Insight into the plugging mechanism in water-continuous hydrate slurries

[Display omitted] •Water-continuous systems which are common in the mature oil/gas fields are studied in a high pressure vertical loop.•Deposition and sloughing of hydrate particles in water-continuous slurry are verified by viscosity measurement and imaging.•The plugging mechanism of the water-continuous system includes crystal particle agglomeration and accumulation/deposition.•Gas hydrate accumulation and sloughing occur intermittently, with sloughing initiated at 0.7 m/s. Oil-water-gas co-transport often occurs in offshore oil/gas production, in which gas hydrate formation could lead to severe flow assurance issues and subsequent safety and environmental risks. As the offshore oil/gas fields mature, water production increases and the flow conditions may convert from an oil-continuous to a water-continuous system. To understand the hydrate plugging mechanism of water-continuous hydrate systems, the flow characteristics of methane hydrate-water slurries was experimentally investigated by using a high pressure vertical loop. The slurry viscosity of different hydrate fractions was measured using an in-line viscometer. Accumulation, deposition and sloughing of the hydrate particles were investigated by video imaging and viscosity measurement. The plugging mechanism in a water-continuous hydrate system was extensively analyzed and hydrate deposition and sloughing were observed. The density difference and agglomeration of hydrate particles is considered as the major cause of hydrate accumulation and deposition, which subsequently instigates plugging in water-continuous systems.