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

Abstract

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.

Gas Hydrate Formation in Water-in-Crude Oil Emulsions: The Role of NaCl in Slurry Stability and Transportability

“…This enables a better understanding of the risks involved and facilitates the implementation of appropriate prevention strategies. 18,19 To understand the gas hydrate formation process in systems comprising water, crude oil, and gas, laboratory experiments require the use of high-pressure apparatuses. In this study, gas hydrate formation experiments were conducted using a highpressure rheometer 17 and a rock-flow cell.…”

“…Therefore, conducting a thorough characterization of the gas hydrate formation process in the produced fluids is of the utmost importance. This enables a better understanding of the risks involved and facilitates the implementation of appropriate prevention strategies. , …”

Mapping Wall Deposition Trends of Gas Hydrates: I. Gas-Water-Hydrate Systems

“…This points to the fact that one needs to look at the microscale, at the scale of the first particles formed in the system where the origin of any macromorphology variation of the system (agglomeration, settling, and deposition) is. In that sense, important advances have recently been done in oil-dominant systems, ,,,, showing that a fast water imprisonment in the porous crystalline structure can prevent agglomeration, culminating in the engineering tool called the hydrate slurry phase map that is able to classify a safe zone of production/transportability when hydrates form. However, these new findings apply to systems where water gets completely entrapped inside the porous, hydrophilic hydrate particles during the first seconds after the onset of hydrate formation, occurring mainly for oil continuous systems (low to intermediary water cuts, although a defined value is yet an open question; refer to Brauner and Ullmann for inversion of the continuous phase in oil–water dispersed flows).…”