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

Abstract

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.

An investigation on gas hydrate formation and slurry viscosity in the presence of wax crystals

“…It indicates that the presence of wax crystals mainly inhibits hydrate nucleation, and the inhibitive effect will be weakened to some extent with the increase of wax content. This is because of the adsorption of the precipitated wax crystals on the surfaces of water droplets in the emulsions, which is probably resulted from the presence of surfactant Span 20 being as one constituent part of AA . As shown in Figure , the distribution of wax crystals in the oil phase leads to a decrease of oil‐water interface surface area for hydrate nucleation.…”

“…Some scholars addressed that the presence of wax crystals would provide crystallization or nucleation sites for hydrate formation and also promote heat transfer to increase hydrate formation rate . Recently, solid wax particles in emulsions were observed to prevent hydrate formation, and the preventive effect was higher with greater amounts of wax …”

Evaluation of Soy Lecithin as Eco‐Friendly Biosurfactant Clathrate Hydrate Antiagglomerant Additive

“…The induction of hydrate crystals and their agglomeration were recorded using a Logitech C521 webcam. The hydrate induction time can be defined as the time at which the hydrate crystals become visible in the experimental solution after the experimental solution was subjected to hydrate stability pressure and temperature conditions (Zheng, Huang, Wang, Long, & Kusalik, ).…”

Effect of the Ethylene Vinyl Acetate Copolymer on the Induction of Cyclopentane Hydrate in a Water-in-Waxy Oil Emulsion System

“…The coupling effect of wax and hydrate is observed in the flow assurance of deep-water oil fields, and the mechanism of wax on influencing the nucleation and growth of hydrate is still lacking. − Chen et al , studied the effect of wax on hydrate formation in a water-in-oil emulsion (Oil phase LP15, Span80 as a surfactant) at a relatively low wax content. Zheng et al found that wax can restrict the induction and formation of CO 2 hydrate in a water-in-oil emulsion (Oil phase -10# diesel). Liu et al illustrated that wax can adsorb at the oil and water interface, affecting the structure of the hydrate shell and inhibiting the mass transfer.…”