Lowering of Clathrate Hydrate Cohesive Forces by Surface Active Carboxylic Acids

The present work uses a micromechanical force apparatus to directly measure hydrate particle–particle cohesion forces in hydrocarbon systems containing various carboxylic acids. Measured cohesive forces provide fundamental insight to the balance between surfactant adsorption kinetics and interfacial thermodynamics in hydrate systems. These results are essential to the accurate prediction of hydrate aggregation in multiphase flow, as encountered in oil/gas production. The present data support the existence of the water capillary bridge between hydrate particles as an essential mechanism for hydrate cohesion in oil continuous systems. The results indicate that, while all surface active compounds tested decreased the water–oil interfacial tension, only some chemicals were effective at reducing the interparticle cohesion force. Through systematic measurements, the data yield new insight into how some acids may alter hydrate surface wettability. Polynuclear aromatic carboxylic acids were found to be highly effective, reducing cohesion forces up to 87 ± 9% for a four-ring conjugated hydrophobic group.