(690h) Container-Free Gas Hydrate Nucleation Using High-Pressure Acoustic Levitation

Understanding hydrate nucleation is of direct relevance to the field of flow assurance in the oil and gas industry. However, due to its stochastic nature and potential apparatus dependencies, hydrate nucleation can be difficult to generalise. Conventionally, studies are performed with high-pressure vessels wherein solid-liquid interfaces generate potential hydrate nucleation sites that are non-trivial to characterise (e.g. microscopic imperfections). To overcome such constraints, we demonstrate here the first statistically significant set of truly container-free hydrate formation measurements using a high-pressure acoustic levitator. In our experiments, water droplets with well-defined geometries were acoustically levitated within a natural gas atmosphere at approximately 65 bar and 7 °C. Hydrate formation on the interface of the ellipsoidal droplets was directly imaged and used to extract induction times. Cumulative probability distribution functions for these induction times at a controlled sub-cooling were constructed and compared with those obtained from conventional measurements and with predictions from classical nucleation theory. Hydrate dissociation within the acoustic field was also compared to that measured in a high-pressure autoclave.