Study of Dynamic Interaction and Adhesion between Water Droplets and Gas Hydrate in Organic Solvents

• Author / Creator

  Chen, Zihui

• In the exploration of offshore reservoirs, the hydrate formation and agglomeration in oil and gas pipelines become the major flow assurance challenges, while the interfacial interactions between hydrate particles and water droplets, for which the presence of salt is inevitable in the deepwater flowlines, are critical for hydrate aggregation. Even though the interaction between water droplets and hydrate particles have been studied, the effects of salts on this interaction have rarely been considered.
  This study aims at understanding the interaction behaviors including both capillary adhesion forces between brine solution droplets and cyclopentane hydrate particle and the influences of different types of salts on the hydrate growth morphology. Capillary adhesion forces are measured using a new instrument, Integrate Thin Film Drainage Apparatus, in both oil and gas bulk phases, while the hydrate growth morphology is observed visually.
  The results showed that the adhesion forces decreased with the increasing of concentrations of NaCl and KCl in water up to 5 wt. %, while the impacts of concentration of either Na2SO4 or CaCl2 on adhesion forces were almost negligible. The adhesion force measured in the gas phase was around twice more than that obtained in the oil phase owing to the wider capillary bridge formation caused by thicker quasi-liquid layer. As observed from the photographic images, the salt solutions with more electronegative ions would delay hydrate growth greatly because these types of salts tended to attract the water molecules more strongly, preventing the formation of hydrate cage and then prohibit the hydrate nucleation more efficiently. Moreover, the longer contact time and the larger solution droplet made critical contributions on the more hydrate formation and higher adhesion force no matter salts present or not, respectively. The hydrate growth rate was not only dependent on the subcooling but also the amount of guest and host components. Specifically, either the lower subcooling or the lack of guest and host components could slow down the hydrate growth rate.
  On the other hand, the surfactants, such as 0.05 g/L asphaltenes and 1 wt. % Span 80, were evaluated as the effective inhibitors to prevent the attachment between water droplets and hydrate particle due to the adsorption layer formed around droplet, resulting in the inhibition of hydrate agglomeration inside pipeline.
  The present work is essential to better understanding of the impacts of different salts on the interaction forces between hydrates and water surface, and hydrate agglomeration in the oil and gas pipelines.

• Subjects / Keywords

  • Salts
  • Gas Hydrates
  • Dynamic Interaction

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-8gnm-j583

• License

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