The Effect of the Hydrate Antiagglomerant on Hydrate Crystallization at the Oil-Water Interface

Clathrate hydrates are ice-like compounds consisting of small gas molecules enclosed in water molecule cages. The formation of gas hydrate in oil and gas pipelines may result in flow assurance failure and serious safety and environmental concerns. Antiagglomeration is a promising method to mitigate gas hydrate risks in hydrocarbon flowlines. Morphological behavior of hydrates in the presence of antiagglomerants can provide important information on the antiagglomeration mechanisms. This study reports the visual observations of the morphology of hydrate formed with a water droplet immersed in cyclopentane with and without the presence of a hydrate antiagglomerant (AA). The effect of AA on the hydrate crystal growth was investigated. The AA exhibited a kinetic inhibition effect. With no AA, a faceted hydrate shell formed around the water droplet was observed. The subcooling can affect the rate of lateral growth. Higher subcooling facilitates hydrate growth. With the presence of 0.04 wt % AA, a hairy and porous morphology of hydrate was observed. At higher AA concentrations, a vertical type of growth after the lateral growth of the hydrate shell was observed. This is probably the first report of vertical growth of cyclopentane hydrate formed with a water droplet. A hypothesis is proposed to explain the vertical growth mechanism of the hydrate crystals.