Defining a Slurry Phase Map for Gas Hydrate Management in Multiphase Flow Systems

This study proposes a criterion for the safe transportability of gas hydrate slurries in oil-dominant flowlines. Fluids chemistry plays a role in how the particles agglomerate, which occurs in the time window the particles take to decrease their porosity because of crystallization in the capillary walls or to seal the water within the pores by the action of chemical additives, completely preventing any water in the outer surface of the particle and avoiding liquid bridge formation (agglomeration). Hydrodynamic aspects come from the lift vs buoyancy/weight forces that tend to suspend/settle the particles, as well as the collision and disruption rates of particles that play a role in the agglomeration process. The criterion is rather simple and shows the importance of the subcooling of crystallization, water cut, mixture velocity, and oil-water interfacial tension that can be lowered by the use of additives. A simple chart for assuring safe, fully suspended slurry flow (low plugging risk) is proposed, called hydrate slurry phase map, and directives of its use for flowline design and management are discussed. Discussion is also given on how to scale up laboratory measurements into field conditions by the proposal of a new dimensionless group, called the Bassani number.