Influence of Unconverted Droplets on Hydrate Aggregation in the Oil-Dominated System

Hydrate agglomeration is the key process that forms hydrate plugging in the transportation of oil/gas in multiphase flow lines. The process of hydrate agglomeration and the involved mechanical behavior between hydrate particles are essential to reveal the mechanism of hydrate agglomeration. In this study, a hydrate dynamic agglomeration observation system was designed, and a novelty method was proposed to observe hydrate agglomeration directly. It suggests that droplets and hydrate particles/debris are simultaneously involved in hydrate agglomeration, and the strong adhesion between droplet and hydrate gives the droplet an important role in capturing and bridging hydrate. Based on the observation, the interaction forces of methane hydrate particle-particle/droplet in model oil were evaluated using a high-pressure micromechanical force apparatus. The results show that hydrate particles' cohesion is around 1 magnitude lower than the adhesion force between hydrate particles and water droplets. With the subcooling increased from 1 to 10 degrees C, the hydrate particle-droplet adhesion force first increases from 59.94 +/- 5.16 to 80.34 +/- 7.36 mN<middle dot>m(-1) and then decreases to 57.41 +/- 4.88 mN<middle dot>m(-1). The reason can be explained as the droplet sintering is an important factor affecting the adhesion force between hydrate particles and droplets. This study provides direct observation and research on the formation and dispersion process of hydrate aggregates, providing insights into the aggregation mechanism of hydrates in natural gas pipelines. In addition, the obtained interaction forces can provide basic data for evaluating the risk of hydrate blockage.