Effect of wax/anti-agglomerant interactions on hydrate depositing systems

• Published in: Fuel (Guildford) 2020-03, Vol.264, p.116573, Article 116573
• Main Authors: Brown, Erika P., Turner, Doug, Grasso, Giovanni, Koh, Carolyn A.
• Format: Article
• Language: English
• Subjects: Agglomeration forces; Anti-agglomerants; Force measurement; Hydrate cohesion; Hydrate/surface adhesion; Hydrates; Hydrophobicity; Incompatibility; Organic chemistry; Pipelines; Stenosis; Waxes
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2019.116573

Clathrate hydrate particle undergoing morphological changes due to the addition of an anti-agglomerant, but stabilized by wax. [Display omitted] •Investigations of the interactions between hydrates, anti-agglomerants (AAs) and waxes.•Micromechanical force measurements were used to explore particle-surface interactions.•Waxes can significantly alter both the hydrate cohesive and adhesive forces.•A effectiveness when wax is present can be compromised, which could result in hydrate agglomeration and potential plug formation. Hydrates and waxes are two of the biggest flow assurance challenges during subsea oil production. They are both depositing species which can cause stenosis of the pipeline, reducing the available area for flow and increasing the pressure load for production. In extreme scenarios, the pipe can become completely blocked by either of these species. However, little is known about the interaction between waxes and hydrates and less still is known about how treatments for hydrates may affect waxes or vice versa. Hydrate deposition in a waxy pipeline may follow significantly different mechanisms from a bare steel pipeline due to a shift from a typically hydrophilic steel surface to a hydrophobic wax-coated surface. This study utilized a micromechanical force measurement apparatus in order to explore some of the interactions between waxes, both surface-deposited and dissolved in the bulk phase, and hydrates which have been treated with anti-agglomerant chemicals. It was found that waxes can significantly alter both the cohesive and adhesive forces caused by hydrate particles, but that the effect when anti-agglomerants are present may vary based on the composition of the anti-agglomerant. This incompatibility is important for operators to understand better, because the ineffectiveness of an anti-agglomerant when waxes are present could result in hydrate agglomeration and potential plug formation.