(246a) Heterogeneous Segregation and Deposition of Gas Hydrate Particles From Continuous Oil Phase At Low Water Cut

In this study, hydrate formation process for pure water and water + decane mixture was investigated by monitoring the torque while stirring the fluids inside autoclave. The torque changes with time for pure water showed that the hydrate formation process could be classified into three different regions and the result was agreeable with the previously reported study with flow loop, where the torque increases due to heterogeneous segregation of hydrate particles from aqueous phase. On the other hands, for water + decane mixture For water + decane mixture, the torque became slightly higher upon hydrate onset (region I) and rapidly increased to the maximum value of 40 N cm. This fast increase of the torque since the conversion of 0.10 indicates that fast segregation of hydrate particles happens (region II). When the conversion approached 0.21, the torque decreased and kept the value at around 22 N·cm (region III). During this region III for water + decane mixture, the magnet stirrer coupling was about to stop as seen in high torque and lots of noise. It can be recall the decane is the continuous phase and thus the stirrer stoppage would be caused by the growth and deposition of hydrate particles.

We visually observed the hydrate onset and growth period through the optical camera in order to understand the difference between the pure water and water + decane mixture. For water + decane mixture hydrate forms in free water droplets suspended in decane phase, than deposition of hydrate-containing water droplets happens on the wall as seen in the picture taken 2 min after the onset. The thickness of the deposition on wall slowly increases as hydrate formation proceeds. These images confirmed that the hydrate deposition on the wall is quite susceptible when hydrates form on water droplets dispersed in liquid decane phase.  This result implies that the flow parameters such as water cut and flow regime would be important factor to understand the segregation and deposition of hydrate particles in offshore flowlines.