Influence of Model Oil with Surfactants and Amphiphilic Polymers on Cyclopentane Hydrate Adhesion Forces

Adhesion forces between cyclopentane hydrate particles were measured at atmospheric pressure and 3.2 degrees C using an improved micromechanical force apparatus. Because of the complexity of crude oil systems, a series of model oils was prepared by adding surface-active components to 200 cP mineral oil as analogues to crude oil systems. The addition of 1 wt % sorbitan monooleate (Span80, a commercial anti-agglomerant), 1 wt % polypropylene glycol (an amphiphilic polymer), and 0.6 wt % commercial naphthenic acid mixture, separately, to a mineral oil and cyclopentane continuous phase, reduced the average interparticle hydrate adhesion force by 37, 65, and 80%, respectively, compared to pure mineral oil and cyclopentane. The 95% confidence bounds of the Span80 and mineral oil data points overlap; therefore, we cannot conclude that Span80 was effective at reducing the adhesion force between hydrate particles. These results indicate that model amphiphilic polymers and commercial naphthenic acid mixtures may be surface-active on the hydrate particle, drastically reducing the agglomeration tendency between hydrate particles; naphthenic acids are found to be the most effective at lowering the adhesive force between particles. The structure of the additive plays a role in determining the extent of surface activity and effectiveness. Compounds with small hydrophilic groups can more efficiently adsorb to the hydrate surface, while additives that induce morphological changes to the hydrate surface may cause non-uniform growth and are more effective in preventing hydrate agglomeration.