Molecular mechanisms responsible for hydrate anti-agglomerant performance

Area of Science:

• Chemical Engineering
• Physical Chemistry
• Materials Science

Background:

• Hydrate formation and water droplet agglomeration pose significant challenges in hydrocarbon production, impacting flow assurance.
• Understanding the interfacial behavior between hydrates, water, and surfactants is critical for mitigating these issues.

Purpose of the Study:

• To investigate the molecular mechanisms governing the coalescence of sI hydrate particles and water droplets in hydrocarbon mixtures.
• To evaluate the efficacy of quaternary ammonium chloride surfactants with varying head group and tail structures in preventing coalescence.

Main Methods:

• Employed steered and equilibrium molecular dynamics simulations.
• Utilized umbrella sampling to obtain free energy profiles.
• Analyzed force-distance profiles and simulation snapshots for visual inspection.

Main Results:

• Surfactants with butyl tripods on the head group and tails similar in size to solvent molecules demonstrated effective anti-agglomerant properties.
• Surfactant head group and tail structure significantly influence the ability to prevent hydrate-water droplet coalescence.
• Adhesion between surfactants and hydrates is facilitated by the butyl tripod, while tail length affects protective film formation.

Conclusions:

• Optimized surfactant design, particularly the butyl tripod head group and compatible tail length, can prevent hydrate-water droplet coalescence.
• These findings offer molecular-level insights for developing effective anti-agglomerants in flow assurance.
• Coalescence is inevitable once a continuous water pathway forms through the anti-agglomerant film.