as asphaltenes. In this study, the influences of dissolved asphaltenes on the properties of oil-water interface and the growth of methane hydrate film were investigated. The morphology of methane hydrate film on the water droplet in the oil phase with different asphaltene concentrations was in-situ visualized in a visual autoclave equipped with microscopic imaging, and the lateral growth rate of the methane hydrate film was measured. The results showed that the addition of asphaltenes could increase the hydrophobicity of the methane hydrate film, inhibit the growth of hydrate, and change the morphology of the hydrate film. The growth rate of the hydrate film was negatively correlated with the asphaltene concentration (0–200 ppm), but stabilized above 200 ppm. In addition, this inhibition effect on the lateral growth rate was negatively correlated with temperature.