Induction Time of Hydrate Formation in Water-in-Oil Emulsions

Blockage of pipelines due to hydrate formation is a major problem for subsea flow assurance. Induction time for hydrate formation from the multiphase system within a pipeline is a critical parameter to determine whether hydrates may form at a given time. In this work, the induction time for hydrate formation in water-in-oil emulsions was investigated under different conditions. For this purpose, an autoclave with an online viscometer was designed and built. Based on the viscosity variation observed in the experiments during hydrate formation, a new avenue for defining induction time is proposed, which should be more convenient for determining the hydrate formation time in some pipelines. As hydrate formation in emulsions is more complicated than in pure water, the effects of several factors were considered in this study, including water cut of the emulsions, shear rate, driving force, and memory effect. Additionally, wax precipitation is also a common problem in subsea pipelines and can impact flow assurance when hydrate formation and wax precipitation both occur. Consequently, the effect of wax solid particles on hydrate formation was also considered in this work. The presence of wax particles is observed to impede hydrate formation. In this work, it is determined from induction time that the hydrate formation is initiated at the water–oil surface for water-in-oil emulsion. Moreover, the memory effect can shorten induction times of hydrate formation due to the remaining small CO2 bubbles at the surface of water droplets.