Microcarriers for smart release of kinetic hydrate inhibitors under hydrate formation condition inside flowlines

Abstract

Hydrate formation in subsea flowlines is one of the main concerns to safely transport the hydrocarbon fluids in the field of flow assurance. To prevent blockage of hydrate, thermodynamic hydrate inhibitors (THIs) have been injected into the subsea flowlines; however, the high injection amount of THIs may drive up operational expenditure (OPEX) with increasing water depth of oil and gas reservoirs. Kinetic hydrate inhibitors (KHIs) have been investigated as an alternative for few decades. In this study, microcapsules were designed using microfluidics concept for efficient release of KHIs at off-shore transport line of hydrocarbon and gas. Hydrate formation kinetics among four different systems, pure water, microcapsules containing poly vinyl caprolactam (PVCap), microcapsules without PVCap, and PVCap aqueous solution was investigated. The dispersive Raman was applied to understand hydrate formation on microcapsules with temperature change under static condition, and autoclave study also was employed to confirm the shear rate effect on microcapsule stability. From the both experiments, it was confirmed that release of KHI solution from microcapsules delayed the formation of hydrate at the target temperature and showed a similar efficacy comparing to the bulk KHI solution under turbulent condition. These results indicated the release of PVCap solution can be controlled by adjusting the membrane thickness of the microcarriers, which would provide operational flexibility to manage the risk of hydrate plug formation.