Rate of hydrate formation in crude oil/gas/water emulsions with different water cuts

The formation of gas hydrates in gas and oil subsea pipelines can result in blockages and shutdowns. Understanding of the formation process and its kinetics will be helpful for predictions of the amount of hydrates expected to form under defined conditions. In the present work, mixed gas hydrates of methane, ethane and propane are formed in crude oil emulsions with different water cuts in a stirred constant volume high pressure cell. The rate of hydrate formation for each crude oil is evaluated at different stirring rates. The stability of the emulsion made by each crude oil is also tested at different water cuts and stirring rates. At 80% water cut, hydrate growth occurs in two steps. The first step displays slow growth. The transition between the steps corresponds with inversion of the emulsion. Regarding the stability of emulsion, more stable emulsions are correlated to higher rates of hydrate formation. The rate of hydrate formation at 50% water cut was higher than at 80% water cut independent of oil composition and stirring rate.

► Rate of hydrate formation is evaluated at different water cuts and stirring rates.
► The rates decrease with increasing the water cut from 50% to 80%.
► At 80% water cut, hydrate growth occurs in two steps.
► The transition between the steps corresponds with inversion of the emulsion.