Surfactant Effect on Hydrate Crystallization at the Oil-Water Interface

Area of Science:

• Petroleum Engineering
• Materials Science
• Physical Chemistry

Background:

• Gas hydrates, particularly clathrate hydrates, present significant economic and environmental risks in the oil and gas industry due to pipeline plug formation.
• Traditional thermodynamic inhibitors are often used, but novel approaches are needed for more efficient hydrate inhibition.

Purpose of the Study:

• To investigate the hydrate-inhibiting performance of nonionic surfactants on cyclopentane clathrate hydrate formation.
• To understand the effect of surfactant concentration and hydrophilic-lipophilic balance (HLB) on hydrate crystallization morphology and interfacial tension.

Main Methods:

• Studied hydrate formation on 2 μL water droplets of cyclopentane at 2 °C with varying concentrations (low, medium, high relative to CMC) of nonionic surfactants (Span 20, Span 80, Pluronic L31, Tween 65).
• Monitored internal droplet pressure changes during crystallization to infer interfacial tension dynamics.
• Analyzed changes in crystal morphology from planar shell to conical growth.

Main Results:

• Surfactant presence induced a morphological shift in hydrate crystallization from planar shell growth to conical growth.
• Low surfactant concentrations (below CMC) resulted in planar crystals and decreased interfacial tension.
• High surfactant concentrations led to conical crystal growth with oscillatory interfacial tension due to crystal release.
• Optimal inhibition was observed for surfactants with a hydrophilic-lipophilic balance (HLB) close to 10.

Conclusions:

• Nonionic surfactants can effectively inhibit cyclopentane clathrate hydrate formation at low concentrations by modifying crystal growth and interfacial properties.
• Surfactant HLB value is critical for effective hydrate inhibition, with values near 10 showing the strongest performance.
• The study provides insights into surfactant-mediated hydrate crystallization, crucial for developing advanced inhibition strategies in the oil and gas sector.