Effects of Salt on the Crystal Growth and Adhesion Force of Clathrate Hydrates

Abstract

In the offshore oil and gas developments, the problems in relation to hydrate flow assurance are always influenced by the existence of salt in the pipeline systems. Even though the salt effects are essential factors associated with the adhesion force between clathrate hydrate and aqueous solutions, the roles of salt in hydrate adhesion behaviors have rarely been considered. This study aims at understanding the effects of salt on not only the adhesion force variations but also the transformation of hydrate growth morphology. The presence of salt did not profoundly influence the change in the adhesion force of the hydrate probe with surfactant-free solutions, whereas it drastically reduced the adhesion force of the hydrate system with surfactant-dissolving aqueous solutions. The experimental results also revealed the inhibition effect of salt on the hydrate crystal growth through the observation of microscopic images. Furthermore, dynamic adhesion behaviors were unprecedentedly captured in terms of gradual increases in adhesion force because of wetting of aqueous solution on the hydrate probe surface and additional hydrate formation. The present work related to the salt effects on the adhesion behaviors could provide novel insights into the dynamic adhesion during the crystal growth of hydrates in the offshore oil and gas production systems.