Investigation on Hydrate Growth at Oil-Water Interface: In the Presence of Wax

In deepwater oil and gas transportation processes, natural gas hydrates (NGHs) can form easily in pipelines considering the suitable temperature and pressure conditions and therefore lead to pipeline plugging. In water- and wax-containing oil systems, waxes can coexist with hydrates and thus contribute to even more severe challenges to deepwater pipeline flow assurance. In the present work, to investigate the effects of wax on hydrate growth at the oil-water interface, several micro experiments were performed in an atmospheric visual cell. According to the micro experimental phenomena, the morphology, porosity, wetness, and growth rate of the hydrate shell were studied and the effects of wax on hydrate growth were investigated. In experiments, two kinds of hydrate shells with different morphologies, porosities, and amounts of wetness were observed. Wax was found to have little effect on the morphology of the hydrate shell. However, wax molecules could remarkably influence the shape of the hydrate shell when the wax content ranged from 1 to 2 wt %. Moreover, wax molecules and crystals can influence the hydrate shell growth rate in terms of interfacial tension, medium concentration, mass/heat transfer resistance, and nucleation sites. The results in this work could provide guidance for hydrate management in wax-containing systems.